摘要：Summaryp-Methyl benzaldehyde (p-MBA) is a class of key chemical intermediates of pharmaceuticals. Conventional industrial processes forp-MBA production involve the consecutive photochlorination, amination, and acid hydrolysis of petroleum-derivedp-xylene, while producing vast pollutants and waste water. Herein, we report a direct, green route for selective synthesis ofp-MBA from acetaldehyde using a diphenyl prolinol trimethylsilyl ether catalyst. The optimizedp-MBA selectivity is up to 90% at an acetaldehyde conversion as high as 99.8%. Intermediate structure and18O-isotope data revealed that the conversion of acetaldehyde top-methylcyclohexadienal intermediates proceeds in an enamine-iminium intermediate mechanism. Then, controlled experiments and D-isotope results indicated that the dehydrogenation ofp-methylcyclohexadienal top-MBA and H2is catalyzed by the same amines through an iminium intermediate. This is an example that metal-free amines catalyze the dehydrogenation (releasing H2), rather than using metals or stoichiometric oxidants.Graphical abstractDisplay OmittedHighlights•A direct route to producep-methyl benzaldehyde from biomass-derived acetaldehyde•Revealing the reaction kinetics and mechanism under reaction conditions•An example of an organic amine-catalyzed dehydrogenation-aromatization reaction
