Dialkyl alkylphosphonate

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. 

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 ... 

G.l.c. studies of tributylphosphine, dialkyl phosphites, and dialkyl alkylphosphonates are reported. Tributyl phosphate in nitric acid can be estimated by g.l.c. if a glass column is used. Tetraethyl pyrophosphate has been directly determined on a nanogram scale by g.l.c., whereas it was found most convenient to first convert the tetra-aryl pyrophosphates by methanolysis to diarylmethyl phosphates. Phosphorochloridates were converted by t-butyl alcohol into t-butyl chloride before analysis. G.l.c. studies of pesticides have been reported and the isomeric thiophosphates (138a) and (138b) have quite different retention times. ... 

Note In Equation 3.2, the product dialkyl alkylphosphonate is shown with the phosphoryl group represented by P=0. It should be noted... 

For the hydrolysis of dialkyl alkylphosphonates to alkylphos-phonic acids Kosolapoff4 used hot concentrated hydrochloric acid, and for more stubborn cases, 48 per cent hydrobromic... 

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... 

Dialkyl hydrogen phosphites are alkylated in high yield under basic liquiddiquid phase-transfer catalytic conditions via the Michaelis-Becker reaction to yield dialkyl alkylphosphonates without serious side reactions [16, 17]. 

Keywords alkyl chloride, trialkyl phosphite, alumina, microwave irradiation, Arbuzov rearrangement, dialkyl alkylphosphonate... 

Siddall III, T.H. Trialkyl phosphates and dialkyl alkylphosphonates in uranium and thorium extraction, Ind. Eng. Chem. 51 (1959) 41 14. 

An alternative to solvent extraction of synthetic materials is supercritical fluid extraction (SFE). The SFE recoveries by using carbon dioxide for a series of alkyl alkylphosphonofluoridates and dialkyl alkylphosphonates from alkyd painted plates, compared favorably with conventional sonication results by using dichloromethane (39). A drawback to... 

Dialkyl alkylphosphonates are of interest as analytes for a number of reasons. They may be present as impurities in nerve agents, and as such may be useful indicators of use or production as they are much more stable in the environment an example is diisopropyl methylphosphonate found in sarin. Dialkyl methylphosphonates may be formed in decontamination reactions of nerve agents in basic formulations containing alcohols or cellusolves. They are also important precursors to nerve agents, for example, dialkyl methylphosphonates are converted to the key... 

Specific analytical methods have not been developed for dialkyl alkylphosphonates. They are usually sufficiently hydrophilic to be partially extracted by water from matrices such as soil and they are detected by the screening methods described above under positive ESI and APCI conditions. They are easily differentiated from isomeric alkyl alkylphosphonic acids by their lack of response under negative ionization conditions (Section 6.2.3, Figure 8) (14). 

Cooper et al. (46) measured vp=0 frequencies for dialkyl alkylphosphonates with a light-pipe GC/ FTIR and found them to be those calculated using the 7t-constant values modified by Nyquist(45). They also discovered that the vp=0 was in the region 1259-1248 cm-1 in dialkyl isopropylphosphonates and in the region 1273-1265 cm-1 in dialkyl n-propylphosphonates. 

Both Kireev et al. (49) and Cooper et al. (46) have studied dialkyl alkylphosphonates also using a Hewlett-Packard (currently Digilab) IRD instrument. 

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. 

This protocol is representative of the Michaelis-Arbuzov reaction in its simplest form, on a large scale. Protocol 1 may be used with minor modification to synthesize other simple dialkyl alkylphosphonates.20 The combination of triisopropyl phosphite 9 and a primary alkyl halide (methyl iodide) means that the formation of the potential by-product diisopropyl isopropylphosphonate is negligible because the product alkyl halide (isopropyl iodide) is a secondary alkyl halide and thus reacts much more slowly with triisopropyl phosphite 9 than does the desired reactant methyl iodide. 

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-... 

These drawbacks are overcome when the standard procedure is developed in the presence of a metallation agent in excess. Thus, when the reaction between dialkyl alkylphosphonates and carboxylic acid esters is allowed to proceed in the presence of LDA in excess (2 eq) in THE at low temperature, the resulting lithium phosphonoenolate is obtained in quantitative yield. Monitoring of the reaction by P-NMR shows the appearance of one signal from the lithium phosphonoenolate... 

Because dialkyl 2-oxo-(0-(alkoxycarbonyl)alkylphosphonates are valuable synthetic intermediates that may be either converted to die corresponding amino compounds or treated with a variety of carbonyl compounds in a Homer-Wadsworth-Emmons reaction,procedures that effect their preparation are of special importance. The Michaelis-Arbuzov reaction, which furnishes low yields, does not appear to be an appropriate method for the preparation of dialkyl 2-oxo-(fl-(alkoxycarbonyl)alkylphosphonates. One of the most attractive synthetic methods involves the chemoselective reaction of a-metallated dialkyl alkylphosphonates with acylating reagents such as carboxylic acid chlorides, cyclic anhydrides, or esters. 

RP(0)(0H)2 Phosphonic acid (alkylphosphonic acid esters dialkyl alkylphosphonate) Phosphonsatire... 

Following the (apparently) initial observations by Griffin and coworkers on the irradiation of mixtures of aryl iodides and trialkyl phosphites, it was evident that the procedure held great promise for synthesis although it was found necessary to employ 3-5 molar excess of phosphite ester (to allow for competitive photostimulated Michaelis-Arbuzov isomerization to dialkyl alkylphosphonate), nevertheless yields were very high, sometimes... 

The anions from simple dialkyl alkylphosphonates and Ida in thf have been mono- and di-silylated and stannylated. ... 

The well established alkylation of phosphorylated benzyl carbanions has been complemented by the arylation of purely alkyl species. Thus, diethyl (chloromethyl)phosphonate reacts with aryllithium reagents to give the diethyl esters of benzylic phosphonic acids The alternative procedure has been adopted in a synthetic route to isoprenyl (phos-phinylmethyl)phosphonates. Here, a lithiated dialkyl alkylphosphonate is acylated using an ester of the phosphonochloridic acid, R P(0)(0H)C1, where R is an isoprenoid residue. The acylation process has also been carried to with (R0)2P(0)C1 or (Me2N)2P(0)Cl ... 

The alkylation, with azomethines, of the dialkyl alkylphosphonates (R0)2p(0)CH2Z (Z = CN or COOEt " ), either as their carbanions or in the presence of AlCl3 ... 

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