Intramolecular Michael-type addition of azadienes to 1,4-naphthoquinones instead of Aza-Diels–Alder cycloaddition: a synthesis of ascididemin

Abstract

α,β-Unsaturated hydrazones tethered by an amino group to 1,4-naphthoquinone or quinoline-5,8-dione do not react by intramolecular aza-Diels–Alder cycloaddition. Instead, these substrates cyclize to form benzo[b]acridine-6,11-dione or pyrido[2,3-b]acridine-5,12-dione derivatives, respectively. This route leads to a highly concise synthesis of the pyridoacridine alkaloid ascididemin.