A Stereodivergent Approach to the Synthesis of gem‐Diborylcyclopropanes

We report a designed stereodivergent strategy for the synthesis of gem‐diborylcyclopropanes. The reaction provides a highly modular approach to prepare cyclopropane ring variants bearing gem‐(Bpin,Bpin), gem‐(Bpin,Bdan), and gem‐(Bpin,BF(3)K), with outstanding levels of stereocontrol. This was achieved by diastereoselective Pd‐catalyzed cyclopropanation reactions of gem‐diborylalkenes with α‐diazoarylacetates and α‐diazoaryl‐trifluoromethyl. The key to the success of this general protocol was the diastereoselective trifluorination reaction of gem‐diborylcyclopropanes, followed by the stereospecific interconversion of the trifluoroborate salts into the Bdan group.