Login In
2019 Volume 39 Issue 6
2019, 39(6): 1511-1521
doi: 10.6023/cjoc201903078
Abstract:
Organosilicon compounds play an important role in pharmaceutical chemistry, material science and organic synthesis. Transition-metal-catalyzed direct silylation of C-H bond, as one of the most concise and efficient methods for the synthesis of organosilanes, has developed rapidly in recent years. In this paper, the recent advance in transition-metal-catalyzed silylation of C-H bonds since 2015 is mainly reviewed.
Organosilicon compounds play an important role in pharmaceutical chemistry, material science and organic synthesis. Transition-metal-catalyzed direct silylation of C-H bond, as one of the most concise and efficient methods for the synthesis of organosilanes, has developed rapidly in recent years. In this paper, the recent advance in transition-metal-catalyzed silylation of C-H bonds since 2015 is mainly reviewed.
2019, 39(6): 1522-1528
doi: 10.6023/cjoc201904030
Abstract:
Axially chiral biaryl skeletons are ubiquitous stuctural motifs that are widely represented in pharmaceuticals and natural products, and have been widely used as privileged chiral ligands/catalysts in asymmetric synthesis. Therefore, the asymmetric construction of these compounds has received tremendous attention. However, the established strategies are mainly limited to the construction of biaryls containing hexatomic aromatics, and the approaches towards atropisomers featuring pentatomic heteroaromatics connected through C-C or C-N bond have emerged gradually only until recently. The main hurdle is basically due to the increased distance of substituents ortho to the axis, which is responsible for lower barriers to rotation, thus rendering the asymmetric synthesis more challenging. This review summarizes recent advances on the enantioselective synthesis of atropisomers featuring pentatomic heteroaromatics.
Axially chiral biaryl skeletons are ubiquitous stuctural motifs that are widely represented in pharmaceuticals and natural products, and have been widely used as privileged chiral ligands/catalysts in asymmetric synthesis. Therefore, the asymmetric construction of these compounds has received tremendous attention. However, the established strategies are mainly limited to the construction of biaryls containing hexatomic aromatics, and the approaches towards atropisomers featuring pentatomic heteroaromatics connected through C-C or C-N bond have emerged gradually only until recently. The main hurdle is basically due to the increased distance of substituents ortho to the axis, which is responsible for lower barriers to rotation, thus rendering the asymmetric synthesis more challenging. This review summarizes recent advances on the enantioselective synthesis of atropisomers featuring pentatomic heteroaromatics.
2019, 39(6): 1548-1556
doi: 10.6023/cjoc201903012
Abstract:
The chiral Cp ligands as stereocontrolling element of asymmetric catalytic reactions have attracted increasing attention. Particularly, designing and synthesizing more versatile chiral Cp ligands became one of the most interested research focuses in asymmetric catalysis. The complexes of various chiral Cp ligands with different transition metals that advanced in recent years, and the applications of these complexes in catalytic asymmetric reactions are reviewed in this paper.
The chiral Cp ligands as stereocontrolling element of asymmetric catalytic reactions have attracted increasing attention. Particularly, designing and synthesizing more versatile chiral Cp ligands became one of the most interested research focuses in asymmetric catalysis. The complexes of various chiral Cp ligands with different transition metals that advanced in recent years, and the applications of these complexes in catalytic asymmetric reactions are reviewed in this paper.
2019, 39(6): 1557-1567
doi: 10.6023/cjoc201903043
Abstract:
Alkaline-earth metals continue to receive growing interest, as they are used as low-cost and non-toxic alternatives to transition-metals in various organic transformations. As ionic character and bond lengths increase along the row in the order Mg2+<Ca2+<Sr2+<Ba2+, bond energies decrease along the same row, the corresponding metal hydrides are apt to the formation of insoluble metal hydrides[AeH2]∞ (Ae=Mg, Ca, Sr, Ba) through Schlenk equilibrium in solution. Recently, a series of alkaline-earth metal hydrides stabilized by suitable ligands were discovered and characterized, and stoichiometric and catalytic reactions with small molecules were studied as well. In this paper, the recent progress in molecular alkaline-earth metal hydrides is reviewed.
Alkaline-earth metals continue to receive growing interest, as they are used as low-cost and non-toxic alternatives to transition-metals in various organic transformations. As ionic character and bond lengths increase along the row in the order Mg2+<Ca2+<Sr2+<Ba2+, bond energies decrease along the same row, the corresponding metal hydrides are apt to the formation of insoluble metal hydrides[AeH2]∞ (Ae=Mg, Ca, Sr, Ba) through Schlenk equilibrium in solution. Recently, a series of alkaline-earth metal hydrides stabilized by suitable ligands were discovered and characterized, and stoichiometric and catalytic reactions with small molecules were studied as well. In this paper, the recent progress in molecular alkaline-earth metal hydrides is reviewed.
2019, 39(6): 1568-1582
doi: 10.6023/cjoc201903044
Abstract:
Asymmetric hydroformylation is one of the most important reactions for preparation of chiral aldehydes from alkenes. Recently, significant progress has been made in this field and a series of new ligands have been developed. Asymmetric hydroformylation of several important alkenes has been achieved, offering efficient and concise methods for the synthesis of chiral aldehydes. In this review, the achievements of asymmetric hydroformylation of typical alkenes and the development of ligands for asymmetric hydroformylation are summarized.
Asymmetric hydroformylation is one of the most important reactions for preparation of chiral aldehydes from alkenes. Recently, significant progress has been made in this field and a series of new ligands have been developed. Asymmetric hydroformylation of several important alkenes has been achieved, offering efficient and concise methods for the synthesis of chiral aldehydes. In this review, the achievements of asymmetric hydroformylation of typical alkenes and the development of ligands for asymmetric hydroformylation are summarized.
2019, 39(6): 1583-1595
doi: 10.6023/cjoc201812042
Abstract:
Tremendous advance has been achieved for the transition-metal free coupling reactions induced by light these years, providing important strategies for the construction of C-N/S/P bonds, which was used frequently in the preparation of pharmaceutical drugs, agricultural products or materials and so on. In this review, the recent advance for the photo-induced coupling reactions for the construction of C-N/S/P bonds under transition-metal free conditions is reviewed.
Tremendous advance has been achieved for the transition-metal free coupling reactions induced by light these years, providing important strategies for the construction of C-N/S/P bonds, which was used frequently in the preparation of pharmaceutical drugs, agricultural products or materials and so on. In this review, the recent advance for the photo-induced coupling reactions for the construction of C-N/S/P bonds under transition-metal free conditions is reviewed.
2019, 39(6): 1596-1612
doi: 10.6023/cjoc201902001
Abstract:
Heterocyclic compounds are widely applied in medicine, fine chemical engineering and the related industrial fields. Consequently, the development of efficient strategies for heterocycle constructions continues to be of great appeal in organic synthesis. In recent years, the I2-catalyzed direct C-H bond functionalizations have emerged as one of the most efficient synthetic protocols to construct diverse heterocycles. In this review, the recent advances in I2-catalyzed C-H bond functionalizations by the types of C-C and C-N/O/S bond formations are summarized, and an outlook of this research filed is given.
Heterocyclic compounds are widely applied in medicine, fine chemical engineering and the related industrial fields. Consequently, the development of efficient strategies for heterocycle constructions continues to be of great appeal in organic synthesis. In recent years, the I2-catalyzed direct C-H bond functionalizations have emerged as one of the most efficient synthetic protocols to construct diverse heterocycles. In this review, the recent advances in I2-catalyzed C-H bond functionalizations by the types of C-C and C-N/O/S bond formations are summarized, and an outlook of this research filed is given.
Recent Advances on the Catalytic Functionalization of Quinoxalin- 2(1H)-ones via C-H Bond Activation
2019, 39(6): 1529-1547
doi: 10.6023/cjoc201904025
Abstract:
Quinoxalin-2(1H)-ones are very important N-heterocyclic moieties found in natural products and pharmaceuticals, and exhibit an amazingly wide spectrum of biological properties. Numerous efforts have been devoted to the development of efficient approaches for the C-H bond activation and functionalization of quinoxalin-2(1H)-ones in recent years, including alkylation, benzylation, acylation, arylation, amination, amidation, phosphonation, and fluoroalkylation. The recent advances in this area are summarized and their reaction mechanisms are discussed.
Quinoxalin-2(1H)-ones are very important N-heterocyclic moieties found in natural products and pharmaceuticals, and exhibit an amazingly wide spectrum of biological properties. Numerous efforts have been devoted to the development of efficient approaches for the C-H bond activation and functionalization of quinoxalin-2(1H)-ones in recent years, including alkylation, benzylation, acylation, arylation, amination, amidation, phosphonation, and fluoroalkylation. The recent advances in this area are summarized and their reaction mechanisms are discussed.
2019, 39(6): 1613-1622
doi: 10.6023/cjoc201901021
Abstract:
Trifluoromethylation using Togni reagents usually releases one equivalent of iodobenzoats as wasteful byproducts. A visible-light-mediated, atom-and step-economical hydrotrifluoromethylation of aromatic alkynes and remote benzoyl-oxylation of α-C(sp3)-H bond of ether with Togni reagent as a bifunctional reagent by means of hydrogen atom transfer strategy was disclosed. The combination of two organic transformations into one reaction not only brings 100% atom economy but also addresses the challenge of stereoselective hydrotrifluoromethylation of aromatic alkynes. This unprecedented protocol offers an important access to a wide range of highly functionalized CF3-containing alkenes with great potential for post-modification.
Trifluoromethylation using Togni reagents usually releases one equivalent of iodobenzoats as wasteful byproducts. A visible-light-mediated, atom-and step-economical hydrotrifluoromethylation of aromatic alkynes and remote benzoyl-oxylation of α-C(sp3)-H bond of ether with Togni reagent as a bifunctional reagent by means of hydrogen atom transfer strategy was disclosed. The combination of two organic transformations into one reaction not only brings 100% atom economy but also addresses the challenge of stereoselective hydrotrifluoromethylation of aromatic alkynes. This unprecedented protocol offers an important access to a wide range of highly functionalized CF3-containing alkenes with great potential for post-modification.
2019, 39(6): 1623-1629
doi: 10.6023/cjoc201902025
Abstract:
An improved method for the synthesis of pentafluoroethylated pyridines through Cu-catalyzed[3+3] cyclo-addition reaction of oxime acetates is reported. The starting materials are more readily available, and these reactions occurred under mild conditions with broad substrate scope and excellent regioselectivity. Mechanistic studies have also been preformed.
An improved method for the synthesis of pentafluoroethylated pyridines through Cu-catalyzed[3+3] cyclo-addition reaction of oxime acetates is reported. The starting materials are more readily available, and these reactions occurred under mild conditions with broad substrate scope and excellent regioselectivity. Mechanistic studies have also been preformed.
2019, 39(6): 1642-1649
doi: 10.6023/cjoc201901004
Abstract:
Asymmetric cycloaddition reactions catalyzed by Inda-BOX 1 metal complex between two kinds of electron-withdrawing alkenes and C, N-diarylnitrone have been studied respectively. Results showed that the 4-substituted products were mainly obtained in both reactions under the best conditions. When N-acryloyl oxazolidinone was used as dipolarophile, the exo/endo selectivity of the reaction was 100/0, and the ee of the exo product was as high as 97%. When N-acryloyl-3, 5-dimethyl pyrazole was used as dipolarophile, the selectivity of exo/endo was 0/100, and the ee of endo product was up to 98%. The relationship of the dipolarophile, the structure of nitrone and the selectivity of the reaction was discussed.
Asymmetric cycloaddition reactions catalyzed by Inda-BOX 1 metal complex between two kinds of electron-withdrawing alkenes and C, N-diarylnitrone have been studied respectively. Results showed that the 4-substituted products were mainly obtained in both reactions under the best conditions. When N-acryloyl oxazolidinone was used as dipolarophile, the exo/endo selectivity of the reaction was 100/0, and the ee of the exo product was as high as 97%. When N-acryloyl-3, 5-dimethyl pyrazole was used as dipolarophile, the selectivity of exo/endo was 0/100, and the ee of endo product was up to 98%. The relationship of the dipolarophile, the structure of nitrone and the selectivity of the reaction was discussed.
2019, 39(6): 1655-1664
doi: 10.6023/cjoc201903050
Abstract:
Due to the lower configuration stability of vinylarenes, arsing from the relatively lower rotational barriers, their catalytic asymmetric synthesis remains a daunting task. Oxindoles moiety are privileged framework of natural products and building blocks of bioactive molecules as well as pharmaceuticals. The asymmetric synthesis of axial chiral vinylarenes fearturing oxindole moiety via sequential carbopalladation/C-H olefination from readily available materials with palladium catalysis has been developed. (4R, 5R)-(-)-2, 2-Dimethyl-α, α, α', α'-tetraphenyl-1, 3-dioxolane-4, 5-dimethanol (TADDOL)-derived phosphoramidite gave products with good yield and moderate ee value. The erosion of optical purity was not observed even after heating the product for 10 h at 110℃, which indicates the excellent stability of the chiral axial.
Due to the lower configuration stability of vinylarenes, arsing from the relatively lower rotational barriers, their catalytic asymmetric synthesis remains a daunting task. Oxindoles moiety are privileged framework of natural products and building blocks of bioactive molecules as well as pharmaceuticals. The asymmetric synthesis of axial chiral vinylarenes fearturing oxindole moiety via sequential carbopalladation/C-H olefination from readily available materials with palladium catalysis has been developed. (4R, 5R)-(-)-2, 2-Dimethyl-α, α, α', α'-tetraphenyl-1, 3-dioxolane-4, 5-dimethanol (TADDOL)-derived phosphoramidite gave products with good yield and moderate ee value. The erosion of optical purity was not observed even after heating the product for 10 h at 110℃, which indicates the excellent stability of the chiral axial.
2019, 39(6): 1672-1680
doi: 10.6023/cjoc201903054
Abstract:
γ-Hydroxyl or γ-alkoxyl-substituted α, β-unsaturated carbonyls widely exist in a variety of natural products and bioactive molecules. Herein, the realization of 1, 4-functionalization of 3-en-1-ynes with alcohols through zinc-catalyzed regioselective N-oxide oxidation is described. This tandem reaction allows the practical synthesis of a range of valuable γ-alkoxyl-substituted-α, β-unsaturated amides in moderate to good yields.
γ-Hydroxyl or γ-alkoxyl-substituted α, β-unsaturated carbonyls widely exist in a variety of natural products and bioactive molecules. Herein, the realization of 1, 4-functionalization of 3-en-1-ynes with alcohols through zinc-catalyzed regioselective N-oxide oxidation is described. This tandem reaction allows the practical synthesis of a range of valuable γ-alkoxyl-substituted-α, β-unsaturated amides in moderate to good yields.
2019, 39(6): 1681-1687
doi: 10.6023/cjoc201902028
Abstract:
The 2-substituted-1, 2, 3, 4-tetrahydroquinoline skeletons are widely found in natural products and have shown antimalarial, antioxidant as well as other biological activities. In this work, MIL-101(Cr)-SO3H is an efficient heterogeneous catalyst for the transfer hydrogenation of a series of 2-substituted quinoline derivatives with Hantzsch ester as the hydrogen source. This protocol operates under mild conditions, tolerates a wide range of 2-substituted quinoline derivatives, and the catalyst could be recovered and reused four times without considerable loss of catalytic activities, which provides a new catalytic system for the construction of 2-substituted-1, 2, 3, 4-tetrahydroquinoline derivatives.
The 2-substituted-1, 2, 3, 4-tetrahydroquinoline skeletons are widely found in natural products and have shown antimalarial, antioxidant as well as other biological activities. In this work, MIL-101(Cr)-SO3H is an efficient heterogeneous catalyst for the transfer hydrogenation of a series of 2-substituted quinoline derivatives with Hantzsch ester as the hydrogen source. This protocol operates under mild conditions, tolerates a wide range of 2-substituted quinoline derivatives, and the catalyst could be recovered and reused four times without considerable loss of catalytic activities, which provides a new catalytic system for the construction of 2-substituted-1, 2, 3, 4-tetrahydroquinoline derivatives.
2019, 39(6): 1688-1694
doi: 10.6023/cjoc201903003
Abstract:
A practical method for the oxidation of aromatic side chains was established for the preparation of aromatic aldehydes and ketones. Using NiCl2 as the catalyst, substituted toluenes were oxidized with Na2S2O8 at the benzylic site for the synthesis of the corresponding aldehydes in the yield of 22%~79%. Ethylbenzene analogs were oxidized more easily to obtain the corresponding ketones with 64%~84% yields. The oxidation of benzyl alcohol analogs was completed to acquire the corresponding carbonyl compounds in shorter time with better selectivity and yields. The method has the advantages such as the mild reaction conditions, no requirement for precious metals or additional promoter, and good selectivity.
A practical method for the oxidation of aromatic side chains was established for the preparation of aromatic aldehydes and ketones. Using NiCl2 as the catalyst, substituted toluenes were oxidized with Na2S2O8 at the benzylic site for the synthesis of the corresponding aldehydes in the yield of 22%~79%. Ethylbenzene analogs were oxidized more easily to obtain the corresponding ketones with 64%~84% yields. The oxidation of benzyl alcohol analogs was completed to acquire the corresponding carbonyl compounds in shorter time with better selectivity and yields. The method has the advantages such as the mild reaction conditions, no requirement for precious metals or additional promoter, and good selectivity.
2019, 39(6): 1711-1719
doi: 10.6023/cjoc201902022
Abstract:
A visible-light-induced[3+2] annulation of arylcyclopropylamines and 1, 2-diarylethanediones was report. A series of α-amino tetrahydrofuran derivatives were synthesized in moderate to good isolated yields under mild reaction conditions. This method would provide an efficient and convenient approach to α-amino tetrahydrofurans which are potentially important buiding blocks in bioactive compounds.
A visible-light-induced[3+2] annulation of arylcyclopropylamines and 1, 2-diarylethanediones was report. A series of α-amino tetrahydrofuran derivatives were synthesized in moderate to good isolated yields under mild reaction conditions. This method would provide an efficient and convenient approach to α-amino tetrahydrofurans which are potentially important buiding blocks in bioactive compounds.
2019, 39(6): 1735-1742
doi: 10.6023/cjoc201901005
Abstract:
A practical ruthenium-catalyzed C(sp2)-H alkenylation and alkylation of 1-benzyl-1H-pyrazole with alkene or a, β-unsaturated ketones under the assistance of pyrazole group were developed. This method has the advantages of high selectivity, providing only the ortho-alkenylation or ortho-alkylation products in high yields. This protocol provides an efficient and new method for the functionalization of 1-benzyl-1H-pyrazoles.
A practical ruthenium-catalyzed C(sp2)-H alkenylation and alkylation of 1-benzyl-1H-pyrazole with alkene or a, β-unsaturated ketones under the assistance of pyrazole group were developed. This method has the advantages of high selectivity, providing only the ortho-alkenylation or ortho-alkylation products in high yields. This protocol provides an efficient and new method for the functionalization of 1-benzyl-1H-pyrazoles.
2019, 39(6): 1753-1760
doi: 10.6023/cjoc201811024
Abstract:
2-(1'-Acetyl-ferrocenyl) benzothiazole (FcSO) probe was synthesized by the acetylization reaction of 2-ferrocenyl benzothiazole, which was obtained from the cyclization reaction of ferrocenecarboxaldehyde with 2-aminothiophenol. Crystal and molecule structures of FcSO probe were characterized by spectra methods and X-ray single crystal diffraction analysis. The recognition ability to Al3+, Cr3+, Fe3+ ions of FcSO probe was researched by three analytical methods of UV-Vis, fluorescence and electrochemistry. The results show that the recognition to Al3+, Cr3+, Fe3+ ions of FcSO probe is effective via three channels, and the detection limits of FcSO probe to Al3+, Cr3+, Fe3+ ions are 7.456×10-6, 3.72×10-6 and 1.35×10-5 mol/L, respectively. 1H NMR research results indicate that the acetyl, ferrocenyl and benzothiazole groups of FcSO probe play important roles in recognizing Al3+, Cr3+, Fe3+ ions.
2-(1'-Acetyl-ferrocenyl) benzothiazole (FcSO) probe was synthesized by the acetylization reaction of 2-ferrocenyl benzothiazole, which was obtained from the cyclization reaction of ferrocenecarboxaldehyde with 2-aminothiophenol. Crystal and molecule structures of FcSO probe were characterized by spectra methods and X-ray single crystal diffraction analysis. The recognition ability to Al3+, Cr3+, Fe3+ ions of FcSO probe was researched by three analytical methods of UV-Vis, fluorescence and electrochemistry. The results show that the recognition to Al3+, Cr3+, Fe3+ ions of FcSO probe is effective via three channels, and the detection limits of FcSO probe to Al3+, Cr3+, Fe3+ ions are 7.456×10-6, 3.72×10-6 and 1.35×10-5 mol/L, respectively. 1H NMR research results indicate that the acetyl, ferrocenyl and benzothiazole groups of FcSO probe play important roles in recognizing Al3+, Cr3+, Fe3+ ions.
2019, 39(6): 1776-1786
doi: 10.6023/cjoc201901006
Abstract:
A convenient copper-catalyzed sulfeno-/seleno-amination of β, γ-unsaturated hydrazones with disulfides/diselenides via radical pathway has been developed. The protocol enables efficient access to various sulfenylated/selenylated pyrazolines under mild reaction conditions.
A convenient copper-catalyzed sulfeno-/seleno-amination of β, γ-unsaturated hydrazones with disulfides/diselenides via radical pathway has been developed. The protocol enables efficient access to various sulfenylated/selenylated pyrazolines under mild reaction conditions.
2019, 39(6): 1630-1641
doi: 10.6023/cjoc201903046
Abstract:
A highly convenient and regioselective synthesis of 1, 3-disubstituted pyrazoles or 1, 3, 4-trisubstituted pyrazoles from Cu(Ⅱ)-catalyzed cascade reactions of saturated ketones with hydrazines or aldehyde hydrazones is presented. Mechanistically, the formation of 1, 3-disubstituted pyrazoles involves the in situ generation of an enone intermediate followed by its[3+2] annulations with hydrazine. On the other hand, the formation of 1, 3, 4-trisubstituted pyrazoles is believed to go through a cascade process including enone formation and its subsequent[2+3] annulation with aldehyde hydrazone. Compared with literature methods, the notable features of the protocol include simple starting materials, general and broad substrate scope, high regioselectivity, good efficiency and excellent atom-economy.
A highly convenient and regioselective synthesis of 1, 3-disubstituted pyrazoles or 1, 3, 4-trisubstituted pyrazoles from Cu(Ⅱ)-catalyzed cascade reactions of saturated ketones with hydrazines or aldehyde hydrazones is presented. Mechanistically, the formation of 1, 3-disubstituted pyrazoles involves the in situ generation of an enone intermediate followed by its[3+2] annulations with hydrazine. On the other hand, the formation of 1, 3, 4-trisubstituted pyrazoles is believed to go through a cascade process including enone formation and its subsequent[2+3] annulation with aldehyde hydrazone. Compared with literature methods, the notable features of the protocol include simple starting materials, general and broad substrate scope, high regioselectivity, good efficiency and excellent atom-economy.
2019, 39(6): 1650-1654
doi: 10.6023/cjoc201903027
Abstract:
The selective catalytic oxidation of amines for the synthesis of imines is important both in laboratory and industrial production. From atom-efficient, economic and environmental view of points, dioxygen selective oxidation of amines was achieved by using wings-opened butterfly-like complex Cu2(ophen)2 as catalyst. It was worth noting that the catalytic system was efficient to the cross-coupling of alcohols with amines, homocoupling of primary amines and oxidative dehydrogenation of secondary amines. The yield is up to 93% and the selectivity of imines is as high as 99%. Avoiding the use of expensive nitroxyl derivatives and base was suitable for practical application.
The selective catalytic oxidation of amines for the synthesis of imines is important both in laboratory and industrial production. From atom-efficient, economic and environmental view of points, dioxygen selective oxidation of amines was achieved by using wings-opened butterfly-like complex Cu2(ophen)2 as catalyst. It was worth noting that the catalytic system was efficient to the cross-coupling of alcohols with amines, homocoupling of primary amines and oxidative dehydrogenation of secondary amines. The yield is up to 93% and the selectivity of imines is as high as 99%. Avoiding the use of expensive nitroxyl derivatives and base was suitable for practical application.
2019, 39(6): 1665-1671
doi: 10.6023/cjoc201903037
Abstract:
A mild method for palladium-catalyzed halogenation of acetanilide with N-chloro-N-fluorobenzenesulfonylamide (CFBSA) as a chlorinating reagent, oxidant, and novel promoting reagent was achieved. The decomposition of byproduct N-fluoroben-zenesulfonylamine in the presence of Pd(OAc)2 could accelerate the process of chlorination. Preliminary mechanism investigation showed that Pd catalyzed anilide directed C-H activation lead to the ortho chlorination selectivity. A series of ortho-chlorinated anilides were obtained in 28%~82% yields.
A mild method for palladium-catalyzed halogenation of acetanilide with N-chloro-N-fluorobenzenesulfonylamide (CFBSA) as a chlorinating reagent, oxidant, and novel promoting reagent was achieved. The decomposition of byproduct N-fluoroben-zenesulfonylamine in the presence of Pd(OAc)2 could accelerate the process of chlorination. Preliminary mechanism investigation showed that Pd catalyzed anilide directed C-H activation lead to the ortho chlorination selectivity. A series of ortho-chlorinated anilides were obtained in 28%~82% yields.
2019, 39(6): 1695-1703
doi: 10.6023/cjoc201812003
Abstract:
The coupling reactions of phenols and nitrogen hetereocycles with aryl halide were catalyzed by a highly active, readily available and easily recoverable heterogeneous Cu catalyst which was prepared by simply stirring an suspension of chitosan in solvent with copper compound. The result showed that chitosan@Cu2O catalyst catalyzed the coupling reactions of aryl halides with phenols and nitrogen hetereocycles to readily give the corresponding products in moderate to excellent yields. The highly active catalyst can be reused many times without losing its catalytic activity.
The coupling reactions of phenols and nitrogen hetereocycles with aryl halide were catalyzed by a highly active, readily available and easily recoverable heterogeneous Cu catalyst which was prepared by simply stirring an suspension of chitosan in solvent with copper compound. The result showed that chitosan@Cu2O catalyst catalyzed the coupling reactions of aryl halides with phenols and nitrogen hetereocycles to readily give the corresponding products in moderate to excellent yields. The highly active catalyst can be reused many times without losing its catalytic activity.
2019, 39(6): 1704-1710
doi: 10.6023/cjoc201903018
Abstract:
A highly chemo-, regio-, and stereo-selective cobalt-catalyzed dehydrogenative silylation of vinylarenes was described. The imidazoline iminopyridine cobalt complex could promote this reaction effectively and improve the chemoselectivity dramatically. This protocol used earth-abundant transition metal, readily available alkenes and hydrosilanes to construct valuable vinylsilanes. The reaction could be carried out in gramscale and the proposed mechanism was also described.
A highly chemo-, regio-, and stereo-selective cobalt-catalyzed dehydrogenative silylation of vinylarenes was described. The imidazoline iminopyridine cobalt complex could promote this reaction effectively and improve the chemoselectivity dramatically. This protocol used earth-abundant transition metal, readily available alkenes and hydrosilanes to construct valuable vinylsilanes. The reaction could be carried out in gramscale and the proposed mechanism was also described.
2019, 39(6): 1720-1726
doi: 10.6023/cjoc201901018
Abstract:
A green, efficient, and recyclable catalytic protocol for Ullmann C-N reaction in water was developed. The catalyst Chi-Gly@CuI was prepared by the cross-linking reaction of chitosan bead with glyoxal and subsequently anchored with copper salt. Chi-Gly@CuI bead of 0.3 mm in mean diameter possesses porous micro-structure demonstrated by scanning electron microscope (SEM). The structure of Chi-Gly@CuI was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and X-ray photoelectron spectroscopy (XPS). This catalytic protocol for Ullmann reaction in water exhibited high applicability, from which the corresponding coupling products were afforded in good to excellent yields. Chi-Gly@CuI could be easily separated from products by simple filtration almost without weight loss. Most notably, after 10 times of recycling, its catalytic activity and chemical stability were still maintained.
A green, efficient, and recyclable catalytic protocol for Ullmann C-N reaction in water was developed. The catalyst Chi-Gly@CuI was prepared by the cross-linking reaction of chitosan bead with glyoxal and subsequently anchored with copper salt. Chi-Gly@CuI bead of 0.3 mm in mean diameter possesses porous micro-structure demonstrated by scanning electron microscope (SEM). The structure of Chi-Gly@CuI was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and X-ray photoelectron spectroscopy (XPS). This catalytic protocol for Ullmann reaction in water exhibited high applicability, from which the corresponding coupling products were afforded in good to excellent yields. Chi-Gly@CuI could be easily separated from products by simple filtration almost without weight loss. Most notably, after 10 times of recycling, its catalytic activity and chemical stability were still maintained.
2019, 39(6): 1727-1734
doi: 10.6023/cjoc201901047
Abstract:
A metal-free polychloromethylation/cyclization cascade of N-allyl anlines is presented, which provides an access to polychloromethyl-substituted indolines with unactivated alkenes as radical acceptors and dicumyl peroxide (DCP) as the initiator. The inexpensive solvents of polychoromethanes (i.e., CH2Cl2, CHCl3 and CCl4) were used in the reaction as di-or trichloromethylating agents. This work has advantages of easy operation, mild conditions, low cost, and broad substrate scope.
A metal-free polychloromethylation/cyclization cascade of N-allyl anlines is presented, which provides an access to polychloromethyl-substituted indolines with unactivated alkenes as radical acceptors and dicumyl peroxide (DCP) as the initiator. The inexpensive solvents of polychoromethanes (i.e., CH2Cl2, CHCl3 and CCl4) were used in the reaction as di-or trichloromethylating agents. This work has advantages of easy operation, mild conditions, low cost, and broad substrate scope.
2019, 39(6): 1743-1752
doi: 10.6023/cjoc201901048
Abstract:
A series of photothermal cyclobutaosmapentalenes with conjugated groups attached to the metallacycle were synthesized from the reaction of OsCl2(PPh3)3 with an organic multiyne and PPh3, followed by a[2+2] cycloaddition with terminal alkynes. These highly conjugated metallacycles showed broad UV-Vis absorption and good photothermal efficiency. These easily synthesized metallacycles represent a type of new photothermal material.
A series of photothermal cyclobutaosmapentalenes with conjugated groups attached to the metallacycle were synthesized from the reaction of OsCl2(PPh3)3 with an organic multiyne and PPh3, followed by a[2+2] cycloaddition with terminal alkynes. These highly conjugated metallacycles showed broad UV-Vis absorption and good photothermal efficiency. These easily synthesized metallacycles represent a type of new photothermal material.
2019, 39(6): 1761-1766
doi: 10.6023/cjoc201901015
Abstract:
Cu(Ⅱ)-promoted C-H nitration of arenes has been disclosed with the aid of N, O-bidentate directing group. The protocol was operationally simple by using NaNO2as the nitration source. Various amide substrates were tolerated in the reaction system, which establishes opportunities for developing simple and facile methods, and enriches the strategies to access aromatic nitro derivatives.
Cu(Ⅱ)-promoted C-H nitration of arenes has been disclosed with the aid of N, O-bidentate directing group. The protocol was operationally simple by using NaNO2as the nitration source. Various amide substrates were tolerated in the reaction system, which establishes opportunities for developing simple and facile methods, and enriches the strategies to access aromatic nitro derivatives.
2019, 39(6): 1767-1775
doi: 10.6023/cjoc201901007
Abstract:
An efficient multicomponent one-pot reaction was developed for the synthesis of α-trifluoromethyl homoallylic hydrazides from the reactions of ethyl trifluoropyruvate, hydrazides and allylic bromide with tin powder in the presence of Brønsted and Lewis acid in 1, 4-dioxane under reflux. The method avoids the use of toxic stannanes and allows easy operation. The reaction proceeds smoothly under mild reaction conditions to give the corresponding products in good yields.
An efficient multicomponent one-pot reaction was developed for the synthesis of α-trifluoromethyl homoallylic hydrazides from the reactions of ethyl trifluoropyruvate, hydrazides and allylic bromide with tin powder in the presence of Brønsted and Lewis acid in 1, 4-dioxane under reflux. The method avoids the use of toxic stannanes and allows easy operation. The reaction proceeds smoothly under mild reaction conditions to give the corresponding products in good yields.
2019, 39(6): 1787-1793
doi: 10.6023/cjoc201902017
Abstract:
This study describes efficient vicinal dibromination and iodoacetoxylation of olefins under mild reaction conditions. The reaction uses ZnAl-XO3--layered double hydroxide (LDHs) (X=Br or I) as an oxidant and LiX as a reductant to generate halogens in situ (ZnAl-XO3--LDH/LiX system). A series of dibromoalkanes (74%~95%) and iodoacetates (75%~93%) were obtained in good to excellent yields with high regio-and stereo-selectivity.
This study describes efficient vicinal dibromination and iodoacetoxylation of olefins under mild reaction conditions. The reaction uses ZnAl-XO3--layered double hydroxide (LDHs) (X=Br or I) as an oxidant and LiX as a reductant to generate halogens in situ (ZnAl-XO3--LDH/LiX system). A series of dibromoalkanes (74%~95%) and iodoacetates (75%~93%) were obtained in good to excellent yields with high regio-and stereo-selectivity.
2019, 39(6): 1794-1801
doi: 10.6023/cjoc201903013
Abstract:
The novel biotin conjugated glaucocalyxin A analogs as potential activity-based protein probes were synthesized with good yields via Cu(Ⅰ) in situ-catalyzed azide-alkyne cycloaddition. Cu(Ⅰ) in situ was good solvated under the optimized condition and shown high catalytic activity. The approach efficiently constructs the even longer linker containing 1, 2, 3-triazole nucleus between bifunctional groups with the advantages of high regioselectivity and operational simplicity.
The novel biotin conjugated glaucocalyxin A analogs as potential activity-based protein probes were synthesized with good yields via Cu(Ⅰ) in situ-catalyzed azide-alkyne cycloaddition. Cu(Ⅰ) in situ was good solvated under the optimized condition and shown high catalytic activity. The approach efficiently constructs the even longer linker containing 1, 2, 3-triazole nucleus between bifunctional groups with the advantages of high regioselectivity and operational simplicity.
2019, 39(6): 1802-1807
doi: 10.6023/cjoc201812033
Abstract:
In the presence of 10 mol% titanocene perfluorobutanesulfonate (1·H2O·THF), reductive cleavage Se-Se bond by zinc dust (1.2 equiv.) at room temperature led to nucleophilic selenium anion species, which reacted with bromoalkanes to afford unsymmetrical selenides in good to excellent yield using commercial tetrahydrofuran (THF) as solvent under N2 atmosphere. The possible reaction mechanism is that zinc dust reduces Cp2TiⅣ(OPf)2 (Pf=SO2C4F9) to produce Cp2TiⅢOPf, which reacts with diaryl diselenides to form the intermediate Cp2TiⅣSeAr(OPf). Then it further reacts with bromoalkanes to produce unsymmetrical selenides. In this paper, the synthesis of asymmetrical selenides catalyzed by 1·H2O·THF/Zn system is first reported. This method has the advantages of mild reaction conditions, simple operation and high yield.
In the presence of 10 mol% titanocene perfluorobutanesulfonate (1·H2O·THF), reductive cleavage Se-Se bond by zinc dust (1.2 equiv.) at room temperature led to nucleophilic selenium anion species, which reacted with bromoalkanes to afford unsymmetrical selenides in good to excellent yield using commercial tetrahydrofuran (THF) as solvent under N2 atmosphere. The possible reaction mechanism is that zinc dust reduces Cp2TiⅣ(OPf)2 (Pf=SO2C4F9) to produce Cp2TiⅢOPf, which reacts with diaryl diselenides to form the intermediate Cp2TiⅣSeAr(OPf). Then it further reacts with bromoalkanes to produce unsymmetrical selenides. In this paper, the synthesis of asymmetrical selenides catalyzed by 1·H2O·THF/Zn system is first reported. This method has the advantages of mild reaction conditions, simple operation and high yield.
