Propylphosphonium hydrogen carbonate ionic liquid supported on nano-silica as a reusable catalyst for the efficient multicomponent synthesis of fully substituted pyridines and bis-pyridines

Abstract

A new supported phosphonium based ionic liquid, propylphosphonium hydrogen carbonate ionic liquid supported on nano-silica (PPHC–nSiO₂), was prepared and characterized by FT-IR, TGA, SEM and ICP techniques. The resulting catalyst was used for the efficient synthesis of fully substituted pyridines via a one-pot multicomponent reaction of aldehydes, malononitrile, and thiols under solvent-free conditions. Expedient synthesis of bis-pyridines from dialdehydes and/or dithiols by using this catalytic system can be considered as a noteworthy advantage of this method. Furthermore, there was no obvious loss of catalytic activity even after 5th cycle.