Chemo- and Stereoselective Dearomative Coupling of Indoles and Bielectrophilic β-Imino Boronic Esters via Imine-Induced 1,2-Boronate Migration.

A new imine-induced 1,2-boronate migration has been developed for achieving chemo- and stereoselective dearomative coupling of C3-substituted indoles and bi-electrophilic β-imino boronic esters, providing rapid access to complex chiral indoline boronic esters with four stereocenters including an all-carbon quaternary stereocenter and a tertiary α-aminoboronic ester. In contrast, coupling of indoles without C3 substitution and β-imino boronic esters provided tetrahydro-1-pyrido[4,3-]indoles via imine-induced 1,2-boronate migration followed by deborylative rearomatization.