SO3H-functionalized MCM-41 as an efficient catalyst for the combinatorial synthesis of 1H-pyrazolo-[3,4-b]pyridines and spiro-pyrazolo-[3,4-b]pyridines

Sulfonic acid-functionalized (SO 3 H-functionalized) mesoporous MCM-41 catalyst was synthesized by anchoring 3-((3-(trimethoxysilyl)propyl)thio)propane-1-sulfonic acid onto MCM-41-type silica and characterized by FT-IR spectroscopy, elemental analysis and scanning electron microscopy (SEM) techniques. The catalyst was used for the efficient multi-component synthesis of 1 H -pyrazolo-[3,4- b ]pyridines and spiro-pyrazolo-[3,4-b]pyridines. Notably, the catalyst could be recycled and reused with negligible loss in activity over seven cycles.