Trialkyl phosphites reactions

It has beem suggested that the mechanism is probably the same as that of the trialkyl phosphite reaction, i.e., chlorination of phosphorus to a chlorophospho-nium species foUowed by alcoholysis and dealkylation. Whether PCI3 or trialkal-phosphites are actually present as discrete entities during the reaction is not... 

In the absence of a tertiary amine, the initial reaction is again the formatfon of a trialkyl phosphite and hydrogen chloride. The latter now reacts rapidly with the trialkyl phosphite to give the alkyl chloride and the dialkyl hydrogen... 

Triethyl phosphite is a colourless mobile liquid, insoluble in water. Trialkyl phosphites are valuable intermediates in the preparation of many organophosphorus compounds they readily form dialkyl esters of alkylphosphonic acids by the Arbusov reaction (p. 311). 

When an alkyl halide is heated with a trialkyl phosphite, an ester of a phos-phonic acid is produced. This is known as the Arbusov Reaction ... 

If R = R, the reaction appears to be catalytic as a small quantity of R Cl will suffice to convert a considerable quantity of the trialkyl phosphite into the dialkyl alkylphosphonate (I). As little as o-i mol. of the alkyl iodide will suffice to isomerise the trialkyl phosphite. 

The reaction proceeds through an intermediate phosphonium salt which can be isolated in some instances. The Michaehs-Arbusov reaction is especially useful for converting trialkyl phosphites, (RO) P, to alkylphosphonic esters, and to esters of phosphonocarboxyhc acids. 

Monoesters of the phosphonic acids are Httle used in industry. The diesters, 0=PR(0R)2, of phosphonic acid are commonly prepared in industry from trialkyl phosphites in a MichaeUs-Arbusov reaction ... 

Formation of esters of inorganic acids (Section 15.9) Alkyl nitrates, dialkyl sulfates, trialkyl phosphites, and trialkyl phosphates are examples of alkyl esters of inorganic acids. In some cases, these compounds are prepared by the direct reaction of an alcohol and the inorganic acid. 

Trimethyl phosphite P(OMe)3 spontaneously iso-merizes to methyl dimethylphosphonate MePO-(OMe)2, whereas other trialkyl phosphites undergo the Michaelis-Arbusov reaction with alkyl halides via a phosphonium intermediate ... 

Curious products isolated by Bailey and Evans from the reaction of benzotrisfuroxan with triphenyl phosphine have been examined by X-ray crystallography by Cameron and Prout. The structures (44-46) were determined.A molecular complex of trialkyl phosphate with benzotrisfurazan is formed using a trialkyl phosphite as reducing agent. 

The Arbusov reaction is one of the best known methods for creating a carbon-phosphorus bond. In its simplest form (Michaelis-Arbusov) an alkyl halide reacts with a trialkyl phosphite to an alkanephosphonic acid diester as shown in Eq. (29) ... 

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

Sulfonic esters are most frequently prepared by treatment of the corresponding halides with alcohols in the presence of a base. The method is much used for the conversion of alcohols to tosylates, brosylates, and similar sulfonic esters. Both R and R may be alkyl or aryl. The base is often pyridine, which functions as a nucleophilic catalyst, as in the similar alcoholysis of carboxylic acyl halides (10-21). Primary alcohols react the most rapidly, and it is often possible to sulfonate selectively a primary OH group in a molecule that also contains secondary or tertiary OH groups. The reaction with sulfonamides has been much less frequently used and is limited to N,N-disubstituted sulfonamides that is, R" may not be hydrogen. However, within these limits it is a useful reaction. The nucleophile in this case is actually R 0 . However, R" may be hydrogen (as well as alkyl) if the nucleophile is a phenol, so that the product is RS020Ar. Acidic catalysts are used in this case. Sulfonic acids have been converted directly to sulfonates by treatment with triethyl or trimethyl orthoformate HC(OR)3, without catalyst or solvent and with a trialkyl phosphite P(OR)3. ... 

Similar reactions between diketopiperazine and either trialkyl phosphites or alkyl phosphinates produced the related cyclic analogs 17 and 18 (24). 

Aliphatic trialkyl phosphites also reacted with HHT 25 under neat conditions and elevated temperatures (>100 °C) to produce glyphosate triesters such as 26 (27). However, the reaction proceeded at much lower temperatures (10 °C) when titanium tetrachloride was present in equimolar amounts (33). 

An interesting variation of this reaction that made use of a three-component, one-pot solventless procedure with the corresponding trialkyl phosphites gave dramatically improved yields of many heterosubstituted glyphosate phosphonate diesters (37). When exactly one equivalent of water, 25, and tris-p-chloroethyl phosphite were mixed and heated under neat conditions for a few hours, nearly quantitative yields of displaced p-chloroethanol and the desired triester product 27 were obtained. If desired, the displaced alcohol was first removed by vacuum distillation, or the mixture could be hydrolyzed directly to GLYH3. Various oxygen, sulfur, nitrogen, cyano, and carboxylate functionalities were similarly accommodated in the trialkyl phosphite. 

This classical C-P bond-forming reaction (51) has seen limited application in the glyphosate arena, presumably for lack of suitable substrates that can tolerate the vigorous reaction conditions. Typically, C-P bond formation occurs when an alkyl halide reacts with excess neat trialkyl phosphite at temperatures exceeding 100 °C, near the boiling point of the phosphite. An Arbuzov-based strategy for glyphosate requires the synthesis of the... 

B. l,3>2>Dioxaphospholens.—The kinetics of the addition of trialkyl phosphites to benzil have been investigated spectrophotometrically. The second-order reaction of trimethyl phosphite in dioxan has activation parameters of A// = 8.4 kcal mol and AS = — 47.5 e.u. In benzene the rate constant increases linearly with low concentrations of added organic acid and decreases linearly with low concentrations of added base. The Diels-Alder mechanism is considered unlikely on the basis of these data, and the slow step is considered to be nucleophilic addition of the phosphite to the carbon of the carbonyl group (see Scheme). 

D. Miscellaneous.—Low yields of the spirophosphoranes (34) were obtained on heating the phosphorane (32) with the aziridines (33). Stable phosphoranes have been obtained from phenanthraquinone mono-imine (35) and trialkyl phosphites, and from 2-chlorotropone (36) and ylides. In the latter reaction cyanomethylenetriphenylphosphorane gave instead the betaine (37). 

A detailed kinetic study of the reaction of trialkyl phosphites (44) with benzil has been carried out (see Chapter 2 for the reactions of a-diketones with trialkyl phosphites). The reaction is first-order in both phosphite and benzil and the rate constant increases with the dielectric constant of the solvent. The authors propose initial attack of phosphite at carbonyl carbon (45), in opposition to the original suggestion by Ramirez, who proposed initial attack at carbonyl oxygen. 

The reaction of dialkyl and trialkyl phosphites with / -quinonedisul-phonimides (65) has evoked considerable interest. Levy and Sprecher isolated the nitrogen phosphorylated product (66) in 80% yield from a reaction with dialkyl phosphite, although other workers claim that attack is at carbon to give (67). 

A useful new method of preparing arylphosphonates (123) involves the reaction of trialkyl phosphites with aryl halides in the presence of a nickel catalyst.The suggested mechanism is via the nickel complex (124), and is non-radical. 

Perkov reaction of a trialkyl phosphite with a-chlorothioacetone leads to the 5-phosphorylated enol derivative (7). Not unexpectedly, the phospho-nate ester (8) is formed as a by-product, and in view of studies on the Perkov... 

The formation and reaction of peroxyl radicals derived by reaction of tervalent phosphorus compounds with oxygen have attracted interest. Photolysis of trialkyl phosphites in oxygenated solutions of aromatic hydrocarbons gives phenols. " Phosphorus trichloride reacts with 1,2-dichloroethylene, in the presence of oxygen, to give (17). It is tempting to suggest that both reactions occur via similar intermediates, e.g. (15) and (16). 

The kinetics of the reaction of trialkyl phosphites, dialkyl aryl-phosphonites, alkyl diarylphosphinites, and triarylphosphines with Sg has been studied the effects of structural changes on the rate (Ph2POR > PhP(OR>2 > P(OR)g > Ph P) and on the Hammett p values are interpreted with respect to the mechanism. A general method to displace mercapto groups from carbon with clean inversion includes... 

The presence of trialkyl phosphite 198 in the above mentioned reduction of the gem-dibromocyclopropanes 150 with dialkyl phosphonate and triethylamine alters the reaction course. Dialkyl cyclopropanephosphonates 199 are produced via reductive phosphonation [104]. Trialkyl phosphite participates in the carbon-phosphorous bond formation. It is supported by the exclusive formation of diisopropyl cyclopropylphosphonate in the phosphonation reaction with diethyl phosphonate and triisopropyl phosphite. (Scheme 74)... 

As in the case of phosphorus trihalides, the phosphorus atom in trialkyl phosphites will undergo addition reactions in which oxygen, sulfur, or selenium is added. The latter two react as elements, but a suitable source of oxygen is hydrogen peroxide. 

Baker has also reported the reaction of butadiene with phenylhydra-zones leading to azoalkenes (example 14, Table IV). This is also a Grig-nard-type reaction which is catalytic. Analogous results were obtained with methylhydrazones (136). A wider scope was recently attained by causing allylic esters to react with phenylhydrazones in the presence of zero-valent nickel complexes having trialkyl phosphites (example 15, Table IV). 

Trialkyl phosphites were found to be more reactive to hydroperoxide than aryl phosphites the activation energy depends on a particular phosphite and ranges from 25 to 77 kJ mol-1. At the same time, the reaction depends weakly on the type of hydroperoxide, which can be seen from the comparison of rate constants for the reactions of two hydroperoxides (solvent was PhCl, T=303K [12]). 

Of these reactions, the reaction of the peroxyl radical with phosphite is the slowest. The rate constant of this reaction ranges from 102 to 103 L mol 1 s 1 which is two to three orders of magnitude lower than the rate constant of similar reactions with phenols and aromatic amines. Namely, this reaction limits chain propagation in the oxidation of phosphites. Therefore, the chain oxidation of trialkyl phosphites involves chain propagation reactions with the participation of both peroxyl and phosphoranylperoxyl radicals ... 

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