Abstract
Selective oxidation of cinnamaldehyde to benzaldehyde under mild conditions has been carried out for the first time in aqueous phase with β-cyclodextrin–chitosan polymer (β-CD–CTS) as a heterogeneous catalyst. Compared with β-cyclodextrin polymer (β-CDP) catalyst, β-CD–CTS showed significant promotion for the oxidation of cinnamaldehyde to benzaldehyde, in which 78% yield of benzaldehyde could be obtained. In addition, the mechanism of the oxidation was proposed according to the experimental results and theoretical calculation. The results indicated that chitosan had played a key role, and the significant promotion of conversion and selectivity for the oxidation could be attributed to inclusion complex formed via intermolecular weak interactions, e.g. hydrogen bonding between cinnamaldehyde and β-CD–CTS. The heterogeneous catalyst could be reused, and its catalytic efficiency remained unchanged, which suggests that the catalyst is efficient for the oxidation of cinnamaldehyde. The results reported herein may be a promising method for the production of benzaldehyde from natural cinnamaldehyde.
Acknowledgement
The authors thank the National Natural Science Foundation of China (Nos 21036009 and 21176268) for providing financial support to this project.