Cu-Catalyzed Site- and Enantioselective Borylcyanation of 1,2-Disubstituted Aryl Alkenes

A catalytic chemo- and enantioselective generation of secondary benzylic copper complexes from Cu-B(pin) (pin=pinacolato) additions to 1,2-disubstituted aryl alkenes followed by in situ site selective cyanation at either aryl group or benzylic position to construct multifunctional alkylboron compounds is presented. The method is distinguished by identification of chiral Cu complexes leading to not only high enantioselectivity but also better efficiency compared with achiral catalysts. In addition, an unprecedented mode of cyanation at benzylic site through dearomative isomerization was disclosed. Functionalization of multifunctional alkylboron products provides useful building blocks that are otherwise difficult to access. A new method for enantioselective borylcyanation of 1,2-disubstituted alkenes promoted by chiral phosphine-Cu complexes was developed. This protocol represents the first catalytic enantioselective approach for simultaneous introduction of a cyano and a boryl group to 1,2-disubstituted alkenes, affording a wide range of chiral multifunctional organoboron compounds.image