Isomerization of α- and β-pinene epoxides over dendritic ZSM-5 zeolites

The selective isomerization of α- and β-pinene epoxides was investigated using dendritic ZSM-5 zeolite catalysts under mild reaction conditions using ethyl acetate as solvent at moderate temperatures (40–70 °C). The highly interconnected dendritic meso-macroporous structure and suitable Brønsted-to-Lewis acid sites balance facilitated efficient epoxide ring opening and rearrangement pathways without the need for additional metal functionalization as active phases. Likewise, the dendritic samples exhibited a superior catalytic activity than a reference hierarchical ZSM-5 material. α-Pinene epoxide reaction yielded mainly campholenic aldehyde and carveol derivatives, while β-pinene epoxide rearranged to myrtanal, perillyl alcohol, and myrtenol. The metal-free nature of the catalyst offers advantages in terms of sustainability and product purity, making it a promising alternative for fine chemical synthesis from renewable terpene resources. Green metrics were calculated for the isomerization of both epoxides, such as atom economy, yield, stoichiometric factor, material recovery parameter, and reaction mass efficiency, demonstrating the green credentials of the process. The kinetic study of α-pinene epoxide into campholenic aldehyde provided an activation energy of 75.6 kJ mol −1 . For β-pinene epoxide, the cis- and trans-myrtanal isomers dominate, exhibiting activation energies of 62.0 and 64.4 kJ mol −1 , respectively. The adsorption of cis- and trans-myrtanal onto the catalyst surface significantly influenced the product distribution of the transformation of β-pinene epoxide over the dendritic zeolite catalyst. Synopsis This contribution presents a sustainable, metal-free catalytic approach, based on dendritic ZSM-5 zeolites, for the pinene epoxide isomerization, including kinetic studies and green metrics evaluation, advancing sustainable chemistry solutions. • Dendritic ZSM-5 enables efficient isomerization of α- and β-pinene epoxides. • Meso-macroporosity and balanced acidity drive selective epoxide ring-opening pathways. • Bimolecular kinetic models successfully described the isomerization of both epoxides. • Dendritic zeolites outperformed the productivity of reported catalysts for epoxides isomerization. • Green metrics demonstrated the greenness credentials of dendritic zeolites as catalysts.