Selectively Deoxygenative Deuteration of Aldehydes by Superwetting Porous Carbon‐Supported Palladium Catalysts

Abstract We present a method of deoxygenative deuteration of aldehydes (DDA) over heterogeneously superwetting porous carbon‐supported palladium catalyst (Pd/SPC), which is efficient for the synthesis of deuterated aromatic compounds with ‐CD 3 group. Exemplified by the DDA reaction of 2‐naphthaldehyde (2‐NAL) to 2‐methylnaphthalene (2‐MNE), the total deuterium incorporation radio in the resultant aromatic hydrocarbons was higher than 95% and the selectivity toward 2‐MNE‐ d 3 reached 87%. The impressed catalytic activity was found relevant to the combined effect of surface wettability and the electron‐rich properties of Pd species of this kind of heterogeneous Pd/SPC catalyst. Mechanistic studies suggest a successive deuteration pathway, that is, hydrogen isotope exchange (HIE), deuterium addition, and ultimate deoxygenative deuteration over Pd/SPC in the cost‐effective D 2 O/H 2 reaction conditions. The in situ‐formed D 2 from the first step HIE between H 2 and D 2 O can be readily captured by the electron‐rich Pd centers, which then boost the subsequent deuterogenolysis of C─O bonds through deuterated alcohol intermediates toward the formation of 2‐MNE‐ d 3 . This work provides a design principle of heterogeneous catalysts for targeted deuterium labeling from aldehyde substrates and may inspire the development of alternative deuterium labeling techniques beyond dominated homogeneous catalysis.