With Trialkyl Phosphites

Reduction of 4-arylmethylidenepyrazol-3-ones 567a,b with triethyl phosphite and 

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A convenient route to steroidal aziridines from the diaxial IN3-olefin adducts, e.g., (99), which undergo elimination with lithium aluminum hydride, was developed by Galle and Hassner. Upon treatment with trialkyl phosphite, these adducts are converted to A-phosphorylated aziridines which are reduced by lithium aluminum hydride to the free steroidal aziridine. 

Using acyl chlorides of fatty acids in connection with trialkyl phosphite leads to surface-active a-hydroxyalkanephosphonic acids according to Eqs. (37)-(39). 

Examples of the intermolecular C-P bond formation by means of radical phosphonation and phosphination have been achieved by reaction of aryl halides with trialkyl phosphites and chlorodiphenylphosphine, respectively, in the presence of (TMSlsSiH under standard radical conditions. The phosphonation reaction (Reaction 71) worked well either under UV irradiation at room temperature or in refluxing toluene. The radical phosphina-tion (Reaction 72) required pyridine in boiling benzene for 20 h. Phosphinated products were handled as phosphine sulfides. Scheme 15 shows the reaction mechanism for the phosphination procedure that involves in situ formation of tetraphenylbiphosphine. This approach has also been extended to the phosphination of alkyl halides and sequential radical cyclization/phosphination reaction. ... 

Alkoxy (R0 ) radicals react at near diffusion controlled rates with trialkyl phosphites to give phosphoranyl radicals [ROP(OR )3] that typically undergo very fast -scission to generate alkyl radicals (R ) and phosphates [OP(OR )3]. In a mechanistic study, trimethyl phosphite, P(OMe)3, has been used as an efficient and selective trap in oxiranylcarbinyl radical systems formed from haloepoxides under thermal AIBN/n-Bu3SnH conditions at about 80 °C (Scheme 27) [64]. The formation of alkenes resulting from the capture of allyloxy radicals by P(OMe)3 fulfils a prior prediction that, under conditions close to kinetic control, products of C-0 cleavage (path a. Scheme 27), not just those of C-C cleavage (path b. Scheme 27) may result. 

A detailed kinetic study of the reaction of trialkyl phosphites (44) with benzil has been carried out (see Chapter 2 for the reactions of a-diketones with trialkyl phosphites). The reaction is first-order in both phosphite and benzil and the rate constant increases with the dielectric constant of the solvent. The authors propose initial attack of phosphite at carbonyl carbon (45), in opposition to the original suggestion by Ramirez, who proposed initial attack at carbonyl oxygen. 

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... 

A variety of substrates has been used in this type of conjugate addition reaction with trialkyl phosphites, with assorted proton sources.361 384 Other types of trivalent phosphorus reagents without acidic (or conjugate base of acidic) sites have also been used successfully for this conjugate addition process, including triaryl phosphites (without dealkylation),369 phosphoramidites,385 389 phospho-nites,363 380 390 and phosphinites.360 380... 

Two unusual reactions should be noted here. Although quinones generally react with trialkyl phosphites to generate phosphate esters,... 

Finally, (3-bromoacrylate esters react with trialkyl phosphites to provide the unsaturated phosphonates (Equation 3.24), presumably through an addition-elimination route.392... 

Bratt, J., and Suschitzky, H., Reactions of polyhalogenopyridines and their N-oxides with benzenethiols, with nitrite, and with trialkyl phosphites, and of pentachloropyridine N-oxide with magnesium, /. Chem. Soc., Perkin l, 1689, 1973. 

Mukmeneva, N.A., Cherezova, E.N., and Zhukova, R.S., Reactions of 3,5-di-terf-butyl-4-hydroxybenzyl acetate with trialkyl phosphites, Russ.. Gen. Chem., 64, 947, 1994. 

Yoneda, S., Kawase, T., and Yoshida, Z.-i., Synthesis of [l-(alkylthio)]- and (1-mercapto)cycloalkanephosphonic esters by the reactions of cycloalkaneth-iones with trialkyl phosphites, /. Org. Chem., 43, 1980, 1978. 

Teichmann, H., Thierfelder, W., and Weigt, A., P-functionalization of P-nitrostyrenes with trialkyl phosphites, /. Prakt. Chem., 319, 207, 1977. 

The earliest developments in transition metal-assisted formation of aromatic C-P linkages were the result of the efforts of Tavs28 that were concerned with the use of Ni(II) halide salts for the reaction of aryl halides with trialkyl phosphites. These reactions involved conditions reminiscent of the Michaelis-Arbuzov reaction (heating at an elevated temperature) and produced arylphosphonate products in reasonable yield (Figure 6.8). 

Similarly, copper salts (cupric and cuprous) facilitate the reaction of aryl halides with trialkyl phosphites in the formation of dialkyl arylphosphonates under conditions like those found in nickel systems.37-39 Again, the copper salts appear to undergo an initial reaction with the phosphites to form a complex that subsequently undergoes reaction with the aryl halide. The requirement for copper is also similar to that for nickel saltstonly a catalytic amount is needed. Further, a preference among halides on the aromatic ring is noted iodide is replaced preferentially to other halides (Figure 6.10).40... 

The use of transition metals for the facilitation of substitution reactions on vinylic carbon has proven to be quite successful. For example, vinylic chlorides in the presence of nickel(II) chloride react with trialkyl phosphites to substitute phosphorus for the halide (Figure 6.17j.71-72 While reminiscent of a direct Michaelis-Arbuzov reaction, including final dealkylation by a chloride ion, the reaction actually involves an addition-elimination process. It appears that chloride provides a more facile reaction than bromide, a characteristic noted in several reaction systems. 

Hall, N. and Proce, R., The copper-promoted reaction of o-halogenodiaryl-azocompounds with nucleophiles. Part I. The copper-promoted reaction of o-bromodiarylazo-compounds with trialkyl phosphites. A novel method for the preparation of dialkyl arylphosphonates, /. Chem. Soc., Perkin I, 2634, 1979. 

King, R.B. and Diefenbach, S.P., Transition-metal cyanocarbon derivatives. 5. Reactions of (l-chloro-2,2-dicyanovinyl)manganese derivatives with trialkyl phosphites. A novel variant of the Michaelis-Arbuzov reaction leading to [2,2-dicyanovinylphosphonato]metal complexes, Inorg. Chem., 18, 63, 1979. 

The main procedure for deoxygenation of similar nitronates is based on their reaction with trialkyl phosphites (Scheme 3.114). These reactions readily proceed with live- (45, 55, 320, 321) and six- membered (143) cyclic nitronates. 

When reacted with trialkyl phosphite in benzene for 1 hr, dialkyl magnates (364, X = F) gave a mixture of amino(trifluoromethyl)methylene-malonates (365) (20% yields), dialkyl trifluoromethyl(substituted amino)-methylenemalonates (366) (40-45% yields), and dialkyl chlorophosphate (-20%) (86ZOB805). The reactions of dialkyl malonates (364, X = F, Cl) and triphenylphosphine in the presence of triethylamine in diethyl ether for 1 hr gave trihalomethyl(substituted amino)methylenemalonates (367) in 87-95% yields. The treatment of a solution of dialkyl trifluoromethyl-(substituted amino)methylenemalonates (366, R1 = Et) in benzene with aqueous hydrochloric acid gave amino(trifluoromethyl)methylene-malonates (368) in 82-84% yields (86ZOB805) (Scheme 32). 

Orthophosphoric and benzylphosphonic acids have been selectively alkylated with triethyl phosphite in a new synthesis of mono-, di-, and triethyl phosphates and of mono- and di-methyl phosphonates.62 A-Methylol carboxamides and sulphonamides react with trialkyl phosphites to give the phosphonate derivatives (78) and (80), respectively.63 However, the mechanism appears to be quite different in each case while the carboamides react by a transesterification-rearrange-ment pathway, the sulphonamides undergo elimination-addition via the imine (79). 

Amongst the reported syntheses of phosphonic esters, one of cyclohexylphos-phonic esters depends on treatment of cyclohexanthione with trialkyl phosphites followed by desulphurization of the intermediate esters (47) with Raney nickel.41... 

DESULFURIZATION WITH TRIALKYL PHOSPHITES Desulfurization of Mercaptans to Hydrocarbons [672]... 

Tetraalkoxyphosphoranylperoxy radical 76 is thought to be formed as an intermediate in the reactions of a dialkyl peroxide with trialkyl phosphite in the presence of oxygen,... 

Reaction of 7V,A-diethyl-2,2,2-trichloroacetamide with trialkyl phosphites or triphenylphosphine to give N, N-diethyl-1,2,2-trichlorovinylamine [152-154],... 

Fourth, the present procedure bears a resemblance to the photochemical reaction of aryl iodides with trialkyl phosphites, by means of which several dialkyl arylphosphonates have been prepared.13 However, prolonged irradiation (>24 hours) in quartz vessels was employed. 

A number of complexes of isatin and metal salts have been reported.220,221 Isatin and N-substituted isatins react with dialkyl phosphites to give 56 and with trialkyl phosphites to give 57.222 The pyrolysis products of isatin have been studied,223 as have those of N-methylisatins.223a... 

Among the more recent approaches to phenoxazines and phenothiazines the reductive cyclization of 2-nitrodiphenyl ethers and sulfides with trialkyl phosphites is the most interesting. Here too a spiro intermediate is involved, produced by attack of an initially formed aryl nitrene on the second aromatic ring. The sulfide (252), for example, reacts with triethyl phosphite to yield 1-methylphenothiazine (253) and it is clear that in this case ring opening of the spiro intermediate also proceeds with a rearrangement of the Smiles type (Scheme 113) (75JCS(P1)2396). 

A range of aromatic alkenes and acrylic acid derivatives have been converted into benzyl alcohols and a-hydroxyalkanoic acids in good yields by a reductive oxidation process. This reaction is accomplished by reaction with oxygen and triethylsilane with a cobalt(II) catalyst, followed by treatment with trialkyl phosphites (equation 30)154. The aromatic olefins may also be converted into the corresponding acetophenone in a modified procedure where the trialkyl phosphite is removed155. In a similar reaction 2,4-alkadienoic acids are converted into 4-oxo-2-alkenoic acids156. 

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