Synthesis of methylene cyclopropane-fused chromenes and dihydroquinolines by sequential [4 + 2]- and [1 + 2]-annulation

A base promoted sequential [4 + 2]- and [1 + 2]-annulation of 2-hydroxychalcones or 2-tosylaminochalcones with prop-2-ynylsulfonium salts was developed.