2,4,5-triphenyl imidazole

Die Umsetzung von Benzylamin mit Tctrachlormcthan unter Kohlenmonoxid- oder Stickstoff-Druck von etwa 7500 Torr (5000 kPa) bei 150° fuhrt unter (Catalyse mit Carbonyl-cobalt- Oder Carbonyl-molybdan-Komplexen zu Gemischen aus 2,4.5-Triphenyl1-Benzyl-2,4,5-triphenyl-imidazol, 2,4,5-Triphenyl-4,5-dihydro- und l-Benzyl-2,4,5-tripheny -4,5-dihydro-imidazol °. 

Aus 1-Methyl-2,4,5-triphenyl- bzw. 1,2-Dimethyl-4,5-diphenyl-imidazol und Acetonitril werden beim Belichten ebenfalls [2 4- 2]-Cycloadditionsprodukte erhalten1250 1251. Dagegen findet mit 1-unsubstituierten Imidazolen wie z.B. 2-Phenyl- und 2,4,5-Triphenyl-imidazol unter Iso-merisierung zu 2H-Imidazolen cine Additon in 2-Stellung statt1250 12S1. 

Irradiation at 313 nm converts 4,5-diphenyl- and 2,4,5-triphenyl-imidazoles into the phenanthroimidazoles (197) by a process which may involve hydrogen abstraction by the solvent (Scheme 105) (72JPC3362). 

Photolysis of benzophenone (23.) with 1-methyl-2,4,5-triphenyl imidazole ( 2) in either acetonitrile solution or in the solid state (33) produces oxetane 21 (eq 6) (30). Irradiation of 4,4 -dimethylbenzophenone (2), 4-methylbenzophenone ( ), and 4-benzoylpyridine (15) in solution in the presence of 22, gives likewise oxetane adducts. In the solid state (33), however, no oxetane is formed from these three ketones. It appears that only 13 can take a relative geometric arrangement with 21 that is suitable for the oxetane formation in the solid state. 

Dimethyl-3,5,6-triphenyl-2,5-dihydro-l,2,4-triazinium iodide yields, after irradiation for 96 hours in propan-2-ol, l-methyl-3,5,6-triphenylpyrazole (34%), l-methyl-2-phenyl-phenanthro[9,10-f/]irnidazole (10%) and 28% starting material.369 l-EthyI-2.4,5-triphenyl-imidazole (15%), 3-phenylphenanthro[9,10-e,]-l,2,4-triazine, 3,4,5-triphenylpyrazole (7%) and 48% starting material are isolated after irradiation of 4-ethyl-2-methyl-3,5,6-triphenyl-2,5-di-hydro-l,2,4-triazinium iodide in propan-2-ol for 100 hours.369... 

Modern scientific research into the non-enzymatically catalyzed chemiluminescence of organic compounds began with Radziszewski s investigations, in 1871, of the oxidation of lophine (2,4,5-triphenyl imidazole (1) by aqueous-alkaline hydrogen peroxide) [3]. 

Also, Zhu and coworkers reported preparing of two high Tg (250° and 258°) polyimides embedded with triphenyl imidazole chromophores. Simultaneous polymerization and poling was carried in situ. The second harmonic generation measurements technology yielded moderate das values of 15 pnW and 16 pnvV. The signals of these poled polymer films were reported to be without any decay at < 150° The relaxation starts rapidly over 195°. The half-decay temperatures, of the samples orientation are as high as 240° and 224° respectively. 

We present here the first experimental demonstration of photochemical bistability in an open reactor. This bistable reaction results from the non-linear properties of a photochromic system the dimer of the triphenylimidazyl radical in chloroform. Hysteresis is observed on the plots of the stationary states of the system over a wide range of flow rates. Within this region, the system is bistable and can be made to flip from one state to the other by an external manipulation. One of the stable states is characterized by a high concentration of violet radicals 2 while in the other the violet radicals are replaced by highly fluorescent compounds. Mechanistic studies showed that this bistability was due to a positive feedback loop. This was thought to arise from the screening effect of the violet radicals 2 with respect to the irradiation of the triphenyl imidazole 3 in combination with an inhibition of the violet radicals 2 by the products of photolysis of triphenylimidazole 3. 

Soon after Hayashi and Maeda s original paper appeared, scientists became interested in the unusual properties of the oxidation product of triphenyl imidazole and related compounds. What was especially of interest was to make structural assignments based on spectroscopic and other data. 

These compounds are easily prepared from the appropriate 2-aminothiazole and acyl chloride (see Section III.2.D) or by general heterocydization methods. Acyl chlorides may be replaced by the corresponding anhydrides (471). Acids themselves may be used as acylating agents provided that the imidazole-triphenyl phosphine mixture is used as a catalyst (472). The Curtius degradation of 247 yields 2-acetamido-4-phenylthiazole (248) (Scheme 149) (473). 

Imidazole, 2,4,5-triphenyl-dipole moment, 5, 351 (71CHE801) 2H-Imidazole, 2,2-dimethyl-4-phenyl- H NMR, 5, 16 (83UP40100)... 

Imidazole 1-oxide, l-methoxy-2,4,5-triphenyl-pK, 5, 384 B-76MI40701, 70AHC(12)103, 80AHC(27)241)... 

Imidazole, 1 -hydroxy-2,4,5-triphenyl-3-oxides reactions, S, 455 Imidazole, iodo-nitrodehalogenation, 5, 396-397 Imidazole, 1-iodo-reactions, S, 454 stability, S, 110 Imidazole, 2-iodo-synthesis, S, 401 Imidazole, N-iodo-, S, 393 reactions, 5, 454 Imidazole, 4-iodo-5-methyl-iodination, 5, 400 Imidazole, 2-isopropyl-4-nitro-N-nitration, 5, 351 Imidazole, 2-lithio-reactions, S, 106, 448 Imidazole, 2-mercapto-l-methyl-as antithyroid drug, 1, 171 mass spectra, 5, 358 Imidazole, 1-methoxymethyl-acylation, S, 402 Imidazole, 5-methoxy-l-methyl-reactions... 

Imidazole, l-methyl-2,4,5-triphenyl-photochemical addition reactions, 4, 421 Imidazole, nitro-applications, 5, 498 IR spectra, 5, 358 mass spectra, 5, 359 quatemization, 5, 386 reactions, 5, 441 reduction, 5, 441 UV spectra, 5, 356 Imidazole, 1-nitro-reactions, 5, 454 Imidazole, 2-nitro-, S, 415 applications, 5, 498 reactions, 5, 96 reduction, 5, 441 synthesis, 5, 378, 395 Imidazole, 4-nitro-deuteration, 5, 417 methylation, 5, 383, 388, 389... 

Another example of the remarkable reactivity of Mg actuated by our procedure is its reaction with nitriles. In this respect, the Mg resembles an alkali metal more than an alkaline earth. Benzonitrile reacts with Mg overnight, in refluxing DME, to give 2,4,6-triphenyl-l,3,5-triazine and 2,4,5-triphenylimidazole in 26 and 27% yield, respectively, based on magnesium. Jhe imidazole was shown to arise, at least in part, from the action of Mg on the triazine. The trimerization of aromatic nitriles to give symmetrical triazines is not unknown, but generally the reactions are... 

Addiert man Aryl-isocyanate an Triphenyl-phosphan-(2-benzimidazolyl-methylimin) (I), so erhalt man 2-Aminocarbony 1-1 -arylimino-2,3-dihydro-lH-benz-imidazole)(IlI). Die Entstehung der Produkte wird iiber ein Carbodiimid-Zwischenprodukt II interpretiert520. 

Ethoxycarbonyl-l-hydroxy-benzimidazol wird offensichtlich auch bei der Umsetzung von Benzofurazan-l-oxid mit (Ethoxycarbonyl-methylen)-triphenyl-phosphoran als Zwischenpro-dukt durchlaufen nach weiterer Reaktion mit (Ethoxycarbonyl-methylen)-triphenyl-phospho-ran wird letztlich ein Gemisch aus J-Ethoxy-2-ethoxycarbonyl- und 2-Ethoxycarhonyl-henz-imidazol erhalten299. 

Different synthetic routes have been used to prepare these carbenes (Scheme 8.6). The most common procedure is the deprotonation of the conjugate acid. In early experiments, sodium or potassium hydride, in the presence of catalytic amounts of either f-BuOK or the DMSO anion were used. ° Then, Herrmann et al. showed that the deprotonation occurs much more quickly in liquid ammonia as solvent (homogeneous phase), and many carbenes of type IV have been prepared following this procedure. In 1993, Kuhn and Kratz" developed a new and versatile approach to the alkyl-substituted N-heterocyclic carbenes IV. This original synthetic strategy relied on the reduction of imidazol-2(3//)-thiones with potassium in boiling tetrahydrofuran (THF). Lastly, Enders et al." reported in 1995 that the 1,2,4-triazol-5-ylidene (Vila) could be obtained in quantitative yield from the corresponding 5-methoxy-l,3,4-triphenyl-4,5-dihydro-l//-l,2,4-triazole by thermal elimination (80 °C) of methanol in vacuo (0.1 mbar). 

Reactions of a number of l-phenylimidazole-2-carboxamides with chlorine in acetic acid, NCS, or hypochlorite failed to introduce chlorine into the 4- or 5-positions (80JHC409). Chlorination of a variety of 2,4-disubstituted imidazoles, however, was quite facile, Thus, 2,4-diesters [83JCS(P1)809] and 2-amino-4-aryl compounds [80IJC(B)526] were readily 5-chlorinated, and even when both the 4- and the 5-positions were blocked, as in 5-aminoimidazole-4-carboxamide, 2-chlorination with iodine monochloride was possible (89MI5). When all three carbons were substituted (e.g., in 2,4,5-triphenyl-, 2-chloro-4,5-diphenyl-, and 2-trichloromethyl-... 

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