Reactions of 2,3-dihydrospiro[1<i>H</i>-4- and 5-azabenzimidazole-2,1′-cyclohexane] with nucleophiles: A potential route to some substituted aromatic heterocycles
results in loss of the Br-atom presumably by an AEa-mechanism. Reduction of the substituted azaisobenzimidazoles with sodium hydrosulfite followed by fission of the cyclohexane ring leads to substituted o-diaminopyridines. They were cyclised in situ with various condens ing agents to give new heterocyclic systems. Equimolar mixtures of some azaisobenzimidazoles and dihydroazabenzimidazoles lead to the
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
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