Nano-Ni@zeolite-Y: preparation and application as a mild and efficient catalyst for green synthesis of pyridopyrazine and quinoxaline derivatives under solvent-free conditions

Recently, the zeolites have attracted a growing interest due to their proper acidity, thermal stability and low cost. The acidity and catalytic activity of zeolite can be dependent on the Lewis and Bronsted acid sites. The dehydration reaction, can decrease the number of proton sites and increase the number of Lewis acid sites. As well as, exchange or relocation of monovalent cations with polyvalent ion creates strong Bronsted centers using the hydrolysis phenomena. These processes can be useful for catalytic reactions such as alcohol dehydration, acylation, esterification, Oxidation, desulfurization and cyclization. Also, nano-zeolites doped with transition metals, with the size of less than 100 nm has attracted a lot of attention of many chemists and activists chemical industry, because of their great applications not only in catalysis, but also in a variety of new applications inclusive chemical sensing, medicine, optoelectronics and etc. [1,2]. On the other hands, quinoxalines [3] and pyrido[2,3-b]pyrazines [4] are an important class of benzo-heterocyclic pyrazine compounds and have been widely used in dyes, pharmaceuticals and electrical/photochemical materials. Looking at the above facts, In this study, we report use of nano-Ni(II)/Y-zeolite (NNZ) as catalyst for the synthesis of quinoxalines and pyrido[2,3-b]pyrazines under very mild reaction conditions. The present methodology offers several advantages than other procedures such as high yields, short reaction times, solvent free conditions and use of a green, reusable, and thermal stability catalyst.