Pentoxide, phosphorus reaction with amides

A variety of catalysts has been used to promote the Clauson-Kaas reaction. The most common are Bronsted acids but a variety of other Lewis acids have also seen some use. An interesting report by Fang used phosphorus pentoxide in toluene to shorten reaction times.Others have commented that care must be taken to rigorously remove water from this reaction with amides to avoid the generation of nitriles. ... 

The amino group of 4-amino-3-pyrazolin-5-ones reacts normally. Acylation occurs readily with a wide variety of acylating agents. Amides are formed by reaction with acid chlorides,50,533,984,1414,1473 acids618,984,1471 and esters in the presence of phosphorus pentoxide.1471 Thioformamides have been prepared by reaction with dithioformic acid and its salts.472,556,1374 Sulfonyl chlorides react to form sulfonamides.98,489,984,1249,1504 Chlorophosphates react with 4-amino-3-pyrazolin-5-ones to form phosphoramide derivatives.509,1498... 

Tetrahydroharman, m.p. 179-80°, has been prepared by a number of workers by a modification of this reaction, viz., by the interaction of tryptamine (3-)5-aminoethylindole) with acetaldehyde or paraldehyde and Hahn et al. have obtained a series of derivatives of tetrahydronorharman by the use of other aldehydes and a-ketonic acids under biological conditions of pH and temperature, while Asahina and Osada, by the action of aromatic acid chlorides on the same amine, have prepared a series of amides from which the corresponding substituted dihydronorharmans have been made by effecting ring closure with phosphorus pentoxide in xylene solution. 

Surfactants are prepared which contain carboxylic acid ester or amide chains and terminal acid groups selected from phosphoric acid, carboxymethyl, sulfuric acid, sulfonic acid, and phosphonic acid. These surfactants can be obtained by reaction of phosphoric acid or phosphorus pentoxide with polyhydroxystearic acid or polycaprolactone at 180-190°C under an inert gas. They are useful as polymerization catalysts and as dispersing agents for fuel, diesel, and paraffin oils [69]. 

Synthesis of the oxadiazolopyrimidone 358 was accomplished by reaction of the amide 357 with phosphorus pentoxide and methylsulfonic acid in low yield <1994PHA880>. Also, its benzologue 360 could only be obtained in very modest yield <2004TL8741> in the case, reaction of the benzonitrile derivative 359 with acetylhydrazine resulted in formation of the bicyclic product 360. 

Nitriles can be prepared by the SN2 reaction of a cyanide ion with a primary alkyl halide. However, this limits the nitriles that can be synthesised to those having the following general formula RCH2CN. A more general synthesis of nitriles involves the dehydration of primary-amides with reagents such as thionyl chloride or phosphorus pentoxide ... 

A synthesis, which leads to enamines in the form of their iminium salts, involves the cyclization of N-fi-arylethyl tertiary amides with phosphorus pentoxide or phosphorus oxychloride (Bischler-Napieralski reaction)441-445. 

SULFURIC OXYCHLORIDE (7791-25-5) SOjClj Forms corrosive mixture with air (Fire Rating 0). Reacts exothermically with water or steam, producing heat and yielding sulfuric acid and HCl vapors. Reacts violently with bases, amines, amides, inorganic hydroxides alkahs, alkali metals, dimethyl sulfoxide, dinitrogen pentoxide, lead dioxide (explosive reaction) N-methylformamide, red phosphorus. Reacts,... 

The isoquinoline ring, although common in natural products, is not as important among pharmaceuticals as is the quinoline ring. Several synthetic methods are available, but we will discuss only the most commonly used one, the Bischler-Napieralski synthesis that was reported in 1893. With some modifications, it is stiU of great value today for the synthesis of isoquinolines. The process is simple and involves the reaction of an acyl derivative (an amide) of a 2-arylethylamine with phosphorus oxychloride or phosphorus pentoxide (Scheme 9.54). The... 

With sodamide, mono- and diamido salts are obtained directly (Chapter 7.3). Ethyl alcohol reacts with the pentoxide to give a mixture of ethyl phosphoric acids (5.291). With phosphorus amides, reaction (4.52) occurs. 

An alternative preparation of a nitrile is illustrated by the reaction of the half-ester of 2,2-diethyl malonate 1.51) ivith SOCI2 and then NH3 to give the amide. Subsequent heating with phosphorus pentoxide led to dehydration and gave nitrile 1.52 Catalytic hydrogenation reduced the nitrile to an aminomethyl group, and acid hydrolysis gave 2,2-diethyl-3-aminopropanoic acid 1.53). 2-Ethyl-2-cyclohexyl-3-aminopropanoic acid and 2-ethyl-2-benzyl-3-aminopropanoic acid were also prepared by this method.30... 

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