Green Synthesis of Pyrano[2,3-c]pyrazoles and Spiro[indoline-3,4ˊ- pyrano[2,3-c]pyrazoles] Using Nano-silica Supported 1,4- Diazabicyclo[2.2.2]octane as a Novel Catalyst

Pyrano[2,3-c]pyrazoles have attracted considerable interest in organic synthesis because of their wide application in medicinal and pharmaceutical chemistry [1]. In addition, spirooxindoles are unique core structures found in pharmaceuticals [2] and natural products such as Spirotryprostatin (A & B), Pteropodine, Marcfortine B and Glesemine [3].In this research, nano-silica supported 1,4-diazabicyclo[2.2.2]octane (nano-SiO2/DABCO) as a novel heterogeneous catalyst was prepared and fully characterized by FT-IR, FESEM, TEM, EDX, TGA/DTA, XRD, BET and elemental (CHN) analysis. This basic nanocatalyst was successfully applied for synthesis of pyrano[2,3-c]pyrazole and spiro-2-oxindole derivatives via a one-pot four-component reaction at ambient temperature.Simplicity, easy work-up, high to excellent yields, short reaction times, ease of recovery of the catalyst and green nature of this protocol make it appealing.