REARRANGEMENT OF S-PHOSPHORYLISOTHIOUREAS INTO N-PHOSPHORYLTHIOUREAS: STEREOCHEMISTRY AT PHOSPHORUS AND MECHANISM

Article abstract of DOI:10.1016/S0040-4020(01)87303-8

Stereochemistry of the rearrangement of S-phosphorylisothioureas into N-phosphorylthioureas has been investigated using two chiral phosphorothioic acid: cyclic 4-methyl-2-oxo-2-mercapto-1,3,2-dioxaphosphorinane (1) and acyclic, optically active O-methyl-O-1-naphtyl phosphorothioic acid (2).Configuration at phosphorus in N-phosphorylthioureas 4 and 9, obtained in the reaction of these thioacids with various carbodiimides, has been established by means of chemical correlation and CD spectra.The title rearrangement has been shown to proceed with full retention of configuration at phosphorus.The stereochemistry of the rearrangement under discussion, as well as the different reactivity of various types of phosphorus thioacids towards carbodiimides have been explained in terms of the mechanism involving pseudorotation of a pentacovalent phosphorus intermediate.