Sc(OTf)₃‐Catalyzed Dearomative [3+2] Annulation of 5‐Aminoisoxazoles with Quinone Imine Ketals or Quinone Monoacetals

Abstract

Abstract Isoxazolines are highly significant for the development of new synthetic methodology and pharmaceutics. Indolines and 2,3‐dihydrobenzofurans are also privileged structures in natural products and pharmaceuticals. In continuation of our ongoing research on transformations of 5‐aminoisoxazoles and quinone derivaties, herein we report Sc(OTf) 3 ‐catalyzed dearomative [3+2] annulations of 5‐aminoisoxazoles with quinone imine ketals (QIKs) and quinone monoacetals (QMAs). A variety of indoline‐ and 2,3‐dihydrobenzofuran‐fused isoxazolines were afforded in moderate to good yields with excellent diastereoselectivities (all cases >20 : 1 dr). This method featured mild reaction conditions, wide substrate scope, and gram‐scale synthesis.