Imidazole thiones

Imidazole-5-thione, 4,4-diphenyl-tautomerism, 5, 368 3 H-Imidazole-2-thione, 1,3-dimethyl-structure, 5, 367 Imidazole-2-thiones acidity, 5, 367 betaines, 5, 372 synthesis, 5, 481 tautomerism, 5, 367 3H-Imidazole-2-thiones synthesis, 5, 473, 6, 992 Imidazolides deacylation, 5, 453 mass spectra, 5, 360 phosphoric acid reactions, 5, 454 reactions, 5, 451-453 Imidazolidine, l-alkyl-3-phenyl-N-oxidation, 5, 427 Imidazolidine, 1,3-benzyl-2-phenyl-oxidation, S, 427... 

The predominance of the thione forms of imidazole-2-thiones and benzimidazole-2-thiones has been established using ultraviolet spectroscopy, and for the former compounds this conclusion is supported by infrared spectroscopic data. ... 

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. 

Method C l-Methyl-3W-imidazol-2-thione (5.7 g, 0.05 mol), the haloalkane (0.05 mol), and TBA-Br (0.97 g, 3 mmol) in aqueous NaOH (40%, 15 ml) are added to PhH (I50ml) and the mixture is stirred for ca. 6 h at 60 °C. The organic layer is separated, dried over molecular sieves, and evaporated. The imidazolyl thioether is isolated by distillation under reduced pressure. 

In contrast, but again not unexpectedly, imidazole-2-thione is dialkylated on the sulphur atom and at the 1 -N position (Scheme 5.22). Even with equimolar amounts of the heterocycle and the alkylating agent, only the dialkylated derivative is isolated [91]. 

N.D. Abramov u. V. v. Trzhtsinskaya, Structure and Properties of Imidazole-2-thiones, Chem. Heterocycl. Compd.25, 1309-1321 (1989). 

Involvement of AModo species in electrophilic C-iodinations needs to be considered since a number of imidazoles are known to form such compounds in basic medium. Charge-transfer complexes, too, are quite well known. They seem to be of the n -type through the unshared electron pair at N-3. Equilibrium constants for their formation are known to increase regularly in line with electron-donating powers of substituents (or vice versa). Some KCT values at 20°C (L M are imidazole (200), 1-methylimidazole (333), 1,2-dimethylimidazole (1165), 4-phenylimidazole (152), and 4,5-diphenylimidazole (141) (83BSB923). The charge-transfer complexes formed between iodine and imidazole-2-thiones appear to involve the sulfur atoms (88JA2586). 

DIMETHYLIHIDAZ0LE-2-THIONE (2H-Imidazole-2-thione, 1,3-dihydro-1,3-dimethyl-)... 

Suszka538 has reported spectroscopic and thermodynamic data on the association of imidazole-2-thiones and 7V,tV -dialkylthioureas with SO2 in a variety of solvents. 

Cycloaddition with thioketones 3-Substituted imidazole 1-oxides 228 react with 2,2,4,4-tetramethylcylobutane-l,3-dithione with formation of l,3-dihydro-2H-imidazol-2-thiones 305 (1998HCA1585, 2011H765). 

Oxidative functionalization of imidazoles is typically not preparatively useful. However, an optimized procedure for direct peracid oxidation of azoles to N-hydroxyazoles was reported [95JCS(P1)243], with imidazoles affording dioxygenated products. In contrast, imidazoles are conveniently converted to imidazole-2-thiones with phenyl chlorothionoformate [95SL239]. 

Treatment of the substituted aminosulfolene (253) with phenyl isothiocyanate in refluxing benzene-pyridine (2 1) gave the perhydrothieno[3,4-rf]imidazole-2-thione 5,5-dioxide (254) (82CHE328). Reaction of 4-halo-2-thiolene (or -thiolane) 1,1-dioxides with dithiocarbamates proceeded similarly to give perhydrothieno[3,4-[Pg.1011]

Thione groups can often be eliminated by oxidation probably the sulfinic acid is the intermediate. Sometimes the sulfinic acid can be isolated (e.g., 740 741), but more often it spontaneously loses SO2. In this way, thiazoline-2-thiones give thiazoles, l,2-dithiole-3-thiones 742 are converted into 1,2-dithiolylium salts 743, l,3-dithiole-2-thiones 744 into 1,3-dithiolylium salts 745, 1,5-disubstituted imidazole-2-thiones into imidazoles <2003JHC229>, and 3-mercapto-l,2,4-triazoles into the parent triazole <2006S156>. In the pyrazole series, 746 also loses an A-methyl group to yield 747. 

The first paper on the synthesis of a thermally stable carbene, which could be kept in a bottle, appeared in 1991. It was entitled A Stable Crystalline Carbene and the main author was Anthony Arduengo (Fig. 8.1) from the Experimental Station of DuPont at Wilmington in the US [14]. He had set out to find a simple preparative route to industrially important imidazole-2-thiones and for this purpose treated imidazolium salts with strong bases and then added sulfur to form the required C=S bond [15, 16]. The ease with which these reactions succeeded, even in dry air, led Arduengo to believe that the respective carbenes, formed by deprotonation of the imidazolium ions, were less unstable than expected. Since the dimerization, as observed in the case of 6, was thought to... 

The Marckwald synthesis116 employed the reaction of a-amino-ketones with cyanates, thiocyanates, and isothiocyanates to yield 3 -imidazol-2-ones or AH-imidazole-2-thiones which are readily converted into imidazoles. The chief limitation of this method, which has been discussed adequately in earlier reviews,1-3 is in the synthesis of the a-aminocarbonyl compounds. The most convenient procedure is by reduction with sodium amalgam of a-amino acids.117 Among recent applications of the method118 119 is the synthesis118 of 4,5-... 

Reduction of 2,4,6-triphenyltriazine gives 2,4,5-triphenylimida-zole,140 while the 1,2,4-triazine ring also contracts to an imidazole141 with zinc dust and acetic acid. Treatment of 2,5-diaminothiazoles with alkali leads to imidazole-2-thiones.142,143... 

Treatment of 2,5-diamino-l,3,4-thiadiazole with an a-haloketone in ethanol, followed by reaction of the resulting 2-imino-3-(a-keto-alkyl)-5-amino-l,3,4-thiadiazoline hydrohalide (33) with aqueous ammonia, and then excess of hydrazine hydrate, leads to 1 -amino-imidazole-2-thiones (34).144... 

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