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Unsubstituted, 5-Aminoimidazoles

The opportunity to tautomerize endows the 4(5)-aminoimidazoles (25 26) with some unique properties and it is appropriate to discuss them separately. [Pg.6]


Only equivocal chemical evidence appears to be available for the unsubstituted aminoimidazoles. The failure of 2-aminoimidazole to undergo diazotization was originally interpreted to indicate that it existed in the imino form more recently, the 4-amino analog has been reported to behave as a normal aromatic amine. The infrared spectra of substituted aminoimidazoles of type 192 193 were con-... [Pg.71]

Unsubstituted, 5-Amino and 5-Unsubstituted, 4-Aminoimidazoles David J. Lythgoe and Christopher A. Ramsden... [Pg.336]

Rapid access to an array of fused 3-aminoimidazoles was conveniently achieved by a Sc(OTf)3 catalyzed three-component cyclocondensation of heterocyclic amidines (such as 2-aminopyridine) and aldehydes with isocyanides (Ugi MCR) [52] or, alternatively, with trimethylsilylcyanide (TMS-CN) [53]. AT-Unsubstituted 3-aminoimidazo[ l,2-a]pyridincs 28 were formed in the latter case (Scheme 19). Microwave dielectric heating of the methanolic... [Pg.65]

Diazo coupling in N-unsubstituted imidazoles occurs with equal case at either C-2 or C-4(5) (or both) in reactions which have been shown to involve reaction of the imidazole anion with the diazonium ion [10]. lire intensely coloured azo dyes which are formed have long been used for identification of imidazoles, especially in qualitative chromatography [7]. The azo groups can be reduced to amino or hydrazine groups, providing a useful alternative approach, especially to 2-aminoimidazoles (see Section 8.3),... [Pg.214]

Unsubstituted 4-aminoimidazoles can be made in 60-80% yields by cyclization of a-amidinonitriles, or more directly by heating an imidate with an a-aminonitrilp. The products are esters of 4-aminoimidazole-2-carboxylic acids. An alternative route cyclizes suitably substituted guanidines in acidic conditions. The guanidines are made, for example, from aminoacetaldehyde dialkyl acetals and cyanamide (see Section 2.2). [Pg.235]

Klotzer and co-workers reported in 1982 a successful amination of an imidazole and its 2-nitro and 2-methyl-4(5)-nitro derivatives with the use of 0-diphenylphosphynyl hydroxylamine [Eq. (10)] (82S592). The reaction was carried out by the action of DPPH on a sodium or lithium salt of the corresponding imidazole in N-methylpyrrolidone media. The product was isolated as an N-benzylideneamino derivative, then hydrolyzed to the unsubstituted N-amine. Since the parent of the series, 1-aminoimidazole, is unstable, this compound was isolated only as its hydrochloride. Ali attempts made by the authors of this review to synthesize 1-aminoimidazole by amination of imidazole with HOSA in alkaline media led to resinification and regeneration of the initial compound. [Pg.97]

Aminoimidazoles are obtained from guanidine, whereas urea or thiourea yield imidazole-2(3//)-one or -thione, respectively. Imidazoles 5 unsubstituted in the 2-position are obtained from a-hydroxy ketones and formamide Bredereck synthesis) ... [Pg.171]

Analogously, a-hydroxy ketones cyclocondense with amidines (to give imidazoles (36)), guanidines (to give 2-aminoimidazoles), and urea or thiourea (to give imidazole-2(3H)-ones or -thiones, respectively). Imidazoles unsubstituted at the 2-position are obtained from a-hydroxyketones and formamide (Brederek synthesis) ... [Pg.224]


See other pages where Unsubstituted, 5-Aminoimidazoles is mentioned: [Pg.6]    [Pg.6]    [Pg.17]    [Pg.31]    [Pg.336]    [Pg.336]    [Pg.134]    [Pg.581]    [Pg.295]    [Pg.317]    [Pg.38]    [Pg.295]    [Pg.346]    [Pg.482]    [Pg.44]    [Pg.346]    [Pg.429]    [Pg.255]    [Pg.295]   


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2- Aminoimidazole

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