Phosphinic azides

A study of the kinetics and products of the thermolysis of a series of diaryl-phosphinic azides has been reported.119 Diethyl 1-diazomethylphosphonates undergo an aldol-type reaction with aldehydes to give l-diazo-2-hydroxyalkylphosphonates (152).120 Acidification of the diazophosphonates (153) possessing a chiral phosphorus centre yields mixtures of diastereoisomers (154) and epimers at C. For given R1 and R2, the reaction becomes increasingly stereoselective for X= OAc < Cl < OTs. It may be argued that protonation of (153) will yield a mixture of diastereoisomeric di-... 

Diphenyl phosphorszldate can be replaced with diethyl phosphorazidate in the above procedure. Use of other azides such as p-toluenesulfonyl azide, p-methoxybenzyloxycarbonyl azide, diphenylphosphinic azide, or diphenylthio-phosphinic azide is less satisfactory. No reaction occurs when trimethylsilyl azide, dimethylthiophosphinic azide, or alkaline azides are used, while decomposition of formed trimethylsilyldiazomethane seems to occur when... 

Nguyen Minh, T., Fitzpatrick, N. J. Intermediacy of nitrene in the Curtius-type rearrangement of phosphinic azides. Insights from ab initio study of the H2P( 0)N. dbiharw. HP( 0) NH interconversion. Polyhedron 1988, 7, 223-227. 

Harger, M. J. P., Westlake, S. Photolysis of some unsymmetrical phosphinic azides in methanol. Relative migratory aptitudes of alkyl groups and phenyl in the Curtius-like rearrangement. Tetrahedron 1982, 38, 3073-3078. 

Denmark, S. E., Dorow, R. L. The stereochemical course of migration from phosphorus to nitrogen in the photo-Curtius rearrangement of phosphinic azides (Harger reaction). J. Org. Chern. 1989, 54, 5-6. 

Finally, elimination of nitrogen from phosphinous azides leads to the formation of cy clophosphazenes ... 

As mentioned above, the decomposition of phosphinous azides may yield monomers that trimerize or tetramerize. 

Phosphinic azides (phosphinoazides) (7.223a) and dialkylamino azides can be prepared by treating the appropriate phosphorus-halogen compound with lithium or sodium azide in an anhydrous solvent such as pyridine or acetonitrile. 

The phosphorodiazide ion (7.223d), R = H, is obtained on hydrolysis of the azidophosphoride anion PCNj), (4.185). Although these anions, and phosphonitrilic azide (7.228) below, are violently explosive, the phosphinous azide (CF3)2PN3 (12.233), the diphenyl derivative (7.228a) and the simple azide P(N3)3 (4.182) appear to be relatively stable as does the trifluoromethyl derivative (7.228b). Decomposition of azides leads to diphosphazanes and various other products [41,42] (below). 

Alkoxytriaminophosphonium salts Phosphinic azides Phosphoric acid triamides... 

Matyjaszewski, K., Franz, U., Montague, R.A., White, M.L. (1994) Synthesis of poly-phosphazenes from phosphoranimines and phosphine azides. Polymer, 35(23), 5005-5011. 

A variety of nucleophiles can be used in the substitution reactions, including halides, alkoxides, amines, phosphines, azides, cyanide, acetylides, and enolate anions. 

Most 8 2 reactions are faster in aprotic solvents and slower in protic solvents. Water tends to promote ionization. In pro-tic media, particularly aqueous media, ionization of tertiary halides occurs to give a carbocation intermediate (more slowly with secondary halides) 9,10,11,12,49, 55,69, 70, 77,86. Carbocation intermediates can be trapped by nucleophiles in what is known at an 8 1 reaction. An 8 1 reaction proceeds by ionization to a planar carbocation containing an sp hybridized carbon, follows first-order kinetics, and proceeds with racem-ization of a chiral center. Carbocations are subject to rearrangement to a more stable cation via 1,2 hydrogen or alkyl shifts 24, 25, 26, 27, 29, 50, 65, 67, 76, 77, 78, 79, 80, 81, 83, 84, 85,87,88, 89. A variety of nucleophiles can be used in the substitution reactions, including halides, alkoxides, amines, phosphines, azides, cyanide, acetylides, and enolate anions 2,3,13,14,36,62,63,88, 89,105. 

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