Enhanced catalytic activity and recyclability for oxidation of cinnamaldehyde catalysed by β-cyclodextrin cross-linked with chitosan

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.