Monoalkyl phosphites

Aminotrimethanephosphonic acid is formed from formamide, acetamide, urea, or alkanenitriles with phosphorous acid [296]. By reaction of monoalkyl phosphite or P406 with glacial acetic acid or the corresponding anhydride ethane-1 -hydroxy-1,1-diphosphonic acid is formed after hydrolysis [297,298]. P406 can be obtained from P4 and 02 in a high yield of 85-90% [299]. 

Partial hydrolysis reactions lead to a monoalkyl phosphite, but complete hydrolysis gives phosphorous acid. The hydrogen atom bound to phosphorus can also be replaced by reaction with sodium, showing that the hydrogen atom has slight acidity. 

They can also be hydrolyzed to give either a monoalkyl phosphite or free H3P03. A salt that serves as a reactive intermediate is formed by reaction with sodium ... 

Oxidation of hypophosphorous acid with carbon tetrachloride and triethylamine at 90 °C in the presence of an alcohol gives dialkyl phosphates (Scheme 2). Monoalkyl phosphites can be converted into... 

Monoalkyl phosphites can be conveniently prepared by alkaline hydrolysis of dialkyl phosphites, followed by acidification of the product. 

Dialkyl phosphite Dithiocarbamic acid esters and monoalkyl phosphites from dialkyl phosphites... 

Mixed dialkyl phosphites from monoalkyl phosphites... 

A-Alkyl-2,1,3-benzoselenadiazolium salts react with sodium hydroxide with elimination of selenium to give A-monoalkyl-o-phenylenediamines <89SC1381>. The thiaselenazolines (38a) and the diselenazolines (38b) are attacked by trialkyl phosphites at Se with elimination of selenophosphate and incorporation of phosphorus into the ring (87) in place of selenium (Equation (8)) <80CB2699>. 

The use of NiCl2 catalysts in the rearrangement of allylic phosphites (and related compounds) to allylic phosphonic (or phosphinic) acids has already been reported (Organophosphorus Chemistry, 1988, 1, 144), and the same authors have now described the use of Ni(cyclooctadiene) catalysts in the presence of bistrimethylsilylacetamide in the reactions between allylic esters,or carbonates, and dialkyl phosphites, monoalkyl alkylphosphonates,or monoalkyl... 

Arbuzov reaction of mixed phosphites such as ethyl bis (trialkylsilyl) phosphite may lead conveniently to monoalkyl acylphosphonates, since in such reactions one of the trialkylsilyl groups is lost preferentially, leading to an ethyl trialkylsilyl acylphosphonate, which can be alcoholysed rapidly. 

Treatment of bromomethyl acetate with the sodium salt of a dialkyl phosphite, followed by deacetylation with methoxide affords the corresponding dialkyl hydroxymethanephosphonate. If this is tosylated with tosyl chloride, and the product treated with nucleosides [protected at the 3 -(and 2 -, if present) hydroxy groups] and sodium hydride in DMF, the monoalkyl ester of a 5 -0-phosphonyl-methyl nucleoside (60) is obtained after deblocking the sugar, and subsequent dealkylation with TMS-iodide affords (61). Like alkyl esters of 5 -mononucleotides, (60) is resistant to acid and alkaline hydrolysis, while (61) is stable in acidic and alkaline media, and is also resistant to hydrolysis by alkaline phosphomono-esterase and snake venom 5 -nucleotidase. Treatment of (61) with DCC and morpholine, and subsequently with orthophosphate or pyrophosphate, affords (62) and (63), respectively. Alkaline phosphomonoesterase from E. co/i hydrolyses the pyrophosphate links in (62) and (63) to give (61) and orthophosphate. The UTP and CTP analogues (63 B = U or C) are inhibitors of uridine kinase from... 

In the NMR spectrum of the methylammonium salt of the monomethyl ester of H-phosphonic add, the phosphorus signal appears at 4.55 ppm as a doublet of quartets with V(P,H) = 600 Hz indicating phosphonate structure. Kers et al. [23] confirm that in the reaction mixture of diethyl H-phosphonate and pyridine or pyridine with 2 equiv. of tertiary base (TEA), there were no signals that could be assigned to Iriethyl phosphite. The results obtained show that the basic activation in these reactions involves at the first step formation of the monoalkyl H-phosphonate anion [(R0)P(0)(H)0] , which further plays the key role in interactions where the phosphorus atom acts as a nucleophile. 

Within this reaction cycle, dialkyl H-phosphonate and carbon tetrachloride react to form dialkyl chlorophosphate and chloroform as the final products of the Atherton-Todd reaction. A simple equilibrium shift (without salt formation) toward the dialkyl phosphite tautomer in step 1 [82] or formation of pentacoordinated phosphorane intermediates in step 2 [84,85] has also been discussed. It has been shown that the rate of this reaction depends on the strength of the applied base [86]. Amines are the most commonly used bases under Atherton-Todd conditions [80-85]. The validity of the deprotonation step in the above mechanism in the case of the base being an amine is, however, questionable, since it has been established that amines are alkylated and not protonated at the nitrogen by dialkyl phosphonates. It has been shown, however, [87] that in the case of basic activation with amines, which are the most commonly used bases, the phosphite intermediates are formed according to a different and more complex pathway (see Section 3.8.1). This pathway includes alkylation of the amine and formation of a monoalkyl H-phosphonate salt. 

In this new scheme, the initial step is the reaction of the amine with dialkyl H-phosphonate to form the corresponding monoalkyl phosphonium salt. The subsequent three steps form the catalytic cycle that leads to product formation. The anion of the monoalkyl H-phosphonate, acting as a base, first deprotonates the dialkyl H-phosphonate to generate the reactive diaUcyl phosphite anion. In the subsequent step, which is the same as in the originally proposed mechanism of that reaction, dialkyl chlorophosphate is formed along... 

The nitrogen atom of amines attacks the a-carbon atom of the alkoxy group of dialkyl H-phosphonates to give the corresponding alkylanunonium salts of the monoalkyl ester of phosphonic acid. These results are in contrast to the oflen-expressed opinion—especially in the cases of amine-promoted reactions of dialkyl phosphonates—that amines deproto-nate dialkyl H-phosphonates to form dialkyl phosphite anions II (Scheme 3.4.). 

Arbuzov reactions (the treatment of phosphites with alkyl halides to yield monoalkyl phosphonates) have been compared with similar transformations of derivatives of other / -block elements of variable valency. ° Transformations of organic derivatives of N, P, As, S, Sb, and other elements, accompanied by a change in the valency of the heteroatom, are considered. The uniqueness of the Arbuzov reaction is explained by specific features of P derivatives, leading to prevailing occurrence of this reaction, in contrast to derivatives of other p-block elements of variable valency, in which competing transformations prevail. 

Borisov G (1967) Attempts at adding dialkyl phosphites and monoalkyl phosphonites to aldehydes and ketones of the naphthalene series. Izv Inst Org Khim Akad Nauk 3 9-16... 

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