DOI: 10.1002/anie.201103199
Catalytic Amination
Improved Ruthenium-Catalyzed Amination of Alcohols with
Ammonia: Synthesis of Diamines and Amino Esters**
Sebastian Imm, Sebastian Bꢀhn, Min Zhang, Lorenz Neubert, Helfried Neumann,
Florian Klasovsky, Jan Pfeffer, Thomas Haas, and Matthias Beller*
Amines are essential intermediates in the chemical industry,
for example, for large-scale production of numerous polymers
and dyes. In addition, they represent interesting building
blocks for the synthesis of pharmaceuticals and agrochem-
icals.[1] In nature a plethora of biologically important com-
pounds such as alkaloids, amino acids, and nucleotides
contain amino groups. Among the different types of amines,
primary amines in particular are useful intermediates for
further derivatization reactions.[2] For the preparation of
aliphatic amines the reductive amination of the corresponding
carbonyl compounds has been the method of choice both on
the laboratory and the industrial scale.
Instead of using aldehydes or ketones it is also possible to
employ alcohols and amines as starting materials. Here, an
initial catalytic dehydrogenation of the alcohol takes place to
give the corresponding carbonyl compound and hydrogen.
Subsequent formation of the imine and final hydrogenation
leads to the desired amination product (Scheme 1).
This overall atom-efficient transformation makes use of
the so-called “borrowing-hydrogen” methodology,[3] also
known as “hydrogen auto-transfer” reaction.[4] Advanta-
geously, the hydrogen required for the final hydrogenation
step is generated completely by dehydrogenation of the
alcohol. Hence, there is no need for additional hydrogen gas.
Furthermore, the sensitive carbonyl compound is produced in
situ in low concentration, thereby minimizing unwanted side
reactions.
Notably, heterogeneously catalyzed aminations of simple
alcohols, for example methanol and ethanol, are performed
on a multi-thousand-ton-scale.[5] Because of the limited
activity of the heterogeneous catalysts, relatively harsh
conditions (> 2008C) are required for alcohol aminations.
Thus, for structurally more diverse alcohols the chemo-
selectivity of the respective reactions is in general low and the
substrate scope has been limited so far. On the other hand,
there is increasing interest to produce and use chemical
products based on functionalized alcohols from renewable
resources.[6] Here, especially biomass-derived carbohydrate
building blocks and fatty acid derivatives constitute interest-
ing and abundantly available feedstocks for the production of
more sustainable polymers.[7] However, to the best of our
knowledge aminations of such challenging substrates with
ammonia have not been described yet.
In order to achieve improved activity and selectivity, the
use of defined organometallic catalysts is an attractive option.
In this respect, the first homogeneously catalyzed aminations
of alcohols using amines were independently reported by
Grigg et al.[8] and Watanabe et al.[9] More recent examples for
the further development of this methodology have come from
the groups of Williams,[10] Fujita,[11] Kempe,[12] Milstein,[13] and
Vogt[14] and from us.[15] Noteworthy, ammonium salts[11b,c,16]
and aqueous ammonia[11a] were successfully applied in the
synthesis of secondary and tertiary amines from alcohols.
The selective amination of primary alcohols with ammo-
nia to give primary amines was first described by Milstein and
co-workers.[13] In the presence of a molecular defined
ruthenium PNP-pincer complex different primary alcohols
were converted into primary amines in good to excellent
yields. More recently, the selective amination of secondary
alcohols with ammonia to give primary amines has been
reported independently by Vogt et al.[14] and by us.[15a]
Based on our continuing interest in “borrowing-hydro-
gen” methodology using alcohols[17] and amines,[18] in a joint
cooperation with industry we became involved in a program
to extend the substrate scope of alcohol aminations. As a
starting point of our investigations we tested the amination of
isosorbide with ammonia (Scheme 2). The resulting diamine
Scheme 1. Catalytic amination of alcohols.
[*] S. Imm, S. Bꢀhn, Prof. Dr. M. Zhang, L. Neubert, Dr. H. Neumann,
Prof. Dr. M. Beller
Leibniz-Institut fꢁr Katalyse an der Universitꢀt Rostock e.V.
Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
E-mail: matthias.beller@catalysis.de
Dr. F. Klasovsky, Dr. J. Pfeffer, Dr. T. Haas
Evonik Degussa GmbH, CREAVIS Technologies & Innovation
Paul-Baumann-Strasse 1, 45772 Marl (Germany)
[**] This work has been supported by Evonik, the Deutsche For-
schungsgemeinschaft (Leibniz prize to M.B.), and the Alexander
von Humboldt Foundation (grant to Z.M.).
Supporting information for this article is available on the WWW
Angew. Chem. Int. Ed. 2011, 50, 7599 –7603
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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