Dialkyl -phosphonates

A few compounds of this type are industrially important as intermediates in the manufacture of insecticides, metal extractants, surfactants and so on. Bis (2-ethylhexyl)phosphonate (iso-octylphosphonate) is obtained from PCI3 and the alcohol, if the reaction is carried out at low temperature with the rapid removal of HCl (6.283). This compound is used to prepare bis (2-ethylhexyl) phosphate (6.284). 

The highly toxic bis (isopropyl)phosphorofluoridate (DFP) (12.143a) is prepared via diisopropyl phosphonate (6.285), and the insecticide Dipterex (Table 12.29) via dimethylphosphonate (6.286). 

Dibutyl phosphonate, (Bu0)2P(0)H, is used as an anti-wear and extreme pressure lubricant in hydraulic fluids and gear oils. 

Like phosphinic acids, phosphonic acids or their acid esters readily form dimers as in (6.287a) or other hydrogen-bonded arrangements. Dialkylphosphonates may also form dimers as in (6.287b) but in this case the H bonding is much weaker (in all phosphorus compounds with P-H bonds the H bonding is generally weak or absent (Chapter 13.1)). 

Aminoethylphosphonic acid (P-ciliatine, ALP) HjN CH2 CHj P(0)(0H)2, is of particular interest because of its occasional occurrence in biological materials (Chapter 11.7). In the organism tetrahymena , 15% of the total phosphorus is present as ALP. It is also found in Japanese sea anemones and in some shellfish. Its biosynthesis and function are not at present completely understood, but phosphonates are currently of much interest in connection with possible alternative systems of metabolism (Chapter 11.7). 

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Dialkyl arylphosphonates and alkenylphosphonates are prepared by the coupling of halides or triflates with the dialkyl phosphonate 783[64l-643]. 

Adducts from various quaternary salts have been isolated, in reactions with aldehydes, a-ketoaldehydes, dialkylacylphosphonates and dialkyl-phosphonates, isocyanates, isothiocyanates, and so forth (Scheme 15) (36). The ylid (11) resulting from removal of a Cj proton from 3.4-dimethyl-S-p-hydroxyethylthiazolium iodide by NEtj in DMF gives with phenylisothiocyanate the stable dipolar adduct (12) that has been identified by its NMR spectrum and reactional product, such as acid addition and thiazolidine obtention via NaBH4 reduction (Scheme 16) (35). It must be mentioned that the adduct issued from di-p-tolylcarbodiimide is separated in its halohydrogenated form. An alkaline treatment occasions an easy ring expansion into a 1,4-thiazine derivative (Scheme 17) (35). 

The chlorination of dialkyl phosphonates provides a convenient synthesis of phosphorochloridates ... 

Phosphoms trichloride reacts readily with oxygen, sulfur, chlorine, and water. It serves as an intermediate in the production of phosphoms oxychloride, phosphoms sulfochloride, phosphoms pentachloride, and phosphonic (phosphorous) acids. PCl is also the raw material for the manufacture of dialkyl phosphonates,... 

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

Et or Bu) and the phosphonation of iodoaromatics with dialkyl phosphonates, although in this case with poorer yields (better results of the dialkyl arylphosphonates are obtained by photostimulation). Chemical oxidation (using AgNO -peroxodi-sulphate) and anodic oxidation of aromatics in the presence of trialkyl phosphites produces dialkyl arylphosphonates in good yields. The Cul-catalysed arylation of dialkyl (cyanomethyl)-phosphonates affords dialkyl (a-cyanobenzyl)phosphonates. ... 

Two papers describe the hydrophosphonation of unsaturated cyclic hydrocarbons. With dialkyl phosphonates, cycloocta-1,5-diene affords the phosphonate esters (66) but in the presence of strong acids, or when using the moderately strong l PtOXDH itself, the monocyclic esters (67) are also formed. Cyclododeca-1,5,9-triene affords a mixture of polycyclic... 

Me(Ph)SiCl2 reacts with dimethyl phosphonate in a 1 1-mixture at 100°C to the O.O-disilylated phosphonate. In contrast to this observation the O-alkyl O-silyl phosphonate is formed solely by reaction of both compounds in acetonitrile at 80°C (line 7,8). An excess of the corresponding phosphonate as polar solvent leads to the mixed ester 2 only. The excess of the dialkyl phosphonate is removed from the mixture by vacuum distillation (line 9). 

The enhanced reactivity of the chlorine atom in the dichloro diorgano silanes can also be observed in Me2(MeO)SiCl 4 or Me(EtO)2SiCl 5. In both cases the O-alkyl O-silylphosphonates (6, 7) are formed in high yields after reaction of 4 or 5 with dialkyl phosphonates. 

Dialkoxydichloro silanes exhibit a higher nucleophilicity compared to the chlorosilanes described before. Diethoxysilyl-bis(0-alkyl)phosphonates of type 8 are formed in 90% yield besides 10% of disilylated phosphonates in the reaction of dialkyl phosphonates with dichlorodiethoxy silanes at 50-80°C. 

Reductive and oxidative transformations of small ring compounds form the basis of a variety of versatile synthetic methods which include functionalization and carbon skeleton construction. Redox mechanisms of organotransition metal compounds play an important role in inducing or catalyzing specific reactions. Another useful route in this area is based on one-electron redox reactions. The redox tautomerism of dialkyl phosphonate also contributes to the efficiency of the reductive transformation of small ring compounds. This review summarizes selective transformations which have a high potential for chemical synthesis. 

The 1-bromo-l-chlorocyclopropanes 191 are reduced to the corresponding chlorocyclopropanes 192 selectively although em-dichlorocyclopropanes do not undergo reduction with dialkyl phosphonate and triethylamine [97]. (Scheme 72)... 

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)... 

A similar transformation is also performed by treatment of 150 with trialkyl phosphite, triethylamine, and water since dialkyl phosphonate is generated by hydrolysis of trialkyl phosphite (Scheme 75). The use of deuterium oxide... 

Janzen, A.F. and Pollitt, R., Reaction of dialkyl phosphonates with hexafluo-roacetone, Can. J. Chem., 48, 1987, 1970. 

General.—Pudovik et al.59 have re-examined some reactions between imines and dialkyl phosphonates reported initially in 1959 by N. Kreutzkamp and G. Gordes, and they have shown that the products of the reactions between dialkyl phosphonates and (70) or (71) are actually (72) and (73), and not the bis(phosphonic acids) (74 R2 = H, Ph) (Scheme 2). They were further able to show that, under milder conditions, the imino-ethers (70) will yield eventually (77), through (75) and (76). 

Another example is the electrocatalytic reaction between aromatic carbonyl compounds and dialkyl phosphonates. Here, rearrangement of the product anion leads to a phosphate as the product [136]. 

Nickel complexes have proved to be active for hydrophosphorylation of alkynes [17a, 25]. Not only the five-membered phosphonate but also commercially available dialkyl phosphonates readily react in the presence of... 

Pudovik and Kuzovleva have studied the reaction of dialkyl phosphonates with ethyl profHolate and have shown diat, in the presence of sodium alkoxide, a bis adduct (470) is formed, whereas with excess of the ester, under similar conditions, a mono adduct (471) is formed (Scheme 74). 

Triisopropyl phosphite [116-17-6] M 208.2, b 58-59 /7mm, n s 1.4082. Distilled from sodium, under vacuum, through a column with glass helices. (This removes any dialkyl phosphonate). 

The formation of dialkyl phosphonates by coupling of monoalkyl phosphonates with support-bound alcohols is discussed in Section 16.2.3. Some additional examples, not related to the synthesis of oligonucleotides, are sketched in Figure 11.3. 

Anions such as N03 were thought to be able to compete more effectively with the more sterically hindered extractants for Th4+ coordination sites. The extraction of Th4+ by monoalkyl phosphoric acid187 and dialkyl phosphonic acids188 has also been reported. 

The ESR spectra of free radicals arising from the action of hydroxyl radicals on several phosphorous compounds (trialkyl phosphate and dialkyl phosphonate) have been studied. In all cases, the radicals observed are due to the removal of a hydrogen atom from the carbon atom adjacent to the oxygen in the ester group (Ca-atoms) (289). 

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