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.