Preparation of Chiral Hydrazines
Cobalt-Catalyzed Asymmetric Hydrogenation of C=N Bonds Enabled by Assisted Coordination and Nonbonding Interactions.
Angew. Chem. Int. Ed. 2019;
18. November 2019 (online)
Zhang and co-workers developed a cobalt-catalyzed hydrogenation of substituted hydrazones, which leads to chiral hydrazines in excellent yield and enantioselectivity. Further functionalization of the hydrozines leads to synthetically useful amines, amides, and pyrazole derivatives.
To emphasize the synthetic value of this hydrogenation, the reaction was performed on a gram scale and a TON of 2000, which is the highest TON for this cobalt-catalyzed asymmetric hydrogenation to date, was achieved. Furthermore, the authors performed deuterium labeling experiments and confirmed that H2, and not i-PrOH, is the hydrogen source for the reaction.