Solvent-free, Silica Catalyzed Intriguing Conversion of 3- Hydrazonobutan-2-one Oxime into Biacetyl Bis-hydrazone Schiff Bases

An expeditious and operationally simple reaction between 3-hydrazonobutan-2-one oxime and different substituted benzaldehydes in the presence of silica afforded an unexpected product, biacetyl bis-hydrazone Schiff bases in good yield on grinding in a mortar at room temperature, instead of expected product 3-(aryl)methylenehydrazonobutan-2-one oxime. Mild reaction conditions involving recyclable mineral support silica, environmentally benign and good yield in short reaction time are remarkable advantages of this protocol. Products were characterized by IR, NMR (¹H and ¹³C) and elemental analyses.