Imidazole 2-amino-1-aryl

Imidazole, 2-amino-1 -methyl-4,5-diphenyl-tautomerism, 5, 368 Imidazole, 2-aroyl-mass spectra, 5, 360 synthesis, 5, 391, 402 UV spectra, 5, 356 Imidazole, 4-aroyl-synthesis, 5, 474 Imidazole, C-aroyl-UV spectra, 5, 356 Imidazole, aryl-nitration, 5, 396, 433 oxidation, 5, 433 Imidazole, 1-aryl-dipole moments, 5, 351 dearylation, 5, 449 ethylation, 5, 448 H NMR, 5, 353 hydroxymethylation, 5, 404 rearrangement, 5, 108 synthesis, 5, 390 thermal rearrangement, 5, 363 Imidazole, 2-aryl-chlorosulfonation, 5, 397 synthesis, 5, 475 Imidazole, 4-aryl-bromination, 5, 399 Imidazole, C-aryl-electrophilic substitution, 5, 432-433 nitration, 5, 433 Imidazole, N-aryl-reactions, 5, 448-449 structure, 5, 448-449 Imidazole, arylmercapto-... 

The reaction of 1-amino-1-deoxyketoses, and their N-alkyl and N-aryl derivatives, with alkyl or aryl isothiocyanates (Huber et al, 1960) was studied in more detail, and new 4-(alditol-l-yl)-l-alkyl(aryl)-3-alkyl(aryl)-l,3-dihydro-2H-imidazole-2-thiones were obtained. These compounds were used as starting materials for the synthesis of OL-histidines, DL-histidine-2-thiol, and other imidazole derivatives of biological interest. 

Hydroxy leuco bases can be converted into the corresponding amino leuco bases by allowing the leuco compound to react with a secondary amine in the presence of acetic acid.78 Examples, 54, of amine bases utilized in this manner are imidazole, 1,2,4-triazine, aryl amine, and cyclohexayl amine. 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

Hydrazine-induced rearrangements have been observed with imidazoles, which contain an A -arylcarboxamide function as part of the ring system. 3-Aryl-5-arylidene-2-methylthioimidazolin-4-one (79) reacts with hydrazine to produce 5-arylidene-3-amino-2-arylimino-imidazolidin-4-one... 

There are many heterocyclic molecules in which 1,3,4-thiadiazoles are fused to other ring systems. For example, Molina et al. developed a procedure for building a thiadiazole ring on to a properly substituted imidazole moiety (Scheme 29). Reaction of l-amino-2-methylthio-4-phenylimidazole (161) with triphenylphosphine dibromide in dry benzene furnished the 2-methylthio-4-phenyl-l-triphenylphosphoranylidenamino imidazole (162) in a 95% yield. With aroyl chlorides at elevated temperature, this gave the 2-aryl-6-phenylimidazo[2,l-Z ][l,3,4]thiadiazoles (164) in yields between 50% and 70% via the imidoyl chloride intermediate (163) which could be isolated and shown to cyclize to the thiadiazole. The method developed for the imidazole ring was also applicable to the thiadiazolotriazine ring system <88H(27)1935). 

Reaction of l-azirine-3-methylaciylates (155) with imidazoles and pyrazoles under mild conditions results in the formation of 2-aza-1,3-dienes (156), which are useful as dienes in hetero Diels-Alder reactions with electron-deficient dienophiles <99JOC49>. When the related methyl 2-aryl-2ff-azirine-3-carboxylate (157) was used as fee substrate, reaction with an amine induced a ting opening by addition of the amino group onto fee C=N bond followed by cleavage to provide enediamine 158 <99JCS(P1)1305>. 

Aus Anilino-guanidin werden mit a -Brom-acetophenonen 4-Aryl-2-(2-phenyl-hydrazino)-imidazole und nicht die ebenfalls als Produkte denkbaren 2-Amino-l-anilino-imidazole erhalten106 (s.a. Bd.X/2, S. 739) ... 

Zur photochemischen Geriistumlagerung von Methyl-imidazolen s. Bd.IV/5a, S.562. 2-(2-Aryl-hydrazino)-imidazole unterliegen in konz. Salzsaure einer Benzidin-Umlagerung zu 2-Amino-4(5)-(4-amino-phenyl)-imidazolen1214,1215 (Bd.Xl/1, S. 847). 

Durch Einwirken von Isoamylnitrit auf 2-Amino-imidazole im sauren Milieu erhalt man die isolierbaren 4-Hydroximmo-4H-imidazole, die sich in heiBem Wasser recht schnell zu 5-Ami-no-3-aryl-l,2,4-oxadiazoIen umlagern232 233. 

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-... 

Aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]-quinazolines Isatoic anhydride could also be reacted with amino-, hydroxyl- or thiolanilines to form 2-(2-aminophenyl)benz-imidazoles, oxazoles or thiazoles, Scheme 5.38. In the case of 2-(2-aminophenyl)benzimidazoles (X=N), the product was formed after 3 min at 150°C in acetic acid. The products could subsequently be further elaborated 6-aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]quinazolines, a four ring system, was formed by treatment of the 2-(2-aminophenyl) benzimidazole (X=N) with different aldehydes in acetic acid at 150°C for 5 min (J. Westman, and K. Orrling, Personal Chemistry, Uppsala, Sweden, unpublished results). Fifteen compounds were synthesised in 20-75% overall yield. This 3 + 5 min procedure should be compared to the conventional heating protocol developed by Devi and co-workers57, where each reaction step was run overnight to eventually afford the products in only 30-50% yield. 

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