Regioselectivity in the reductive cleavage of pyrogallol derivatives: reductive electrophilic substitution of acetals of 2,3-dimethoxyphenol

Abstract

Acetals of 2,3-dimethoxyphenol were used as the starting materials for the transformation of 1,2,3-trioxygenated benzenes into various 1-oxygenated-2,3-dicarbon-substituted benzenes, via regioselective reductive electrophilic substitution of the 2-methoxy group, followed by conversion into the corresponding triflates and a Pd-catalysed cross-coupling reaction. The regioselectivity of the reductive cleavage is ascribed to twisting of the leaving methoxy group out of the plane of the aromatic ring by the two ortho substituents. According to this methodology, a new synthesis of lunularic acid is presented.