Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro-ku, Tokyo, 152-8552, Japan.
Chemistry. 2022 Jun 7;28(32):e202200657. doi: 10.1002/chem.202200657. Epub 2022 May 2.
Optically active cyclopropanes have been widely investigated especially from the views of pharmaceutical and agrochemical industries, and substituting one of the methylenes with the difluoromethylene unit should be promising for developing novel biologically relevant compounds and functional materials. In this paper, the copper-catalyzed enantioselective hydrosilylation of gem-difluorocyclopropenes to provide the corresponding chiral gem-difluorocyclopropanes is presented. The use of copper(I) chloride, chiral ligands including bidentate BINAPs and monodentate phosphoramidites, and silylborane Me PhSi-Bpin accompanying sodium tert-butoxide in methanol was appropriate for the enantioselective hydrosilylation of the strained C=C double bond, and the resultant chiral difluorinated three-membered ring was unambiguously characterized. Subsequent activation of the silyl groups in enantio-enriched gem-difluorocyclopropanes showed substantial reduction of the enantiopurity, indicating cleavage of the distal C-C bond leading to the transient acyclic intermediates.
具有光学活性的环丙烷受到了广泛的研究，特别是在药物和农用化学品领域，用二氟亚甲基单元取代其中一个亚甲基，有望开发出新型具有生物相关性的化合物和功能材料。本文介绍了铜催化的立体选择性氢硅烷化反应，用于合成相应的手性 gem-二氟环丙烷。使用氯化亚铜、包括联萘二膦（BINAP）双齿配体和单齿磷酰胺配体在内的手性配体、以及三甲基甲硅烷基硼烷 MePhSi-Bpin 与叔丁醇钠在甲醇中，适用于应变 C=C 双键的立体选择性氢硅烷化反应，得到的手性氟化三环以明确的方式进行了表征。随后对具有对映体过量的手性 gem-二氟环丙烷中的硅烷基进行活化，表明对映体纯度显著降低，这表明远端 C-C 键断裂导致瞬态无环中间体的形成。
