P-CHIRAL THIOXOPHOSPHORANESULFENYL CHLORIDES RR'P(S)SCL - A UNIQUE STEREOCHEMICAL PROBE TO STUDY NUCLEOPHILIC DISPLACEMENT AT A DICOORDINATE SULFUR CENTER

A stereospecific synthesis of P-chiral sulfenyl chlorides 6a,b has bee n developed from P-chiral sulfenylamide 9a,b,c by a novel procedure em ploying 2Me(3)SiCl + 2EtOH as the reagent of choice. The sulfenylamide s 9a,b,c were prepared either by stereospecific reaction of the P-chir al hydrogen phosphinothioate 8a with aminosulfenyl halides or separati on of a mixture of diastereomeric 9a,b,c by crystallisation. P-Chiral chlorides 6a,b were allowed to react with secondary amines such as mor pholine or dicyclohexyl amine. All these displacement reactions procee d with almost complete stereochemical integrity at the phosphorus atom . These observations support a synchronous mechanism of bond breaking and bond formation during nucleophilic displacement at the dicoordinat e sulfur atom. The same can be said about the reaction of sulfenamides 9a,b,c with hydrogen chloride. (C) 1998 Elsevier Science Ltd. All rig hts reserved.