Catalytic Enantioselective Synthesis of Highly Functionalized Difluoromethylated Cyclopropanes.

The first catalytic asymmetric synthesis of highly functionalized difluoromethylated cyclopropanes is described. The method, based on a rhodium-catalyzed cyclopropanation of difluoromethylated olefins, gives access to a broad range of cyclopropanes bearing ester, ketone, or nitro functional groups. By using Rh ((S)-BTPCP) as a catalyst, the corresponding products were obtained in high yields and high diastereo- and enantioselectivities (up 20:1 d.r. and 99 % ee). This methodology allowed preparation of enantioenriched difluoromethylcyclopropanes for the first time.