Annulation of phosphole sulfides via [3 + 2] cycloaddition with nitrones

Abstract

Owing to the unique electronic structure of phospholes, it is difficult to realize the annulation of phospholes with the endocyclic CC bond. Herein we report the [3 + 2] cycloaddition reaction between phosphole sulfides and nitrones, affording the phospholene fused isoxazolidine skeleton with high yields and excellent regioselectivity. The oxygen atom is attached to the β carbon atom of the phosphole exclusively. The CC bond in the product cannot react with the nitrone. This work demonstrates that slightly antiaromatic phosphole sulfides are capable of acting as 2π-electron components in cycloaddition reactions.