Relay Zn(ii)- and Au(i)-catalyzed aziridination/cyclization/ring expansion sequence to form 3-benzazepine derivatives

Abstract

The synthesis of 3H-benzo[d]azepine-2-carboxylates from 2-alkynylphenyl aldimines and α-diazo esters using Zn(II) and Au(I) catalysts is described. In this relay catalysis, Zn(II) catalyzes the addition of α-diazo ester to the imine of 2-alkynylphenyl aldimine to afford expected trans-aziridine selectively while Zn(OTf)₂ gives a mixture of cis/trans aziridines from common imines. Subsequently, Au(I) catalyzes intramolecular cyclizations of such trans-aziridine/alkyne functionalities to form the observed 3H-benzo[d]azepines. This catalysis represents the new synthetic utility of 2-alkynylphenyl aldimines, eluting the prior formation of isoquinoliniums salts.