A convenient synthesis of linear pyridinoimidazo[1,2- a]pyridine and pyrroloimidazo[1,2- a]pyridine cores

Two new imidazo[1,2- a]pyridine derivatives, pyridinoimidazo[1,2- a]pyridine ( 10) and pyrroloimidazo[1,2- a]pyridine ( 16), were synthesised from 2-amino-4-methyl-5-nitropyridine ( 1) by linear cyclisation, making use of dimethylformamide dimethylacetal (DMFDMA) as an agent of vinylamine functionalisation. This report describes first the formation of pyridine and pyrroloimidazopyridine from ( 1), and then the formation of pyridine-fused and pyrrolo-fused pyridine by the Friedländer method and reductive cyclisation followed by treatment of the resulting adduct with chloroacetaldehyde.