Palladium-catalyzed cross-coupling of stereospecific potassium cyclopropyl trifluoroborates with aryl bromides

Stereospecific cyclopropanation of alkenylboronic esters of pinacol followed by in situ treatment with excess KHF2 afforded the corresponding potassium cyclopropyl trifluoroborates in high yields, which then underwent Suzuki-Miyaura cross-coupling reactions with aryl bromides to give cyclopropyl-substituted arenes in good yields with retention of configuration. This promises to be a useful method for the synthesis of enantiomerically pure cyclopropanes.