Phosphonates alkylphosphonates

Phosphonic acid is an intermediate in the production of alkylphosphonates that are used as herbicides and as water treatment chemicals for sequestration, scale inhibition, deflocculation, and ion-control agents in oil weUs, cooling tower waters, and boiler feed waters. For example, aqueous phosphonic acid reacts with formaldehyde and ammonium chloride in the presence of hydrochloric acid to yield aminotri(methylenephosphonic acid) [6419-19-8]. 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Phosphoms trichloride may also be used directly ia the production of trialkyl phosphites, dialkyl phosphonates, and dialkyl alkylphosphonates ... 

Olefination Reactions Involving Phosphonate Anions. An important complement to the Wittig reaction involves the reaction of phosphonate carbanions with carbonyl compounds 253 The alkylphosphonic acid esters are made by the reaction of an alkyl halide, preferably primary, with a phosphite ester. Phosphonate carbanions are generated by treating alkylphosphonate esters with a base such as sodium hydride, n-butyllithium, or sodium ethoxide. Alumina coated with KF or KOH has also found use as the base.254... 

Mixed phosphonate acid esters can also be prepared from alkylphosphonate monoesters, although here the activation is believed occur at the alcohol.57... 

Reactions and Properties of Phosphonic and Phosphinic Acids and their Derivatives.-A free radical mechanism has been proposed to account for the cleavage of the phosphorus-carbon bond in the alkylphosphonic acids (155) by E coli to give a mixture of alkane (methane only, from methylphosphonic acid) and terminal alkene. 

Reactions of Phosphonic and Phosphinic Acid Derivatives.—The reactions of phos-phonic and thiophosphonic amides and chlorides with carboxylic acid chlorides and amides have been discussed.101 Dialkyl alkylphosphonates and alkyl dialkylphos-phinates may be used for the iV-alkylation of imidazoles, triazoles, and pyrroles.105... 

Diethyl l-< Acylamino)alkylphosphonates 18 by Addition of an Enamine to Diethyl Acyliminomethyl-phosphonate 17 General Procedure 1501... 

In the family of phosphonates (RO)2R PO, the aryl derivatives were more stable than the related alkyl compounds, and the benefit was higher than the effect observed from alkylphosphate to alkylphosphonate (96). The same tendency has been observed with dithiophosphinic acids (RO)R PSSH namely, aromatic ligands were more resistant to hydrolysis and radiolysis than aliphatic compounds (49, 61). It was noted that the introduction of chlorine into the phenyl rings reinforced the radiolytic stability of the extractant (49, 61). 

The use of negative ion APCI allows selective detection of phosphonic acids in the presence of neutral and basic analytes. Alkyl alkylphosphonic acids are easily distinguished from isomeric dialkyl... 

Figure 8. LC/MS mass chromatograms, positive APCI showing the detection of four isomeric alkyl alkylphosphonic acids (1 Hg/ml) and two dialkylalkyl phosphonates (10 p,g/ml) (upper), negative APCI showing selective detection of the phosphonic acids, a. i-PrMPA and EEPA (unresolved), b. methyl n-PrPA, c. n-PrMPA, d. ethyl methyl methylphosphonate, and e. dimethyl ethylphosphonate (lower)...

Figure 9. LC/ESI/MS TIC of six alkylphosphonic acids separated on a porous graphitic carbon stationary phase. (Reprinted from Journal of Chromatography A, 849, Mercier etal, Liquid chromatography analysis of phosphonic acids on porous graphitic carbon stationary phase with evaporative tight-scattering and mass spectrometry detection, pp. 197-207 (1999), with permission from Elsevier)...

Direct UV detection of alkylphosphonic acids through the formation of sodium borate complexes has been reported (9). While native alkylphosphonic acids exhibit negligible absorbance above 200 nm, borate complexation shifted their absorption maxima such that they were readily detected at either 214 nm or 254 nm. The buffer system consisted of 10 mM sodium tetraborate with complexation occurring in solution at pH 7 and higher. The reported detection limits on the order of nanograms. The UV, IR, NMR, and mass spectra of various borate/phosphonic acid esters were also reported. 

The Michaelis-Arbuzov reaction is the most used and well-known method for the synthesis of phosphonates and their derivatives and may also be used to synthesize phosphinates and tertiary phosphine oxides. The simplest form of the Michaelis-Arbuzov reaction is the reaction of a trialkyl phosphite, 3, with an alkyl halide, 4, to yield a dialkyl alkylphosphonate, 6, and new alkyl halide, 7 (Scheme 2). During this transformation the phosphorus atom of a ter-valent phosphorus(III) species (3) acts as a nucleophile resulting in the formation of an intermediate alkoxy phosphonium salt 5, containing a new [P—C] bond. The precise structure of the intermediates 5 is a subject of debate—as reflected by common reference to them as pseudophosphonium salts —with a penta-coordinate species (containing a [P—X] bond) being proposed and detected in some cases.18 Decomposition (usually rapid under the reaction conditions) of the intermediate 5 by nucleophilic attack of X- on one of the alkyl groups R1, with concomitant formation of a [1 =0] bond yields the product pentavalent phosphorus(V) compound (6) and the new alkyl halide, 7. 

R-P(0H)2[R-P(0)(H)0H] Phosphonous acid (alkylphosphonous acid esters dialkyl alkylphosphonite) phosphonige Satire... 

RP(0)(0H)2 Phosphonic acid (alkylphosphonic acid esters diaUcyl alkylphosphonate) Phosphonsaiire... 

The base-promoted reaction of fluoroalcohols RfOH (Rf=CF3CH2 H(CF2)CH2, C2F5CH2, C3F7CH2, (CF3)2CH with alkyl phosphonic dichlorides is an excellent method for the synthesis of bis(fluoroalkyl) alkylphosphonates (Rf0)2P(0)R. ... 

Whereas alkylphosphonic diesters react readily with lithium or organomagnesium reagents with the formation of the metallated phosphonate carbanions, the reactions between such esters and the metals themselves result, by contrast, in dealkylation of the ester groups involving both C-0 and P-0 cleavage traces of unsaturated hydrocarbons, even including alkynes and aromatics, are thought to be formed by radical-induced reactions. 

Alkylphosphonate esters. Phosphonate esters with P-alkyl groups of different chain lengths can be prepared from iodoalkylphosphonates (alkyl being methyl, ethyl, propyl) and 1 -alkenes by a radical addition process, using an initiating system comprising BujSnCl, NaBH, and EtjB (Oj). 

Trialkylstannylalkyl)phosphonates, R3SnCHR P(0)(0R")2> can be prepared by lithia-tion of the alkylphosphonate followed by reaction with the alkyltin chloride (equation 6-20),56 or by an Arbuzov reaction between an iodomethyltin compound and a phosphite (equation 6-21).57 The activated Sn-C bond will then add to a dipolar double bond, and the phosphonate group can be reduced to CH2PH2 with lithium aluminium hydride. 

The first reported application of this reaction is described by A. N. Pudovlk et al.C 25) who reacted the ethyl esters of bromoacetic acid and chloroacetic acid with various phosphonate esters. His group used molar ratios of the phosphonate and the haloacetate, and obtained a mixture of the mono- and dl-carbethoxy alkylphosphonates. 

Meisters, A., and Swan, J. M., Organophosphorus compounds. Part 5. Dialkyl alkylphosphonates from alkyl haUdes and sodium dialkyl phosphonates in liquid ammonia, Aust. J. Chem., 18, 163. 1965. 

Unquestionably, the most attractive procedure for the preparation of dialkyl l-(trimethylsilyl)meth-ylphosphonates is the carbanionic route. The obvious transmetallation difficulties occurring when carbanionic reagents are employed in conjunction with activated methylene groups have led to the development of procedures based on the trapping of a-metallated phosphonates with chlorosilanes in the presence of lithium diisopropylamide (LDA) in excess. For example, the addition at -70°C of chlorotrimethylsilane (1 eq) to a solution of dialkyl 1-lithioalkylphosphonates prepared from dialkyl alkylphosphonates (1 eq) and LDA (2 eq) produces, after workup, dialkyl l-(trimethylsilyl)alkylphos-phonates in 75-90% yields of isolated product, via the quantitative and clean generation of stable dialkyl l-lithio-l-(trimethylsilyl)alkylphosphonates (Scheme Varying the phosphorus reac-... 

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