Preparation of phenolic compounds by decarboxylation of hydroxybenzoic acids or desulfonation of hydroxybenzenesulfonic acid, catalysed by electron rich palladium complexes

Phenolic compounds can be prepared by catalytic decarboxylation of 4-hydroxybenzoic acid or desulfonation of 4-hydorxybenzene sulfonic acid. Palladium complexes are shown to be highly active in the decarboxylation reaction, but complexes of platinum or ruthenium also show some activity in this reaction. Highly electron donating diphosphines such as BDTBPMB or monophosphines such as (PBu3)-Bu-t were found to be more effective than the less donating dppe or PPh3. The addition of D2O led to deuteration of the aromatic ring mainly in the position ortho to the hydroxyl group. Phenol can also be generated by SO3 extrusion from 4-hydroxybenzenesulfonic acid catalysed by highly electron rich palladium complexes.