Organo-Phosphorus-Sulfur Heterocycles By Reactions of Phenylphosphines with Ketones

The reaction of phenylphosphine (PhPH2) with ketones showed conversion into a 5-membered heterocyclic ring of the type P2SOC if 2–2.5 equivalents of sulfur (S8) were used. X-Ray data and 31P, 13C, 1H NMR spectra proved the formation of the (Z) diastereomer of 1,3,2,4-oxathiadiphospholane 1 ((PhPS)2SOCMe2) if acetone is used. Mechanistic studies displayed that small changes in the reaction pathway lead toward the formation and characterization of intermediates including 1,3,2,4,5-dithiatriphospholane, 2,4,5-triphenyl-2-sulfide (PhP)3S3 and 1,3,2,4-oxathiadiphospholane, and 5,5-dimethyl-2,4-diphenyl-2-sulfide ((PhPS)(PhP)SOCMe2), which undergo reactions with acetone, subsequently yielding the abovementioned heterocyclic ring.