Phosphite reactions

The hydrogen bound to phosphorus in phosphorous acid, HPO(OH)2, exchanges at rates convenient for study by the changes in intensity of the related lines in the raman spectrum . The systems involve high acid concentrations e.g. 5 g H3PO3 in 5 ml D2O). The rate coefficients at 23 °C are reported as about 5.7 X 10 sec (for H3PO3 in D2O) and 2.3 x 10 sec (for D3PO3 in H2O), but isotope effects cannot be determined since too many variables are present. 

The reaction of phosphite with iodine has attracted attention 

Since the publication of the exchange results , there is no substantial objection to the proposition that moderately slow phosphite reactions involve the tautomeric structure. Silver and Luz have presented evidence which appears to establish tautomeric change as kinetically significant but only with acid concentrations greater than 1 M. The rate equation for the iodine oxidation, viz. 

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The anhydride (72) gives quite different products, (73) and (74), with tris(dimethylamino)phosphine to those previously obtained with triethyl phosphite. The formation of (73) and (74) is suggested to involve keten intermediates and an alternative mechanism is proposed for the phosphite reaction. 

Rate Constants and Activation Energies of Triphenyl Phosphite Reaction with Different Hydroperoxide [21]... 

The preparations described here are developed from published work by Malatesta et al.5 and from more recent studies in the contributors own laboratory.2 The cobalt and nickel complexes are prepared by reduction of the corresponding metal nitrates with sodium tetrahydroborate in the presence of excess ligand, whereas the syntheses of the rhodium and platinum complexes involve simple ligand exchange processes. The preparative routes are suitable for use with triphenyl- or p-substituted triphenyl phosphites reactions involving o- or m-substituted triphenyl phosphites give much reduced yields of products which are difficult to crystallize and are very air-sensitive. These features probably reflect the unfavorable stereochemistry of the o- and m-substituted ligands. 

We close now with the case of the interesting Arbuzov rearrangement of trimethyl-phosphite (reaction 22) ... 

Treatment of the molybdenum alkylidyne complex 191 with 300 atm CO affords a mixture of three products the products of substitution of one and two phosphite ligands and complex 192 [Eq. (154)] (91). The methox-ycarbonyl group in 192 may have arisen from the reaction of an intermediate ketenyl ligand with methanol (derived from hydrolysis of trimethyl-phosphite). Reaction of the compounds 193 with xylylisocyanide was shown to give complexes 194 [Eq. (155)] (91). The products contain the... 

Nucleoside phosphites. Reaction of a nucleoside with phosphorous acid and di-p-tolylcarbodiimide in pyridine affords the nucleoside phosphite in good yield." Thus... 

It has beem suggested that the mechanism is probably the same as that of the trialkyl phosphite reaction, i.e., chlorination of phosphorus to a chlorophospho-nium species foUowed by alcoholysis and dealkylation. Whether PCI3 or trialkal-phosphites are actually present as discrete entities during the reaction is not... 

Huorinated etiolates are generally difficult to form. Ishihara and coworkers used fluorovinyl phosphates, which can be prepared from a-fluoro ketones and sodium diethyl phosphite. Reaction of these fluorinated enol phosphates with a reagent prepared from lithium aluminum hydride (LiAIH4> and cop-per(II) bromide, zinc(II) chloride, tin(II) chloride or bromine afforded the enolate (Scheme 34).The reaction of the enol phosphate with the reagents mentioned above suggests that the metal cation of the enolate is an aluminum species, though its actual structure is not known at present. 

A variant of the Mannich reaction using an equilibration between phosphorus acid and a trialkyl phosphite was developed [36]. The trialkyl phosphite was synthesised in situ by the reaction of phosphorus trichloride with PO, with the formation of tris (2-chloropropyl) phosphite (reaction 18.14). By equilibration of phosphorus acid with tris (2-chloropropyl) phosphite, bis (2-chloropropyl) phosphite (reaction 18.15) is formed which, by reaction with oxazolidine, gives an interesting phosphonate polyol containing phosphorus, chlorine and nitrogen (reaction 18.16) ... 

The unstable triethoxyphosphoranes (2) have been generated by the reaction of oxalylcarbamates with triethyl phosphite. Reaction of (2) in situ with bromo-trimethylsilane or hydrogen bromide in acetic acid gave the corresponding phosphonates (3) in high yield and so provides a new and most convenient route to the synthetically useful amino(diethoxyphosphoryl)-acetic esters (4) (Schone... 

Phosphoramidites (89), derived from enamines, react with carboxylic acids in an irreversible manner because of the low basicity of the eliminated enamine. The anhydrides (90) may also conveniently be obtained from enol phosphites. Reactions of (89) with phenol were also studied and the kinetics found to be characteristic for bimolecular processes . In contrast to other carboxylic acid halides, acyl fluorides give tervalent phosphorus fluorides with tervalent esters (Scheme 7). ... 

Several modifications of the original Cadogan-Sundberg triethyl phosphite reaction conditions have been reported. 

Reaction with aldehyde to phosphonium salt adducts containing 2 or 3 mol aldehydes/mol phosphite. Reaction widi water gives a-hydroxyaUcyl-phosphinate esters, acetal phosphonate, and eventually phosphinic acids [19, 21] (see Chapter9). 

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