图图式1 可见光诱导的二氟烷基化反应
Figure 图式1. Visible light promoted carbodifluoroalkylation reaction via aryl migration
引用本文:
周能能, 胥攀, 李伟鹏, 成义祥, 朱成建. 可见光催化的高炔丙醇经过1, 4芳基迁移实现二氟烷基化反应[J]. 化学学报,
2017, 75(1): 60-65.
doi:
10.6023/A16070375
Citation: Zhou Nengneng, Xu Pan, Li Weipeng, Cheng Yixiang, Zhu Chengjian. Visible Light Promoted Carbodifluoroalkylation of Homopropargylic Alcohols via Concomitant 1, 4-Aryl Migration[J]. Acta Chimica Sinica, 2017, 75(1): 60-65. doi: 10.6023/A16070375
Citation: Zhou Nengneng, Xu Pan, Li Weipeng, Cheng Yixiang, Zhu Chengjian. Visible Light Promoted Carbodifluoroalkylation of Homopropargylic Alcohols via Concomitant 1, 4-Aryl Migration[J]. Acta Chimica Sinica, 2017, 75(1): 60-65. doi: 10.6023/A16070375
可见光催化的高炔丙醇经过1, 4芳基迁移实现二氟烷基化反应
English
Visible Light Promoted Carbodifluoroalkylation of Homopropargylic Alcohols via Concomitant 1, 4-Aryl Migration
Abstract:
Fluorinated compounds have gained much attention because of their unique electronegativity, metabolic stability and bioavailability, and thus, the synthesis of organofluorine compounds has found wide applications in pharmaceuticals, agrochemicals, and materials science. Among them, the incorporation of a difluoromethyl group (CF2) into organic compounds is of great concern in medicinal chemistry owing to its isosterism with the hydroxyl group. Therefore, the development of new difluoroalkylation methods has attracted great interest in synthetic organic chemistry. Visible light-driven photocatalysis as an eco-friendly and powerful theme has been widely utilized in organic synthesis. In particular, free radical fluorination is emerging as a powerful tool for C-F bond formation, especially under the catalysis of visible light. Recent progress on the visible light-promoted directing difluoroalkylation using ethyl bromodifluoroacetate provided an efficient approach to the target. Herein, we report a contribution towards visible light induced carbodifluoroalkylation of homopropargylic alcohols with the use of ethyl bromodifluoroacetate as a source of difluorinated moieties. This strategy provides a facile way to access functional-difluorinated alkenes through a tandem radical difluoroalkylation and 1, 4-aryl migration process. A representative procedure for this reaction is as following:An oven-dried Schlenk tube (10 mL) was equipped with a magnetic stir bar, homopropargylic alcohols (0.2 mmol), fac-Ir (ppy)3 (0.02 equiv., 0.004 mmol), 2-bromo-2, 2-difluoroacetate (2.5 equiv. 0.5 mmol), Na2HPO4 (2 equiv., 0.4 mmol). The flask was evacuated and backfilled with Ar for 3 times. 0.5 mL of dry DMA and 0.5 mL of dry DCE were added with syringe under Ar. The tube was placed at a distance (app. 5 cm) from 33 W fluorescent light bulb, and the resulting solution was stirred at ambient temperature under visible-light irradiation. After the reaction was finished, the mixture was then diluted with MTBE (20 mL×2) and water. The combined organic layers were dried over sodium sulfate and the solvent concentrated in vacuo and the residue was purified by chromatography on silica gel to afford the corresponding products.
-
1 引言
含氟化合物由于其独特的电负性、代谢稳定性和生物药效性引起了广泛关注, 因此, 它们被广泛应用在医药、农业化学品和材料科学中[1].在过去的几十年中, 引入三氟甲基和单氟甲基的方法已被广泛研究[2, 3].然而, 有机分子中引入二氟烷基的方法仍然有限[4].此外, CF2基团不仅可以作为醚氧的等极化线和等比容线, 同时也可作为亲脂性氢键供体[5].因此, 发展新的引入二氟烷基的高效方法成为了有机合成化学一个热点领域.
可见光催化反应作为一个生态友好、功能强大的方法已经被广泛应用到有机合成中[6].而且, 自由基氟化反应逐渐成为一个生成C-F键的强大工具, 尤其是在可见光的催化作用下.在2011年, 斯蒂芬森首次报道了在可见光催化下, 活化的卤代烷(BrCF2CO2Et)作为一个CF2前体, 成功实现了对烯烃的二氟烷基化反应.随后, 一系列的由活化的卤代烷(BrCF2CO2Et)作为CF2自由基的方法被报道出来[7].最近, 我们课题组报道了可见光催化下烯丙醇经过1, 2-芳基迁移过程成功实现了二氟烷基化反应(图式1)[7g].基于我们对合成含氟化合物的兴趣[8], 本文报道以二氟溴乙酸乙酯为二氟烷基来源, 可见光催化下高炔丙醇经过1, 4芳基迁移实现了二氟烷基化反应(图式1).
2 结果与讨论
2.1 反应条件的优化
根据以往的文献, 我们利用1, 4-二苯基丁-3-炔-1-醇(1a)作为模板底物, 以二氟溴乙酸乙酯作为二氟试剂, fac-Ir (ppy)3作为光催化剂, 展开研究.我们发现反应在室温下, 氩气气氛中, 乙腈作溶剂, 仅得到9%的目标产物2a和少量的副产物3a.为了提高产物产率, 我们对反应条件进行了优化.首先, 我们对催化剂进行了筛选, 发现Ru (bpy)3(PF6)2和Eosin Y都不能促使反应发生(表 1, Entries 2, 3).随后溶剂筛选表明, DMA作溶剂时能够得到比乙腈更高的收率(41%), 而将溶剂换为二氯甲烷、三氯甲烷、1, 2-二氯乙烷或者DMF时, 该反应只能得到少量的产物(表 1, Entries 4~8).当向反应体系中加入不同碱(如K2CO3, Cs2CO3, Et3N, 2, 6-Lutidine, Na2HPO4)时, 我们发现, Na2HPO4成为最优选择, 产率得到57%(表 1, Entries 9~13).当我们把溶剂换成DMA和1, 2-二氯甲烷的1:1(体积比)混合溶剂时, 目标产物的产率可以达到63%(表 1, Entries 9~13).控制实验表明当不加光敏剂或者无可见光照射时, 反应无法进行.
表1
反应条件的优化a
Table1.
Optimization of reaction condition
Entry Photocatalyst Base Solvent Yieldb/% Yieldb/% 1 fac-Ir (ppy)3 - MeCN 9 Trace 2 Ru (bpy)3(PF6)2 - MeCN N.R N.R 3 Eosin Y - MeCN N.R N.R 4 fac-Ir (ppy)3 - DCM Trace Trace 5 fac-Ir (ppy)3 - CHCl3 Trace Trace 6 fac-Ir (ppy)3 - DCE 14 Trace 7 fac-Ir (ppy)3 - DMF 33 15 8 fac-Ir (ppy)3 - DMA 41 12 9 fac-Ir (ppy)3 K2CO3 DMA Trace Trace 10 fac-Ir (ppy)3 Na2CO3 DMA Trace Trace 11 fac-Ir (ppy)3 Et3N DMA Trace Trace 12 fac-Ir (ppy)3 2, 6-Lutidine DMA 25 19 13 fac-Ir (ppy)3 Na2HPO4 DMA 57 12 14 fac-Ir (ppy)3 Na2HPO4 DMA/DCE (V:V=1:1) 63 (10)d 9 15 - Na2HPO4 DMA/DCE (V:V=1:1) N.R N.R 16c fac-Ir (ppy)3 Na2HPO4 DMA/DCE (V:V=1:1) N.R N.R areaction condition: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb under Ar at room temperature for 24 h. bIsolated yield. c In the dark. dThe amount of recovered starting material is given in parentheses. 表1 反应条件的优化a
Table1. Optimization of reaction condition2.2 底物普适性的考察
在最优的反应条件下, 我们研究了可见光催化下对一系列二级高炔丙醇的二氟烷基化反应.首先, 我们对来自不同取代苯甲醛的高炔丙醇进行了研究.我们可以发现, 苯环上取代基的位置不同对反应结果影响不大(2b~2f).同时, 苯环的邻位或者对位有吸电子取代基时, 同样可以得到相应的产物(2h~2j).为了明确目标产物的构型, 我们进行了1H-1H NOESY实验(详见支持信息).随后, 我们对连在炔键上的苯环上的取代基进行了研究.从表 2数据中我们可以看出, 苯环上无论是吸电子基团还是供电子基团, 都能得到中等收率的二氟烷基化产物(2k~2p).在反应过程中, 原料有部分未反应完, 同时也有少量环化产物生成, 导致该反应产率普遍较低.值得注意的是, 当噻吩连在炔键上时, 我们同样可以得到目标产物2q.
表2
二级高炔丙醇的二氟烷基化普适性考察a
Table2.
Scope of carbodifluoroalkylation of secondary homopropargylic alcohols
Compd. Yield/% E/Z 
53 (12)b 
47 (15)b 
58 (14)b 
49 (21)b 17:1c 
47 (15)b 7:1c 
36 (22)b 
31 (19)b 14.5:1c 
33 (26)b 
49 (16)b 
51 (18)b 
53 (16)b 
55 (17)b 11:1c 
63 (12)b 
48 (21)b 
36 (19)b 
35 (26)b 5.5:1c aReaction conditions: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb, 24 h, r.t. b The amount of recovered starting material is given. cThe ratio of 2 to its isomer was determined by 1H NMR analysis of the crude product. 表2 二级高炔丙醇的二氟烷基化普适性考察a
Table2. Scope of carbodifluoroalkylation of secondary homopropargylic alcohols随后, 我们将这一反应应用到各种三级高炔丙醇中.从表 3中我们可以看出, 对称的α, α-二芳基高炔丙醇(1r~1u)可以得到中等收率的目标产物.分析可以得出不同的取代基对反应结果影响不大.当反应底物是不对称的底物1v时, 我们只得到了芳基迁移后的产物, 这与我们开始猜测的反应机理一致.
表3
三级高炔丙醇的二氟烷基化普适性考察a
Table3.
Examples of carbodifluoroalkylation of tertiary homopropargylic alcohols
Compd. Yiled/% 
56 (25)b 
65 (15)b 
54 (21)b 
43 (18)b 
31 (16)b aReaction conditions: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb, 24 h, r.t. b The amount of recovered starting material is given. 表3 三级高炔丙醇的二氟烷基化普适性考察a
Table3. Examples of carbodifluoroalkylation of tertiary homopropargylic alcohols2.3 可能的反应机理和结论
为了进一步了解该反应的反应机理, 我们进行了自由基捕截实验.我们发现, 当反应体系中加入自由基捕截剂TEMPO时, 没有目标产物生成, 说明该反应经历了单电子转移过程.基于以前的文献报道和本实验的工作, 我们对该反应提出了一个可能的机理(图式2).首先, 可见光照射下, fac-Ir (ppy)3经历了金属到配体的电荷转移(MLCT), 生成激发态的[fac-Ir (Ⅲ)(ppy)3*].[fac-Ir (Ⅲ)(ppy)3*]被二氟溴乙酸乙酯氧化淬灭生成自由基A和[fac-Ir (Ⅳ)(ppy)3]+.接着, 自由基A进攻碳碳叁键形成对应的相对稳定的自由基中间体B.接着, 反应可能朝着两个不同的方向进行.途径a中, 碳中心自由基经历热力学控制的五元环化, 进而生成中间体E[9].E随后经历分子内的1, 4芳基反应形成新的碳中心自由基F, F经由单电子转移(SET)过程, 转化为G完成光氧化循环.最后, G脱质子生成目标产物2.途径b中, 自由基B转化为自由基C[10], 随后C被[fac-Ir (Ⅳ)(ppy)3]+氧化形成正离子D, 最后脱质子生成副产物3.
图图式2 可能的反应机理
Figure 图式2. Plausible mechanism
我们发展了一种可见光催化下高炔丙醇经过1, 4芳基迁移实现二氟烷基化反应.该反应以二氟溴乙酸乙酯作为二氟烷基化试剂, 以良好的收率合成了一系列的二氟戊酸乙酯类化合物.机理分析表明, 1, 4芳基重排经历了一个自由基中间体.
3 实验部分
可见光催化下的高炔丙醇的二氟烷基化反应的实验方法:向10 mL干燥的封管中依次加入光敏剂fac-Ir (ppy)3(0.02 equiv., 0.004 mmol), 二氟溴乙酸乙酯(2.5 equiv., 0.5 mmol), Na2HPO4(2 equiv., 0.4 mmol)和底物1a(0.2 mmol), 随后反应管置换氩气, 氩气条件下加入0.5 mL的干燥DMA和0.5 mL干燥DCE, 随后将反应管密封, 光照条件下, 室温条件下搅拌24 h, 反应完毕后, 向反应混合液中加入水和甲基叔丁基醚, 萃取有机相并用硫酸钠干燥, 减压浓缩后得到的混合物进行柱层析石油醚/乙酸乙酯(V:V=15:1~4:1)分离纯化, 以63%收率得到目标产物2a.
-
-
[1]
(a) Filler, R.; Kobayashi, Y.; Yagupolskii, L. M. Organofluorine Compounds in Medicinal Chemistry and Biomedical Applications, Elsevier, Amsterdam, 1993. (b) Romanenko, V. D.; Kukhar, V. P. Chem. Rev. 2006, 106, 3868. (c) Muller, K.; Faeh, C.; Diederich, F.; Science 2007, 317, 1881. (d) Furuya, T.; Kuttruff, C.; Ritter, T.; Curr. Opin.Drug Discovery Dev. 2008, 11, 80. (e) Ojima, I. Fluorine in Medicinal Chemistry and Chemical Biology, Wiley-Blackwell, 2009. (f) Liang, T.; Neumann, C. N.; Ritter, T. Angew. Chem., Int. Ed.2013, 52, 8214. (g) Ni, C.; Zhu, L.; Hu, J. Acta Chim. Sinica 2015, 73, 90. (倪传法, 朱林桂, 胡金波, 化学学报, 2015, 73, 90.). (h) Zhang, K.; Xu, X.; Qing, F. Chin. J. Org. Chem. 2015, 35, 556. (张柯, 徐修华, 卿凤翎, 有机化学, 2015, 35, 556.)
-
[2]
For some reviews on fluorination, see: (a) Grushin, V. V. Acc. Chem. Res. 2010, 43, 160. (b) Cahard, D.; Xu, X.; Couve-Bonnaire, S.; Pannecoucke, X. Chem. Soc. Rev. 2010, 39, 558. (c) Furuya, T.; Kamlet, A. S.; Ritter, T. Nature 2011, 473, 470. (d) Lin, A.; Huehls, B.; Yang. J. Org. Chem. Front. 2014, 1, 434. For recent examples, see: (e) Li, W.; Zhu, Y.; Duan, Y.; Zhang, M.; Zhu, C. Adv. Synth. Catal. 2015, 357, 1277. (f) Shen, X.; Miao, W.; Ni, C.; Hu, J. Angew. Chem., Int. Ed. 2014, 53, 775. (g) Shen, X.; Min, Z.; Ni, C.; Zhang, W.; Hu, J. Chem. Sci. 2014, 5, 117.
-
[3]
For some reviews on trifluoromethylation, see: (a) Nie, J.; Guo, H.; Cahard, D.; Ma, J. Chem. Rev. 2011, 111, 455. (b) Tomashenko, O. A.; Grushin, V. V. Chem. Rev. 2011, 111, 4475. (c) Studer, A. Angew. Chem., Int. Ed. 2012, 51, 8950. (d) Furuya, T.; , Kamlet, A. S.; Ritter, T. Nature 2011, 473, 470. For recent examples, see: (e) Gao, P.; Shen, Y. W.; Fang, R.; Hao, X. H.; Qiu, Z. H.; Yang, F.; Yan, X. B.; Gong, X. J.; Liu, X. Y.; Liang, Y. M. Angew. Chem., Int. Ed. 2014, 53, 7629. (f) Liu, J. B.; Chen, C.; Chu, L. L.; Qing. F. L. Angew. Chem., Int. Ed. 2015, 54, 11839. (g) Sahoo, B.; Li, J. L.; Glorius, F. Angew. Chem., Int. Ed. 2015, 54, 11577.
-
[4]
For recent examples, see: (a) Li, L.; Wang, F.; Ni, C.; Hu, J. Angew. Chem., Int. Ed. 2013, 52, 12390. (b) Min, Q.; Yin, Z.; Feng, Z.; Guo, W.; Zhang, X. J. Am. Chem. Soc. 2014, 136, 1230. (c) Feng, Z.; Min, Q.; Xiao, Y.; Zhang, B.; Zhang, X. Angew. Chem., Int. Ed. 2014, 53, 1669. (d) Wang, X.; Liu, G.; Xu, X.; Shibata, N.; Tokunaga, E.; Shibata, N. Angew. Chem., Int. Ed. 2014, 53, 1827. (e) Chang, D.; Gu, Y.; Shen, Q. Chem. Eur. J. 2015, 21, 6074. (f) He, Y. T.; Wang, Q.; Li, L. H.; Liu, X. Y.; Xu, P. F.; Liang, Y. M. Org. Lett. 2015, 17, 5188. (g) Lin, Q. Y.; Xu, X. H.; Zhang, K.; Qing, F. L. Angew. Chem., Int. Ed. 2016, 55, 1479. (h) Xie, J.; Zhang, T.; Chen, F. Mehrkens, N.; Rominger, F.; Rudolph, M.; Hashmi, A. S. Angew. Chem., Int. Ed. 2016, 55, 2934.
-
[5]
(a) Blackburn, C. M.; England, D. A.; Kolkmann, F. J. Chem. Soc. Chem. Commun. 1981, 930. (b) Blackburn, G. M.; Kent, D. E.; Kolkmann, F. J. Chem. Soc., Perkin Trans. 1 1984, 1119. (c) Erickson, J. A.; Mcloughlin, J. I. J. Org. Chem. 1995, 60, 1626. (d) Kitazume, T.; Kamazaki, T. Experimental Methods in Organic Fluorine Chemistry, Gordon and Breach Science, Tokyo, 1998.
-
[6]
For recent reviews on photoredox catalysis, see: (a) Xuan, J.; Xiao, W. J. Angew. Chem., Int. Ed. 2012, 51, 6828. (b) Yoon, T. P.; Ischay, M. A.; Du, J. Nat. Chem. 2010, 2, 527. (c) Narayanam, J. M. R.; Stephenson, C. R. J. Chem. Soc. Rev. 2011, 40, 102. (d) Tucker, J. W.; Stephenson, C. R. J. J. Org. Chem. 2012, 77, 1617. (e) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322; (f) Xi, Y.; Yi, H.; Lei, A. Org. Biomol. Chem. 2013, 11, 2387. (g) Xie, J.; Jin, H.; Xu, P.; Zhu, C. Tetrahedron Lett. 2014, 55, 36.
-
[7]
(a) Yu, C.; Iqbal, N.; Park, S.; Cho, E. Chem. Commun. 2014, 50, 12884. (b) Sun, X.; Yu, S. Org. Lett. 2014, 16, 2398. (c) Su, Y. M.; Hou, Y.; Yin, F.; Xu, Y. M.; Li, Y.; Zheng, X.; Wang, X. S.; Org. Lett. 2014, 16, 2958. (d) Wang, L.; Wei, X.; Jia, W.; Zhong, J.; Wu. L.; Liu, Q. Org. Lett. 2014, 16, 5842. (e) Nguyen, J. D.; Tucker, J. W.; Konieczynska, M. D.; Stephenson, C. R. J. J. Am. Chem. Soc. 2011, 133, 4160. (f) Wallentin, C. J.; Nguyen, J. D.; Finkbeiner. P.; Stephenson, C. R. J. J. Am. Chem. Soc. 2012, 134, 8875. (g) Jung, J.; Kim, E.; You. Y.; Cho, E. Adv. Synth. Catal. 2014, 356, 2741. (h) Gu, Z. X.; Zhang, H. L.; Xu, P.; Cheng, Y. X.; Zhu. C. J. Adv. Synth. Catal. 2015, 357, 3057. (j) Xu, P.; Hu, K. D.; Gu, Z. X.; Cheng, Y. X.; Zhu, C. J. Chem. Commun. 2015, 51, 7222.
-
[8]
(a) Li, W.; Zhu, X.; Mao, H.; Tang, Z.; Cheng, Y.; Zhu, C. Chem. Commun. 2014, 50, 7521. (b) Qu, C. H.; Xu, P.; Ma, W. J.; Cheng, Y. X.; Zhu, C. J. Chem. Commun. 2015, 51, 13508. (c) Gu, Z. X.; Zhang, H. L.; Xu, P.; Cheng, Y. X.; Zhu, C. J. Adv. Synth. Catal. 2015, 357, 3057. (d) Xu, P.; Wang, G. Q.; Zhu, Y. C.; Li, W. P.; Cheng, Y. X.; Li, S. H.; Zhu, C. J. Angew. Chem., Int. Ed. 2016, 55, 2939.
-
[9]
For reviews on aryl migration: (a) Studer, A.; Bossart, M. Tetrahedron 2001, 57, 9649. (b) Chen, Z. M.; Zhang, X. M.; Tu, Y. Q. Chem. Soc. Rev. 2015, 44, 5220.
-
[10]
For the aryldifluoroacetylation of alkynes reaction, see: Fu, W. J.; Zhu, M.; Zou, G. L.; Xu, C.; Wang, Z. Q.; Ji, B. M. J. Org. Chem. 2015, 80, 4766. http://www.ncbi.nlm.nih.gov/pubmed/25843358
-
[1]
-
图式1 可见光诱导的二氟烷基化反应
Scheme 1 Visible light promoted carbodifluoroalkylation reaction via aryl migration
表 1 反应条件的优化a
Table 1. Optimization of reaction condition
Entry Photocatalyst Base Solvent Yieldb/% Yieldb/% 1 fac-Ir (ppy)3 - MeCN 9 Trace 2 Ru (bpy)3(PF6)2 - MeCN N.R N.R 3 Eosin Y - MeCN N.R N.R 4 fac-Ir (ppy)3 - DCM Trace Trace 5 fac-Ir (ppy)3 - CHCl3 Trace Trace 6 fac-Ir (ppy)3 - DCE 14 Trace 7 fac-Ir (ppy)3 - DMF 33 15 8 fac-Ir (ppy)3 - DMA 41 12 9 fac-Ir (ppy)3 K2CO3 DMA Trace Trace 10 fac-Ir (ppy)3 Na2CO3 DMA Trace Trace 11 fac-Ir (ppy)3 Et3N DMA Trace Trace 12 fac-Ir (ppy)3 2, 6-Lutidine DMA 25 19 13 fac-Ir (ppy)3 Na2HPO4 DMA 57 12 14 fac-Ir (ppy)3 Na2HPO4 DMA/DCE (V:V=1:1) 63 (10)d 9 15 - Na2HPO4 DMA/DCE (V:V=1:1) N.R N.R 16c fac-Ir (ppy)3 Na2HPO4 DMA/DCE (V:V=1:1) N.R N.R areaction condition: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb under Ar at room temperature for 24 h. bIsolated yield. c In the dark. dThe amount of recovered starting material is given in parentheses. 
下载: 导出CSV
表 2 二级高炔丙醇的二氟烷基化普适性考察a
Table 2. Scope of carbodifluoroalkylation of secondary homopropargylic alcohols
Compd. Yield/% E/Z 53 (12)b 47 (15)b 58 (14)b 49 (21)b 17:1c 47 (15)b 7:1c 36 (22)b 31 (19)b 14.5:1c 33 (26)b 49 (16)b 51 (18)b 53 (16)b 55 (17)b 11:1c 63 (12)b 48 (21)b 36 (19)b 35 (26)b 5.5:1c aReaction conditions: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb, 24 h, r.t. b The amount of recovered starting material is given. cThe ratio of 2 to its isomer was determined by 1H NMR analysis of the crude product.
下载: 导出CSV
表 3 三级高炔丙醇的二氟烷基化普适性考察a
Table 3. Examples of carbodifluoroalkylation of tertiary homopropargylic alcohols
Compd. Yiled/% 56 (25)b 65 (15)b 54 (21)b 43 (18)b 31 (16)b aReaction conditions: 1a (0.2 mmol), BrCF2CO2Et (0.5 mmol), base (0.4 mmol), photocatalyst (2 mol%), solvent (1 mL), 33 W fluorescent light bulb, 24 h, r.t. b The amount of recovered starting material is given.
下载: 导出CSV
-
扫一扫看文章
计量
- PDF下载量: 18
- 文章访问数: 2528
- HTML全文浏览量: 398
下载:
