In recent years, developments in the aerobic oxidation of
alcohols have attracted much attention, and a number of
methods using various transition-metal catalysts have been
reported.[1] In addition, amines can also be oxidized to
oximes, imines, amides, nitriles, or azo compounds under
aerobic conditions similar to those of alcohol oxidation reac-
tions.[2] Therefore, the direct synthesis of amides from alco-
hols and amines through selective oxidation of alcohols is
one of the most challenging transformations [Eq. (1)].[3]
no mention was made of the reusability of the catalyst in
this system.
On the other hand, nanoporous gold (AuNPore) has at-
tracted much attention recently because of its successful ap-
plication in catalysis.[7,8] This material is a nonsupported,
monolithic, nanostructured bulk metal and consists of a
three-dimensional network of gold ligaments. It can be fab-
ricated easily by selective removal of less noble metals, such
as Ag[9] or Cu,[10] from their alloys with Au under chemical
or electrochemical dealloying conditions. This material ex-
hibited remarkable catalytic activities in some transforma-
tions, such as CO oxidation[11] and oxidative coupling of
MeOH in the gas phase,[12] as well as in oxidations of orga-
nosilanes[8a] and alcohols[8c] in the liquid phase. However,
the chemoselectivity induced by this material has not yet
been investigated for any catalytic reactions.[13] In this
report, we achieved the selective aerobic oxidation of meth-
anol in the coexistence of oxidizable amines with AuNPore
catalysts and established a facile direct formamide synthesis
under mild conditions (Scheme 1). Furthermore, we clarified
For example, in 2008 Christensen et al. reported direct ox-
idative amidation from butanol and hexylamine in the pres-
ence of TiO2-supported gold nanoparticle (AuNP) catalysts.
However, the selectivity of N-hexylbutanoic amide stem-
ming from alcohol oxidation was unfortunately very low, be-
cause the oxidation of hexylamine could not be sup-
pressed.[4] To avoid the selectivity problem, Riisager et al.
performed oxidative methyl esterification and in situ amida-
tion in a one-pot, two-step reaction. Nevertheless, accept-
ACHTUNGTRENNUNG
able alcohols and amines are quite limited.[5] Although the
selectivity has been improved recently by modifying the cat-
alytic properties of nanoparticles,[6] direct N-formylation of
amines from a mixture of methanol and amines still remains
difficult because methanol is far less reactive than ordinary
alcohols under mild conditions. Recently, one example has
been reported by Haruta and co-workers that used AuNPs
supported on NiO.[6d] However, this reaction required high
oxygen pressure and a high reaction temperature. Moreover,
Scheme 1. Aerobic oxidation of the mixture of methanol and alkylamine.
that the catalytic properties of AuNPore were enhanced sig-
nificantly by the synergistic effects of the residual silver in
the material.
[a] Dr. S. Tanaka, Prof. Dr. Y. Yamamoto, Prof. Dr. N. Asao
WPI Advanced Institute for Materials Research
Tohoku University, Sendai 980-8577 (Japan)
Fax : (+81)22-217-6165
Four different types of AuNPore catalysts were fabricated
as follows.[14] AuNPore-1 was fabricated by dealloying a
Au30Ag70 alloy thin foil 40 mm in thickness in 70% HNO3 at
room temperature.[9] The atomic composition of the result-
ing AuNPore-1 was found to be Au97Ag3 by EDX analysis,
and a scanning electron microscopy (SEM) study revealed
the formation of fine and uniform ligaments and a nanopo-
rous structure. Both the ligaments and the pores were
around 30 nm in size (Figure S1a in the Supporting Informa-
tion). AuNPore-2 and AuNPore-3 were fabricated from Au–
Al alloys by free corrosion in acidic or basic aqueous solu-
tion, respectively, according to procedures reported in the
literature.[15] The multicomponent nanoporous composite
AuNPore-4 was also prepared along the lines of Zhangꢁs
report.[16,17] The atomic compositions of the resulting AuN-
Pores are shown in Table 1.
[b] Dr. T. Minato
International Advanced Research and Education Organization
Tohoku University, Sendai 980-8578 (Japan)
[c] Dr. E. Ito, Prof. Dr. M. Hara
Flucto-Order Functions Research Team
RIKEN, Wako 351-0198 (Japan)
[d] Dr. T. Minato, Dr. Y. Kim
Surface & Interface Laboratory
RIKEN, Wako 351-0198 (Japan)
[e] Prof. Dr. M. Hara
Department of Electronic Chemistry
Tokyo Institute of Technology, Yokohama 226-8502 (Japan)
[f] Prof. Dr. Y. Yamamoto
State Key Laboratory of Fine Chemicals
Dalian University of Technology (DLUT)
Dalian 116023 (P.R. China)
The reaction of octylamine with MeOH was examined in
the presence of AuNPore-1 under an oxygen atmosphere at
608C for 20 h. N-octylformamide (2a) was obtained as the
Supporting information for this article is available on the WWW
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Chem. Eur. J. 0000, 00, 0 – 0
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