PMO-NH/saccharin composite: an efficient metal-free catalyst for the synthesis of spiropyrazolo[3,4-b]pyridines and pyrazolopyrido[2,3-d]pyrimidines

In this work, we report the development of a saccharin-incorporated periodic mesoporous organosilica composite (PMO-NH/Sac) as an efficient and recyclable metal-free catalyst for the synthesis of spiropyrazolo[3,4- b ]pyridines and pyrazolopyrido[2,3- d ]pyrimidines under mild conditions. The catalyst was prepared by physical adsorption of saccharin onto amine-functionalized periodic mesoporous organosilica (PMO-NH). The resulting material exhibited a uniform mesoporous structure (pore size: 6.7 nm) with a high surface area (286 m²/g) and well-dispersed active sites. The structure of the prepared PMO-NH/Sac was confirmed by BET, XRD, FT-IR, TEM, EDS-MAP, and TGA analyses. PMO-NH/Sac efficiently promoted the target reactions, affording the desired products in excellent yields (88–96%) within short reaction times (10–65 min). Furthermore, the antibacterial activity of two synthesized derivatives ( 1 g and 1 h ) was evaluated against Staphylococcus aureus and Escherichia coli using the agar well diffusion method, showing promising biological potential. The catalyst demonstrated good stability and could be reused multiple times with only 3–5% loss of activity. The superior catalytic performance of PMO-NH/Sac highlights its potential as a sustainable and versatile material for green synthetic applications.