1H-imidazol-3-ium tricyanomethanide {[HIM]C(CN)3} as a nanostructured molten salt catalyst: application to the synthesis of pyrano[4,3aEurob]pyrans

In this work, we have synthesized a novel nanostructured molten salt, H-1-imidazol-3-ium tricyanomethanide {[HIMI]C(CN)(3)} (1), as an efficient and green protocol-compatible catalyst. This new molten salt has been fully characterized by different analytical techniques, such as FT-IR, (HNMR)-H-1, (CNMR)-C-13, thermal gravimetric analysis, derivative thermal gravimetric analysis, differential thermal analysis, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Additionally, the catalytic activity of {[HIMI]C(CN)(3)} (1, 2 mol%) has been tested in a three-component domino Knoevenagel condensation reaction. A range of structurally diverse aromatic aldehydes (2a-p), malononitrile (3), and 4aEurohydroxyaEuro6aEuromethylaEuro2HaEuropyranaEuro2aEuroone (4) are tolerated for the synthesis of 2-amino-7-methyl-5-oxo-4-aryl-4,5-dihydropyrano[4,3-b]pyran-3-carbonitrile derivatives (5a-p) under neat conditions at 50 A degrees C. The obtained results have demonstrated that catalyst 1 shows interesting catalytic properties, such as clean reaction profile, cost-effectiveness, and green conditions. Importantly, the aforementioned catalyst is thermally stable with a 171 A degrees C melting point not showing any significant loss in catalytic activity after 7 reaction cycles.