Catalytic Asymmetric Synthesis of Chiral Dihydrobenzofurans through a Formal [4+1] Annulation Reaction of Sulfur Ylides and In Situ Generated ortho‐Quinone Methides

Abstract

The first example of a catalytic asymmetric formal [4+1] annulation reaction between sulfur ylides and in situ generated ortho‐quinone methides (o‐QMs) is reported in this work. A C2‐symmetric chiral urea was identified to be the best H‐bonding catalyst, affording a wide range of chiral 2,3‐dihydrobenzofurans in high yields and moderate enantioselectivities [70–98 % yields, up to 89:11 e.r. (enantiomeric ratio)].