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