Phosphite, diethyl, reaction with

Trimethyl phosphite does not react with chloroacetyl chloride through a Michaelis-Arbu-zov/Perkow reaction sequence. It gives an acylpseudophosphonium salt, which, in turn, reacts readily with trimethyl phosphite to give a new adduct. Subsequent warming affords dealkylation to give the final dimethyl l-(dimethoxyphosphinyloxy)vinylphosphonate (Scheme 7.3). More interesting from the mechanistic standpoint is the use of diethyl trimethylsilyl phosphite. In reaction with chloroacetyl chloride at 30°C, the initial adduct loses MejSiCl rapidly to give diethyl 2-chloroacetylphosphonate in 37% yield." ... 

Similarly, diethyl trimethylsilyl phosphite reacts with acetyl bromide at low temperature to produce diethyl 1-oxoethylphosphonate in 83% yield. Diethyl trimethylsilyl phosphite, on reaction with ketene, gives diethyl l-(trimethylsilyloxy)vinylphosphonate, which can be hydrolyzed or alcoholyzed to diethyl 1-oxoethylphosphonate. ... 

The rigid, planar pyridine analog 111 was isolated in low yield by first hydrolyzing the known (67) pyridine diethyl phosphonate 109 to the corresponding free acid 110 followed by permanganate oxidation (2). An alternative synthesis of 111 has recently been reported (68). Alkylation of pyridine-2-carboxylate -oxide with dimethylsulfate and subsequent reaction with the sodium salt of diethyl phosphite gave the triester 112, which was readily converted to 111. 

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)... 

Symmetrical cyclic triazines (masked imines) have been used in reaction with diethyl trimethylsilyl phosphite to provide phosphonates bearing silyl-substituted a-aminophosphonates.349... 

A comparison of the suitability of solvents for use in Srn 1 reactions was made in benzenoid systems46 and in heteroaromatic systems.47 The marked dependence of solvent effect on the nature of the aromatic substrate, the nucleophile, its counterion and the temperature at which the reaction is carried out, however, often make comparisons difficult. Bunnett and coworkers46 chose to study the reaction of iodoben-zene with potassium diethyl phosphite, sodium benzenethiolate, the potassium enolate of acetone, and lithium r-butylamide. From extensive data based on the reactions with K+ (EtO)2PO (an extremely reactive nucleophile in Srn 1 reactions and a relatively weak base) the solvents of choice (based on yields of diethyl phenylphosphonate, given in parentheses) were found to be liquid ammonia (96%), acetonitrile (94%), r-butyl alcohol (74%), DMSO (68%), DMF (63%), DME (56%) and DMA (53%). The powerful dipolar aprotic solvents HMPA (4%), sulfolane (20%) and NMP (10%) were found not to be suitable. A similar but more discriminating trend was found in reactions of iodobenzene with the other nucleophilic salts listed above.46 Nearly comparable suitability of liquid ammonia and DMSO have been found with other substrate/nucleophile combinations. For example, the reaction of p-iodotoluene with Ph2P (equation (14) gives 89% and 78% isolated yields (of the corresponding phosphine oxide) in liquid ammonia and DMSO respectively.4 ... 

A synthetic approach to /3-sultams containing a direct bond between a tri- or tetracoordinated phosphorus atom and the nitrogen atom of the 1,2-thiazetidine 1,1-dioxide ring has been realized by direct phosphitylation or phosphorylation at nitrogen. Unfortunately, attempts to synthesize N-phosphorylated /3-sultams by reaction with diethyl phosphorochloridate and diethyl phosphorobromidate, generated in situ from diethyl phosphate and carbon tetrachloride or carbon tetrabromide, failed. However, when the /3-sultam is treated with freshly distilled diethyl phosphorochloridite or tetramethylphosphorodiamidous chloride in the presence of triethylamine, the expected AHliethy I phosphite and iV-phosphorodiamidous /3-sultams 150 are obtained (Equation 10). /3-Sultams unsubstituted... 

Alkali metal salts of diethyl phosphite (122) act as nucleophiles or electron donors in their reaction with diethyl phosphorochloridate (123). Evidence was provided that formation of the direct P(IV)-P(IV) bond proceeds via a single electron transfer process (SET) from phosphite anion to phosphorochloridate (Scheme 34). ... 

Finally, carbohydrate ligands of enantioselective catalysts have been described for a limited number of reactions. Bis-phosphites of carbohydrates have been reported as ligands of efficient catalysts in enantioselective hydrogenations [182] and hydrocyanations [183], and a bifunctional dihydroglucal-based catalyst was recently found to effect asymmetric cyanosilylations of ketones [184]. Carbohydrate-derived titanocenes have been used in the enantioselective catalysis of reactions of diethyl zinc with carbonyl compounds [113]. Oxazolinones of amino sugars have been shown to be efficient catalysts in enantioselective palladium(0)-catalyzed allylation reactions of C-nucleophiles [185]. 

Schmidt and Wong have developed 2-diethyl and 2-dibenzyl phosphite derivatives of NeuSAc 80 [86] and 81 [87], individually. Both of the 2-phosphite derivatives can be prepared from a 2-hydroxy derivative of NeuSAc 79 by the reaction with ClP(OEt)2 in the presence of Hiinig s base, and by the reaction of A,iV-diethyl phosphoro amidite and tetrazole, respectively (O Scheme 24). 

Treatment of 1,1 -dibromocyclopropanes with triethyl phosphite in the presence of triethylamine and water at 90 °C gives mixtures of diethyl cis- and fra .t-cyclopropylphosphonates 1 (A and B, reductive phosphonation) (Table 24). The relative amount of the reactants is crucial for the outcome of the reaction. In the absence of water the dibromide is recovered almost quantitatively, and if too much water is used, the dibromides may be reduced to the corresponding monobromocyclopropanes, in particular if an electron-withdrawing group is attached to the ring (see Section 5.2.1.1.1.5.1.). Evidence implies that diethyl phosphonate, which is formed by hydrolysis of triethyl phosphite, plays an important role in the phosphonation reaction. This is supported by the observation that reductive phosphonation also can be carried out at 90 °C using a mixture of triethyl phosphite, diethyl phosphonate and triethylamine (C and 1,1-Dichlorocyclopropanes are unreactive under these conditions. 

As shown in Section 2.2.2.3.1., bicyclopropylidene (1) is capable of undergoing [2-1-2] cycloadditions with electron-deficient alkenes such as diethyl fumarate under nickel(O) catalysis. The [3 -I- 2] cyclodimer and a cyclotrimer are obtained only as minor products from this reaction. In contrast, exclusive [3 -I- 2] cycloaddition can be achieved with many other substrates when palladium(O) catalysts are employed. These cycloaddition products are also produced with phosphite-modified nickel(O) catalysts, but both yields and selectivities are markedly lowered. The reactions of 1 with norbornadiene and norbornene serve as examples for the reaction with strained hydrocarbons, providing the cyclodimers 2 and 3 in 61% and 66% yield, respectively. ... 

With perfluoroethylene, where the polarization is absent, the main product is diethyl ethylphos-phonate. When a tertiary base is present, the isomerization rate is lower, and diethyl trifluorovi-nylphosphonate can be isolated in 10-15% yields. The reactivity of perfluoroalkenes in the reaction with trialkyl phosphites falls as showed in Figure 3.1." ... 

Wessolowski, H., Rdschenthaler, G.-V., Winter, R., and Gard, G.L., 2,2-Dilhioro-l-(pcnlalhioro-Z -sulfanyl)]ethylene and l,L3,3,3-pentafluoropropene. Reactions with diethyl(trimethylsilyl) and frw(trimethylsilyl)phosphite. Phosphorus, Sulfur Silicon Relat. Elem., 60, 201, 1991. 

Kawamoto, A.M., and Campbell, M.M., A new method for the synthesis of a phosphonic acid analogue of phosphoserine via a novel 1,1-difluorophosphonate intermediate, J. Fluorine Chem.. 81, 181, 1997. Burton, D.J., Naae. D.G., Flynn, R.M., Smart, B.E., and Brittelli, D.R.. Phosphine- and phosphite-mediated difluorocarbene exchange reactions of (bromodifluoromethyl)phosphonium salts. Evidence for facile dissociation of (difluoromethylene)triphenylphosphorane. J. Org. Chem.. 48. 3616, 1983. Li, A.-R., and Chen. Q.-Y., Diethyl iododifluoromethylphosphonate. A new synthetic method and its reaction with alkynes. Synthesis, 606, 1996. 

Unsaturated 3-fonnylphosphonates can be prepared by a Michaelis-Arbuzov reaction that employs l,l-diethoxy-4-bromo-2-butene as the masked formyl group. Reaction with triethyl phosphite at ISS C gives diethyl 4,4-diethoxy-2-butenylphosphonate in 50% yield. Deprotection is accomplished in 98% yield using a cold-saturated aqueous solution of tartaric acid. ... 

The chlorination process is extended to the preparation of 1-substimted-1-fonnyhnethylphos-phonates with comparable yields (53-92%). 5-3°8 Contrary to the previously reported results, the reaction of triethyl phosphite with trichloroacetaldehyde does not give diethyl 1,1-dichloro-1-formylmethylphosphonate (Michaelis-Arbuzov product) instead, the isomeric diethyl 2,2-dichlo-rovinylphosphate (Perkow product) is formed in 98% yield. However, protection of the formyl group before reaction with triethyl phosphite provides the expected diethyl 1,1-dichloro-l-formyl-methylphosphonate selectively in high yield (80%). ... 

The synthesis of DECP by the reaction of diethyl phosphite with an alkali metal cyanide in CCI4 is reported to be difficult to reproduce. In contrast, when the experiment is done with diethyl chlorophosphate and fresh NaCN containing catalytic amounts of NaOH in refluxing CgHg, consistent yields of DECP (up to 46%) are obtained (Scheme 6.1). The addition of a phase-transfer catalyst does not improve the yield, and the use of polar aprotic solvents (MeCN, DMP, DMSO) completely inhibits the reaction. The reaction of diethyl chlorophosphate with trimethylsilyl cyanide in the presence of TiCl4 leads to a mixture of DECP and partially silylated DECP. ... 

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