An unexpected transformation by reduction of isoxazolines

Aromatic nitrile oxides undergo regio- and stereo-specific 1,3-dipolar cycloaddition reactions with racemic 5-hydroxy-4-methyl-1,5-dihydropyrrol-2-one derivatives 1. In each case, a single product 3 results from an anti approach to the hydroxyl group, the oxygen of the 1,3-dipole being attached to C-5 of pyrrolidinones. A detailed study of a procedure for the selective reduction of Δ2-isoxazolines to the corresponding vinylogous amide derivatives is reported.