Mixed valent copper oxide nanocatalyst on Zeolite-Y for mechanochemical oxidation, reduction and C–C bond formation reaction

Abstract

Copper oxide (CuO) nanocatalyst supported on zeolite-Y appeared as an excellent solid phase catalyst for promoting different oxidation, reduction, and C–C bond formation reactions. The ultrafine zeolite Y supported CuO nanocatalyst selectively produced different derivatives of benzimidazoles in absence of any acids. Selective catalytic oxidation of various benzyl alcohols to the corresponding benzaldehydes was achieved under solvent-free condition using benzimidazole as the proton abstracting source. Under similar condition reduction of benzaldehyde to benzyl alcohols and the nitro-aldol condensation reaction was achieved within a very limited period through the grinding process. CuO–Y served as a suitable catalyst for the selective formation of aldehydes, alcohols, nitro-aldols, and derivatives of benzimidazole. One of the significant advantages of this technique was the non-requirement of any toxic acids, reducing agents like NaBH4, hydrazine hydride. All the reactions occurred with high yield and selectivity in absence of any solvent. Isopropanol was used as the internal reducing agent during aldehyde reduction eliminating toxic chemicals like NaBH4. More promisingly the catalyst was able to reduce selectively one aldehydic group in presence of the other such as terephthaldehyde. Some of the salient features of the process were the control oxidation of benzyl alcohol with H2O2 under mechanochemical condition, room temperature reduction of benzaldehyde without the formation of toluene. The change in the crystallite size of zeolite-Y was believed to play a crucial role in bringing high selectivity in the catalytic oxidation and reduction process.