Caffeine supported on boehmite nanoparticles: An efficient ionic liquid catalyst for synthesis of pyrazolopyranopyrimidines

In the recent years, basic ionic liquids (BILs) have been successfully presented as catalysts to catalyze various reactions such as the Heck reaction, Michael addition reaction, and Markovnikov addition reaction1-2.Although the catalytic ability of basic ILs has been successfully demonstrated in many reactions, the chemical industry still prefers to use heterogeneous catalysts due to their easy separation. Furthermore, it has been reported that supported ILs lead to more improvements in efficiency than homogenous ILs3-4. Therefore, it is highly desirable to support basic ILs onto solid supports. The reaction of 3-chloropropyl boehmite nanoparticles (BNPs) with caffeine in acetonitrile afforded BNPs-3-propyl-imidazolopyridinium chloride [BNPs-Caff]Cl as a new BNPsupported ionic liquid (IL) catalyst. [BNPs-Caff]Cl proved to be an efficient heterogeneous catalyst for the synthesis of pyrazolopyranopyrimidinesvia a One-Pot four-component reaction of hydrazine hydrate, ethyl acetoacetate, barbituric acid, and an aldehyde. The attractive features of this method are simple procedure, clean reaction, use of a reusable catalyst, easy workup, and performing a multi-component reaction (MCR) in water.