Mechanism into selective oxidation of cinnamaldehyde using β-cyclodextrin polymer as phase-transfer catalyst

Selective oxidation of cinnamaldehyde to benzaldehyde in the presence of bicarbonate and hydrogen peroxide and catalyzed by beta-cyclodextrin polymer (beta-CDP) was investigated. beta-CDP was utilized as the phase-transfer catalyst in this study. The immobilized beta-cyclodextrin possessing a hydrophobic host cavity was found to be efficient as mass-transfer promoters for the oxidation of cinnamaldehyde. Benzaldehyde could be obtained in 63% yield under optimal reaction conditions. The results indicate the complex formed between cinnamaldehyde and beta-CDP via the intermolecular weak interactions, e.g., hydrogen bond was the reason why the conversion and selectivity could be significantly promoted. Finally, the reusability of the catalyst was also evaluated. Its catalytic activity remained unchanged even after recycled for six times, which suggests it is an efficient catalyst for oxidation of cinnamaldehyde. (C) 2012 Elsevier Ltd. All rights reserved.