Synthesis of a new imidazo[4,5-b]pyridin-5-one via a vicarious nucleophilics substitution of hydrogen

摘要

A new imidazo[4,5-b]pyridin-5-one was prepared in five steps from 4(5)-nitro-lH-imidazole via a vicarious nucleophilic substitution of hydrogen of l-benzyl-4-nitro-l H-imidazole with the carbanion generated from chloroform and potassium tert-butoxide.Hydrolysis of l-benzyl-5-dichloromethyl-4-nitro-lH-imidazole and Knoevenagel condensation between the resulting aldehyde and diethyl malonate catalyzed by titanium(IV) chloride gave the corresponding 4-nitroimidazole bearing at 4 position the diethyl methylenemalonate group.Reduction and cyclization afforded the required ethyl 1 -benzyl-5-oxo-4,5-dihydro-lH-imidazo[4,5-b]pyridine-6-carboxylate.