The regiospecific preparation of 1,4-dioxygenated anthraquinones: a new route to islandicin, digitopurpone, and madeirin
Abstract
A direct, versatile, one-step synthesis of anthraquinones which exhibits total regioselectivity (>99%) and involves the reaction of the anion of 4- or 7-methoxy-3-phenylsulphonylphthalides with variously substituted quinone monoacetals is reported.