Reactions of Phosphorus under Oxidizing Conditions

The combustion of white phosphorus felt or red phosphorus butyl rubber will produce smoke. Smoke is an aerosol comprised of oxides of phosphorus (phosphorus pentoxide and phosphorus trioxide), some of their transformation products (see Section 3.2), and a small amount of unburnt phosphorus. The aerosol components in the smoke will undergo dispersion and chemical transformation in air to form acids or phosphorus, and will ultimately deposit from air to the hydrosphere and the lithosphere. The main components of the aerosol deposited over water and soil are acids of phosphorus. Under oxidizing conditions in soil and water, phosphorus acids will be transformed to phosphate or polyphosphates. Under reducing conditions, the disproportionation reaction of phosphorus acid can produce phosphine, and the gas may be released to the atmosphere. The fate of deposited unbumt phosphorus in water and soil has already been discussed in the preceding paragraph. 

D. Miscellaneous.—A further study of the reactions of diphenyl-phosphine oxide with tetracyclone has confirmed that the reaction yields the oxide (30) under mild, basic conditions, and that the reaction is thermally reversible. The displacement of halogen from phosphorus by amino-compounds has been used in the synthesis of a number of aminofluoro-phosphine oxides (31), and of A-methyl-AA-bis(dichlorophosphinyl)-amine (32). ... 

The dipolar character of phosphorus ylides is shown by their reactions with nucleophiles (e.g. aldehydes and ketones) or with electrophiles (e.g. proton donors). Ylides Ph3P=CHR (R = alkyl) are readily hydrolysed, even by cold water, so it is usual to carry out reactions involving them under anhydrous conditions. An inert atmosphere (usually nitrogen) is also necessary as oxidation... 

Intramolecular N-H bond cleavage of ammonia, allqrlamines and aty-lamines by oxidative addition to tricoordinate phosphorus compounds (a -P) (5) leading to pentacoordinated adducts have been reported by Radosevich et al. These reactions proceeded smoothly under mild conditions in homogenous solution giving rise to structurally robust phos-phorane adducts (6) as depicted in Scheme 2. 

A Michael-type addition reaction of phosphine generated from red phosphorus in concentrated aqueous KOH solution has been noted to provide moderate isolable yields of pure organophosphorus products.27 For example, tris-(2-cyanoethyl)phosphine is produced in 45% isolable yield from acrylonitrile, and tris-(2-[y-pyridyl]ethyl) phosphine oxide is isolated in 40% yield from 4-vinylpyridine under these conditions. Excellent yields of the tertiary phosphine oxide, tris-(2-cyanoethyl)phosphine oxide, have been reported using white phosphorus in absolute ethanol with KOH at ice/salt-bath temperatures.28 A variety of solvent systems were examined for this reaction involving a Michael-type addition to acrylonitrile. Similarly, tris-(Z-styryl)phosphine is produced from phenylacetylene under these conditions in 55% isolated yield. It is noteworthy that this last cited reaction involves stereospecific syn- addition of the phosphine to the alkyne. 

Overend, Montgomery and Wiggins60 noted an interesting reaction between isomannide and phosphorus tribromide. None of the expected 2,5-dibromo-2,5-didesoxy-l,4 3,6-dianhydro-D-mannitol (LIX) was isolated instead, ring scission took place and l,6-dibromo-l,6-didesoxy-D-mannitol (LX) was formed. Since no such ring scission occurs with hydrobromic acid under similar conditions it was probable that the phosphorus tribromide itself had effected the ring breakdown by direct attack on the oxide rings. 

The second class of benzo-fused heterocycles accessible from benzofuroxans are benzimidazole oxides. In this case only one carbon from the co-reactant is incorporated in the product. With primary nitroalkanes 2-substituted l-hydroxybenzimidazole-3-oxides (46) are formed via displacement of nitrite, and / -sulfones behave similarly. The nitrile group of a-cyanoacetamides is likewise eliminated to alford 2-amide derivatives (46 R = CONRjX and the corresponding esters are formed in addition to the expected quinoxaline dioxides from acetoacetate esters. Under similar conditions secondary nitroalkyl compounds afford 2,2-disubstituted 2//-benzimidazole-1,3-dioxides (47). Benzimidazoles can also result from reaction of benzofuroxans with phosphorus ylides <86T3631>, nitrones (85H(23)1625>, and diazo compounds <75TL3577>. 

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