Stereochemistry of the acyclic phosphono- and phosphino-thiocyanide isomerisation into corresponding isothiocyanidates : Synthesis of optically active thiocyanidates > P(O)SCN isothiocyanidates > P(O)NCS,isocyanidates > P(O)NCO and related phosphorylated derivatives of carbonic acid

Optically active t-butylphenylphosphinothiocyanidate Bu^tPhP(O)SCN 3 and t-butyl-O-methyl-phosphonothiocyanidate Bu^t(MeO)P(O)SCN 7 have been prepared by condensation of the corresponding sulphenyl chlorides > P(O)SCl with trimethylsilylcyanide and isomerised into optically active t-butyl-O-methyl-phos-phonoisothiocyanidates Bu^t(MeO)P(O)NCS 8. Chirality at P in and the optical purity of the chiral phosphino (phosphono) thiocyanidates and isothiocyanidates have been determined by chemical correlations. It has been demonstrated that the thiocyanate ion and amine catalysed thiocyanidate-isothiocyanidate isomerisation > P(O)SCN → > P(O)NCS occurs stereospecifically with inversion of configuration at the P center. This result can be rationalized by postulation of a phosphorane intermediate, formed by nucleophilic attack of the SCN^- anion on phosphorus, in which thiocyanate and isothiocyanate groups occupy apical positions. In connection with these studies a number of novel optically active phosphorylated derivatives of carbonic acid, > P(O)NHCSNHR, > P(O)NCCl₂, > P(O)NCO and > P(O)NHCOOBu^t, have also been synthesised.