Organophosphorus compounds. Part CL. Synthesis of ‘stable’ tetra-o-alkyl sym-monothiopyrophosphates

Abstract

Oxophosphoranesulphenyl chlorides react readily with dialkyl phosphites giving, in high yield, simple and mixed sym-thiopyrophosphates (RO)₂P(O)–S–P(O)(OR′)₂, uncontaminated by any catalyst for the ready isomerization into the unsymmetrical isomers, P(O)–O–P(S), which has marred earlier procedures. The reaction involves nucleophilic attack by the phosphorus atom on the sulphur atom of the sulphenyl chloride and formation of a quasiphosphonium complex. Some side reactions resulting from the great reactivity of sym-monothiopyrophosphates are also described.