Chiral Thiourea Catalyzed Enantioselective Cascade Synthesis of 2,3‐Dihydrobenzofurans

Abstract

We established an efficient asymmetric cascade pathway for the construction of trans‐2,3‐dihydrobenzofurans. This reaction proceeds via a Michael addition followed by an oxa‐substitution, employing in‐situ generated pyridinium ylide and ortho‐hydroxy chalcone derivatives in the presence of a chiral thiourea catalyst at ambient temperature. This method accomplishes good to excellent yields and adequate stereoselectivity, with up to 84 % ee and >20 : 1 diastereomeric ratio. A key advantage of this cascade [4+1] annulation approach is its ability to construct chiral DHBs under mild conditions with notable yields and selectivity.