Reactions of Keten Acetals. Part I. A Simple Synthesis of Some Naturally Occurring Anthraquinones

Abstract

A study of the condensation of keten acetals with some halonaphthoquinones has led to the simple and regiospecific synthesis of some naturally occurring anthraquinones: catenarin, helminthosporin, emodin, and chrysophanol. The results show unambiguously that a previously proposed mechanism is erroneous. The reaction of these acetals with chloromaleic anhydride also provided a one-step preparation of some substituted phthalic anhydrides.