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 C
C 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.