(R)-4-phenyloxazolidin-2-thione: an efficient chiral auxiliary for [4+2] cycloaddition of 1-aminodiene and activated phosphonodienophiles

A theoretical model for the facial selectivity of N-dienyl oxazolidin-2-(thi)one and thiazolidin-2-thione 2a–c is presented. Our analysis provides a clear understanding of factors controlling stereoselectivity in reaction of these dienes, and allows predictions of high diastereoselectivity in the case of oxazolidin-2-thionyl diene (2b). The application of this diene to the synthesis of β- and γ-aminophosphonic derivatives is then investigated. Under classical conditions or under microwave activation, the D–A reaction of diene 2b leads to aminophosphonic chirons with high regio- and stereoselectivities.