Wei Xiao-Jing, Boon Wout, Hessel Volker, Noël Timothy
Department of Chemical Engineering and Chemistry, Micro Flow Chemistry & Process Technology, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven, The Netherlands.
ACS Catal. 2017 Oct 6;7(10):7136-7140. doi: 10.1021/acscatal.7b03019. Epub 2017 Sep 11.
The development of synthetic methodologies which provide access to both stereoisomers of α,β-disubstituted olefins is a challenging undertaking. Herein, we describe the development of an operationally simple and stereoselective synthesis of difluoromethylated styrenes via a visible-light photocatalytic decarboxylation strategy using -Ir(ppy) as the photocatalyst. Meta- and para-substituted cinnamic acids provide the expected -isomer. In contrast, -substituted cinnamic acids yield selectively the less stable -product, whereas the -isomer can be obtained via continuous-flow processing through accurate control of the reaction time. Furthermore, our protocol is amenable to the decarboxylative difluoromethylation of aryl propiolic acids.
开发能够获得α,β-二取代烯烃两种立体异构体的合成方法是一项具有挑战性的工作。在此，我们描述了一种操作简单且立体二立体选择性合成二氟甲基化苯乙烯的方法，该方法通过使用-Ir(ppy)作为光催化剂的可见光光催化脱羧策略实现。间位和对位取代的肉桂酸可得到预期的-异构体。相比之下，-取代的肉桂酸选择性地生成稳定性较差的-产物，而-异构体可通过精确控制反应时间的连续流动处理获得。此外，我们的方法适用于芳基炔丙酸的脱羧二氟甲基化反应。
