2-Mercapto-4- imidazole

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-4-carbaldehyde, 5-mercapto-1 -phenyl-reactions, 5, 444 Imidazolecarbaldehydes oxidation, 5, 437 Imidazole-2-carbaldehydes condensation reactions, 5, 436 deacylation, 5, 93 decarbonylation, 5, 436 oximes, 5, 436 reactions, 5, 93... 

Imidazole-5-carboxamide, 4-cyano-reduction, 5, 435 synthesis, 5, 461, 472 Imidazole-5-carboxamide, 4-mercapto-oxidation, 5, 445... 

To a stirred mixture of 140 parts nitric acid (d = 1.37), 1 part sodium nitrate and 240 parts water are added portionwise 89 parts dl-1-(1-phenylethyl)-2-mercapto-5-(ethoxycarbonyl)-imidazole. After the addition is complete, the whole is stirred for 2 hours at room temperature. The free base Is liberated by addition of solid sodium carbonate and the whole is extracted with 120 parts anhydrous ether while heating. The aqueous layer is separated and extracted twice with 80 parts anhydrous ether. 

The l-acyl-3-methylimidazole-2-thiones are easily obtained either from bis-l-methyl-2-imidazole disulfide, a carboxylic acid, and triphenylphosphine, or from 2-mercapto-l-methylimidazole and a carboxylic acid chloride in the presence of triethylamine.[32 ... 

A strictly dehned region of chemical shifts of C2, C4, and C5 atoms in A-oxides of 4A-imidazoles allows to dehne clearly the position of the A-oxide oxygen atom (102). Chemical shifts of the a-C nitrone group in a-N-, O-, and S-substituted nitrones are located in the region of 137 to 150 ppm (388, 413). On the basis of 13C NMR analysis of 3-imidazoline-3-oxide derivatives, the position of tautomeric equilibria in amino-, hydroxy-, and mercapto- nitrones has been estimated. It is shown that tautomeric equilibria in OH- and SH-derivatives are shifted toward the oxo and thioxo forms (approximately 95%), while amino derivatives remain as amino nitrones (413). In the compounds with an intracyclic amino group, an aminonitrone (A) - A-hydroxyaminoimino (B) tautomeric equilibrium was observed (Scheme 2.76), depending on both, the nature of the solvent and the character of the substituent in position 2 of the heterocycle (414). 

Instead of the amino group, position 4 of the imidazole ring was involved in the reaction of 5-amino-2-mercapto-1 -methylimidazole (226) and EMME when they were heated under nitrogen, giving 4-imidazolylmethylenemalo-nate (227) (78H241). The same product was obtained when the hydrochloride of imidazole (226) was reacted with N,N-dimethylaminomethylene-malonate in DMF or acetic acid. 

Ochiai, who reported in 1936 the first synthesis of the imidazo[2,l-h]thia-zole system (36CB1650), transformed ethyl 2-mercapto-5-methyl-imidaz-oIe-4-carboxylate with monochloroacetone into 2-(acylalkylthio)-imidazole 36. Refluxing 36 in phosphorus oxychloride yields ethyl 3,5-dimethylim-idazo[2,l-h]thiazole-6-carboxylate. No cyclization could be achieved by heating 36 in acetic anhydride because N-acylation (to 37) inhibited further reaction to the bicyclic system. 

Veerabhadraiah et al. (89SUL167) treated 4,5-disubstituted 2-mercapto-imidazoles with 3-(a>-bromoacetyl)coumarins and obtained ketones that on subsequent cyclization with PPA furnished 2,5,6-trisubstituted imidazo[2,l-h]thiazoles 38. 

The preparation of imidazo[2,l-h][l,3,4]thiadiazoles from imidazoles was reported only in a few cases. Thus treatment of A-acetylamino-2-mercapto-imidazole with POCI3 yields 113 (63LA113 77M665). Cyclocondensation of 114 with thiocyanates in PPA gives 115 (94KGS421). 

Bei Imidazolen, die an einem oder zwei Ring-C-Atomen Hydroxy-, Mercapto- oder Amino-Gruppen tragen, sind durch Keto-Enol-Tautomerie mehrere tautomere Formen moglich. Als Beispiel mogen die vier moglichen Tautomeren von 2-Hydroxy-imidazol dienen ... 

Hydroxy- bzw. Mercapto-imidazole liegen normalerweise in der Oxo- bzw. Thiono-Form vor4 ... 

Substituierte l-(Ethoxycarbonyl-methyl)-4-mercapto-5-phenyl-imidazole allgemeine Arbeitsvorschrift78 ... 

Synthesen unter Einsatz von Harnstoffen oder Thioharnstoffen fiihren mit a-Hydroxy-ketonen zu 2-Hydroxy- bzw. 2-Mercapto-imidazolen, die, wenn einer der beiden Reste R1 oder R2 oder beide ein H-Atom sind, als tautomere 2-Oxo-2,3-dihydro-116-119 (s.a. Bd. VIII, S. 166) bzw. 2-Thiono-2,3-dihydro-imidazole vorliegen120,121. 

Auf ahnliche Weise wird aus 3-Amino-2-oxo-tetrahydrofuran (2-Amino-4-butanolid) 4-(2-Hydroxy-ethyl)-2-mercapto-imidazol hergestellt149. 

Herstellung von 4- (2-Amino-ethyl) -2-mercapto-imidazol durch Quecksilber-katalysierte Hydrolyse von l,4-Bis-[phthalimido]-2-butin und anschlieBende Umsetzung mit Salzsaure und Kaliumthiocyanat170 ... 

SchlieBlich kann man statt Thiocyanaten auch Arylisothiocyanate (s.Bd. IX, S. 883 u. Bd. E4, S.881) oder Alkyl-isothiocyanate172 173 mit a-Aminosauren bzw. a-Amino-carbonyl-Verbin-dungen umsetzen. In diesem Fall erhalt man als Produkte 1-substituierte 4-Hydroxy-2-mer-capto- bzw. 2-Mercapto-imidazole ... 

Phosgen(III)289 entstehen 1,2-Dihydroxy- bzw. 1-Hydroxy-2-mercapto-imidazole ... 

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