Application of Metal-Organic Frameworks with Sulfonic Acid Tags in the Synthesis of Pyrazolo[3,4- b ]pyridines via a Cooperative Vinylogous Anomeric-Based Oxidation.

Herein, we report the design and synthesis of Co-MOF-71/imidazole/SO 3 H as a novel porous catalyst with sulfonic acid tags. The structure and morphology of the catalyst were investigated using various techniques such as Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction, scanning electron microscopy (SEM), SEM elemental mapping, energy-dispersive X-ray spectroscopy, Barret-Joyner-Halenda, and N 2 adsorption-desorption isotherms. Co-MOF-71/imidazole/SO 3 H was studied in the preparation of novel pyrazolo[3,4- b ]pyridines under mild and green conditions via a cooperative vinylogous anomeric-based oxidation. A wide range of mono and bis pyrazolo[3,4- b ]pyridines were synthesized with good to excellent yields (65-82%). A hot filtration test for the heterogeneous nature of the catalyst indicated the high stability of the prepared catalyst. The recyclability of Co-MOF-71/imidazole/SO 3 H is another advantage of the present methodology. The structures of the final products were confirmed using FT-IR, 1 H-NMR, and 13 C-NMR spectroscopic techniques.