On the stereoselectivity of cycloaddition of C-aryl- and C-aroyl-substituted nitrones to (S)-5-hydroxymethyl-2(5H)-furanone

Stereoselectivity of the nitrone cycloaddition with (S)-5-hydroxymethyl-2(5H)-furanone is discussed. C-Aryl nitrones undergo highly regio- and face-selective cycloaddition reaction with lactone, the products result from approach anti to the hydroxymethyl group of the dipolarophile, the oxygen of the 1,3-dipole becoming attached to the beta-carbon of the enone unit. Contraversely, cycloaddition of C-benzoyl nitrone afforded also the second possible regioisomer. Endo-exo diastereoselectivity is affected significantly by the substituent on the nitrone and in the case of C,N-diphenyl nitrone by temperature, too.