Stereodivergent Approach to the Synthesis of gem-Diborylcyclopropanes

We report a novel designed stereodivergent strategy for the synthesis of gem-diborylcyclopropnes. The reaction provides a highly modular approach for the preparation of cyclopropane rings variants bearing gem-(Bpin,Bpin), gem-(Bpin,Bdan), and gem-(Bpin,BF3K) , with outstanding levels of stereocontrol. This was achieved by diastereoselective Pd-catalyzed cyclopropanation reactions of gem-diborylalkenes with α-diazoarylacetates and α-diazoaryl-trifluoromethyl. Key to the success of this general protocol was the diastereoselective trifluorination reaction of gem-diborylcyclopropanes followed by a stereospecific interconversion of the trifluoroborate-salts into the Bdan group.