Palladium-catalyzed chemoselective intramolecular cyclization of bromoanilinoalkenenitriles

Abstract

α-(o-Bromoanilino)alkenenitriles 1a–f and 2a–e and α-(N-alkenylamino)-β-(o-bromophenyl)propanenitrile 7a–c< and 8a–c undergo palladium-catalyzed conversion into o-(methylamino)benzonitrile 12, o-[(alkenylamino)ethenyl]benzonitriles 24a–c, N-alkenylanilines 26b, 26c, 3-benzazepines 29a, 29c, 31a and 32a, γ-carbolines 36 and pyrrolo[3,2-b]indole 45. The reactions involve intramolecular additions of arylpalladium to the cyano group and subsequent processes such as cyano group transposition, hydrolysis, electrocyclization, ethyl group transfer and oxidative aromatization. A general mechanism for the palladium-catalyzed arylation of a cyano group is proposed.