No abstract

An organocatalytic system based on an unprecedented proline analogue and iron oxide magnetic nanoparticles (Prn/Fe 2 O 3 @SiO 2) was designed and employed in vanillin production from isoeugenol and vanillyl alcohol. Full characterization of the obtained catalyst revealed the successful functionalization of the nanoparticle surface with the organic moieties. The activity of the magnetic bifunctional material was compared with its proton-unexchanged counterpart. Interestingly, the oxidation of isoeugenol resulted in being highly dependent on the acidic functionalities of the organocatalyst. Nonetheless, the catalytic performance of the proton-unexchanged catalyst suggested that the acidic and basic sites of the Prn/Fe 2 O 3 @SiO 2 exhibited a synergic effect, giving rise to higher conversion and selectivity. The presence of bifunctional groups in the proline analogue, together with the magnetic properties of the iron oxide nanoparticles, could lead to high efficiency, versatility, recoverability, and reusability.

An efficient direct synthesis of dehydrodecaline derivatives is reported via a tandem aldol condensation-Diels-Alder cycloaddition process under Lewis acidic conditions. Addition of dienophile moieties to conjugated dienes, formed in situ from the condensation of enone 1 with aldehydes, lead to high-yield stereoselective synthesis of the final endo products in relatively short time periods. Products precipitate upon concentration of the organic phase and are purified by recrystallization.