Synthesis of 5-Substituted Isoxazolidines by [3 plus 2] Cycloaddition of Nitrones Generated in an Unusual Way from Nitrosobenzene and Styrene

Abstract

A new synthetic method toward 5-substituted isoxazolidines by [3 plus 2] cycloaddition of nitrones generated from nitrosobenzene and styrene was discovered. The formation of nitrones from nitrosobenzene and mono-substituted aromatic styrenes was demonstrated. The cycloaddition reactions between styrenes and nitrosobenzenes work well when a moderate excess of styrenes was employed. The labeling studies support that cleavage of the styrene double bond occurred and accounted for all the carbons in the starting materials and products. A [3 plus 2] dipolar cycloaddition is implicated by the available mechanistic data and allows for the rapid assembly of various substituted isoxazolidines directly from nitrosobenzenes, electron deficient alkenes, and styrene.