New N-substituted dipolarophiles in 1,3-dipolar cycloaddition of nitrones
Résumé
(N-Vinyl)-1,3-oxazolidin-2-ones, -1,3-oxazolidine-2-thi-ones and -N′-methylimidazolidin-2-one were conveniently used as new dipolarophiles in thermal 1,3-dipolar cycloaddition involving activated nitrones, and led to new 5-N-substituted isoxazolidines in high yields. A moderate to total trans-diastereoselectivity was observed, increasing with the degree of substitution at C-4.