Stereoselective Synthesis of Trisubstituted Alkenes via Cobalt-Catalyzed Double Dehydrogenative Borylations of 1-Alkenes

A highly selective cobalt-catalyzed single and double dehydrogenative borylations (DHBs) of terminal alkenes have been developed for the synthesis of trans-monoborylalkenes and diborylalkenes, respectively. While the cobalt-catalyzed double DHBs of aryl 1-alkenes with 2 equiv of bis(pinacolato)diboron (B2pin2) in the presence of 1 equiv of CsF in DMF produce 1,1-diborylalkenes selectively, the double DHBs with alkyl 1-alkenes generate cis-1,2-diborylalkenes in a selective manner. The 1,1-diborylalkene products are further applied to stepwise and stereospecific cross-couplings with aryl halides to create trisubstituted alkenes, including triaryl alkenes.