Dialkyl phosphorochloridates

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

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... 

Preparation of diethyl 3-trifluoromethylphenylphosphonate — Reaction of a Grignard reagent with a dialkyl phosphorochloridate... 

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... 

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. 

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. 

Zirconocene dichloride has been reported to serve as catalyst for the addition of dialkyl phosphorochloridates across the triple bond of terminal alkynes.159 DIBAL is used with the terminal alkyne system to generate the dialkyl 1-alkenylphosphonate products. 

It was quite obvious that the fusion of phosphoric anhydride and ammonium bifluoride would not form the basis of a practicable method. We accordingly paid attention to entirely different methods of preparation. Brief reference has already been made to two new general methods (pp. 5, 7). The first and more important of these new methods depended upon the conversion of a dialkyl phosphorochloridate into the corresponding dialkyl phosphorofluoridate by means of an inorganic fluoride. Con-lideration therefore had to be given to the most convenient method for preparation of the intermediate phosphoro-chloridate.1 In the first instance three methods for the preparation of chloro compounds (I) were considered ... 

True phosphoric anhydrides are prepared by a method strictly analogous to reaction (c), viz. by the action of a dialkyl phosphorochloridate (p. 43) on the silver dialkyl phosphate ... 

The reaction between a dialkyl phosphorochloridate and a silver dialkyl phosphate has already been referred to (p. 100). 

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. 

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. 

On reaction with alcohols, these compounds give alkyl phosphorodichloridates and alkyl thiophosphorodichloridates, respectively, which can be converted with a second mole of alcohol in the presence of an acid-binding base to dialkyl phosphorochloridate and its thio analogues (Fletcher et al., 1948 Melnikov et at., 1959). 

The dialkyl phosphorochloridates discussed earlier can also be prepared by chlorination of dialkyl phosphonates (Hardy et al., 1944 Jenkins, 1944 McCombie et al., 1945) ... 

The phosphorylation of a,e or B,Y-unsaturaCed ketones (as carbanions obtained through the use of lithium tetramethyl-piperidide) with dialkyl or diaryl phosphorochloridates affords... 

Substituted-indoles have been N-phosphorylated with dialkyl phosphorochloridates after initial metallation with lithium diisopropylamide che reverse dephosphorylation is brought about by tetrabutylammonium fluoride.N,0-Diprotected cryptophane has been phosphorylated and then deprotected to give N(1)-phosphotryptophane. 

The interaction of secondary alcohols with either triphenyl phosphate or diphenyl phosphorochloridate under conditions of thermolysis provides alkenes through effective dehydration. Mixtures of dialkyl hydrogenphosphates and alkyl dihydrogenphosphates (generated from an alcohol and P4O10) act as alkylating agents for alcohols and phenols. ... 

Or Ao-substituted aryl Grignard reagents introduce a steric factor in the reaction with dialkyl phosphorochloridates (26,44). Consequently... 

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... 

Electron-diffraction measurements on trimethyl phosphate are best interpreted by assuming the presence of two rotational isomers the molecular parameters reported are cf(P=0) 1.477 cf(P—O) 1.580 d 0—C) 1.432 A, Z.OPO 105.2°, and Z.POC 118.4°. Thermal condensation reactions between trialkyl phosphates and dialkyl phosphorochloridates give monophosphorus side-products in addition to alkyl pyrophosphates. Detailed examinations of such systems suggest that oxonium-type intermediates such as (111) are involved rather than quasi-phosphonium complexes. 

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