A concise synthetic approach to brazilin via Pd-catalyzed allylic arylation

Abstract

A short synthetic route to the trimethyl ether of brazilin was developed in 6 steps from 7-methoxychromene with 78% overall yield. Regioselective installation of a formyl group onto 7-methoxychromene followed by reduction and acetylation afforded allylic acetate. Palladium-catalyzed allylic coupling of allylic acetate with arylboronic acid provided direct access to 3-benzylchromene which was converted to the target molecule upon ensuing dihydroxylation and acid-catalyzed cyclization in a highly concise manner.