N-Heterocyclic Carbene Catalyzed Deuteration of Aldehydes in D2O

An N-heterocyclic carbene (NHC)-catalyzed direct deuteration of aldehydes in a mixed solvent of deuterium oxide (D2O) and cyclopentyl methyl ether was established. The present deuteration is possibly initiated by the formation of a Breslow intermediate from the aldehyde and the NHC, with subsequent trapping by D2O providing the monodeuterated aldehyde.