Stereochemistry of alkaline hydrolyses of 1,3,2-oxazaphospholidine-2-thiones and related reactions

Abstract

Essentially exclusive cleavage, with retention of configuration, of the endocyclic P–O bond occurs during basic hydrolysis of 2-alkoxy-1,3,2-oxazaphospholidine-2-thiones. In the 2-methyl analogues, P–O bond cleavage occurs with both inversion and retention of configuration and also obtained are products from P–N bond cleavage with inversion. These results are consistent with reaction mechanisms which require nucleophilic attack at phosphorus opposite nitrogen in preference to oxygen. A term, apical potentiality, introduced to refer to apical preference during reactions, is intended to be quite distinct from the term apicophilicity which describes apical preference in stable phosphoranes. S-Alkyl groups are displaced from NN-dialkyl phosphoramidothioates with retention of configuration, but with inversion in the corresponding phosphono-derivatives.