An efficient synthesis of polysubstituted tetrahydrofuran and indene derivatives via the Lewis acid-mediated cycloadditions of VCPs with aldehydes

A variety of polysubstituted tetrahydrofuran and indene derivatives were prepared in moderate to excellent yields via the cycloadditions of vinylidenecyclopropanes with common aldehydes in the presence of Lewis acid. The polysubstituted tetrahydrofuran 3 could undergo further transformations to the indene product 4 and furan derivatives 5.