Imide-amide rearrangement of cyclic phosphorimidates: A mechanistic study

Studies aimed at the development of new synthetic pathways for the preparat ion of chiral cyclic oxaza and diaza phosphoramides suitable for use in asy mmetric chemistry led us to the investigation of the imide-amide rearrangem ent of cyclic phosphorimidates. As a result of this work new types of oligo meric organophosphorus compounds, formed by a novel 1,4-addition type ring opening polymerisation, were identified. These compounds are the stable int ermediates of the imide-amide rearrangement, which upon heating yield the p reviously reported rearranged product, A detailed study of the mechanism of the Lewis acid catalysed imide-amide rearrangement and stereochemical cont rol of the final products is reported. As a result, the full mechanism was elucidated and evidence of retention of configuration at the rearranged car bon atom is presented. Substituent effects were rationalised based on molec ular modelling calculations.