Novel and rapid approach for benzanthrone synthesis: BBr3-promoted annulation of 8-aryl-1-naphthoic acid derivatives

Abstract

The synthesis of 3-methoxy-benzanthrones was achieved in two steps by Suzuki–Miyaura coupling and BBr₃-promoted Friedel–Crafts acylation under mild conditions with an overall yield of 17–74% and tolerance toward various substrates using commercially available reagents. The competitive mechanism between demethylation and Friedel–Crafts acylation was first rationalized via a deuterium-labelling experiment and DFT calculations. Basic photochemical characteristics of 3-methoxy-benzanthrones and 3-hydroxy benzanthrones were investigated, and the benzanthrones were found to possess excellent photochemical properties. Additionally, using this novel strategy, alkaloid oxoglaucine with a similar tetracyclic skeleton was successfully synthesized with a 70% overall yield via two steps.