Palladium-catalysed dual ring-opening [3 + 4] annulation of isatoic anhydrides with cyclic iodoniums to build tribenzo[b,d,f]azepines and a mechanistic DFT study

Abstract

A Pd(0)-catalysed dual ring-opening, decarboxylative/decarbonylative [3 + 4] annulation of readily available (6-membered) isatoic anhydrides with (5-membered) cyclic iodoniums to efficiently build (7-membered) tribenzo[b,d,f]azepines was developed. The tandem C–N and C–C bond formations were completed quickly, within 1 h, and showed steric-hindrance-enforced regioselectivity of unsymmetric diaryliodoniums. Moreover, DFT calculations were conducted, and revealed a preference for the Pd catalyst to insert into the weaker C–O bond of isatoic anhydride, followed by a tandem decarboxylation and decarbonylation process.