Cycloaddition reactions of C,N-diphenylnitrone to methylene-γ- butyrolactones

Abstract

Cycloaddition of C,N-diphenylnitrone to α-methylene-γ- butyrolactone afforded two diastereomeric 5-spirosubstituted isoxazolidines with high selectivity. Structural assignment was ascertained by NMR studies and an X-ray diffraction experiment on a single crystal of the major isomer and the diastereoselectivity was rationalized on examination of the alternative transition states leading to the two diastereoisomers.