Ruthenium‐Catalyzed Three‐Component Alkylation: A Tandem Approach to the Synthesis of Nonsymmetric N,N‐Dialkyl Acyl Hydrazides with Alcohols

The borrowing hydrogen strategy has been applied in the synthesis of nonsymmetric N,N‐dialkylated acyl hydrazides via a tandem three‐component reaction catalyzed by a phosphine free diaminocyclopentadienone ruthenium tricarbonyl complex. This strategy represents the first direct one‐pot approach to nonsymmetric functionalized acyl hydrazides. Different aromatic acyl hydrazides underwent dialkylation with a variety of primary or secondary alcohols and methanol or ethanol as alkylating agents in mild reaction conditions and good yields. Deuterium labelling experiments suggested that the primary or secondary alcohol was the hydrogen source in this tandem process. DFT calculations show that the combination of the tandem mixed product cannot be perfectly explained neither structurally nor electronically, but might be dependent of the physical state of the aldehyde or ketone intermediate (gaz vs. liquid) at the reaction temperature.