ALPHA-PHOSPHORYL SULFOXIDES .11. SULFENYLATION OF ALPHA-PHOSPHORYL SULFOXIDES AND A GENERAL-SYNTHESIS OF OPTICALLY-ACTIVE KETENE DITHIOACETAL MONO-S-OXIDES

Sulfenylation and selenenylation of alpha-phosphoryl sulfoxides 1 with S-methyl methanethiosulfonate and phenylselenenyl bromide, respective ly, affording alpha-methylsulfenyl-and alpha-phenylselenenyl-alpha-pho sphoryl sulfoxides 8 and 9 are described. Sulfenylation of (+)-(S)-dim ethoxyphosphorylmethyl p-tolyl sulfoxide 2 gave a mixture of optically active diastereoisomers of the sulfoxide 8a which is a key substrate in the Horner-Wittig synthesis of enantiomeric ketene dithioacetal mon o-S-oxides 10. The E/Z ratio of geometrical isomers of 10 was determin ed and briefly discussed. The crystal and molecular structure of 1-p-t olylsulfinyl-1-methylsulfenyl-2-phenyl-ethene 10a is reported. (C) 199 7 Elsevier Science Ltd.