2-Imino-imidazole

An efficient one-pot synthesis of some novel azolo[l,5-a]pyrimidines, via enaminonitriles, has been described <00SC1985>. The utility of 3-aminocinnamonitrile in the synthesis of new pyrazolo[l,5-a]pyrimidines has been reported <00ZN(B)321>. The synthesis of novel arylaminopyrazolo[3,4-d]pyrimidin-4-ones has been described <99IJC(B)1075>. The synthesis and properties of a-Thiagra, a substituted 5-(2-thienyl)pyrazolo[4,3-d]pyrimidin-7-one bioisostere of Viagra, have been described <00H(53)2643>. Imidazo[4,5-b]pyrazines are obtained by the reaction of 4-amino- 5-imino-imidazole derivatives with acetophenone dimethylacetal . 

Sonication of (imino)imidazole 537 in the presence of lithium followed by treatment with CS2 and quenching with diiodomethane affords imidazolo-fused thiadiazepinedithione 538 (Scheme 274) <1999H763, CHEC-III(13.16.9.5)516>. 

Even in tricyclic bis-imidazole 57, for which the potential imino-tautomer 57b would be stabilized by the intramolecular N-H -N bond, the only observable form is the amino tautomer 57a (Scheme 30) [73KGS807 76AHC(S1), p. 431]. 

Nitroimidazoles substituted by an aromatic ring at the 2-position are also active as antitrichomonal agents. Reaction of p-fluorobenzonitrile (83) with saturated ethanolic hydrogen chloride affords imino-ether 84. Condensation of that intermediate with the dimethyl acetal from 2-aminoacetaldehyde gives the imidazole 85. Nitration of that heterocycle with nitric acid in acetic anhydride gives 86. Alkylation with ethylene chlorohydrin, presumably under neutral conditions, completes the synthesis of the anti-... 

The benzyl 1,2,4-thiadiazolium salt 59 can be isomerized to the 5-imino-l,2,4-thiadiazolidine 60 when treated with a strong base like potassium /-butoxide (Equation 17) <1997ZOR1728>. If the 2-substituent is replaced with a tosylmethyl group and the 5-position substituent is a diphenylamino in place of an aniline such as compound 61, then a rearrangement occurs to give an imidazole 62 (Equation 18) <1997ZOR1728>. 

Oxidation of mono-iV -oxides 4H -imidazole (223) and (224) with Pb02 in methanol leads to the formation of stable a,a-dimethoxy-substituted nitroxyl radicals (271) and methoxy substituted imino nitroxyl radicals (INR) (272)-(274) (Scheme 2.101) (514). 

In contrast, the reaction of acid-catalyzed nucleophilic addition of alcohols to derivatives of AH -imidazol-1 -oxide (219) and (224) leads only to nitronyl nitroxyl (221) and imino nitroxyl (274) radicals (518). 

Oxidative Animation of Nitrones to a-Amino-Substituted Nitroxyl Radicals Similar to the oxidative methoxylation reaction, oxidative animation of 4H -imidazole TV-oxides, in amine saturated alcohol solutions, give stable nitroxyl (282), nitronyl nitroxyl (283), imino nitroxyl (284) and (285) radicals with the amino group at the a-carbon atom of the nitroxyl group (Scheme 2.107) (520, 521). The observed influence of substituents on the ratio of animation products at C2 and C5 atom is close to the ratio observed in the previously mentioned oxidative methoxylation reaction. It allows us to draw conclusions about the preference of the radical cation reaction route. 

Imidazole, purification of, 48, 45 reaction with phosgene, 48, 44 Imldazole, 1,1 -carbonyldi-, 48, 44 Imidazolium chloride, 48, 46 3-Imino-l-( -tolylsulfonyl)pyrazolidine, from 3-amino-3-pyrazoline sulfate and / -toluenesulfonyl chloride, 48, 9... 

Diamino-2,l>3-benzothiadiazole 201 undergoes cyclization on reaction with selected aromatic aldehydes <2004T2953>. Thus, reactions with pyrene-l-carboxaldehyde or naphthalene-1-carboxaldehyde in refluxing toluene produce the corresponding imidazoles 202 in moderate yields, whereas reactions with /i-(Ar,Ar-dimethylamino)benz-aldehyde and /i-[Ar,Ar-di(4-methylphenyl)amino]benzaldehyde under similar conditions gave the corresponding 5-imino derivatives 203 (Scheme 13). 

Werden Aldehyde mit Amin-Hydrochloriden, lsonitrilen und Kaliumcyanat in Methanol/Was-ser-Gemischen umgesetzt, so werden 4-Imino-2-oxo-imidazolidine (4-Amino-2-hydr-oxy-imidazole) erhalten42d ... 

Eine verwandte Reaktion ist die Umsetzung von Olefinen mit verschiedenen Carbonsaure-nitrilen und Nitrosylium-hydrogensulfat. Hier wird in einer Folgereaktion ein zweites Molekiil Olefin an das zunachst gebildete 1-Hydroxy-imidazol addiert, und es entstehen (l-(Hydrox-imino-alkyl)-imidazol-3-oxide64. Die Ausbeuten sind jedoch mit 5-30% nur maBig,... 

Bei Einsatz von z. B. 3,5-Dimethyl-l-(imino-isopropylamino-methyl)-pyrazo]/ai-Brom-aceto-phenon erhalt man infolge Hydrolyse des nicht isolierten 2-(3,5-Dimethyl-pyrazolo)-l-isopro-pyl-4-phenyl-im idazols 2-Hydroxy-1 - isopropyl-4 -phenyl- imidazol (51 %)105 ... 

Die aus l,2-Bis-[amino-imino-methyl]-hydrazin mit Benzoinen gebildeten 1,2-Bis-[4,5-diar-yl-imidazol-2-yl]-hydrazine (Hydrazo-imidazole) werden bereits bei ihrer Herstellung durch Luftsauerstoff zu den entsprechenden Bis-[4,5-diaryl-2-imidazolyl]-diazenen oxi-diert109 ... 

Eine mit der Wallach-Synthese verwandte Reaktion ist die saurekatalysierte Cyclisierung von a-Imino-oximen338. Hier wird ebenfalls das C-Atom der N-CAlkyl-Gruppe in 2-Stellung des Imidazol-Rings eingebaut. 

Imidazol-Derivate. So cyclisieren a-(l-Imino-alkylamino)-carbonsaure-nitrile unter Basenka-talyse in Gegenwart von Acylierungsmitteln (z. B. Essigsaureanhydrid oder Kohlensaure-chlo-rid-estern) zu 4(5)-Acylamino-imidazolen354 ... 

Dimethyl-3-(2-oxo-2-phenyl-ethyl--bromid lagert sich beim Kochen mit Triethylamin in Acetonitril in 2-(2-Imino-5-phenyl-2,3-dihydro-oxazol-3-yl)-4,6-dimethyl-pyrimidin um. Aus diesem werden durch Kochen in Alkoholen mit 4-Methyl-benzolsulfonsaure als Katalysator 2-Alkoxy-l-(4,6-dimethyl-2-pyrimidyl)-4-phenyl-imidazole oder durch Erhitzen mit primaren oder sekundaren Aminen ebenfalls in Gegenwart von 4-Methyl-benzolsulfonsaure 2-Alkylamino-l-(4,6-dimcthyl-2-pyrimidyl)-4-phe-nyl-imidazole erhalten374 ... 

Die Bestrahlung 1-substituierter 2-Methyl-5-nitro-imidazole in einem Wasser/1,4-Dioxan (9 1)-Gemisch mit einer Quecksilber-Hochdrucklampe fiihrt iiber die Bildung eines 3-Hydrox-imino-5-oxo-4,5-dihydro-imidazols als primares Photoprodukt zu 3-Aminocarbonyl-5-me-thyl-l,2,4-oxadiazolen103 235 ... 

The second arm of the scheme involves first a reaction of the (3-beta ketoester (7-1) with nitrous acid. The first product from nitrosation on the activated carbon spontaneously rearranges to afford oxime (7-2). Treatment with acetyl chloride then affords the (9-acylated oxime (7-3). Condensation of that compound with the imino ether from propionitrile leads to the formation of the imidazole (7-4). 

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