Dialkyl phosphinous acids

Dialkyl phosphinic acids form complexes [R2P(0)0H]2 SnC, with tin tetrahalides, which when heated form chain polymers of type. 

FIGURE 5.8 Comparison of (a) dialkylphosphoric, (b) dialkylphosphonic, and (c) dialkyl-phosphinic acid extractants. 

Another example is the extraction of zinc, cadmium, or lead by a dialkyl phosphinic acid (R2PO2H) into a nonpolar diluent such as an alkane. A non-polar diluent favours the formation of uncharged non-polar metal complexes. 

Rickelton, W. A., Flett, D. S. West, D. W. (1984). Cobalt-nickel separation by solvent extraction with bis(2,4,4 trimethylpentyl)phosphinic acid. Solvent Extraction and Ion Exchange, 2, 6,815-838, ISSN 0736-6299 Robertson, A. J. (Cytec Industries) (2001). Phosphonium salts. WO 01/87900 Robertson, A. J. (1983). Process for the preparation of highly purified, dialkyl phosphinic acids. US 4 374 780, WO/2006/047545A2... 

The base-catalyzed condeasation of 2-thiophenealdehyde with dialkyl phosphorous acid leads to a-(2-thienyl )phosphinic acid. ... 

The reaction of dialkyl esters of 1,2-alkadienylphosphonic and phosphinic acids with methyl and phenylsulphenyl chloride, leads exclusively to 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives [113-115],... 

Acetals have been used in the presence of Lewis acids, particularly zinc chloride and ferric chloride, for the addition of phosphorus-halogen species to prepare 1-alkoxyphosphonic dichlorides and dialkyl 1-alkoxyphosphonates (from phosphorus trichloride and dialkyl phosphinous chlorides, respectively).143-145 It should be noted that good yields of these types of products have also been reported in the absence of catalysts.146 147 Other types of substrates have also been used in these types of processes. These include acylals,148 amidals,149 orthoformates,150 and orthoacetates.151... 

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... 

Mono- and disulfur substitutes of diesters of phosphoric acids, phosphonic acids, and phosphinic acids, possessing soft-donor atoms in their structures, present large An(III)/Ln(III) selectivities, especially the dialkyl-dithiophosphinic acid used in the Chinese CYANEX 301 process or its chlorophenyl derivative used in the German ALINA process. 

Sulfur-donor Extractants The CYANEX 301 Process. Various dialkyl-(mono/di)-thio(phosphoric/phosphinic) acids, such as di(2-ethylhexyl)-di-thiophosphoric acid (HDEHDTP), bis(2,4,4-trimethylpentyl)-thiophosphinic acid (CYANEX 272), bis(2,4,4-trimethylpentyl)-monothiophosphinic acid (CYANEX... 

Quinazolin-2(l//)-ones 7 react readily with hydrophosphorous acid or with trialkyl phosphites to afford the corresponding quinazoline-4-phosphinic acids or dialkyl quinazoline-4-phospho-nates 8 in good yields. If an alkyl group is present in position 4 of the quinazolin-2(l//)-one, for the reaction with trialkyl phosphites additional activation of the imine bond is required to overcome steric constraints and the hydrochlorides of 4-alkylquinazolin-2(l/f)-ones react readily with trialkyl phosphites to give 8 in 77-98% yield. " ... 

Attack on Unsaturated Carbon.- A versatile route to phosphinic acids (15) is the 1,4-addition of bis(trimethylsilyl) phosphonite (16) to a,p-unsaturated esters.The pyrophoric (16) was prepared in s/fu from triethylammonium phosphinate silylation and 1,4-addition can be repeated to give (17), or performed in one step if symmetrical phosphinic acids (17) are wanted. Tervalent phosphorus acid esters (18) react with dialkyl acetylenedicarboxylates in the presence of carbon dioxide to give 1,2-oxa-phospholenes (19) these reacted further with an excess of the phosphorus reagent to give different ylids, (20) or (21), dependant on the number of methoxy groups in (18). 

Hydroxyalkyl)phosphonic acids, and also the related phosphinic acids, are normally obtained from hydrogen phosphonates and aldehydes or ketones. The reactions between perfluoroacetone and mixed dialkyl hydrogen phosphonates are noteworthy in that the expected products (129) may be accompanied by the phosphoric triesters (130). Trimethylsilyl alkylene P(III) triesters (131) are also useful starting materials when acted upon by aromatic aldehydes or by (1-oxoalkyl)phosphonic acid esters, the initial... 

The simple dialkyl and diarylphosphines are liquids with unpleasant odors and are susceptible to oxidation. The products of most secondary phosphine oxides tend invariably to be the phosphinic acid produced by tautomerization and further oxidation. 

In a variation, high yields of phosphonium salts (77%) have been claimed to be obtained from the reaction of white phosphorus and benzyl halides, XC Y nClA2 with the aid of metal or metal salt (CuCl) catalysis The reaction may also be carried out in a high boiling solvent. Here dialkylation prevails and tlie phosphinic acid (PhCH2)2P(O)OH is isolated after hydrolysis... 

Abramov, V.S., and Savintseva, R.N., Reactions of dialkyl phosphinates with aldehydes and ketones. Part 28. Esters of a-hydroxy-P-chloroethylphosphonic acids and a,P-epoxyethylphosphonic acids, Khim. Org. Soedin. Fosfora, Akad. Nauk SSSR Otd. Obshch. Tekh. Khim., 129, 1967 Chem. Abstr., 69, 67465y, 1968. 

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... 

The cyclic phosphinic acids, the 4-hydroxy-1,4-oxaphosphinine 4-oxides (312), may be made by acid-promoted cyclization of bis-(j8-chlorostyryl)-phosphinic acids (Equation (22)) <84ZOB1481, 85ZOB780), and their esters (313) result from the reaction of bromomethyl ketones with dialkyl alkynylphosphonites (Equation (23)) <89DOK(304)625>. 

The metal phosphinates are prepared from metal salts and dialkyl or diarylphos-phosphinic acids utilizing melt or solution systems. The metal polyphosphinates are utilized as additives e.g., Cr(III) polyphosphinates thicken silicones to greases and improve their high-pressure physical properties. Chromium and titanium polyphosphinates impart antistatic properties to a wide range of plastics. 

Alkyl esters of phosphonous and phosphinous acid also react readily y with carbon tetrachloride, while analogous aryl esters, e.g., EtP(OPh)2, are resistant even at 160° (152,173). The reaction of bromotrichloro-methane with triethyl phosphite, which occurs smoothly at 80° to furnish dialkyl trichloromethylphosphonate in excellent yield (99%), is light catalyzed. Chloroform is unchanged in the presence of triethyl phosphite (98,156) even under drastic conditions, and diethyl dichloro-methylphosphonate is not produced unless a free radical initiator is present (118). 

The use of trichloroacetaldehyde is also to be particularly noted. Although reactions between this aldehyde and various dialkyl hydrogenphosphonates have been report- 269,274,294,295 it is the dimethyl ester of (l-hydroxy-2,2,2-trichloroethyl)phosphonic acid which has received particular attention, and which has been studied widely from the structural point of view in the light of its commercial importance as the powerful insecticide dipterex (also known as trichlorphon and chlorophos). Polyfluoroalkyl esters of the related alkyl(l-hydroxy-2,2,2-trichloroethyl)phosphinic acids have been prepared by the unusual combination of chloral hydrate and the bis(polyfluoroalkyl) alkylphosphonite ester ... 

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