Regioselective bromination of 1,4-naphthoquinones

Abstract

1,4-Naphthoquinones unsymmetrically substituted in the benzenoid ring undergo bromination at the 2- and/or 3-positions. The isomeric composition of the products is strongly influenced by the conditions of bromination, addition of hydrogen bromide usefully complementing the conventional procedure involving addition of bromine. In favourable cases, involving methoxynaphthoquinones, these two procedures afford controlled access to individual 2- and 3-bromo derivatives.