Diastereoselective Synthesis of 1,2,3-Substituted Potassium Cyclopropyl Trifluoroborates via an Unusual ZincBoron Exchange

Diastereoselective cyclopropanation of an allylic alcohol with a gem-dizinc carbenoid followed by an unusual zinc-boron exchange and further treatment with excess KHF2 afforded 1,2,3-syn-cis-substituted cyclopropyl trifluoroborates in 5863% overall yields. The potassium cyclopropyl trifluoroborates underwent Suzuki-Miyaura cross-coupling reactions to give 1,2,3-functionalized cyclopropanes in good yields. Finally, an oxidation-epimerization sequence gave access to 1,2,3-transsubstituted cyclopropyl trifluoroborate.