Regiospecific bromination of condensed tetralones via aryloxydifluoroborn chelates

Abstract

Bromination (Br₂, CCl₄) of the anthracenone derivative (1b) under thermal or photochemical conditions gives the expected bromo-compound (1d) whereas photochemical bromination of the aryloxydifluoroboron complexes (2a,b) gives products (2c,d) of benzylic substitution; conversion of (2c) and (3a,b) into anthraquinone derivatives including madeirin (4) is described and extension of the regiospecific bromination procedure to the bicyclic difluoroboron complex (5a) is illustrated.