Chiral 2-vinyl-1,3,2-oxazaphospholidin-2-ones: new dienophiles for asymmetric Diels–Alder reactions

Abstract

Diels–Alder reactions of chiral dienophiles: (2R,4S)- and (2R,4S)-2-vinyl-1,3,2-oxazaphospholidin-2-ones (3 and 4) derived from (S)-valinol with cyclopentadiene led to mixtures of endo- and exo-adducts with high diastereofacial selectivity (>90% for 3 and 80 and 88% respectively for 4); an explanation is proposed based on X-ray crystallographic structures for the dienophile and the derived endo-cycloadduct 5.