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

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),-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.

Automated summary

Isoxazolines are important for the development of synthetic methodology and pharmaceutics. In this study, a new method using Sc(OTf) catalyst for the dearomative [3 + 2] annulation of 5-aminoisoxazoles with quinone imine ketals (QIKs) and quinone monoacetals (QMAs) was reported. This method allows for the synthesis of fusion compounds of indolines and 2,3-dihydrobenzofurans with isoxazolines, with good yields and diastereoselectivities.