Copper-Catalyzed Asymmetric Synthesis of Borylated cis-Disubstituted Indolines.

A copper-catalyzed, intramolecular borylative cyclization of vinyl arenes with imines is reported, which affords enantio-enriched indolines as a single diastereomer under mild conditions. A benzylcopper species is generated by Cu-Bpin addition to the alkene, which then acts as a nucleophile for intramolecular imine addition. The reaction is applicable to various vinyl arenes with an imine moiety at the ortho-position, including heterocycles, for formation of borylated indolines in good yields and ee values up to 90 %.