The synthesis and ring-contraction of halogenated hydroxyquinones; a new synthesis of cryptosporiopsin

Abstract

Syntheses of 2,6-dichloro-and 2,6-dibromo-3-hydroxy-5-alkyl-1,4-benzoquinones have been developed involving oxidation of trihalogenoresorcinol derivatives with Fremy's salt. The reactions of these quinones have been studied and their ring-contraction to cyclopentenoid structures on treatment with N-halogenosuccinimides is reported. This sequence of reactions has been used in an efficient synthesis of the fungal metabolite cryptosporiopsin.