Phosphonyl halides

Pentavalent phosphorus derivatives can be converted to phosphonyl halides or phosphine oxides by partial hydrolysis or by other oxygen donors. 

Specialty-chemical level production (kilograms) of phosphines is achieved by hydride reductions of halophosphines, phosphonyl halides and esters and phosphinyl halides and esters, e.g. ... 

The rate of hydrolysis of isopropyl methylphosphonofluoridate (sarin) in sea water has been measured. In solvents of low polarity the rate of solvolysis of phosphinyl and phosphonyl halides is catalysed by hydrogen chloride, the catalytic effect decreasing along the series as shown ... 

The Arbuzov rearrangement has been widely used for the synthesis of a variety of phosphorus related compounds, including phosphonates, phosphinates, tertiary phosphine oxides,phosphonyl, and phosphonyl halides. Some of these products can be used for the Wittig Reactions, such as in the synthesis of carotene. " ... 

Phosphonic (phosphonyl) halides and phosphinic (phosphinyl) halides (6.177) may be obtained from the corresponding phosphonic and phosphinic acids by the action of PCI5 or SOCI2. 

Phosphonyl halides may be obtained from the phosphonous halide by oxidation with sulphuryl chloride, nitrogen dioxide or oxygen (6.184). With some compounds direct oxidation of a solution may be effected with blown air (6.185). 

Phosphonyl halides react with SF4 or SbF3 to give tetrafluorophosphoranes (6.506), and phosphorus pentasulphide converts them into the corresponding thiohalides (9.426). Phosphonyl halides form cyelic boron-phosphorus compounds with sodium borohydride (9.35) and phosphonic diamides with amines (7.158). 

The hydrolysis of phosphonic dihaUdes with warm water (6.190) leads to phosphonic acids and aqueous alkali gives the salts. If the phosphonyl halides are reacted with alcohols in the presence of abase such as pyridine, the corresponding phosphonic esters can be obtained. 

Selenium dioxide,a triethylamine-sulphur dioxide complex, diphosphorus tetraiodide, and various phosphonyl halides and imidazoles have been recommended for dehydrating aldoximes to form nitriles. 

Phosphonoformic acid (85) decarboxylated in acid solution, and it was proposed that the uncatalysed reaction involved a simple decarboxylation of the zwitterion. The acid-catalysed reaction showed some kinetic similarity to that of mesitoic acid and an elimination of carbon dioxide as trihydroxymethylcarbonium ion was preferred. Participation of the trans vicinal phosphonyl group in the solvolysis of the halides (86) and (87) has been deduced from rate measurements. In the norbornene derivatives, the relative rates of loss of chloride from (87a) and (87b) were 5 x 10 1. 

Epoxide Aziridine Phosphoryl/phosphonyl/ phosphinyl halide Azo... 

Synthetic Methods.— Direct routes to phosphonic acid derivatives from olefins and phosphorus halides continue to be explored. In the presence of oxygen, phosphorus tribromide reacts with olefins by a radical mechanism in a manner analogous to the corresponding chloride, giving 2-bromoalkyl-l-phosphonyl dibromides. The reaction of phosphorus trichloride and per-chloryl fluoride with hex-1-ene gives moderate yields of (55), the direction of... 

Studies of Equilibria, Shift Reagents, and Solvent Effects.—Several studies of halogen-exchange equilibria have been reported, e.g. the exchange between phosphoryl, phosphonyl, and phosphinyl halides, P and P halides (27)... 

The steroidal a-(isocyanomethyl)phosphonates (130) and (133) have been synthesized by methylation of the carbanions (129) and (132), respectively.66 Compounds (130) and (133) behave as N,P-ketals in that they can be hydrolysed to the corresponding ketones (131) and (134) (Scheme 10). A range of a-substituted a-aminophosphonic acids (136) have been prepared in moderate to excellent yield by the alkylation of the protected a-aminophosphonate (135) with alkyl and aryl halides and Michael acceptors under phase transfer catalysis (Scheme 11).67 The reactions of the lithium carbanion of diethyl prop-2-enyIphosphonate (137) with a,P-unsaturated ketones and esters have been investigated.6S Attack can be at the a- or y-positions in the phosphonate although in all cases Michael addition to the a, p-unsaturated carbonyl is preferred to attack at carbonyl carbon. In some examples simple adducts (138) are formed, but in more complex cases addition is followed by cyclisation to give (139) (Scheme 12). The bisphosphonate (141), which is a potent inhibitor of myo-inositol monophosphatase, has been prepared with the phosphonylation of the carbanion of (140) as a key step.6 9... 

Among the other developed approaches to novel P-ylides, the synthesis of a-sulfanyl-a-phosphonyl phosphonium ylides (58) in quantitative yields via the addition of two equivalents of trialkylphosphites to phosphonodithio-formates should be mentioned. The subsequent reaction of these ylides with alkyl or benzyl halides gives stabilized sulfonium ylides (59) while their heating (18-150 h, 110 °C) leads to a-sulfanyl methylene bis-phosphonates through protonation-dealkylation intramolecular reactions. The synthesis... 

An important preparative method is the reaction of alkylmagnesium halides with phosphoryl, phosphonyl or phosphinyl halides (6.112-6.114). 

Phosphonyl and phosphinyl halides may be obtained from halophosphoranes by limited hydrolysis (6.187, 6.188), by bubbling sulphur dioxide through a solution or suspension in an inert solvent (6.189), or by reaction with a carboxylic acid (6.190). 

The addition of phosphorus pentachloride to alkenes and alkynes yields complexes of the type RPClj PClg, which, when treated with sulphur dioxide, will give phosphonyl chlorides (6.197). Hydrolysis of the aluminium trichloride complexes (6.151) and (6.152) will also give phosphonyl or phosphinyl halides (6.198). 

The lower molecular weight phosphonyl and phosphinyl halides are colourless liquids which fume in air. They hydrolyse easily to phosphonic and phosphinic acids, and react with alcohols to give the corresponding esters (6.199, 6.200). Their reactivity decreases as the size of the group R is increased. 

M. Fild and R. Schmutzler, Phosphonyl and phosphinyl halides, J.I.G. Cadogan, Organophosphorus Reagents in Organic Synthesis, Vol. 4, Academic Press, London, 1979. 

Phosphonyl radicals can be generated by photolysis or radical abstraction from secondary phosphine oxides, alkyl phosphinates or dialkyl phosphonates. They can be obtained from tertiary butoxy radicals and dialkyl phosphites or tetra alkyl diphosphites (13.175) and (13.176). Phosphonyl radicals react with alkyl halides according to (13.177). 

Et0)2P=0 radicals, obtained from t-BuO and (Et0)2P(H)=0, abstract halogen from alkyl halides, with competition studies being used to establish relative rates. Absolute second-order rate constants for reaction with butyl halides are 10 times slower for the phosphonyl radical compared with Et3Si. Phosphinyl-radical intermediates are implicated from ESR and P cidnp experiments when ketoximato-phosphorus(III) intermediates (formed from ketoximes and X2PCI at low temperatures) rearrange... 

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