Asymmetric synthesis of spiro-structural 2,3-dihydrobenzofurans<i>via</i>the bifunctional phosphonium salt-promoted [4 + 1] cyclization of<i>ortho</i>-quinone methides with α-bromoketones

Abstract

A practical and scalable method for highly stereoselective construction of spiro-2,3-dihydrobenzofurans<italic>via</italic>cyclization of<italic>ortho</italic>-quinone methides and α-bromoketones by bifunctional phosphonium salt catalysis was developed.