Synthesis of methylene cyclopropane-fused chromenes and dihydroquinolines by sequential [4 + 2]- and [1 + 2]-annulation
作者:Tianyu Lu、Xuange Zhang、Zhiwei Miao
DOI:10.1039/d0ob00389a
日期:——
A base promoted sequential [4 + 2]- and [1 + 2]-annulation of 2-hydroxychalcones or 2-tosylaminochalcones with prop-2-ynylsulfonium salts has been developed to give the corresponding methylene cyclopropane fused dihydroquinolines or chromenes in moderate to good yields. This transformation has advantage of wide substrate scope and functional group tolerance as well as excellent regioselectivity. Prop-2-ynylsulfonium
divergent (4 + 2) annulations of δ-acetoxy allenoates 1 are reported. The chemical behavior of 1 under DABCO catalyst was found to be substrate dependent. Allenoate 1 with an aromatic group at δC preferentially reacted with salicylaldehyde derivative 2, delivering 4H-chromenes 3. On the other hand, allenoates 1 with an alkyl group at δC readily underwent (4 + 2) annulations with oxo diene 4 to afford