Chiral vinyl phosphine oxides: double asymmetric induction in the 1,3-dipolar cycloaddition to chiral nitrones. Kinetic resolution of a racemic phospholene oxide

The 1,3-dipolar cycloaddition of nitrones with chiral vinylphosphine oxides or sulfides provides 5-phosphinyl substituted isoxazolidines with selectivity up to 99:1. Use of chiral nitrones allows a more generalized stereoselective synthesis of these compounds, also by means of a double asymmetric induction. With a racemic phospholene oxide, the high diastereofacial selectivity of the cycloaddition gives rise to a single 4-phosphinyl substituted isoxazolidine from each enantiomer. Moreover, a certain degree of enantiomeric discrimination permits a partial kinetic resolution of the phospholene oxide.