Synthesis and reactions of novel imidazo[4,5-b]pyridine building blocks

The synthesis of a novel imidazo[4,5- b ]pyridine and its partially saturated derivative relied on Michael addition of 1-methyl-1 H -imidazol-4-amine to fumaric/maleic or acetylene dicarboxylates, followed by intramolecular cyclization into target compounds. The common transformations of the resulting pyridine carboxylate were performed to obtain a series of building blocks, i.e. carboxylic acids, amides, and amines. The pyridone fragment was transformed into the fused bromopyridine moiety which was used for Buchwald–Hartwig and Suzuki cross-coupling reactions providing a versatile access to an extended scope of imidazopyridines. All synthesized building blocks could be considered as promising purine bioisosteres for the synthetic and medicinal chemistry.