Direct Synthesis of Symmetrical Azines from Alcohols and Hydrazine Catalyzed by a Ruthenium Pincer Complex: Effect of Hydrogen Bonding

Azines
(2,3-diazabuta-1,3-dienes) are a widely used class of compounds
with conjugated CN double bonds. Herein, we present a direct
synthesis of azines from alcohols and hydrazine hydrate. The reaction,
catalyzed by a ruthenium pincer complex, evolves dihydrogen and can
be run in a base-free version. The dehydrogenative coupling of benzylic
and aliphatic alcohols led to good conversions and yields. Spectroscopic
evidence for a hydrazine-coordinated dearomatized ruthenium pincer
complex was obtained. Isolation of a supramolecular crystalline compound
provided evidence for the important role of hydrogen bonding networks
under the reaction conditions.