First Rational Synthesis of the Thiothiono Analogue of an Unsymmetrically Substituted Phthalic Anhydride

Abstract

Treatment of the dithiolane derivative of an alpha-carboxyethyl benzaldehyde with LDA at -78 degrees C smoothly produced the thiothionophthalic anhydride. The mechanism is proposed to involve loss of ethene and attack of an intermediate dithiocarboxylate onto the ester. Heating the thiothionophthalic anhydride gave the 3, 3'-bithiophthalide.