Polyphosphate amides

Diarylimidazohnes 119 that act as potential P2X receptor antagonists have been prepared by microwave-assisted cyclization of amino amides in the presence of TMS-polyphosphate at 140 °C for 8 min [78]. This reaction seems quite general (for variations on R) as more than 35 compounds have been prepared with this method (Scheme 41). 

The reaction of 151 with methanol to give dimethyl phosphate (154) or with N-methylaniline to form the phosphoramidate 155 and (presumably) the pyrophosphate 156 complies with expectations. The formation of dimethyl phosphate does not constitute, however, reliable evidence for the formation of intermediate 151 since methanol can also react with polymeric metaphosphates to give dimethyl phosphate. On the other hand, reaction of polyphosphates with N-methylaniline to give 156 can be ruled out (control experiments). The formation of 156 might encourage speculations whether the reaction with N,N-diethylaniline might involve initial preferential reaction of monomeric methyl metaphosphate via interaction with the nitrogen lone pair to form a phosphoric ester amide which is cleaved to phosphates or pyrophosphates on subsequent work-up (water, methanol). Such a reaction route would at least explain the low extent of electrophilic aromatic substitution by methyl metaphosphate. 

Trimethylsilyl polyphosphate (PPSE),1 The reagent is prepared from P205 and [(CHj),Si]20. It is a colorless, volatile liquid, soluble in the usual organic solvents. It is comparable to polyphosphate ester for the Beckmann rearrangement of oximes to amides (3, 230 231). but it is prepared more easily. 

Conversion of amides into nitriles may be effected by treating them with a variety of dehydrating reagents. Among those that have been employed are phosphorus pentoxide, phosphorus pentachloride,170 ethyl polyphosphate,171... 

A. V. Chetkauskaite, L. L. Grinius and L. M. Mukhin (1988). Stimulating action of polyphosphates on peptide formation from glycine and phenylalanine amides under abiogenic conditions (in Russian). 

Ketoximes may be rearranged directly to amides under a wide variety of conditions. Phosphorus pen-tachloride, phosphorus oxychloride, thionyl chloride, trimediylsilyl iodide (TMS-I), formic acid, poly-phosphoric acid, trimediylsilyl polyphosphate and mineral acids have all been successfully employed. Representative procedures using these and other reagent systems have been documented previously. ... 

Pictet-Spengler cyclization, 161 Pinacol rearrangements, 51 B-(3>a-Pinanyl-9-borabicyclo[3.3.1 ]-nonane, 320-321 Piperidine, 183 Piperidine enamines, 16 Piperidines, 18 Piperonal, 232 Piperylene, 372 N-Pivaloylaniline, 69 Platinum catalysts, 321 Podophyllotoxin, 165 Polygodial, 167 Polymethoxyarenes, 368 Polymethylpyrimidines, 345 Polynucleotides, 88 Polyphosphate ester, 437 Polyphosphoric acid, 321-322 Potassioacetone, 73 Potassium-Alumina, 322 Potassium bis(trimcthylsilyl)amide, 38 Potassium f-butoxide, 323 Potassium carbonate, 323 Potassium-18-Crown-6, 322 Potassium cyanide, 324 Potassium cyclopentadienide, 111 Potassium 2,6-di-f-butyl-4-methylphen-oxide, 48... 

HETEROCYCLES Copper phcnylace-tylide. Dichlorobis(benzonitrile)palladium. N-Dichloromethylene-N,N-dimcthylammo-nium chloride. Diiminosuccinonitrile. Dimethyl acetylenedicarboxylate. Dipotassium cyanodithioimidocarbonate. Ethoxy-carbonyl isothiocyanate. Ethyldiisopropyl-amine. Ethylene oxide. Hydrogen fluoride. Isocyanomethane-phosphoric acid diethyl ester. Lead tetraacetate. Lithium aluminium hydride. Methylhydrazine. Phosphoryl chloride. Polyphosphate ester. Polyphosphoric acid. Potassium amide. Potassium hydroxide. Tolythiomethyl isocyanide. Tosylmethyl isocyanide, Trichlo-romethylisocyanide dichloride. Trimethyl-silyldiazomethane. 

Besides cyclic esters and carbonates, six-membered cyclic depsipeptides and a five-membered cyclic phosphate were subjected to lipase-catalyzed ring-opening polymerizations, yielding poly (ester amide)s190 and polyphosphate,191 respectively. High temperatures (100—130 °C) were required for the polymerization of the former monomers. 

Phthalic acid, 259 Phthalic anhydride, 104 a-Picoline, 161 a-Picoline N-oxide, 161 Picolinic acid, 16 Picramic acid, 271 Picric acid, 271 Pinacol reduction, 7 Pinosylvin, 31 Piperazines, 322 Piperidine, 33, 291 2-Piperidone, 194 Pivaldehyde, 105 Podophyllotoxin, 337 Podophyllotoxone, 337 Polonovski reaction, 308 Polyisoprenoids, 300-301 Polymethoxybenzophenones, 30—31 Polymethylhydrosiloxane, 294 Polyphosphate ester (PPE), 229-230 Polyphosphoric acid, 227, 231—232 Potassium, 232, 233 Potassium acetate, 96 Potassium amide, 232—233, 310 Potassium azodicarboxylate, 100 Potassium r-butoxide, 26, 45, 47, 77-78, 85, 133, 188, 212, 222, 225, 233-234, 236, 246... 

Formulations usually contain a combination of different anodic and cathodic inhibitors. Commonly used are ortho- and polyphosphates, phosphonates, tannins, lignins, benzoates, silicates, chromates, molybdates, nitrites, nitrates, zinc salts, aromatic azoles, carboxylic acids, amides, amines, soluble oils, and oxygen scavengers, such as hydrazine and sulfites [3, 46]. Some of these substances (e.g. silicates) are employed predominantly in synergy with other inhibitors, whereas in other cases the combination of inhibitors may have adverse effects (e.g. nitrites and organic amines or amides may form carcinogenic nitrosamines at elevated temperatures). 

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