Cascade assembly of the benz[a]anthraquinone ring system common to the angucycline antibiotics

A benz[a]anthraquinone ring system, common to a group of angucycline antibiotics, has been prepared by a unique cascade of reactions. The reaction sequence was initiated by a Suzuki–Miyaura cross-coupling between a bromoquinone and vinyl boronic anhydride. The reaction product is proposed to undergo a 6π-electron cyclization triggered by reductive activation of the quinone. The reaction process is proposed to be autocatalytic.