N‐Substituted Hydrazones by Manganese‐Catalyzed Coupling of Alcohols with Hydrazine: Borrowing Hydrogen and Acceptorless Dehydrogenation in One System

: An unprecedented one-step synthesis of N-substituted hydrazones by coupling of alcohols with hydrazine is reported. This partial hydrogen-borrowing reaction is catalyzed by a new manganese pincer complex under mild reaction conditions, thus liberating water and dihydrogen as the only byproducts. Mechanistic insight, based on the observation of intermediates, is provided.