Formerly unknown phosphazides with N-trifluoroacetamido groups at the phosphorus atom were obtained by the imination of N-(diphenylphosphino)-N-phenyltrifluoroacetamide with aryl azides. Stability of the phosphazides was found to depend on the nature of the radical at the amide nitrogen atom. The phosphazides were shown to readily eliminate nitrogen to yield phosphinimines that undergo the aza-Wittig thermal rearrangement into N-phosphorylated trifluoroacetamidines.A few examples of stable phosphazides obtained by imination of P(III) derivatives with organic azides are known [1]. The structure of some of them have been proved by X-ray diffraction [2]. N-Arylphosphazides are stabilized by bulky and electron-acceptor substituents in the azide phenyl ring, as well as bulky and preferentially donor substituents on phosphorus. Thus, the phosphazide obtained from picryl azide and trimorpholino phosphite is so stable that it could not be converted into corresponding phosphazo compounds [3].Proceeding with our research [4,5] into the properties of N3P III -phosphorylated trihaloacetamides and aiming at preparing formerly unknown types of phosphazides, we turned to reactions of N-methyl-and N-phenyl-N-phosphinotrifluoroacetamides with aryl azides.
ÄÄÄÄÄÄÄÄÄÄÄÄIt was found that amidophosphines I slowly react with azides II to give formerly unknown phosphazides III that have substituted N-trifluoroacetamido groups on phosphorus. Compounds IIIa and IIIb are the only phosphazides we could isolate individual as yellowish amorphous materials. In the absence of solvents, they can be stored for 7310 days. Compounds IIIc and IIId converted into corresponding phosphinimides, gradually during reaction and fast on heating. Phosphazides IIIa and IIIb eliminated nitrogen on heating to 40350oC.Comparison of the properties of N-aryltriphenyl phosphazides [6] and our prepared compounds shows that replacement of even one phenyl group on phosphorus by the fairly bulky N-phenyl-N-trifluoroacetamide group renders phosphazides much more stable.Ic IIa!IIc IIIa!IIId IVa!IVd Va!Vd I, R = X = Ph (a); R = Me, X = Ph (b), OEt (c). II, R< = Ph (a), p-FC 6 H 4 (b), p-NO 2 C 6 H 4 (c). III, R = X = Ph, R< = Ph (a), p-FC 6 H 4 (b); R = Me, R< = p-NO 2 C 6 H 4 , X = Ph (c), OEt (d). IV, R = Ph, R< = X = Ph (a), R< = p-FC 6 H 4 , X = Ph (b); R = Me, R< = p-NO 2 C 6 H 4 , X = Ph (c), OEt (d). V, R = X = Ph, R< = Ph (a), p-FC 6 H 4 (b); R = Me, R< = p-NO 2 C 6 H 4 , X = Ph (c), OEt (d).
ÄÄÄÄÄÄÄÄÄÄÄÄPhosphinimines IV undergo the aza-Wittig rearrangement, partially during their synthesis and completely under reflux in toluene or xylene, to form N-phosphorylated trifluoroacetamidines V (see [4]). This conversion suggests that the electron-acceptor iminophosphoryl and trifluoromethyl groups strongly favor polarization of the carbonyl group.
EXPERIMENTALThe IR spectra were obtained on a UR-20 spec-
