Palladium-catalyzed chemoselective intramolecular cyclization of 2-bromoaryl alkenenitriles

The chemoselectivity in the palladium-catalyzed intramolecular cyclization of 2-(o-bromoaryl)alkenenitriles depends on the nature of alpha-substitutents. 2-(o-Bromoanilino)alkenenitriles attacked the cyano group, followed by the cyano group transposition and hydrolysis, to give o-(methylamino)benzonitrile. 2-(o-Bromobenzyl)alkenenitriles, 2-(o-bromophenylthio)alkenenitriles and 2-(o-bromophenoxy)-alkenenitriles attacked the olefinic double bonds and led to 1-vinyl-2-indancecarbonitrile, 1,2,3,4-tetrahydronaphthalene-2-carbonitriles, 3,4-dihydro-2H-benzo[b]oxine-2-carbonitriles, and 3,4-dihydro-2H-benzo[b]oxine-2-carbonitriles. A general mechanism for the palladium-catalyzed arylations is proposed.