Phosphorus acid anhydrides compounds

The related elements nitrogen and phosphorus combine with oxygen to form those oxides which are to be expected on the basis of the position of these elements in the periodic table. In addition, nitrogen forms several other oxides (Table 11.10). Although each of these compounds has its own specific uses or participates in certain reactions that render these oxides of scientific interest, the emphasis here is on the relationship between these oxides (acid anhydrides) and the corresponding acids. 

Compounds of phosphorus (III) are readily oxidized by [bis(acyloxy)iodo]-benzenes in this way, the reaction with triphenylphosphine led to the formation of acid anhydrides at room temperature ... 

Toxic) Preliminary drying is accomplished by stirring over potassium carbonate for 24h. A further 24h over 3A sieve or boric anhydride gives moderately dry solvent (- 50ppm) but much better results are obtained by stirring over phosphorus pentoxide (5% w/v) for 24h and then distilling. Drawbacks of this method are the formation of substantial quantities of coloured residue, and the possibility that the product is contaminated with traces of acidic impurities. If the acetonitrile is required for use with very acid sensitive compounds it is best to redistil it from potassium carbonate. 

Heteropoly-compounds of Molybdenum and Phosphorus.— Heteropoly-compounds include those acids and salts which contain acid anhydrides of one or more elements combined with a hydrate or salt of the acid of another element.- Compounds which contain the acid anhydride and the acid hydrate or salt of the same element—for example, polychromates, polytungstates, etc.—are distinguished as isopolycompounds. 

A number of piperazine-2,5-diones (a-amino acid anhydrides ) has been converted to pyrazines by the action of phosphorus halides. Baxter and Spring (312) first described the conversion of isoleucine anhydride (45) with phosphoryl chloride to 2,5-di-s-butyl-3,6-dichloropyrazine (46, X = Cl) and 2,5-di-s-butyl-3-chloropyrazine (46, X = H), and of DL-alanine anhydride (47) similary to 2,5-dichloro-3,6-dimethylpyrazine (48, X = Q) and 3from alanine anhydride does not involve an oxidation step, whereas the formation of 2,5-dichloro-3,6-dimethylpyrazine involves the oxidation of an intermediate dihydropyrazine derivative. Treatment of DL-alanine anhydride with phosphoryl chloride in the presence of a tertiary base (dimethylaniline) gave only the monochloro derivative the intermediate dichlorodihydropyrazine presumably loses hydrogen chloride and gives the stable aromatic 3-chloro-2,5-dimethylpyrazine. 

This compound will be referred to again in connection with the synthesis of salicylic acid (p. 717). The acid ester of phenol and sulphuric acid, phenyl sulphuric acid, CeHs—O—SO2OH, is a constituent of animal urine. The esters of phenols and organic acids are not readily formed by the direct action of the acids, in which respect the phenols again resemble tertiary alcohols. They may be prepared from phenols by the action of acid chlorides acid anhydrides or a mixture of the acid and phosphorus oxychloride. 

The reaction of N-arylsulfonylsuinmides with a range of trivalent phosphorus compounds gave near quantitative yields of the phosphinimides and the sulfide. I Addition of protic solvents led to reduction products, which contain, besides the original sulfides, an alkyl-exchanged sulfide in which the alkyl group derived from the alcohol. 126.127 other derivatives, (acid anhydride, amide, ester or thioester) were formed in the presence of carboxylic acid derivatives. 128,129 xhese reactions were favoured by the dipolar nature of the intermediately formed sulfurane. 127... 

The preferred bases include triethylamine, amidines, and guanidines. Dehydration of the carbamate has been done with phosphorus trichloride, phosphorus oxytrichloride, phosphorus pentoxide, acetic anhydride, benzenesulfonic acid anhydride, o-sulfobenzoic anhydride (2.14), or other similar compounds. 

Alcohol oxidations using acid anhydrides, such as acetic anhydride and benzoic anhydride, and phosphorus pentoxide with DMSO, have also been found to proceed in mild conditions to give the corresponding carbonyl compounds in good yields.27-29 The method is general and is especially useful for sterically hindered hydroxyl groups however, the reactions often suffer from concomitant formation of methylthiomethyl ether by-products. 

Several types of anhydrides of tervalent phosphorus acids are known and have been prepared by electrophilic substitution reactions at phosphorus. Examples are the phosphi-nous acid anhydrides 52 (equation 157), 53 (equation 158), prepared from a chlorophos-phine or an aminophosphine , and 54 (equation 159) Aminophosphines react with carbon disulphide to give ionic addition compounds at low temperatures, but dithiocar-bamate anhydrides (55) at room temperature (equation 160) Aminophosphines form analogous carbamate anhydrides with carbon dioxide, but isothiocyanates give ionic addition products, not insertion products ... 

The phosphinosulphonates (5), prepared from the appropriate phosphino-imidazole (4), are oxidizable to the phosphinyl compounds (6). More interestingly, they can isomerize into the phosphinylsulphinate (7) when allowed to come to ambient temperature. Other examples of (5) in which = R = OEt or OPr do not isomerize in this way. The preparation of phosphorus-sulphonic anhydrides (6) has been re-investigated and three efficient methods have been described for their synthesis these are (a) the trifluoromethanesulphonic acid-assisted reaction of a phosphinic acid with a sulphonic triazolide, (Jb) interaction of a phosphinyl-imidazole and a sulphonic acid, and (c) the use of a sulphonic anhydride in reaction (6). ... 

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