Phosphorous acid amides mixed

A solution of 7.5 g (0.1 mol) of 1,3-propanolamine and 20.2 g of triethylamine in 100 cc of absolute dioxane is added dropwise at 25°C to 30°C while stirring well to a solution of 25.9 g (0.1 mol) of N,N-bis-(p-chloroethyl)-phosphoric acid amide dichloride in 100 cc of absolute dioxane. After the reaction is complete, the product is separated from the precipitated triethylamine hydrochloride and the filtrate is concentrated by evaporation in waterjet vacuum at 35°C. The residue is dissolved in a large amount of ether and mixed to saturation with water. The N,N-bis-(p-chloroethyl)-N,O-propylene phosphoric acid diamide crystallizes out of the ethereal solution, after it has stood for some time in a refrigerator, in the form of colorless water-soluble crystals. MP 48°C to 49°C. Yield 65% to 70% of the theoretical. 

With the use of a family of three structurally related cyclic phosphoric acids (P-mix) as resolving agent, a diastereoisomerically pure salt containing the (25,5R)-enantiomer in 99% ee precipitates. The resolved t/ rc< -(4-methylthiophenyl)serine amide (Figure 7.5) can be used as an intermediate in the synthesis of thiamphenicol.22 Note that the individual phosphoric acids give salts of lower... 

Carboxylic acids can also be activated by the formation of mixed anhydrides with various phosphoric acid derivatives. Diphenyl phosphoryl azide, for example, is an effective reagent for conversion of amines to amides.140 The proposed mechanism involves formation of the acyl azide as a reactive intermediate. 

Figure 7.2 illustrates the phosphorus pentoxide-mediated dehydration of a primary amide to a nitrile, using the transformation of nicotine amide (A) into nicotine nitrile (B) as an example. The reaction of phosphorus pentoxide at the carboxyl oxygen furnishes the partially ring-opened iminium ion E (simplified as F) via the polycyclic iminium ion C. E is deprotonated to give the mixed anhydride G from imidic acid and phosphoric acid. Imidic acids are characterized by the functional group R-C(=NH)-OH. This anhydride is transformed into the nitrile B by an El elimination via the intermediate nitrilium salt D. Nitrilium salts are iV-pro-tonated or V-alkylated nitriles. 

Thionyl chloride is frequently the reagent of choice for the dehydration of higher-molecular-weight amides, since the secondary products are gaseous and the nitrile is more readily purified. Oftentimes, the higher fatty acids are converted to the nitriles in a single operation via the intermediate ammonium salts and amides. For this purpose, dry ammonia gas is passed into the molten acids at 290-300° the yields of nitriles are excellent (80-85%). A small amount of 85% phosphoric acid appreciably reduces the reaction time. Another procedure consists in passing the acid vapors mixed with ammonia over silica gel at 500°. This technique... 

In peptide synthesis it is necessary to activate the carboxyl group (COOH-group) during the reaction involving amide bond formation. Earlier methods of COOH-activation were based on the formation of acid chlorides, anhydrides (either mixed or symmetrical carboxyanhydrides, as well as mixed anhydrides of inorganic acids such as sulfuric or phosphorous acids), and azides (Schroder and Lubke, 1965). It was soon... 

The various ways in which esters of cellulose and phosphorous adds can be synthesized are esterification cellulose with free acids alcoholysis, with cellulose, of the esters and amides of phosphoric adds and esterification with mixed anhydrides df phosphoric adds and carboxylic adds. 

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