Facile synthesis of indole- or benzofuran-fused benzo[a]carbazole-1,4-diones using a tandem two-step reaction sequence.

An efficient three-step approach was developed to assemble indole- or benzofuran-fused benzocarbazole-1,4-diones in 42-53% overall yield. This approach includes AgOAc-promoted oxidative cyclization of 2,6-di-bromocyclohexene-1,4-dione with indol-3-ylpropanoid acid, condensation of the resulting bromocarbazole intermediates with phenols or anilines, followed by Pd(OAc)-catalyzed cyclization. Such convenient synthetic protocol and the novelty of the corresponding products will largely assist our drug design and development program.