A NEW STEREOSELECTIVE SYNTHESIS OF PHOSPHIRANES

The synthesis of phosphiranes from primary phosphines and diol ditosyl ates was found to be stereoselective, and chiral phosphiranes were pre pared from optically pure diols. The four optical isomers df 1-mesityl -2,3-dimethylphosphirane, (2S,3S)-(+)-3, (2R,3R)-(-)-4, anti-cis-(meso )-5, and syn-cis-(meso)-6, were all synthesized from mesitylphosphine and the corresponding diol ditosylates. Compound 6 was unstable, but c ompounds 3, 4, and 5 were all isolated in pure form. Their structure a ssignments were based on the NMR coupling constants J(P-H) and J(P-C) The phosphiranes were transformed into tungsten pentacarbonyl complexe s. Tungsten tetracarbonyl-triphenylphosphine complexes (22, 23, 24) of compounds 3, 4, and 5 were synthesized in high yields by the reaction of the phosphiranes and W(CO)(4)(PPh(3))(THF). The absolute stereoche mistry of the phosphiranes 3, 4, and 5 was determined by X-ray crystal structure analysis of compounds 22, 23, and 24. Stereochemical effect s on NMR coupling constants and mass spectra of the phosphiranes are d iscussed.