Dialkyl phosphites phosphorochloridate

G.l.c. studies of tributylphosphine, dialkyl phosphites, and dialkyl alkylphosphonates are reported. Tributyl phosphate in nitric acid can be estimated by g.l.c. if a glass column is used. Tetraethyl pyrophosphate has been directly determined on a nanogram scale by g.l.c., whereas it was found most convenient to first convert the tetra-aryl pyrophosphates by methanolysis to diarylmethyl phosphates. Phosphorochloridates were converted by t-butyl alcohol into t-butyl chloride before analysis. G.l.c. studies of pesticides have been reported and the isomeric thiophosphates (138a) and (138b) have quite different retention times. ... 

Preparation of diallyl phosphorochloridate — Preparation of a dialkyl phosphorochloridate from a dialkyl phosphite by the Todd reaction... 

The closely related Todd reaction, useful for the preparation of dialkyl phosphorochloridates and phosphoramidates, also involves the use of amines with dialkyl phosphites.146152 180-182 Although the reaction proceeds using preformed salts of the dialkyl phosphites,183 the use of tertiary amines facilitates the reaction by allowing all reagent materials to be in solution. Biphasic reaction systems utilizing phase-transfer catalysts and crown ethers have also been successful for this reaction.158-161... 

Small amounts of amine salt are also generated as a side product.8-10 Other oxidative chlorinating approaches have been used with dialkyl phosphites as well, including methods using copper(II) chloride,11 sulfuryl chloride,12 and elemental chlorine.13 All of these provide the target dialkyl phosphorochloridate in high yield. 

On pp. 45 and 57 we referred to the action of chlorine1 and of N-chlorosuccinimide2 on dialkyl phosphites producing dialkyl phosphorochloridates. We have made use of the latter in producing a variety of esters of orthophosphoric acid and of phos-phoramidates, and reference has already been made to many such reactions (p. 82). These processes are, in a sense, phosphorylations of the alcohols or of the amines respectively. 

Esters of pyrophosphorous add can be prepared by using sodium dialkyl phosphite and a dialkyl phosphorochloridite (5.321). If a phosphorochloridate ester is used, an ester of hypophosphoric acid is obtained (5.322). 

Trialkyl phosphites undergo reaction with molecular halogen via a mechanism reminiscent of the Michaelis-Arbuzov reaction to form the dialkyl phosphorochloridate in good yield (Equation 4.4).7 With cyclic esters, the halogen performing the displacement reaction at carbon remains attached within the molecule. 

Harvey, R.G., Reactions of triethyl phosphite with activated olefins. Tetrahedron, 22, 2561, 1966. Okamoto, Y, A convenient preparation of dialkyl 3-(dialkoxyphosphinyl)-l-propenyl phosphate derivatives. Addition of the mixed reagent trialkyl phosphite/diaUcyl phosphorochloridate to a,P-unsaturated aldehyde, Chem. Lett., 87, 1984. 

Attack by phosphorus on halogen is rather well established for the reaction of hexachlorocyclopentadiene (7) with trialkyl phosphites (65,214), providing the corresponding dialkyl phosphorochloridate and... 

The greater nucleophilic reactivity of silyl phosphites towards organohalogen compounds results in a greater complexity in product composition thus, dialkyl trimethylsilyl phosphites and CCI4 afford the dialkyl (trichloromethyl)phosphonates in yields of 50-60%, together with various halogenated silicon-containing products and a dialkyl phosphorochloridate (in up to 30% yield)". ... 

Titanium tetrachloride is an efficient reagent for the conversion of trialkyl phosphites and dialkyl hydrogen phosphonates into dialkyl phosphorochloridates. Imidazolides and dialkyl or diaryl phosphoric acids react with acyl fluorides - benzoyl fluoride and oxalyl difluoride being the reagents of choice - to give quantitative yields of the phosphoryl fluorides. The procedure is adaptable to the preparation of fluorides of carbohydrate phosphates in this field, the reaction between the ceu bohydrate and tris-l//-imidazolylphosphine oxide or sulphide with the replacement of one imidazole... 

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