76902-24-4Relevant articles and documents
2,3-Dihydrospiro[1H-4- and 5-azabenzimidazole-2,1'-cyclohexane] (= spiro[cyclohexane-1,2'(3'H)-1'H-imidazo[4,5-b]pyridine] and spiro[cyclohexane-1,2'(3'H)-1'H-imidazo[4,5-c]pyridine]): Reactions with nucleophiles
Schwoch,Kramer,Neidlein,Suschitzky
, p. 2175 - 2190 (2007/10/02)
The readily available title compounds 4a and 24 react with N-, O-, S-, and C-nucleophiles in presence of MnO2 to give the corresponding mono- or disubstituted 2H-azabenzimidazoles (= azaisobenzimidazoles), e.g., 11-18 and 26a-h, respectively, or 2,3-dihydro-1H-azabenzimidazoles (= dihydro-azabenzimidazoles) such as 9 and 10 and 27 and 28, respectively, by a 1,4- or 1,6-Michael addition (Schemes 2 and 4). The bromo-dihydro-1H-azabenzimidazole 4b lost the Br-atom when treated with piperidine or morpholine yielding the corresponding disubstituted 2H-azabenzimidazole 21 (Scheme 3). Reductive ring opening of the substituted spiro compounds leads to mono- and disubstituted diaminopyridines which are intermediates for fused pyridine ring systems with substituents often not available by conventional routes and of potential pharmaceutical interest (see 32-37). E.g., starting from 4a, a three-step synthesis of the analgesic flupirtine maleate (= ethyl {2-amino-6-[(4-fluorobenzyl)amino]pyridin-3-yl}carbamate maleate = Katadolon; 39) and of its non-fluorinated derivative D-7195 is described. Its analogue 40 was similarly made from the spiro compound 24.
Heterocyclisation via Selective Elimination: Reaction of 2,3-Diaminopyridine with Acyclic Ketones under Thermal Conditions
Dubey, Pramod Kumar,Ratnam, C. V.
, p. 863 - 865 (2007/10/02)
Reactions of 2,3-diaminopyridine and its 5-bromo analogue with three symmetrical and nine unsymmetrical acyclic ketones under thermal conditions have been studied.The reactions have yielded 2-substituted-1H-imidazopyridines by the elimination of one of the C2-substituents from the probable, though unisolated, intermediates 2,2-disubstituted-2,3-dihydro-1H-imidazopyridine derivatives.Elimination of one of the groups in the case of symmetrical ketones and preferentially of benzyl group in the case of benzyl methyl ketone has been observed.All the three alkyl phenyl ketones studied afford 2-phenylimidazopyridine by the selective loss of the alkyl group.Elimination of branched alkyl group has been noticed in the reactions involving methyl t-butyl and methyl i-propyl ketones, while the preferential elimination of methyl group is observed in the case of methyl n-alkyl ketones.Suitable explanations have been offered for the observed selective eliminations.
