1,3-Dipolar Cycloaddition of N-Substituted Dipolarophiles and Nitrones: Highly Efficient Solvent-Free Reaction.

New isoxazolidines were synthesized in good to excellent yields by I ,3-dipolar cycloaddition of N-vinylamide dipolarophiles and nitrones. Strikingly, solvent-free conditions gave high conversion and yields, shortened reaction time, and minimized degradation products. N-Vinyloxazolidin-2-one and its analogues used in these cycloaddition reactions were conveniently prepared in excellent yields by a modified version of Buchwald's one-step copper-catalyzed vinylation using vinyl bromide. From the adducts, a two-step access to various unsymmetric aspartate derivatives was also described. [ABSTRACT FROM AUTHOR]