Phosphorochloridites esters

The reaction is performed most simply by the addition of the propargylic alcohol to a solution of the phosphorus halide. Rearrangement of the phosphorus ester proceeds at ambient temperature or with mild heating. When phosphorus trihalides are used, the product can be isolated as the phosphonic dichloride.168169 Aqueous workup provides the phosphonic acid.162 In most instances, however, a dialkyl phosphorochloridite with only a single halogen on phosphorus available for reaction with alcohol has been used.165 170 174... 

The chemical basis for the phosphite triester approach is the observation, that dialkyl phos-phorochloridites such as (CjHjOJjPCI react very rapidly at the 3 -OH of nucleosides in pyridine even at low temperatures. In contrast, the reactions of analogous chloridates, e.g. (C2HjO)2POCIi require several hours at room temperature. It was later found that phosphite esters can be oxidized quantitatively to the phosphates by using iodine in water and that clean condensation of phosphorochloridites with nucleosides can be achieved in THF at -78 °C. To develop this chemistry into a useful synthetic procedure it was necessary to establish which... 

The reaction of a phosphonamidite (79) with a trifluoracetyl ester (80), to give a phosphonite (81), has been shown to be catalysed by 4-dimethylaminopyridine. In contrast to an earlier report where a similar reaction proceeded with retention of configuration at phosphorus, the present system gave an equal amount of the two diastereomers (81). A mechanism is proposed which involves attack of an alkoxide, formed by de-trifluoracetylation of (80), on an equilibrating DMAP-intermediate (82). Another unusual substitution reaction is one between an alkoxyborane (83) and a phosphite (84). The phosphite was prepared in situ from acetylacetone and diethyl phosphorochloridite, and the substitution occurred under very mild conditions and gave high yields of phosphates after oxidation. 

Lee, K., and Wiemer, D.E, Reaction of diethyl phosphorochloridite with enolates. A general method for synthesis of P-keto phosphonates and a-phosphono esters through C-P bond formation, J. Org. Chem., 56, 5556, 1991. 

Attack on saturated carbon.- a-Hydroxyketones with diethyl-phosphorochloridite and ferric chloride gave 2-oxoalkylphospho-nates (1), probably via 2-oxoalkyl phosphites (2) which rearrange to (1) in the presence of the Lewis acid catalyst. No rearranged product was observed in the absence of the oxo group, and a-hydroxy esters gave the H-phosphonates (3). The 1,3,2-oxaza-... 

Other reactions between cyclic phosphorochloridites or cyclic esters and dienes are summarized in Scheme here, A and B are O, S or Se, and may be different or identical, and X = Cl, Br, NCS, or OR, and the conversion is brought about when mixtures of reactants are heated together in sealed tubes for extended time periods. As in the many examples known in which the reacting system, as a whole, is sulphur-free, the nature of the intermediate can be in doubt, and probably depends on the nature of the substituents, particularly those directly connected to phosphorus thus some reactants may interact through a covalent, pentacoordinate species 27, whereas others form a pseudoquatemary intermediate 28. It may also be that one intermediate structure is transformed into the second before the ultimate formation of the 3-phospholene (29). Also, in accord with these ideas, thiophosphorus(III) halides have been obseved to react with a,j5-unsaturated ketones to give, ultimately, l,2-oxa-4-phospholenes as their 2-sulphides (30) (Scheme 3)45 8. reactions carried out in acetic acid solution the products are said to be the esters... 

An alternative to the Arbuzov route to P-keto phosphonates (40), alkylation of diethyl phosphorochloridite (41) with enolates followed by air-oxidation of the phosphonite, has been evaluated. Although some enolphosphate was formed, the ratios of P-C to P-O products were better than 12.5 1 under optimized conditions, and the products were easy to purify. The reaction is also useful for preparation of a-phosphono esters (42). A full paper has appeared on a new reagent (43) for the determination of optical purities of chiral alcohols or thiols. It is superior to previous reagents because of the large chemical shift difference between the diastereomeric products (44). 

The reaction between cyclic ketone enolates and diethyl phosphorochloridite followed by aerial oxidation of the intermediate P(III) esters, yields mixtures of C - and (7-phosphorylated products. The formation of the (1 -oxoalkyl)phosphonic diesters was optimized using diethyl ether as solvent (although better yields were sometimes obtained for reactions in Et20/THF when hexamethylphosphoric triamide was added) when the... 

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). 

An alternative synthesis of pyrophosphite esters is by condensation of alkyl phosphorochloridites using water and triethylamine (5.323), while another way of making hypophosphoric esters is by condensation of alkyl phosphorochloridates with sodium (5.324). 

Hydroxy-2,2-diphenylethyl phenyl sulfide allowed to react with methyllithium in tetrahydrofuran, then at 0 with o-phenylene phosphorochloridite, and the intermediate crude phosphorous ester refluxed 3 hrs. in dioxane 1,1-diphenyl-ethylene. Y 83%. F. e. s. I. Kuwajima, S. Sato, and Y. Kurata, Tetrah. Let. 1972, 737 f. method cf. R. M. Coates and R. L. Sowerby, Am. Soc. 94, 5386 (1972). 

Phosphonous acid esters from phosphorochloridites s. U, 699 Phosphinic acids from phosphonic acid dihalides s. tA, 700... 

There are several procedures for conversion of alcohols to iodides which are based on alkoxyphosphonium intermediates. One involves preparation of a cyclic phosphite ester from the alcohol and o-phenylene phosphorochloridite. Treatment of the cyclic phosphite ester with iodine then generates the alkyl iodide ... 

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