Imidazoline-2-thiol

Combinations of N- and 5-alkylation in 2-imidazoline-2-thiols can lead to 5,6-dihydro-4//-imidazo[2,l-6]thiazoles when the heterocycles are treated with ketones in the presence of a halo-genating agent. This is a variant of the Hantzsch thiazole synthesis <92SC1293>. A further example of A-acylation in combination with nucleophilic substitution is the conversion of 2-chloro-2-imi-dazoline into (131) when it is treated with pyridine and an aryl isocyanate <87JCS(P1)1033>. 2-Imidazolines like clonidine are also known to A-nitrosate <93JCS(P2)59l>. Intramolecular alkylation is exemplified in the base-induced rearrangement of 2,5-diaryl-4-chloromethyl-2-imidazolines (132) into pyrimidines (Scheme 64) <93JOC6354>. 

Chemical stabilizers have been used to reduce the rate of oxygen-promoted degradation of polysaccharides at T>225°F. Methanol and sodium thiosulfate are the most commonly used (86). Sodium dithio-carbamate, alkanolamines, and thiol derivatives of imidazolines, thiazolines, and other heterocyclic compounds have also been tested for this application. Calcined dolomite (B7) and Cu(l) and Cu(ll) salts (88) have been reported to increase the thermal stability of HEC. 

A recent report shows that 1,2,3,4-benzotetrazine 1,3-dioxide nitroderivatives 73 (R=N O2) are thiol dependent N O-donors and potent activators of the sGC [73]. Activation of the sGC was inhibited in the presence either of ODQ or of the N O scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethy]imidazoline-l-oxyl-3-oxide (carboxy-PTIO). All products inhibited A DP-induced aggregation of human platelets, with the potency sequence 7-nitro >5,7-dinitro >5-nitro. 

Similar to M11O2, BaMn04 is able to oxidize functional groups other than alcohols, including primary amines,76b anilines,76b,83a imidazolines,90 saturated hemiacetals91 and thiols.84a,88b... 

Keywords mercaptobenzimidazol, imidazoline-2-thiol, phenacylbromide, thiuro-nium salt, waste-free, solid-solid reaction... 

Solid 2-mercaptobenzimidazole 1 (300 mg, 2.00 mmol) or imidazoline-2-thiol 4 (204 mg, 2.00 mmol) and phenacylbromide 2 (398 mg, 2.00 mmol) were ball-milled at room temperature for 1 h. The yield of pure product 3 or 5 was 100%. 

Ethvlenethiourea (2-mercaptoimidazolinej imidazolidine-2-thione imidazoline-2-thiol, VIII) is a water-soluble white crystalline solid used extensively in curing elastomers (rubbers, e.g., polychloroprenes, polyacrylates, etc.) It is also present as an impurity in the ethylene bisdithiocarbamates widely used as fungicides. When the fungicides are present as a contaminant in heated foods, they may be converted to the ethylenethiourea (ref. 

SCHEME 11.1 Native chemical ligation and a concept using amino acid having thiol at the (i position. Acm, acetamidomethyl PG, protecting group VA-044,1,2 - azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride. 

Imidazolidine-2-thiones (or 2-ones) have been shown by NMR studies to exist entirely in these forms rather than as the possible 2-mercapto-(or 2-hydroxy-)2-imidazoIines (80CS(15)193). The thione structure for benzimidazolinethiones is supported by UV, IR and dipole moment measurements. In addition, an X-ray study of l-(j8-D-ribofuranosyl)benz-imidazoline-2-thione confirms its thione (59) rather than the thiol (60) structure (Scheme 19). 

In contrast to the 2,4-dioxoimidazoles (and such compounds as 5-phenyl-2-thiohydan-toin), there is convincing evidence (UV, IR, NMR data) that imidazolidine-2,4-dithiones exist mainly in the thione-thiol forms (84 Scheme 27). The two tautomers (85,86) have been separated in 5,5-diphenylimidazoIidine-2,4-dithione in KBr the C=N bands appear at 1495 and 1575 cm , respectively. In the 5,5-spiropentane analogues the structure related to (85) increases in importance as the solvent polarity increases. As mentioned above, the oxo-thione structures for imidazolin-4-one-thiones is supported by IR spectra in the solid state, and by UV spectra in ethanol. The partially fixed derivatives (87,88 Scheme 28) can be crystallized separately, but give identical spectra in solution. Both X-ray crystal structures and solid state IR spectra confirm the existence of two structures (87 y(C=0) 1690, r(C=N) 1510-1490 cm ) and (88 r(C=0) 1720, r(C=N) 1590-1575 cm ). As with the dithiones, the importance of the cross-conjugated form (88) increases with decrease in solvent polarity. 

Compounds of this type include some of the imidazolinones or imidazolinethiones which can be in equilibrium with the fully aromatic hydroxy or thiol forms (Section 4.06.5.1). The non-aromatic forms may be quite stable in some instances, but may also react in the aromatic form. Thus, 5//-imidazolin-4-ones (170) are acylated under Schotten-Baumann conditions on the exocyclic oxygen. When the reaction conditions are altered it is possible to obtain products of JV-acylation and A(,0-diacylation (71CHE746). With the same compound a Mannich reaction takes place at the 5-position, and phosphoryl chloride gives products of O- and (V-phosphorylation rather than nucleophilic chlorination (Scheme 81). 

Diphenylimidazoles, along with 4//-imidazoline-5-thiones (24) and the iminothiazolines (25), are formed when diphenylglycine thioamides are cyclized in boiling toluene by aluminum chloride (Scheme 12). Use of hydrogen chloride in hot dioxane gave only (24). Rather similar treatment of W-formylsarcosine-AT-methylthioamide with acid leads to 1,3-dimethylimidazolium-4-thiols (80AHC(27)24l). 

In the uncondensed imidazoles the standard method reacts an a-aminocarbonyl compound with a thiocyanate (see Section 4.1 and Table 4.1.1). If a 2-alkylthioimidazole is required directly, one can combine an N-alkyT or A -arylcarbonimidodithioate in refluxing acetic acid with the aminocarbonyl substrate (see Section 4.1 and Scheme 4.1.3). Alternatively, reaction between thiourea and a two-carbon synthon (ot-hydroxy-, a-halogeno-, a-dicarbonyl) leads to imidazoline-2-thiones (see Section 4.3). In sulfuric acid, 3-butynylthiourea cyclizes to 4,5-dimethylimidazolin-2-thione (see Section 2.2.1). 1-Substituted 2-methylthioimidazoles can be made, albeit in rather poor yields, from appropriately substituted 2-azabutadienes (see Section 3.2 and Scheme 3.2.3), and 2-arylthioimidazoles are available in moderate yields from benzyl isocyanides and arylsulfenyl chlorides (see Section 4.2 and Scheme 4.2.12). Ring transformations of 5-amino-2-alkylaminothiazoles and 2-acylamino-5-aminothiazoles may have occasional applications (see Section 6.1.2.7). The ease with which a thiol group or imidazole or benzimidazole can be alkylated, in comparison with the annular nitrogens, usually makes it more convenient to prepare alkylthioimidazoles from the thiols (or thiones). 

Synonyms 1-Methylimidazole-2-thiol 1-Methyl-4-imidazoline-2-thione... 

AI3-16292 Akrochem etu-22 Aperochem ETU-22 CCRIS 298 4,5-Dihydro-2-mercaptoimidazole 4,5-Dihydroimidazole-2(3H)-thione EINECS 202-606-9 Ethylenethiourea Ethylene thiourea Ethylene thiouree I Ethylene thiouree 1,5Ethylene-2-thiourea 1,3-Ethylenethiourea ETU HSDB 1643 lmidazole-2(3H)-thione, 4,5-dihydro- Imidazolidinethione Imidazoline, 2-mercapto- Imidazoline-2-thiol 2-lmidazoline-2-thiol 2-lmidazolidinethione Imidazoline-2(3H)-thione Mercaptoimidazoline 2-Merkaptoimidazolin 2-... 

Pyrazoloimidazolothiazole (36 R = H, Ph) (Table 4) has been prepared using bromo-methylpyrazolones (186 R = H, Ph) and 2-thiol-l-imidazoline <90jiC6io>. 

CAS 96-45-7 EINECS/ELINCS 202-506-9 Synonyms ETU 2-lmidazoiidinethione imidazoline-2-thiol 2-Mercaptoimidazoiine Empirical C3H6N2S Formula NHCH2CH2NHCS Properties Wh. to pale green crystals, faint amine odor si. sol. in cold water very sol. in hot water si. sol. in R.T. methanol, ethanol, acetic acid, naphtha insol. in hydrocarbon soivs. m.w. 

---