Imidazopyridine is one of the important fused bicyclic 5-6 heterocycles and it is recognized as a "drug prejudice" scaffold due to its wide range of applications in medicinal chemistry. This moiety is also useful in material science because of its structural character. Synthesis of this moiety from the easily available chemicals is desirable due to its tremendous use in the various branches of chemistry. Here we report a review on the synthesis of this scaffold employing different strategies such as condensation, multicomponent reactions, oxidative coupling, tandem reactions, aminooxygenation, and hydroamination reactions.

A visible light mediated, metal-free process for the thiocyanation of imidazoheterocycles has been developed using eosin Y as a photoredox catalyst under ambient air at room temperature. A library of 3-(thiocyanato)imidazo[1,2-a]pyridines with broad functionalities have been synthesized in high yields. This methodology is also applicable for the selenocyanation of imidazo[1,2-a]pyridine.

The keen success has been achieved towards the synthesis of new product and process as the twelve principle of "Green Chemistry" was formulated in 1990s. These products and processes are more compatible with human health, society and the environment. In this review a collection of researches has been documented from the view point of green chemistry. The main theme of this review is neat reactions which are solvent and catalyst-free reactions. Neat reactions in absence of any solvents and catalysts with the concise forms of microwaves, ball milling neat reactions have been described.

2-a]pyridines by exploiting the bielectrophilic nature of nitroolefins. This methodology could be successfully applicable for the synthesis of zolimidine, a useful drug for the treatment of peptic ulcer. The reaction proceeds through Michael addition followed by intramolecular cyclization and in situ denitration.

Visible light promoted cross-dehydrogenative coupling reaction has been emerged as an excellent strategy for the direct formation of C-C/C-heteroatom bonds from simple compounds. Use of renewable energy resources and inessential...