ORGANIC
LETTERS
2013
Vol. 15, No. 3
650–653
Cobalt-Catalyzed Acceptorless Alcohol
Dehydrogenation: Synthesis of Imines
from Alcohols and Amines
Guoqi Zhang and Susan K. Hanson*
Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545,
United States
Received December 19, 2012
ABSTRACT
A cobalt catalyst has been developed for the acceptorless dehydrogenation of alcohols and applied to synthesize imines from alcohols and
amines. Deuterium labeling studies suggest that the reaction proceeds by an initial reversible alcohol dehydrogenation step involving a cobalt
hydride intermediate.
The acceptorless dehydrogenation of alcohols is an
efficient and atom-economical method to convert alcohols
intocarbonylcompounds and otherderivatives.1,2 Alcohol
dehydrogenation has applications in hydrogen storage and
production, as a selective and low-temperature route to
generate hydrogen from biomass-derived alcohols and
carbohydrates.3 It also has synthetic applications, includ-
ing the oxidant-free synthesis of carbonyl compounds,4 and
tandem coupling reactions involving CÀN andCÀC bond
formation5,6 for the synthesis of imines7 and amides8 and the
β-functionalization of alcohols.9 Despite the importance of
this transformation, examples of homogeneous catalysts for
the acceptorless dehydrogenation of alcohols have thus
far been limited to precious metals, especially Ru,10 Rh,11
and Ir.12 The development of nonprecious metal catalysts
would be a significant advance from the perspective of cost,
abundance, and sustainable chemistry.
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Herein, we report an earth-abundant metal cobalt cata-
lyst for the acceptorless dehydrogenation of alcohols and
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10.1021/ol303479f
Published on Web 01/11/2013
2013 American Chemical Society