The reactivity of diphenylvinylphosphinetowardsnitrones is dominated by the dipolarophilic nature of its double bond rather than by the ability of the PIII to act as an oxygen acceptor.
Direct synthesis of isoxazolidinylphosphines by cycloaddition of nitrones to diphenylphosphinoethenes and x-ray structure of 7,7-dimethyl-1-oxo-1-phenyl-3-diphenylphosphinyl-hexahydro-1H-pyrrolo [1,2-c] [1,3,2] oxazaphosphorine
The 1,3-dipolar cycloaddition reaction of N-alkyl nitrones with diphenylvinylphosphines affords directly isoxazolidinylphosphines in satisfactory yields and in regio- and stereoselective manner. The parent diphenylvinylphosphine was found to favor the formation of 5-phosphinoisoxazolidines whereas diphenylpropenylphosphine gave instead the 4-phosphinoisoxazolidine regioisomer. However, in reactions utilizing an alkylarylvinylphosphine and/or N-arylnitrone, oxidation of the phosphine by the nitrone reagent was found to precede the cycloaddition. An attempted conversion of the bicyclic isoxazolidine derived from 2,2-dimethyl-dihydro-2H-pyrrole 1-oxide and diphenylvinylphosphine to the perhydropyrrolo[1,2-c] [1,3,2]oxaza-phosphorine ring system was accomplished through the use of the corresponding phosphine oxide derivative and provided a single diastereoisomer of the desired pyrrolooxazaphosphorinane characterized ultimately in the form of its dioxide hydrate by the X-ray diffraction technique.