Palladium-catalyzed synthesis of o-acetylbenzoic acids: a new, efficient general route to 2-hydroxy-3-phenyl-1,4-naphthoquinones and indolo[2,3-b]naphthalene-6,11-diones

We describe here a new, efficient general synthesis of o-acetylbenzoic acids by Heck palladium-catalyzed arylation of n-butyl vinyl ether with o-bromobenzoic acid esters and the use of these compounds as starting materials for the synthesis of 3-benzylideneisochroman-1,4-diones, which readily rearrange to 2-hydroxy-3-phenyl-1,4-naphthoquinones. The application of this strategy to the synthesis of indolo[2,3-b]naphthalene-6,11-diones is also described.