A New Stereoselective Synthesis of Phosphiranes

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Abstract
The synthesis of phosphiranes from primary phosphines and diol ditosylates was found to be stereoselective, and chiral phosphiranes were prepared from optically pure diols. The four optical isomers of 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 compounds 3, 4, and 5 were all isolated in pure form. Their structure assignments were based on the NMR coupling constants JP-H and JP-C. The phosphiranes were transformed into tungsten pentacarbonyl complexes. 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(PPh3)(THF). The absolute stereochemistry of the phosphiranes 3, 4, and 5 was determined by X-ray crystal structure analysis of compounds 22, 23, and 24. Stereochemical effects on NMR coupling constants and mass spectra of the phosphiranes are discussed.