Patent GB-1246312-A (GB)
Title: 4,5-substituted n-oxy and hydroxy hydroimidazoles
IPC: C07D233/06
Filed: 1968-10-10
Abstract: 1,246,312. N-Oxy and hydroxy-hydroimidazoles. SYNTEX ENERGY RESEARCH Inc., and VARIAN ENERGY. 10 Oct., 1968 [10 Jan., 1968; 26 June, 1968], No. 48093/68. Heading C2C. Novel di- and tetra-hydromidazoles having tertiary carbon atoms in the 4- and 5-positions, each tertiary carbon being bonded to three other carbon atoms, the carbon atom in the 2-position carrying a hydrogen atom and a further hydrogen atom or an organic group attached by means of a carbon atom forming part of the organic group in the case of the tetrahydroimidazoles, or carrying a hydrogen atom or an organic group attached by means of a carbon atom forming part of the organic group in the case of the dihydroimidazoles, and having at least one oxygen-bearing nitrogen atom in the imidazole ring, the nitrogen and oxygen together having one of the structures are prepared by condensing a bis-hydroxylamine, in which the hydroxylamine groups are attached to adjacent tertiary carbon atoms, with an aldehyde, or a functional derivative thereof, an orthoformate or a carbonate to obtain imidazoles containing the partial ring structure and, if required, oxidizing this product to form the alternative nitrogen and oxygen structures. Preferred imidazoles have the Formulµ I, II, III, IV and V in which X is an anion, R<SP>5</SP> is hydrogen or an organic group attached by means of a carbon atom and K<SP>1-4</SP> are each C 1-12  alkyl, alkenyl, alkynyl or aryl groups or R<SP>1</SP> and R<SP>2</SP> and/or R<SP>3</SP> and R<SP>4</SP> together represent C 3-10  alkylene or alkenylene groups. Preferred co-reactants of the bis-hydroxylamines include aldehydes R<SP>5</SP>CHO where R<SP>5</SP> is an alkyl, aryl or heterocyclic radical optionally substituted by other groups, including a further aldehydic group, whereby bis-hydroimidazoles are obtained, compounds R<SP>5</SP>CHXX<SP>1</SP> where X and X<SP>1</SP>, which are eliminated in the condensation, are halogen, -OR<SP>1</SP>, -NR<SP>1</SP> 2  or -SR<SP>1</SP> (R<SP>1</SP> being hydrogen or an aryl or alkyl group), compounds R<SP>5</SP>COX where X is halogen or other replaceable group and R<SP>5</SP> is an electron-withdrawing group, e.g. a haloalkyl or carbonyl group, or orthoesters R<SP>5</SP>CXX<SP>1</SP>X<SP>11</SP> where X is halogen, -OR<SP>1</SP>, -NR<SP>2</SP> 1  or -SR<SP>1</SP>. The group R<SP>5</SP> may be modified after ring formation, e.g. conversion of a chloromethyl group to an iodomethyl group or replacement of organic values of R<SP>5</SP>, e.g. alkoxycarbonyl or hydroxymethyl, by hydrogen. Oxidizing agents for converting the N,N<SP>1</SP> - dihydroxytetrahydroimidazoles ' to other N-O forms are selected in accordance with the required product, e.g. lead dioxide yields, depending on conditions, the dihydroimidazoles of the Formula (III) or the free radicals of the Formula (I), the latter being reduced to the former by treatment with metallic sodium or to the imidazoles of the Formula (IV) by refluxing in ethanolic HC1, the second reduction being reversed by H 2 O 2  oxidation. The free radicals I can be further oxidized, e.g. with chlorine, SO 2 Cl 2  or CF 3 COOH, to the ionic form of the Formula (V), strong oxidants which are readily reduced to the free radical. Oxidation of the dihydroxy form of the Formula (II) may be effected simultaneously with the ring-forming condensation. The preparation of a variety of 4,4,5,5-tetra-methylhydroimidazoles from the preferred hydroxylamine reactant, 2,3-dihydroxylamino-2,3. dimethylbutane. 2,3 -Dihydrozylamino-2,3-dimethylbutane is prepared by treating 2-nitropropane with bromine to obtain 2,3-dinitro- 2,3-dimethylbutane which is subsequently reduced with Zn to the hydroxylamine.