ZnCl₂ Promoted Formal (3+2) Cycloaddition Reactions of 2-Alkoxy-1,4-benzoquinones with 2H-Chromenes

Abstract

A simple, mild, inexpensive and highly efficient method for the synthesis of 2,2-dimethyldihydropyranopterocarpans (4a–h and 5a–b) by formal (3+2) cycloaddition reactions of 2-alkoxy-1,4-benzoquinones (3a–b) with 2H-chromenes (1a–d and 2) using ZnCl₂ at room temperature has been developed.