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2020 Volume 40 Issue 11
2020, 40(11): 3493-3516
doi: 10.6023/cjoc202007004
Abstract:
Cinchona alkaloids widely exist in nature, which have attracted extensive interest of researchers because of their readily availability, biological activity, unique structural properties, and easy modification. With the development of asymmetric synthetic chemistry, cinchona alkaloids and their derivatives have been used as a privileged class of chiral catalysts or ligands in many catalytic asymmetric reactions. In particular, a variety of cinchona alkaloid-derived chiral catalysts and ligands have been developed and applied by organic chemists in catalytic asymmetric synthesis in rencent years. The recent progress made in this field over the past few years is summarized. Moreover, the related reaction mechanisms and future development prospects are also discussed.
Cinchona alkaloids widely exist in nature, which have attracted extensive interest of researchers because of their readily availability, biological activity, unique structural properties, and easy modification. With the development of asymmetric synthetic chemistry, cinchona alkaloids and their derivatives have been used as a privileged class of chiral catalysts or ligands in many catalytic asymmetric reactions. In particular, a variety of cinchona alkaloid-derived chiral catalysts and ligands have been developed and applied by organic chemists in catalytic asymmetric synthesis in rencent years. The recent progress made in this field over the past few years is summarized. Moreover, the related reaction mechanisms and future development prospects are also discussed.
2020, 40(11): 3517-3535
doi: 10.6023/cjoc202003057
Abstract:
In the past decades, transition metal-catalyzed C—H activation has experienced tremendous growth and revolutionized the field of organic synthesis. Several elegant strategies have been developed to promote reactivity and control precise site-selectivity. Among which, transient directing group strategy has been recognized to be an efficient and powerful approach for selective C—H functionalization. In contrast to traditional directing groups with covalent linkage, transient directing group strategy circumvents the covalent installation and removal of directing groups, which significantly improve the synthetic efficiency and broaden the range of synthetic applications. The recent advances in imine-based transition directing groups are summarized, providing an overview of recent achievements in this cutting-edge research field over the past few years. For clarity, it is classified into two sections according to the type of substrate and the type of activated hydrocarbon bond. Emphasis is placed on the fully discussion of various transient directing groups and their applications. Finally, the limitations of previous works and perspectives on this cutting-edge area are also described.
In the past decades, transition metal-catalyzed C—H activation has experienced tremendous growth and revolutionized the field of organic synthesis. Several elegant strategies have been developed to promote reactivity and control precise site-selectivity. Among which, transient directing group strategy has been recognized to be an efficient and powerful approach for selective C—H functionalization. In contrast to traditional directing groups with covalent linkage, transient directing group strategy circumvents the covalent installation and removal of directing groups, which significantly improve the synthetic efficiency and broaden the range of synthetic applications. The recent advances in imine-based transition directing groups are summarized, providing an overview of recent achievements in this cutting-edge research field over the past few years. For clarity, it is classified into two sections according to the type of substrate and the type of activated hydrocarbon bond. Emphasis is placed on the fully discussion of various transient directing groups and their applications. Finally, the limitations of previous works and perspectives on this cutting-edge area are also described.
2020, 40(11): 3559-3595
doi: 10.6023/cjoc202006072
Abstract:
Among various 1, 3-dipoles of cyclic azomethine imines, C, N-cyclic azomethine imines are the most widely used reagents in the construction of diverse tetrahydroisoquinoline derivatives. The developments of reactions with C, N-cyclic azomethine imines including [3+2], [3+3], [3+4], [5+1], [3+1] cycloaddition reactions and miscellaneous reactions are summarized. The properties of reactions, reaction processes and synthetic applications are discussed. Finally, the prospects of the reaction with this reagent are also proposed.
Among various 1, 3-dipoles of cyclic azomethine imines, C, N-cyclic azomethine imines are the most widely used reagents in the construction of diverse tetrahydroisoquinoline derivatives. The developments of reactions with C, N-cyclic azomethine imines including [3+2], [3+3], [3+4], [5+1], [3+1] cycloaddition reactions and miscellaneous reactions are summarized. The properties of reactions, reaction processes and synthetic applications are discussed. Finally, the prospects of the reaction with this reagent are also proposed.
2020, 40(11): 3605-3619
doi: 10.6023/cjoc202006033
Abstract:
Organoboron compounds are valuable synthetic intermediates and widely used in the synthesis of medicine, pesticide and organic optoelectronic materials due to their extensive resouce and highly transformable ability. Among various organoboron compounds, the synthesis and transformation of alkylboron compounds have attracted much attention. As a sustainable and green energy, visible light shows an important effect in organic systhesis. Tetracoordinated alkylboron compounds could occur single electron transfer (SET) process to generate alkyl radical for further transformations. Herein, the recent advances in the photoinduced transformation of alkyl boron compounds are summarized.
Organoboron compounds are valuable synthetic intermediates and widely used in the synthesis of medicine, pesticide and organic optoelectronic materials due to their extensive resouce and highly transformable ability. Among various organoboron compounds, the synthesis and transformation of alkylboron compounds have attracted much attention. As a sustainable and green energy, visible light shows an important effect in organic systhesis. Tetracoordinated alkylboron compounds could occur single electron transfer (SET) process to generate alkyl radical for further transformations. Herein, the recent advances in the photoinduced transformation of alkyl boron compounds are summarized.
2020, 40(11): 3620-3632
doi: 10.6023/cjoc202006068
Abstract:
In recent years, decatungstate [W10O32]4- as a catalyst has attracted much attention in the field of photocatalytic organic synthesis. With the catalysis of decatungstate, the C—H bond of substrate can be converted into the corresponding radical via a hydrogen atom transfer (HAT) progress under light irradiation. In this review, we summarized the recent advances of the application of decatungstate as a photocatalyst for the C—H functionalization to construct C—C, C—N, C—F bonds.
In recent years, decatungstate [W10O32]4- as a catalyst has attracted much attention in the field of photocatalytic organic synthesis. With the catalysis of decatungstate, the C—H bond of substrate can be converted into the corresponding radical via a hydrogen atom transfer (HAT) progress under light irradiation. In this review, we summarized the recent advances of the application of decatungstate as a photocatalyst for the C—H functionalization to construct C—C, C—N, C—F bonds.
2020, 40(11): 3633-3645
doi: 10.6023/cjoc202006081
Abstract:
Due to the potential applications of fullerene derivatives in materials science and biological science, chemists have been devoted to their synthesis over the past 30 years, and have reported a great diversity of synthetic protocols to fun-ctionalize fullerenes. Among the numerous methods, electrochemical synthesis has been considered to be a novel and efficient strategy due to its mild reaction conditions, good regioselectivity and relatively high yield. The electrochemical functionalizations of [60]fullerene-fused heterocycles have recently attracted wide interest, because electroreduction results in the carbon-heteroatom bond breaking and rearrangement of the heterocyclic moieties on the fullerene skeleton, consequently providing new addition patterns of fullerene derivatives. The electrochemical reactions of [60]fullerene-fused heterocycles since 2011 are reviewed.
Due to the potential applications of fullerene derivatives in materials science and biological science, chemists have been devoted to their synthesis over the past 30 years, and have reported a great diversity of synthetic protocols to fun-ctionalize fullerenes. Among the numerous methods, electrochemical synthesis has been considered to be a novel and efficient strategy due to its mild reaction conditions, good regioselectivity and relatively high yield. The electrochemical functionalizations of [60]fullerene-fused heterocycles have recently attracted wide interest, because electroreduction results in the carbon-heteroatom bond breaking and rearrangement of the heterocyclic moieties on the fullerene skeleton, consequently providing new addition patterns of fullerene derivatives. The electrochemical reactions of [60]fullerene-fused heterocycles since 2011 are reviewed.
2020, 40(11): 3646-3655
doi: 10.6023/cjoc202006079
Abstract:
Methylation of arenes is one of the versatile approaches to achieve structural modification in organic and medicinal chemistry. Installation of a methyl group onto an aromatic ring can lead to significant improvenent of the physical properties and biological activity of this molecule, thusly the effect oftentimes is called the"magic methyl effect". During the past few years, visible-light-induced photocatalysis has emerged as a powerful tool for the development of efficient transformations in organic synthesis. Compared to traditional radical mediated reactions, the use of visible light as energy input is more environmentally benign. Recently, a series of aryl methylation reactions enabled by visible light photoredox catalysis have been reported and applied in the synthesis of pharmaceutically-interested products. In this review, the recent progress of visible-light-induced aryl methylation reactions is briefly summaried, with discussions of different reaction pathways.
Methylation of arenes is one of the versatile approaches to achieve structural modification in organic and medicinal chemistry. Installation of a methyl group onto an aromatic ring can lead to significant improvenent of the physical properties and biological activity of this molecule, thusly the effect oftentimes is called the"magic methyl effect". During the past few years, visible-light-induced photocatalysis has emerged as a powerful tool for the development of efficient transformations in organic synthesis. Compared to traditional radical mediated reactions, the use of visible light as energy input is more environmentally benign. Recently, a series of aryl methylation reactions enabled by visible light photoredox catalysis have been reported and applied in the synthesis of pharmaceutically-interested products. In this review, the recent progress of visible-light-induced aryl methylation reactions is briefly summaried, with discussions of different reaction pathways.
2020, 40(11): 3656-3671
doi: 10.6023/cjoc202006052
Abstract:
In recent years, mechanoluminescence, as a unique luminescence phenomenon, exhibited huge potential applications and rapid development in stress detection, anti-counterfeiting, encryption, light sources and bio-imaging, etc. Recently, great efforts have been made on molecular aggregation science, molecular packing and intermolecular interaction in the solid state have been deeply understood, directly promoting the development and application of mechanoluminescence and photoluminescence materials. The phenomenon and mechanism of mechanoluminescence were firstly introduced, the relationship between mechanoluminescence and aggregation behaviors of organic compounds were discussed in detail. The measurement and characterization of mechanoluminescence, the relationship between applied stress and mechanoluminescence intensity, and the color of mechanoluminescence were briefly introduced, then, the current application of mechanoluminescence was highlighted. In the end, the prospect of organic mechanoluminescence materials was afforded.
In recent years, mechanoluminescence, as a unique luminescence phenomenon, exhibited huge potential applications and rapid development in stress detection, anti-counterfeiting, encryption, light sources and bio-imaging, etc. Recently, great efforts have been made on molecular aggregation science, molecular packing and intermolecular interaction in the solid state have been deeply understood, directly promoting the development and application of mechanoluminescence and photoluminescence materials. The phenomenon and mechanism of mechanoluminescence were firstly introduced, the relationship between mechanoluminescence and aggregation behaviors of organic compounds were discussed in detail. The measurement and characterization of mechanoluminescence, the relationship between applied stress and mechanoluminescence intensity, and the color of mechanoluminescence were briefly introduced, then, the current application of mechanoluminescence was highlighted. In the end, the prospect of organic mechanoluminescence materials was afforded.
2020, 40(11): 3672-3685
doi: 10.6023/cjoc202006076
Abstract:
Inspired by enzyme allosteric catalysis, the study on artificial stimuli-responsive asymmetric catalytic systems has attracted more and more attentions in recent years. In order to precisely control the catalytic activity and stereoselectivity, stimuli-responsive functionalities have been introduced into the catalyst design. A variety of asymmetric reactions featuring on/off-switchable catalysis and/or stereodivergent catalysis have been successfully achieved by using light-, coordination-, pH-and redox-driven chiral switchable catalysts. By selecting representative examples, the catalyst design principles, allosteric mechanism and their applications in switchable asymmetric reactions sre mainly introduced. At the same time, advantages and limitations of this emerging field are summarized, and perspectives for its future development are given.
Inspired by enzyme allosteric catalysis, the study on artificial stimuli-responsive asymmetric catalytic systems has attracted more and more attentions in recent years. In order to precisely control the catalytic activity and stereoselectivity, stimuli-responsive functionalities have been introduced into the catalyst design. A variety of asymmetric reactions featuring on/off-switchable catalysis and/or stereodivergent catalysis have been successfully achieved by using light-, coordination-, pH-and redox-driven chiral switchable catalysts. By selecting representative examples, the catalyst design principles, allosteric mechanism and their applications in switchable asymmetric reactions sre mainly introduced. At the same time, advantages and limitations of this emerging field are summarized, and perspectives for its future development are given.
2020, 40(11): 3686-3696
doi: 10.6023/cjoc202006008
Abstract:
C—H oxidation represents one of the most important reactions in organic chemistry. In particular, asymmetric C—H oxidation, which can directly convert simple alkanes into chiral alcohols, ketones, aldehydes and so on, provides more economic and efficient access to the synthesis of complex molecules. Although increasing efforts have been devoted to this area, asymmetric C—H oxidation is still far away from the goal due to the inert nature of C—H and the subtle stereo-difference of C—H bonds. The factors that dictate the selectivity of asymmetric C—H oxidation, mechanism of the C—H oxidation catalyzed by enzyme and some successful examples achieved by biomimetic metal complexes bearing various ligands are reviewed.
C—H oxidation represents one of the most important reactions in organic chemistry. In particular, asymmetric C—H oxidation, which can directly convert simple alkanes into chiral alcohols, ketones, aldehydes and so on, provides more economic and efficient access to the synthesis of complex molecules. Although increasing efforts have been devoted to this area, asymmetric C—H oxidation is still far away from the goal due to the inert nature of C—H and the subtle stereo-difference of C—H bonds. The factors that dictate the selectivity of asymmetric C—H oxidation, mechanism of the C—H oxidation catalyzed by enzyme and some successful examples achieved by biomimetic metal complexes bearing various ligands are reviewed.
2020, 40(11): 3697-3713
doi: 10.6023/cjoc202004045
Abstract:
Palladium-catalyzed organic transformations is an important branch of organometallic chemistry. Because it can efficiently construct carbon-carbon bonds and carbon-heteroatom bonds, palladium catalysis has been widely used in synthetic chemistry, material science and pharmaceutical industry. However, some of these reactions suffer from harsh reaction conditions, including high temperature and strong base. On the other hand, the visible-light photoredox catalysis employs the visible light as the energy source to generate highly reactive intermediates and realize many novel transformations, which are rare under the normal thermal reaction conditions, under mild reaction conditions. However, there are also limitations in reaction types and substrate scope in this field. In order to solve such problems in these two fields, organic chemists have merged the visible-light photoredox catalysis and palladium catalysis, realizing a series of novel organic transformations through the electron transfer or energy transfer between photosensitizer and organic palladium complex under mild conditions with high efficiency and selectivity, which has broad substrate scope and great application potential. In these transformations, visible-light photoredox catalysis and palladium catalysis both play their respective roles and cooperate well. The application of visible light photoredox and palladium dual catalysis in organic synthesis is summarized and the future research directions in this field are analyzed, which might help the further development of this field.
Palladium-catalyzed organic transformations is an important branch of organometallic chemistry. Because it can efficiently construct carbon-carbon bonds and carbon-heteroatom bonds, palladium catalysis has been widely used in synthetic chemistry, material science and pharmaceutical industry. However, some of these reactions suffer from harsh reaction conditions, including high temperature and strong base. On the other hand, the visible-light photoredox catalysis employs the visible light as the energy source to generate highly reactive intermediates and realize many novel transformations, which are rare under the normal thermal reaction conditions, under mild reaction conditions. However, there are also limitations in reaction types and substrate scope in this field. In order to solve such problems in these two fields, organic chemists have merged the visible-light photoredox catalysis and palladium catalysis, realizing a series of novel organic transformations through the electron transfer or energy transfer between photosensitizer and organic palladium complex under mild conditions with high efficiency and selectivity, which has broad substrate scope and great application potential. In these transformations, visible-light photoredox catalysis and palladium catalysis both play their respective roles and cooperate well. The application of visible light photoredox and palladium dual catalysis in organic synthesis is summarized and the future research directions in this field are analyzed, which might help the further development of this field.
2020, 40(11): 3714-3737
doi: 10.6023/cjoc202005007
Abstract:
Calixarenes, pillararenes and their analogues are composed of hydroxy-or alkoxy-substituted aromatic rings bridged by methylene or methenyl groups, which can be collectively called as macrocyclic arenes. Macrocyclic arenes have attracted much attention and increasing interests because of their unique structures, easily synthesis and derivatization, electron-rich cavities and wide applications in supramolecular chemistry, and they have also become one of the most significant and studied synthetic macrocyclic hosts during the last decades. Recently, with the rapid development of macrocycles and supramolecular chemistry, various types of novel macrocyclic arenes except the classic macrocyclic arenes such as calixarenes and pillararenes have been reported. The construction and functionalization of novel macrocyclic arenes have become the new focus and hot topic of macrocyclic and supramolecular chemistry. The recent advances in the synthesis and properties of novel macrocyclic arenes are summarized. It is expected that this review will be helpful to the research of macrocyclic arenes and promote the development of macrocyclic arene chemistry.
Calixarenes, pillararenes and their analogues are composed of hydroxy-or alkoxy-substituted aromatic rings bridged by methylene or methenyl groups, which can be collectively called as macrocyclic arenes. Macrocyclic arenes have attracted much attention and increasing interests because of their unique structures, easily synthesis and derivatization, electron-rich cavities and wide applications in supramolecular chemistry, and they have also become one of the most significant and studied synthetic macrocyclic hosts during the last decades. Recently, with the rapid development of macrocycles and supramolecular chemistry, various types of novel macrocyclic arenes except the classic macrocyclic arenes such as calixarenes and pillararenes have been reported. The construction and functionalization of novel macrocyclic arenes have become the new focus and hot topic of macrocyclic and supramolecular chemistry. The recent advances in the synthesis and properties of novel macrocyclic arenes are summarized. It is expected that this review will be helpful to the research of macrocyclic arenes and promote the development of macrocyclic arene chemistry.
2020, 40(11): 3748-3759
doi: 10.6023/cjoc202004008
Abstract:
The advent of visible light photoredox catalysis has transformed the way of single-electron transfer (SET) processes and accessing radical species. As a result, the chemistry of nitrogen-centered radicals has witnessed a remarkable gain in interest. Specifically, under visible light photoredox catalysis, iminyl radicals can be generated from oxime derivatives, such as O-acyl oximes, O-aryl oximes and α-imino-oxy acids. Meanwhile, the reactivity of iminyl radcials is investigated systematically. Iminyl radicals can undergo four major classes of reactions, namely addition to arenes, intramolecular hydrogen atom transfer and subsequent reactions, addition to alkenes, Norrish type-I fragmentation (cleavage of α-carbon-carbon bonds) and subsequent reactions. In this review, the most significant progresses in the use of oximes and their derivatives as iminyl precursors are discussed and their engagement in photoredox-mediated transformations is outlined.
The advent of visible light photoredox catalysis has transformed the way of single-electron transfer (SET) processes and accessing radical species. As a result, the chemistry of nitrogen-centered radicals has witnessed a remarkable gain in interest. Specifically, under visible light photoredox catalysis, iminyl radicals can be generated from oxime derivatives, such as O-acyl oximes, O-aryl oximes and α-imino-oxy acids. Meanwhile, the reactivity of iminyl radcials is investigated systematically. Iminyl radicals can undergo four major classes of reactions, namely addition to arenes, intramolecular hydrogen atom transfer and subsequent reactions, addition to alkenes, Norrish type-I fragmentation (cleavage of α-carbon-carbon bonds) and subsequent reactions. In this review, the most significant progresses in the use of oximes and their derivatives as iminyl precursors are discussed and their engagement in photoredox-mediated transformations is outlined.
2020, 40(11): 3760-3776
doi: 10.6023/cjoc202003061
Abstract:
Due to its alkene moiety and highly strained aziridine scaffold, vinylaziridines represent a versatile type of synthetic building blocks and can undergo various chemcial transformations. These transformations enabled facile synthesis of a wide range of nitrogen-containing compounds, especially diverse nitrogen heterocycles, inculding azetidines, pyrrolidines, piperidines, azacycloheptanes and so on. Moreover, development of simple and efficient synthetic methods for various substituted vinylaziridines, stimulating their applications in the fields of organic synthesis, medicinal and agrochemistry, as well as fine chemistry. In recent years, such type of reagents continue to attract considerable research efforts from chemists and enjoyed rapid development. The representative examples of nucleophilic ring-opening and cyclization reactions of vinyl-aziridines over the past five years are summarized. Moreover, the prospects of further development are also disscussed.
Due to its alkene moiety and highly strained aziridine scaffold, vinylaziridines represent a versatile type of synthetic building blocks and can undergo various chemcial transformations. These transformations enabled facile synthesis of a wide range of nitrogen-containing compounds, especially diverse nitrogen heterocycles, inculding azetidines, pyrrolidines, piperidines, azacycloheptanes and so on. Moreover, development of simple and efficient synthetic methods for various substituted vinylaziridines, stimulating their applications in the fields of organic synthesis, medicinal and agrochemistry, as well as fine chemistry. In recent years, such type of reagents continue to attract considerable research efforts from chemists and enjoyed rapid development. The representative examples of nucleophilic ring-opening and cyclization reactions of vinyl-aziridines over the past five years are summarized. Moreover, the prospects of further development are also disscussed.
2020, 40(11): 3794-3801
doi: 10.6023/cjoc202005046
Abstract:
Although the chiral separation techniques represented by the polysaccharides-based chiral stationary phases are almost matured, the chiral separation for complex samples remains a challenge. To this end, two dimensional liquid chromatography has been developed rapidly. Recently, to achieve the chiral separation with two dimensional liquid chromatoraphy, the development of the ultrafast liquid chromatography has caused considerable attention. The development of ultrafast liquid chromatography and two-dimensional liquid chromatography also caters to the development of high-throughput organic synthesis technology. In this review the recent progress in the chiral separation by the ultrafast and two-dimensional liquid chromatography is summarized. This review focuses on the progress in the techniques of the chiral packing materials for ultrafast chromatography, the chiral separation strategy and its application in complex samples. Finally, the application perspective of ultra-fast and two-dimensional liquid phase in high-throughput organic synthesis techniques is prospected.
Although the chiral separation techniques represented by the polysaccharides-based chiral stationary phases are almost matured, the chiral separation for complex samples remains a challenge. To this end, two dimensional liquid chromatography has been developed rapidly. Recently, to achieve the chiral separation with two dimensional liquid chromatoraphy, the development of the ultrafast liquid chromatography has caused considerable attention. The development of ultrafast liquid chromatography and two-dimensional liquid chromatography also caters to the development of high-throughput organic synthesis technology. In this review the recent progress in the chiral separation by the ultrafast and two-dimensional liquid chromatography is summarized. This review focuses on the progress in the techniques of the chiral packing materials for ultrafast chromatography, the chiral separation strategy and its application in complex samples. Finally, the application perspective of ultra-fast and two-dimensional liquid phase in high-throughput organic synthesis techniques is prospected.
2020, 40(11): 3802-3811
doi: 10.6023/cjoc202004040
Abstract:
As a class of macrocyclic host with excellent water solubility, low biotoxicity and high charge density, multi-charged cyclodextrins have been extensively studied because they can interact with organic/inorganic/biological molecules through multiple synergistic forces such as the hydrophobic cavities and electrostatic interactions to construct the smart supramolecular assemblies with stable topology, functional diversity and stimulus responsiveness. The latest research progress of pH-, photo-, enzyme-, redox-, magnetic-and multi-stimulus responsive smart supramolecular assemblies, which are constructed by typical positively/negatively charged and amphiphilic multi-charged cyclodextrins including their application in the fields of drug delivery, controlled release and sensory detection is introduced, and the challenges and future developments of multi-charged cyclodextrin smart supramolecular assemblies are discussed.
As a class of macrocyclic host with excellent water solubility, low biotoxicity and high charge density, multi-charged cyclodextrins have been extensively studied because they can interact with organic/inorganic/biological molecules through multiple synergistic forces such as the hydrophobic cavities and electrostatic interactions to construct the smart supramolecular assemblies with stable topology, functional diversity and stimulus responsiveness. The latest research progress of pH-, photo-, enzyme-, redox-, magnetic-and multi-stimulus responsive smart supramolecular assemblies, which are constructed by typical positively/negatively charged and amphiphilic multi-charged cyclodextrins including their application in the fields of drug delivery, controlled release and sensory detection is introduced, and the challenges and future developments of multi-charged cyclodextrin smart supramolecular assemblies are discussed.
2020, 40(11): 3812-3827
doi: 10.6023/cjoc202006051
Abstract:
Driven by nowadays' computing power, big data technology as well as learning algorithm, artificial intelligence (AI) has gained trenmendous attentions and become a transformative approach in many research areas. One of the most extensively explored AI approaches in chemistry is (deep) machine learning, which provides new twists in the fields of organic chemistry. The workflow of machine learning (ML) study in organic chemistry is briefly introduced. Meanwhile, the application of ML in the accurate prediction of chemical properties, molecular de novo design, chemical reaction prediction, retrosynthetic analysis and artificial intelligence synthetic machine are also summarized. In the end, the current challenges in this field are analyzed and discussed.
Driven by nowadays' computing power, big data technology as well as learning algorithm, artificial intelligence (AI) has gained trenmendous attentions and become a transformative approach in many research areas. One of the most extensively explored AI approaches in chemistry is (deep) machine learning, which provides new twists in the fields of organic chemistry. The workflow of machine learning (ML) study in organic chemistry is briefly introduced. Meanwhile, the application of ML in the accurate prediction of chemical properties, molecular de novo design, chemical reaction prediction, retrosynthetic analysis and artificial intelligence synthetic machine are also summarized. In the end, the current challenges in this field are analyzed and discussed.
2020, 40(11): 3536-3558
doi: 10.6023/cjoc202010025
Abstract:
Eight-membered carbocycles are widely found in natural products with significant biological activities and other molecules ranging from perfumes to potential materials. Therefore, accessing these eight-membered carbocycle embedded molecules is important for drug discovery, biological investigation, fragrance industry, material development and many other fields. However, the synthesis of eight-membered carbocycles is still posing challenges to synthetic chemists. Hence, tremendous efforts have been endeavored by many leading chemists to discover and develop new reactions in order to synthesize eight-membered carbocycles. Among these reactions, transition-metal-catalyzed cycloadditions of [m+n], [m+n+o], [m+ n+o+p] have evolved as powerful tools to achieve this aim. This topic has been reviewed in 2010. Summarized here are many new developments in this field and applications of the previously developed reactions in natural product synthesis since then.
Eight-membered carbocycles are widely found in natural products with significant biological activities and other molecules ranging from perfumes to potential materials. Therefore, accessing these eight-membered carbocycle embedded molecules is important for drug discovery, biological investigation, fragrance industry, material development and many other fields. However, the synthesis of eight-membered carbocycles is still posing challenges to synthetic chemists. Hence, tremendous efforts have been endeavored by many leading chemists to discover and develop new reactions in order to synthesize eight-membered carbocycles. Among these reactions, transition-metal-catalyzed cycloadditions of [m+n], [m+n+o], [m+ n+o+p] have evolved as powerful tools to achieve this aim. This topic has been reviewed in 2010. Summarized here are many new developments in this field and applications of the previously developed reactions in natural product synthesis since then.
2020, 40(11): 3596-3604
doi: 10.6023/cjoc202008039
Abstract:
Enantioselective hydroboration of ketones and imines provides a powerful method to access valuable chiral alcohols and amines which are widely used in organic synthesis, materials science, pharmaceutical, agrochemistry and fine chemical industry. After invented in 1991, pinacolborane (HBpin) as a stable, commercially available and measurably simple reductive reagent has been widely applied in hydroboration of carbonyl derivatives, imines and nitriles and relevant mechanistic investigation. In the past 5 years, HBpin has also been employed for asymmetric catalytic hydroboration (CHB) to access chiral alcohols and amines. The enantioselective CHB reactions of ketones and imines using HBpin are outlined according to the classification of different catalysts, such as earth abundant transition metals, main group elements, and rare-earth metals.
Enantioselective hydroboration of ketones and imines provides a powerful method to access valuable chiral alcohols and amines which are widely used in organic synthesis, materials science, pharmaceutical, agrochemistry and fine chemical industry. After invented in 1991, pinacolborane (HBpin) as a stable, commercially available and measurably simple reductive reagent has been widely applied in hydroboration of carbonyl derivatives, imines and nitriles and relevant mechanistic investigation. In the past 5 years, HBpin has also been employed for asymmetric catalytic hydroboration (CHB) to access chiral alcohols and amines. The enantioselective CHB reactions of ketones and imines using HBpin are outlined according to the classification of different catalysts, such as earth abundant transition metals, main group elements, and rare-earth metals.
2020, 40(11): 3738-3747
doi: 10.6023/cjoc202003022
Abstract:
The recent developments in asymmetric organotransition metal-catalyzed electrochemistry (AOMCE) are summarized. AOMCE processes can be divided into oxidative and reductive variants. In terms of oxidations, asymmetric functionalization of olefins, oxidative kinetic resolution of secondary alcohols or aldehydes, and asymmetric C—H functionalization reactions have been developed. Reductive processes discussed include asymmetric electrochemical carboxylation with carbon dioxide, asymmetric electrochemical decarboxylation, and asymmetric reductive coupling reactions. The combination of chiral ligands, transition-metal catalysts, and electrochemistry provides a novel angle by which to address the longstanding fundamental challenge of stereoinduction in traditional electrochemical organic synthesis.
The recent developments in asymmetric organotransition metal-catalyzed electrochemistry (AOMCE) are summarized. AOMCE processes can be divided into oxidative and reductive variants. In terms of oxidations, asymmetric functionalization of olefins, oxidative kinetic resolution of secondary alcohols or aldehydes, and asymmetric C—H functionalization reactions have been developed. Reductive processes discussed include asymmetric electrochemical carboxylation with carbon dioxide, asymmetric electrochemical decarboxylation, and asymmetric reductive coupling reactions. The combination of chiral ligands, transition-metal catalysts, and electrochemistry provides a novel angle by which to address the longstanding fundamental challenge of stereoinduction in traditional electrochemical organic synthesis.
Porous Organic Polymers as Heterogeneous Catalysts for Visible Light-Induced Organic Transformations
2020, 40(11): 3777-3793
doi: 10.6023/cjoc202003070
Abstract:
The recent applications of porous organic polymers (POPs) as heterogeneous catalysts for visible light-induced organic transformations are summarized. POPs are constructed from conjugated organic monomers, having the features of convenient synthesis and characterization, high stability for quick recovery and reuse, structural diversity as well as high modifiability. POPs possess rigid conjugated frameworks, relatively large surface areas, tunable porosity and typically insoluble in water or organic solvents, and thus ideal platforms for the development of heterogeneous catalysts. Through incorporating conjugated sensitizer units into the backbones or attaching the sensitizers to the backbone linkers, POPs can be developed as efficient heterogeneous photocatalysts for visible light-induced organic transformations. Due to their high stability and insolubility, POP catalysts can be easily recovered through filtration or centrifugation and recycled. POP-based photocatalysis combines visible light utility and catalyst recycling and thus represents a green and sustainable technique.
The recent applications of porous organic polymers (POPs) as heterogeneous catalysts for visible light-induced organic transformations are summarized. POPs are constructed from conjugated organic monomers, having the features of convenient synthesis and characterization, high stability for quick recovery and reuse, structural diversity as well as high modifiability. POPs possess rigid conjugated frameworks, relatively large surface areas, tunable porosity and typically insoluble in water or organic solvents, and thus ideal platforms for the development of heterogeneous catalysts. Through incorporating conjugated sensitizer units into the backbones or attaching the sensitizers to the backbone linkers, POPs can be developed as efficient heterogeneous photocatalysts for visible light-induced organic transformations. Due to their high stability and insolubility, POP catalysts can be easily recovered through filtration or centrifugation and recycled. POP-based photocatalysis combines visible light utility and catalyst recycling and thus represents a green and sustainable technique.
2020, 40(11): 3828-3836
doi: 10.6023/cjoc202006059
Abstract:
As a typical representative of thiopeptide antibiotics, nosiheptide (NOS) possesses very good antibacterial activity. However, due to poor water solubility and low bioavailability, its clinical application is hampered. Due to its complex structure, it is difficult to obtain analogues with improved physical and chemical properties via total chemical synthesis. Based on the previous studies on the biosynthesis of nosiheptide, the side-ring 3-methyl-2-indoleic acid (MIA) analogues were used as chemical small molecule probes to explore the substrate tolerance of enzymes involved in NOS biosynthesis pathway in NOS-producing bacteria via the co-fermentation of probe molecules with mutant strain and the combination of high resolution mass spectrometry data of fermentation products. The results showed that enzymes involved in NOS biosynthesis pathway had a considerable tolerance to MIA analogues substituted by F, Cl and CH3, however, MIA analogues substituted by large steric hindrance group, such as NO2, CF3 and Ph, were not tolerated. The position, the size and the property of the substituted groups of MIA also affected the steps of identification, transport and upload of the related enzymes involved in NOS biosynthesis. The present study not only explored the substrate tolerance of enzymes involved in NOS biosynthesis pathway, but also was expected to obtain NOS analogues via biosynthetic pathway engineering. What's more, it provides valuable information for using directed evolution technology to improve the substrate tolerance of enzymes in the rate-limiting steps of NOS biosynthesis and to expand the use of NOS-producing bacteria to obtain more analogues.
As a typical representative of thiopeptide antibiotics, nosiheptide (NOS) possesses very good antibacterial activity. However, due to poor water solubility and low bioavailability, its clinical application is hampered. Due to its complex structure, it is difficult to obtain analogues with improved physical and chemical properties via total chemical synthesis. Based on the previous studies on the biosynthesis of nosiheptide, the side-ring 3-methyl-2-indoleic acid (MIA) analogues were used as chemical small molecule probes to explore the substrate tolerance of enzymes involved in NOS biosynthesis pathway in NOS-producing bacteria via the co-fermentation of probe molecules with mutant strain and the combination of high resolution mass spectrometry data of fermentation products. The results showed that enzymes involved in NOS biosynthesis pathway had a considerable tolerance to MIA analogues substituted by F, Cl and CH3, however, MIA analogues substituted by large steric hindrance group, such as NO2, CF3 and Ph, were not tolerated. The position, the size and the property of the substituted groups of MIA also affected the steps of identification, transport and upload of the related enzymes involved in NOS biosynthesis. The present study not only explored the substrate tolerance of enzymes involved in NOS biosynthesis pathway, but also was expected to obtain NOS analogues via biosynthetic pathway engineering. What's more, it provides valuable information for using directed evolution technology to improve the substrate tolerance of enzymes in the rate-limiting steps of NOS biosynthesis and to expand the use of NOS-producing bacteria to obtain more analogues.
2020, 40(11): 3847-3852
doi: 10.6023/cjoc202006070
Abstract:
Supramolecular polymers are regarded as a new kind of dynamic materials. The study of supramolecular polymers not only helps to understand the law of self-assembly, but also provides theoretical support for the development of smart materials. Herein, three dioxyphenylene bridged ditopic ureidopyrimidinone (UPy) derivatives M1~M3 are studied. These molecules could undergo supramolecular polymerization via quadruple hydrogen bonding. The only difference in their structure is the length of the oligo(ethylene oxide) chain as spacers. The supramolecular polymerization based on ring-chain equilibrium of these molecules were studied by a series of experiments including concentration-dependent 1H NMR, NOESY, and viscosity measurement, which showed that the spacer length has a big impact on the ring-opening supramolecular polymerization process. And the main reason for this is the different strengths of π-π interaction between the dioxyphenylene unit and the dimerized UPy motif in the cyclic monomer form. M1 with the shortest spacer lacks this kind of π-π interaction while M3 with the longest spacer possesses a weak π-π interaction, both leading to small value of CPCs. By contrast, M2 with a moderate length of spacer has a strong π-π interaction, resulting in a high CPC value (189 mmol·L-1). Finally, the host-guest complexation between M1~M3 with the π-electron deficient bipyridinium-based cyclophane "blue-box" were further investigated, which shows that only M3 could perform host-guest complexation. From this interesting model, new insight into the relationship between molecular structure and supramolecular polymerization is discovered, which is important for creating tailor-made supramolecular polymeric materials.
Supramolecular polymers are regarded as a new kind of dynamic materials. The study of supramolecular polymers not only helps to understand the law of self-assembly, but also provides theoretical support for the development of smart materials. Herein, three dioxyphenylene bridged ditopic ureidopyrimidinone (UPy) derivatives M1~M3 are studied. These molecules could undergo supramolecular polymerization via quadruple hydrogen bonding. The only difference in their structure is the length of the oligo(ethylene oxide) chain as spacers. The supramolecular polymerization based on ring-chain equilibrium of these molecules were studied by a series of experiments including concentration-dependent 1H NMR, NOESY, and viscosity measurement, which showed that the spacer length has a big impact on the ring-opening supramolecular polymerization process. And the main reason for this is the different strengths of π-π interaction between the dioxyphenylene unit and the dimerized UPy motif in the cyclic monomer form. M1 with the shortest spacer lacks this kind of π-π interaction while M3 with the longest spacer possesses a weak π-π interaction, both leading to small value of CPCs. By contrast, M2 with a moderate length of spacer has a strong π-π interaction, resulting in a high CPC value (189 mmol·L-1). Finally, the host-guest complexation between M1~M3 with the π-electron deficient bipyridinium-based cyclophane "blue-box" were further investigated, which shows that only M3 could perform host-guest complexation. From this interesting model, new insight into the relationship between molecular structure and supramolecular polymerization is discovered, which is important for creating tailor-made supramolecular polymeric materials.
Tris(trimethylsilyl)silane/O2-Promoted and Photo-accelerated Conversion of Alkyl Iodides to Alcohols
2020, 40(11): 3853-3857
doi: 10.6023/cjoc202006055
Abstract:
A mild method for the conversion of alkyl iodides to alcohols was developed. The transformation was promoted by tris(trimethylsilyl)silane/O2 and accelerated by photoredox catalysis under visible light irradiation conditions. Various alkyl iodides, including primary, secondary and tertiary iodides, can be smoothly converted to the corresponding alcohols in 38%~99% yields.
A mild method for the conversion of alkyl iodides to alcohols was developed. The transformation was promoted by tris(trimethylsilyl)silane/O2 and accelerated by photoredox catalysis under visible light irradiation conditions. Various alkyl iodides, including primary, secondary and tertiary iodides, can be smoothly converted to the corresponding alcohols in 38%~99% yields.
2020, 40(11): 3866-3872
doi: 10.6023/cjoc202007005
Abstract:
A convenient K2S2O8-initiated radical cascade cyclization for the construction of 4-sulfonated cyclopenta[gh]-phenanthridines from 2-alkynylnitriles and sodium sulfinates has been explored under metal-free conditions. This protocol features mild conditions, good functional group tolerance and broad substrate scope. A variety of potentially bioactive 4-sulfonated cyclopenta[gh]phenanthridines were facilely synthesized via direct annulation.
A convenient K2S2O8-initiated radical cascade cyclization for the construction of 4-sulfonated cyclopenta[gh]-phenanthridines from 2-alkynylnitriles and sodium sulfinates has been explored under metal-free conditions. This protocol features mild conditions, good functional group tolerance and broad substrate scope. A variety of potentially bioactive 4-sulfonated cyclopenta[gh]phenanthridines were facilely synthesized via direct annulation.
2020, 40(11): 3873-3880
doi: 10.6023/cjoc202006071
Abstract:
gem-Difluoroalkenes have wide applications in the drug designs and act as the synthon of molecules containing fluoride. The current researches on the electrochemical syntheses of gem-difluoroalkenes are limited to the silylation of enolated trifluoromethyl ketones. Herein, by using graphite felt as electrodes, the electrochemical allylic hydrodefluorination of α-trifluoromethyl cinnamates is realized using gaseous ammonia as hydrogen source, giving gem-difluorostyrenes in moderate to good yields. The usage of ammonia and graphite felt cathode is important to inhibit the cathodic hydrogen evolution, keeping the electron transfer from cathode to substrate with high selectivity. The cyclic voltammetry (CV) and square wave voltammetry (SWV) analyses support a stepwise electron transfer process to achieve the C—H bond formation and C—F bond cleavage.
gem-Difluoroalkenes have wide applications in the drug designs and act as the synthon of molecules containing fluoride. The current researches on the electrochemical syntheses of gem-difluoroalkenes are limited to the silylation of enolated trifluoromethyl ketones. Herein, by using graphite felt as electrodes, the electrochemical allylic hydrodefluorination of α-trifluoromethyl cinnamates is realized using gaseous ammonia as hydrogen source, giving gem-difluorostyrenes in moderate to good yields. The usage of ammonia and graphite felt cathode is important to inhibit the cathodic hydrogen evolution, keeping the electron transfer from cathode to substrate with high selectivity. The cyclic voltammetry (CV) and square wave voltammetry (SWV) analyses support a stepwise electron transfer process to achieve the C—H bond formation and C—F bond cleavage.
2020, 40(11): 3881-3888
doi: 10.6023/cjoc202006075
Abstract:
The introduction of methyl group into aromatic compounds is a valuable transformation. A large number of known methods use organohalides as the starting materials. However, those methods require pre-synthesized methyl metal reagents or toxic methyl electrophiles. Herein, a palladium-catalyzed reductive coupling reaction between aryl bromides and trimethylsilyl-diazomethane is developed, and the following desilicification process can afford the methylated products. This transformation has broad functional group tolerance and allows methylation of (hetero)aryl halides in moderate to good yields. Thus, it has the potential to be an attractive approach for methylation of organic. In addition, this reductive coupling can also serve as an efficient way for the introduction of silylmethyl group.
The introduction of methyl group into aromatic compounds is a valuable transformation. A large number of known methods use organohalides as the starting materials. However, those methods require pre-synthesized methyl metal reagents or toxic methyl electrophiles. Herein, a palladium-catalyzed reductive coupling reaction between aryl bromides and trimethylsilyl-diazomethane is developed, and the following desilicification process can afford the methylated products. This transformation has broad functional group tolerance and allows methylation of (hetero)aryl halides in moderate to good yields. Thus, it has the potential to be an attractive approach for methylation of organic. In addition, this reductive coupling can also serve as an efficient way for the introduction of silylmethyl group.
2020, 40(11): 3895-3907
doi: 10.6023/cjoc202005096
Abstract:
A Brønsted acid-catalyzed substitution reaction of 2-indolylmethanols with tryptophols has been established, which afforded a series of 2, 2'-bisindolylmethanes in high yields (up to 98% yield) with chemoselectivity. This protocol not only provides an efficient method for constructing biologically important 2, 2'-bisindolylmethane frameworks, but also has realized a substitution reaction of 2-indolylmethanols, which will enrich the chemical property of 2-indolylmethanols. Moreover, this approach has utilized the C(2)-nucleophilicity of tryptophols, which provided a good example for controlling the chemoselectivity in tryptophol-involved reactions.
A Brønsted acid-catalyzed substitution reaction of 2-indolylmethanols with tryptophols has been established, which afforded a series of 2, 2'-bisindolylmethanes in high yields (up to 98% yield) with chemoselectivity. This protocol not only provides an efficient method for constructing biologically important 2, 2'-bisindolylmethane frameworks, but also has realized a substitution reaction of 2-indolylmethanols, which will enrich the chemical property of 2-indolylmethanols. Moreover, this approach has utilized the C(2)-nucleophilicity of tryptophols, which provided a good example for controlling the chemoselectivity in tryptophol-involved reactions.
2020, 40(11): 3934-3943
doi: 10.6023/cjoc202004027
Abstract:
Current 1, 6-conjugate addition typically focused on pre-synthesized para-quinone methides bearing a δ-mono substituent for tertiary stereocenter formation. Here, an efficient 1, 6-aza-conjugate addition of primary anilines to pre-prepared δ-CN-δ-aryl disubstituted para-quinone methides for facile access to sterically hindered amines with a fully substituted α-car-bon center has been described. The mild and expeditious method exhibited broad scopes of both aniline and para-quinone methide components. The generality of the method in modular preparation of medicinally valuable, sterically hindered amines was further demonstrated by using cyclic secondary amines like morpholine and imidazole as nucleophilic components.
Current 1, 6-conjugate addition typically focused on pre-synthesized para-quinone methides bearing a δ-mono substituent for tertiary stereocenter formation. Here, an efficient 1, 6-aza-conjugate addition of primary anilines to pre-prepared δ-CN-δ-aryl disubstituted para-quinone methides for facile access to sterically hindered amines with a fully substituted α-car-bon center has been described. The mild and expeditious method exhibited broad scopes of both aniline and para-quinone methide components. The generality of the method in modular preparation of medicinally valuable, sterically hindered amines was further demonstrated by using cyclic secondary amines like morpholine and imidazole as nucleophilic components.
2020, 40(11): 3944-3952
doi: 10.6023/cjoc202004041
Abstract:
A visible-light driven asymmetric Giese radical addition catalyzed by a bifunctional chiral-at-metal rhodium complex has been developed. para-Aminobenzyl radicals generated from para-aminophenylacetic acids could undergo a 1, 4-addition in a highly enantioselective approach to α, β-unsaturated 2-acyl imidazoles, and a variety of corresponding adducts were obtained in moderate to high yields with excellent enantioselectivities. This reaction features high enantioselectivity, mild reaction conditions and an operationally simple procedure. A plausible reaction mechanism is proposed based on our research and literature precedents on dual functional chiral-at-metal catalysis.
A visible-light driven asymmetric Giese radical addition catalyzed by a bifunctional chiral-at-metal rhodium complex has been developed. para-Aminobenzyl radicals generated from para-aminophenylacetic acids could undergo a 1, 4-addition in a highly enantioselective approach to α, β-unsaturated 2-acyl imidazoles, and a variety of corresponding adducts were obtained in moderate to high yields with excellent enantioselectivities. This reaction features high enantioselectivity, mild reaction conditions and an operationally simple procedure. A plausible reaction mechanism is proposed based on our research and literature precedents on dual functional chiral-at-metal catalysis.
2020, 40(11): 3837-3846
doi: 10.6023/cjoc202006043
Abstract:
A catalytic system capable of selectively promoting the cyclopropanation reaction and C—S bond cleavage reaction was established. For the reactions between phenyl vinyl sulfide and diazoacetonitrile (generated by in situ method), the cyclopropanation reaction products were obtained under the catalysis of hemin chloride, and the C—S bond cleavage reaction products were generated in the presence of FePc. All the reations were operated without inert gas protection or high temperature, and the target products were obtained by stirring at room temperature for 1 h in moderate to excellent yields.
A catalytic system capable of selectively promoting the cyclopropanation reaction and C—S bond cleavage reaction was established. For the reactions between phenyl vinyl sulfide and diazoacetonitrile (generated by in situ method), the cyclopropanation reaction products were obtained under the catalysis of hemin chloride, and the C—S bond cleavage reaction products were generated in the presence of FePc. All the reations were operated without inert gas protection or high temperature, and the target products were obtained by stirring at room temperature for 1 h in moderate to excellent yields.
2020, 40(11): 3858-3865
doi: 10.6023/cjoc202007021
Abstract:
Among the more than 800 alkaloids isolated from skins of arrow poison-frog, batrachotoxin had attracted the most widespread attention of scientists from several fields, due to its potent cardio and nerve toxicities and challenging structure. A new strategy, which is different from all the previous total syntheses (one racemic and two enantioselective), is disclosed. This strategy features the formation of the CDE skeleton and then the ABCDE core of batrachotoxin by a key Diels-Alder reaction between A ring and CDE framework. Because A ring segment is a known compound, the first key of synthesis resides in the construction of the CDE framework. Thus, in addition to the new synthetic strategy, the synthesis of a functionalized CD ring system is developed. The synthesis started from the preparation of 2-allylcyclopentane-1, 3-dione and its Michael addition with hex-1-en-3-one. The Hajos-Wiechert-type reaction of the adduct was investigated under optimized conditions using L-phenylalanine as an organocatalyst and D-camphorsulfonic acid (D-CSA) as an additive, the desired Robinson annulation proceeded smoothly to give the desired cyclization product in 75% yield and 81% ee. The latter was converted into a functionalized CD skeleton that bears all elements for elaborating to CDE framework in seven steps.
Among the more than 800 alkaloids isolated from skins of arrow poison-frog, batrachotoxin had attracted the most widespread attention of scientists from several fields, due to its potent cardio and nerve toxicities and challenging structure. A new strategy, which is different from all the previous total syntheses (one racemic and two enantioselective), is disclosed. This strategy features the formation of the CDE skeleton and then the ABCDE core of batrachotoxin by a key Diels-Alder reaction between A ring and CDE framework. Because A ring segment is a known compound, the first key of synthesis resides in the construction of the CDE framework. Thus, in addition to the new synthetic strategy, the synthesis of a functionalized CD ring system is developed. The synthesis started from the preparation of 2-allylcyclopentane-1, 3-dione and its Michael addition with hex-1-en-3-one. The Hajos-Wiechert-type reaction of the adduct was investigated under optimized conditions using L-phenylalanine as an organocatalyst and D-camphorsulfonic acid (D-CSA) as an additive, the desired Robinson annulation proceeded smoothly to give the desired cyclization product in 75% yield and 81% ee. The latter was converted into a functionalized CD skeleton that bears all elements for elaborating to CDE framework in seven steps.
2020, 40(11): 3889-3894
doi: 10.6023/cjoc202005026
Abstract:
By using sulfonyl hydrazines and ketene dithioacetals as starting materials, the regioselective annulation providing 3-alkylthiolated pyrazoles has been realized in the low cost and easily available NaHSO4 catalytst. The reactions were realized in 1, 4-dioxane medium and 80 ℃ heating, whereby a seris of 3-alkylthiol pyrazoles possessing N-sulfonyl structure have been efficiently synthesized.
By using sulfonyl hydrazines and ketene dithioacetals as starting materials, the regioselective annulation providing 3-alkylthiolated pyrazoles has been realized in the low cost and easily available NaHSO4 catalytst. The reactions were realized in 1, 4-dioxane medium and 80 ℃ heating, whereby a seris of 3-alkylthiol pyrazoles possessing N-sulfonyl structure have been efficiently synthesized.
2020, 40(11): 3908-3915
doi: 10.6023/cjoc202005025
Abstract:
A metal-free, BCl3 mediated borylative cyclization of 2-(1-alkynyl)-2-alken-1-ones leading to synthetic valuable multi-functionalized naphthalene boronates in one step was developed. The boronate functionality present in the product provides many opportunities for derivatization. The salient features of this reaction include moderate to good yields, gram-scale synthesis and diverse synthetic transformations. In the meantime, the new synthetic applications of 2-(1-alkynyl)-2-alken-1-ones have been developed.
A metal-free, BCl3 mediated borylative cyclization of 2-(1-alkynyl)-2-alken-1-ones leading to synthetic valuable multi-functionalized naphthalene boronates in one step was developed. The boronate functionality present in the product provides many opportunities for derivatization. The salient features of this reaction include moderate to good yields, gram-scale synthesis and diverse synthetic transformations. In the meantime, the new synthetic applications of 2-(1-alkynyl)-2-alken-1-ones have been developed.
2020, 40(11): 3916-3924
doi: 10.6023/cjoc202005014
Abstract:
Two isomers of azulene and indacenodithiophene (IDT)-based compounds 1 and 2 were designed and synthesized, according to the different connections of azulene unit with IDT through its electron-rich five-membered ring and the electron-deficient seven-membered ring, respectively. The UV-Vis spectra, electrochemical properties and proton-responsive properties of 1 and 2 were studied. Compounds 1 and 2 show obviously different physicochemical properties and device performance of organic field-effect transistors (OFET). Both compounds 1 and 2 have reversible proton response characteristics. The end absorption peaks of these two compounds are between 400 and 600 nm before protonation. With the addition of trifluoroacetic acid (TFA), the absorption peaks are red shifted to 550~850 nm. When they are protonated fully (TFA volume ratio is about 1%), they are red shifted about 200 and 177 nm, respectively. The color of compounds 1 and 2 in dichloromethane solution before protonation is red after the adequate protonation. It turned to blue and returned to its original color after the addition of triethylamine. OFET thin film devices of 1 and 2 showed an order of magnitude difference, with hole mobilities of 4.14×10-3 and 1.05×10-5 cm2·V-1·s-1, respectively. The different connections of IDT and azulene units through the electronic rich five-membered ring and the electronic deficient seven-membered ring of azulene greatly affect the materials' device performance as well as their physicochemical properties, providing valuable insights for developing azulene-based novel organic functional molecules.
Two isomers of azulene and indacenodithiophene (IDT)-based compounds 1 and 2 were designed and synthesized, according to the different connections of azulene unit with IDT through its electron-rich five-membered ring and the electron-deficient seven-membered ring, respectively. The UV-Vis spectra, electrochemical properties and proton-responsive properties of 1 and 2 were studied. Compounds 1 and 2 show obviously different physicochemical properties and device performance of organic field-effect transistors (OFET). Both compounds 1 and 2 have reversible proton response characteristics. The end absorption peaks of these two compounds are between 400 and 600 nm before protonation. With the addition of trifluoroacetic acid (TFA), the absorption peaks are red shifted to 550~850 nm. When they are protonated fully (TFA volume ratio is about 1%), they are red shifted about 200 and 177 nm, respectively. The color of compounds 1 and 2 in dichloromethane solution before protonation is red after the adequate protonation. It turned to blue and returned to its original color after the addition of triethylamine. OFET thin film devices of 1 and 2 showed an order of magnitude difference, with hole mobilities of 4.14×10-3 and 1.05×10-5 cm2·V-1·s-1, respectively. The different connections of IDT and azulene units through the electronic rich five-membered ring and the electronic deficient seven-membered ring of azulene greatly affect the materials' device performance as well as their physicochemical properties, providing valuable insights for developing azulene-based novel organic functional molecules.
2020, 40(11): 3925-3933
doi: 10.6023/cjoc202004025
Abstract:
1, 2-Diols have important applications in pesticides, chiral medicines and fine chemicals. A Pd(Ⅱ)-catalyzed 1, 2-diacetoxylation method using readily available acetic acid as the oxygen source and oxygen as the oxidant was developed. For the 1, 2-diacetoxylation of conjugated dienes, the reaction proceeds with high 1, 2-regioselectivity. This protocol has good substrate scope for conjugated dienes possessing aryl-, ester-and carbonyl groups. The catalytic products can be transformed to 1, 2-diols through simple alcoholysis or hydrolysis, therefore it is an efficient method for the synthesis of 1, 2-diols.
1, 2-Diols have important applications in pesticides, chiral medicines and fine chemicals. A Pd(Ⅱ)-catalyzed 1, 2-diacetoxylation method using readily available acetic acid as the oxygen source and oxygen as the oxidant was developed. For the 1, 2-diacetoxylation of conjugated dienes, the reaction proceeds with high 1, 2-regioselectivity. This protocol has good substrate scope for conjugated dienes possessing aryl-, ester-and carbonyl groups. The catalytic products can be transformed to 1, 2-diols through simple alcoholysis or hydrolysis, therefore it is an efficient method for the synthesis of 1, 2-diols.
2020, 40(11): 3953-3962
doi: 10.6023/cjoc202003050
Abstract:
In an attempt to search new antiresistance acetohydroxyacid synthase (AHAS, EC 2.2.1.6) inhibitors to combat weed resistance associated with AHAS mutation (P197L), a series of pyrimidyl-salicylate derivatives containing alkoxy side chain were designed via the strategy of "conformational flexibility analysis" and then synthesized. Nine compounds showed excellent antiresistance property against P197L mutant. Their resistance factor (RF) values ranged from 0.31 to 1.00. Especially, 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluoroethoxy)benzoic acid (5l) was further identified as the most promising antiresistance AHAS inhibitor due to quite low RF value (RF=0.31) and sub-micromolar inhibition toward both wild-type AtAHAS and P197L mutant. Furthermore, 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-methoxyethoxy)benzoic acid (5a), 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(3-methoxypropoxy)benzoic acid (5f), 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluoroethoxy)benzoic acid (5l), and 2-(2, 2-difluoroethoxy)-6-((4, 6-dimethoxypyrimidin-2-yl)oxy)benzoic acid (5m) also exhibited potent herbicidal activities against sensitive and resistant (P197L-AHAS) Descurainia sophia at 150 g of active ingredient (ai)/ha. Even at the dosage as low as 37.5 g ai/ha, compound 5l still maintained over 85% weed control toward the above two weeds, which has the great potential to be developed as new lead to control herbicide-resistant weeds caused by P197L mutation.
In an attempt to search new antiresistance acetohydroxyacid synthase (AHAS, EC 2.2.1.6) inhibitors to combat weed resistance associated with AHAS mutation (P197L), a series of pyrimidyl-salicylate derivatives containing alkoxy side chain were designed via the strategy of "conformational flexibility analysis" and then synthesized. Nine compounds showed excellent antiresistance property against P197L mutant. Their resistance factor (RF) values ranged from 0.31 to 1.00. Especially, 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluoroethoxy)benzoic acid (5l) was further identified as the most promising antiresistance AHAS inhibitor due to quite low RF value (RF=0.31) and sub-micromolar inhibition toward both wild-type AtAHAS and P197L mutant. Furthermore, 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-methoxyethoxy)benzoic acid (5a), 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(3-methoxypropoxy)benzoic acid (5f), 2-((4, 6-dimethoxypyrimidin-2-yl)oxy)-6-(2-fluoroethoxy)benzoic acid (5l), and 2-(2, 2-difluoroethoxy)-6-((4, 6-dimethoxypyrimidin-2-yl)oxy)benzoic acid (5m) also exhibited potent herbicidal activities against sensitive and resistant (P197L-AHAS) Descurainia sophia at 150 g of active ingredient (ai)/ha. Even at the dosage as low as 37.5 g ai/ha, compound 5l still maintained over 85% weed control toward the above two weeds, which has the great potential to be developed as new lead to control herbicide-resistant weeds caused by P197L mutation.
2020, 40(11): 3963-3968
doi: 10.6023/cjoc202007052
Abstract:
The enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were described based on the asymmetric hydrogenation of racemic δ-hydroxy esters via kinetic resolution. With optically active chiral δ-hydroxy ester (S)-4 and chiral 1, 5-diol (R)-5 obtained by asymmetric hydrogenation of racemic ethyl 5-hydroxyoctanoate (rac-4) with chiral spiro iridium catalyst Ir-(R)-SpiroPAP as chiral starting materials, the efficient enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were achieved by using intramolecular reductive amination and N-substitution/cyclization, respectively, as a key step to construct the chiral aza-bicyclic[4.3.0]nonane skeleton and chiral piperidine ring. This provides new efficient methods for enantioselective syntheses of indolizidine and piperidine alkaloids.
The enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were described based on the asymmetric hydrogenation of racemic δ-hydroxy esters via kinetic resolution. With optically active chiral δ-hydroxy ester (S)-4 and chiral 1, 5-diol (R)-5 obtained by asymmetric hydrogenation of racemic ethyl 5-hydroxyoctanoate (rac-4) with chiral spiro iridium catalyst Ir-(R)-SpiroPAP as chiral starting materials, the efficient enantioselective syntheses of (-)-indolizidine 167B and (+)-coniine were achieved by using intramolecular reductive amination and N-substitution/cyclization, respectively, as a key step to construct the chiral aza-bicyclic[4.3.0]nonane skeleton and chiral piperidine ring. This provides new efficient methods for enantioselective syntheses of indolizidine and piperidine alkaloids.
2020, 40(11): 3969-3970
doi: 10.6023/cjoc202000073
Abstract:
2020, 40(11): 3971-3972
doi: 10.6023/cjoc202000074
Abstract:
2020, 40(11): 3973-3975
doi: 10.6023/cjoc202000075
Abstract:
2020, 40(11): 3976-3977
doi: 10.6023/cjoc202000076
Abstract:
2020, 40(11): 3978-3979
doi: 10.6023/cjoc202000077
Abstract:
2020, 40(11): 3980-3981
doi: 10.6023/cjoc202000078
Abstract:
2020, 40(11): 3982-3983
doi: 10.6023/cjoc202000079
Abstract:
2020, 40(11): 3984-3985
doi: 10.6023/cjoc202000080
Abstract:
2020, 40(11): 3986-3987
doi: 10.6023/cjoc202000081
Abstract:
2020, 40(11): 3988-3989
doi: 10.6023/cjoc202000082
Abstract:
