Rapid synthesis of unsaturated alcohols under mild conditions by highly selective hydrogenation

Article abstract of DOI:10.1039/c3cc41526k

Ir-ReO_x/SiO₂ acted as a highly active and selective heterogeneous catalyst for the hydrogenation of unsaturated aldehydes to unsaturated alcohols in water at low H₂ pressure (0.8 MPa) and low temperature (303 K). The catalysis is derived from the synergy between Ir metal and ReO_x.

Full text of DOI:10.1039/c3cc41526k

ChemComm
View Article Online
View Journal
COMMUNICATION
Rapid synthesis of unsaturated alcohols under mild
conditions by highly selective hydrogenation†
Cite this: DOI: 10.1039/c3cc41526k
Masazumi Tamura, Kensuke Tokonami, Yoshinao Nakagawa and Keiichi Tomishige*
Received 28th February 2013,
Accepted 6th May 2013
DOI: 10.1039/c3cc41526k
www.rsc.org/chemcomm
Ir–ReOx/SiO2 acted as a highly active and selective heterogeneous selectivity have been prepared using various techniques6–12 such
catalyst for the hydrogenation of unsaturated aldehydes to unsaturated as introducing additives,6,7 modifying the active metal with second
alcohols in water at low H2 pressure (0.8 MPa) and low temperature metal components,8 tuning the particle sizes of catalysts9 or using
(303 K). The catalysis is derived from the synergy between Ir metal and oxide supports that strongly interact with the active metals.10
ReOx.
However, most of the catalysts sacrifice the activity to attain high
selectivity,7,11,12a resulting in much lower activity than that of
Selective hydrogenation of unsaturated aldehydes including conventional noble metal catalysts. For the hydrogenation of
a,b-unsaturated aldehydes produces unsaturated alcohols, crotonaldehyde to crotyl alcohol, which is one of the most
which are important intermediates in the synthesis of fine chemicals difficult reactions to proceed selectively, Nishiyama12a reported
like flavor, fragrance and pharmaceutical compounds.1 Thermo- 100% selectivity of crotyl alcohol using Sn-modified silica-coated
dynamically and kinetically, a CQC bond is more easily hydro- Pt catalysts, but the yield (4.1%) and turnover frequency (TOF)
genated than a CQO bond and so the selective hydrogenation of based on the amount of Pt (0.5 hÀ1) were very low. In contrast,
unsaturated aldehydes to unsaturated alcohols is still a challenging Mitsudome12b demonstrated the highest yield of 87% with the
task. Conventional hydrogenation catalysts such as Pd, Rh, Ni and AgNP@CeO2 catalyst, but the TOF (4.9 hÀ1) was very low in spite
Pt mainly provide saturated aldehydes or saturated alcohols as over- of high temperature (423 K) and high H2 pressure (1.5 MPa). In
hydrogenated compounds.2 Traditionally, excellent CQO selectivity total, the previously reported yield and TOF did not exceed 87%
is obtained by the stoichiometric NaBH4 or LiAlH4 reduction. and 126 hÀ1, respectively, which are far from the satisfactory
However, this method has some drawbacks such as handling of level (Table S1, ESI†). Moreover, these catalysts suffer from high
the reducing agent and production of equivalent salts. To overcome temperature (Z323 K), high H2 pressure (Z2 MPa) or use of
these problems, significant efforts have been made to search for organic solvents. No catalyst presented both high activity and
catalytic systems that are able to efficiently and selectively hydro- selectivity under mild and eco-friendly reaction conditions.
genate CQO bonds of the substrates having both CQO and CQC Therefore, a novel catalysis system to accomplish both high
bonds using hydrogen (H2) as a reductant. To date various homo- activity and high selectivity in an environmentally benign solvent
geneous and heterogeneous effective catalysts have been developed such as H2O and under the mild conditions such as low H2
and high selectivity has been achieved in some cases. Homogeneous pressure and low temperature is desired to be developed.
catalysts have been intensively investigated because of their high
Ionic hydrogenation is an effective method to selectively
activity and selectivity, and many studies were performed using Ru, hydrogenate polarized double bonds such as carbonyl group as
Rh, Ir, W and other metals with some ligands.3–5 Noyori and Bullock known using homogeneous catalysts such as Ru complexes.3–5
have reported an efficient catalyst of an Ru complex with phosphine When H2 is used as a reductant, it is heterolytically cleaved into
ligands for selective hydrogenation of various unsaturated aldehydes hydride and proton species. As reported in our previous studies
and ketones.3,4 However, in the aspect of the catalyst/substrate on hydrogenolysis of polyols, Ir–ReOx/SiO2 (ref. 13a) can be an
separation and reusability, heterogeneous catalysts are desired to efficient catalyst to produce hydride species on the catalyst.
be developed. Effective heterogeneous catalysts that show high Therefore, Ir–ReOx/SiO2 may be a new catalyst for selective and
active hydrogenation of CQO bonds by ionic hydrogenation.
Our results indeed demonstrate that the Ir–ReOx/SiO2 catalyst
acts as a highly active and selective catalyst in the selective
hydrogenation of various unsaturated aldehydes to unsaturated
Graduate School of Engineering, Tohoku University, Aoba 6-6-07, Aramaki, Aoba-ku,
Sendai, 980-8579, Japan. E-mail: tomi@erec.che.tohoku.ac.jp;
Fax: +81-22-795-7214; Tel: +81-22-795-7214
alcohols in H2O even at a low H2 pressure of 0.8 MPa and a low
temperature of 303 K.
† Electronic supplementary information (ESI) available: Details of characteriza-
tion methods and NMR spectra. See DOI: 10.1039/c3cc41526k
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.

View Article Online
Communication
ChemComm
Table 1 Selective hydrogenation of crotonaldehyde by various catalystsa
Table 2 Effect of H2 pressurea
Selectivity (%)
Entry PH (MPa) t (h) Conv. (%) Crotyl alcohol Butanal 1-Butanol
Selectivity (%)
2
Entry Catalyst
Conv. (%) Crotyl alcohol Butanal 1-Butanol
1
2
3
4
5
8
4
2
0.8
0.1
0.1 43.0
0.25 37.0
0.5 36.7
92.0
91.1
93.1
95.0
93.8
3.4
3.7
2.6
3.4
2.6
4.1
4.0
3.7
1.3
3.2
1
2
3
4
Ir–ReOx/SiO2-0.5
34.9
43.0
44.3
38.6
91.7
92.0
91.1
91.9
0.3
0.9
33.0
19.5
3.6
6.8
0
4.0
3.4
3.9
3.8
4.1
4.4
4.2
23.2
4.1
19.0
21.3
13.0
9.9
2.4
3.5
2.0
0
Ir–ReOx/SiO2-1
Ir–ReOx/SiO2-2
Ir–ReOx/SiO2-3
1
4
43.3
34.8
3.3
a
5
6
7
Rh–ReOx/SiO2-0.5 96.9
Pd–ReOx/SiO2-0.5 94.3
Ru–ReOx/SiO2-0.5 21.4
76.3
94.8
48.0
56.2
79.1
82.0
96.5
96.1
31.8
0
Reaction conditions: crotonaldehyde 3.0 mmol, H2O 3.0 g, Ir–ReOx/
SiO2-1 50 mg, T = 303 K.
8
9
Pt–ReOx/SiO2-0.5
5% Pt/C
2.0
66.5
28.1
98.3
catalysts (max TOF = 126 h ,
À1 12c max TON = 6612d based on the
10
11
12
13
14
15
5% Ru/C
total metal, as given in Table S1, ESI†). Based on the surface
number of Ir (dispersion = 0.1613a), Ir–ReOx/SiO2-1 showed a
5% Rh/C
5% Pd/Cb
4% Ir/SiO2
3.6% Re/SiO2
None
>99
0
63.7
0
high TON of 5500 and an initial TOF of 12 600 hÀ1
.
5.4
0.1
0
Next, the effect of H2 pressure on the hydrogenation of
crotonaldehyde was examined (Table 2). The activity is
—
—
—
a
Reaction conditions: crotonaldehyde 3.0 mmol, H2O 3.0 g, catalyst decreased by the decrease in H2 pressure. In contrast, the
b
50 mg, T = 303 K, PH = 8 MPa, t = 0.1 h. Catalyst 10 mg.
2
dependence of selectivity on H2 pressure is not so strong, and
at 0.8 MPa of H2 pressure the highest selectivity is obtained (95%).
In general, selective hydrogenation of unsaturated aldehydes has
been carried out at high pressure (Z2.0 MPa) or high temperature
(Z323 K). It should be noted that this reaction system is a first
example achieving high selectivity and adequate activity in H2O at
low H2 pressure (o1.0 MPa) and ambient temperature (303 K). In
total, we selected the 0.8 MPa H2 pressure as an optimal H2
pressure in the following study.
To verify whether the observed catalysis is derived from
Ir–ReOx/SiO2 or leached Ir species, the selective hydrogenation of
crotonaldehyde was carried out under the optimal conditions and
the Ir–ReOx/SiO2-1 catalyst was removed from the reaction mixture
by filtration at approximately 60% conversion of crotonaldehyde.
After the removal of the catalyst, the filtrate was reacted under the
same conditions. In this case, no reaction proceeded (Fig. S2,
ESI†). Moreover, it was confirmed using coupled plasma atomic
emission spectroscopy (ICP-AES) that no Ir species was present in
the filtrate (o0.1 ppm). These results indicate that the observed
catalysis is intrinsically heterogeneous.
A further advantage of this catalytic system is its reusability.
We conducted the reuses of Ir–ReOx/SiO2 for the selective
hydrogenation of crotonaldehyde (Fig. S3, ESI†). The catalyst
can be easily retrieved from the reaction mixture by filtration.
For each successive use, the catalyst was washed with water
three times to remove the products, followed by drying at 383 K
for 12 h and calcination in air at 773 K for 1 h.13e After this
treatment, the recovered catalyst was reused at least three times
without a marked loss of its high catalytic efficiency. XRD,
TEM and XAFS analyses, and the CO adsorption experiment of
Ir–ReOx/SiO2 showed that the state of Ir–ReOx/SiO2 hardly
changed before and after the reaction (Fig. S4–S9 and Tables
S2–S5, ESI†), which indicates that Ir–ReOx/SiO2 is very robust
under the reaction conditions. The structure of Ir–ReOx/SiO2
was as follows: supported Ir is in the metallic state and the Re
species form low-valent (B+3) oxide clusters (ReOx) that partially
cover the Ir metal surface.13a,b,e
We prepared a series of ReOx modified SiO2-supported metal
catalysts with various noble metal components and with the
same Re/M molar ratio (Re/M = 0.5): M–ReOx/SiO2-0.5 (M = Ir,
Rh, Pd, Ru, Pt) and a series of Ir–ReOx/SiO2-X (X = 0.5, 1, 2, 3),
where X is the Re/Ir molar ratio. The selective hydrogenation of
crotonaldehyde to crotyl alcohol in water at 303 K and 8 MPa H2
was carried out as a model reaction for the optimization of
metal components and/or compositions (Table 1). Among the
M–ReOx/SiO2-X (entries 1–8) and conventional hydrogenation
catalysts such as carbon-supported transition metal catalysts
(entries 9–12), Ir–ReOx/SiO2 catalysts showed the highest selectivity
(>90%). It should be noted that both the activity and selectivity of
Ir–ReOx/SiO2 were much higher than those of Ir/SiO2 (entry 13) and
ReOx/SiO2 (entry 14). These results suggest that the synergy
between Ir and ReOx generates the high activity and high selectivity
of Ir–ReOx/SiO2 simultaneously. In the aspect of activity, selectivity
and Re metal amount, Ir–ReOx/SiO2-1 is an optimal catalyst for the
hydrogenation of crotonaldehyde. Time-course of the selective
hydrogenation of crotonaldehyde was measured (Fig. S1, ESI†).
After 8 h, the yield of crotyl alcohol reached 90% with 91%
selectivity. This yield is higher than the ones reported for hetero-
geneous catalysts (Table S1, ESI†).
A gram-scale experiment (Scheme 1) was carried out using
2.1 g (30 mmol) of crotonaldehyde in 30 g of water using
Ir–ReOx/SiO2-1 (150 mg, Ir = 0.1 mol%) at 343 K for 3 h to
provide crotyl alcohol in 83% yield at 92% conversion and 90%
selectivity. The turnover number (TON) and initial TOF14 based
on the total Ir metal were calculated to be 880 and 2016 hÀ1
respectively. To the best of our knowledge, these values are
much higher than those reported previously for heterogeneous
,
The substrate scope of the selective hydrogenation is listed
in Table 3. Hydrogenation of a,b-unsaturated aldehydes over
Scheme 1 Scale-up reaction for the hydrogenation of crotonaldehyde over
Ir–ReOx/SiO2-1.
c
Chem. Commun.
This journal is The Royal Society of Chemistry 2013

View Article Online
ChemComm
Communication
Table 3 Selective hydrogenation of various unsaturated aldehydes over Ir–
the selective hydrogenation of crotonaldehyde. Therefore ReOx is
responsible for the promotion of substrate adsorption and the
assistance of heterolytic dissociation of H2 to H+ and HÀ species,
leading to high activity and high selectivity, respectively.
In conclusion, Ir–ReOx/SiO2 showed high activity and selectivity
in the hydrogenation of unsaturated aldehydes to unsaturated
alcohols in water at a low H2 pressure of 0.8 MPa and a low
temperature of 303 K. The gram-scale experiment at 8 MPa H2
pressure and 343 K with Ir–ReOx/SiO2 provided a record TON of
5500 and an initial TOF of up to 12 600 hÀ1 based on surface Ir
without the loss of selectivity. Various unsaturated aldehydes can
be converted to the corresponding unsaturated alcohols including
useful chemicals in high yields. This catalyst system is generated
by the synergy between Ir metal and ReOx, which provides high
selectivity while drastically raising the activity without sacrificing
the activity of noble metals.
a
ReOx/SiO2
Con-
version Yield
Selectivityb (%)
t
Entry Aldehyde
Product
(h) (%)
(%) Product AL SA
1
2
3
8
5
4
99
>99
95
90
90
87
91
90
92
0
0
2
8
9
6
4
5
6
6
96
99
89
93
96
0
0
6
95
4e
(91c )
6
7
8
6
85
91
70
88
82
97
3d 15 f
0
3g
14
8
6
6
93
80
78
80
84
0
0
Notes and references
9
>99
1
¨
1 (a) L. A. Saudan, Acc. Chem. Res., 2007, 40, 1309; (b) P. Maki-Arvela,
´
J. Hajek, T. Salmi and D. Y. Murzin, Appl. Catal., A, 2005, 292, 1;
>99
10
6
6
>99
>99
>99
>99
0
0
1
0
(c) S. Nishimura, Handbook of Heterogeneous Catalytic Hydrogenation
for Organic Synthesis, Wiley, New York, 2001.
2 (a) S. Fujita, Y. Sano, B. M. Bhanage and M. Arai, J. Catal., 2004,
225, 95; (b) A. Ghosh and R. Kumar, Microporous Mesoporous Mater.,
2005, 87, 33.
3 T. Ohkuma, H. Ooka, T. Ikariya and R. Noyori, J. Am. Chem. Soc.,
1995, 117, 10417.
4 P. J. Fagan, M. H. Voges and R. M. Bullock, Organometallics, 2010,
29, 1045.
(97c )
>99
11
(99c )
a
Reaction conditions: substrate 3.0 mmol, H2O 3.0 g, Ir–ReOx/SiO2-
1 50 mg, T = 303 K, PH = 0.8 MPa. AL = aldehyde, SA = saturated
b
2
c
d
alcohol. Isolated yield. Conjugated aldehyde (0.6%), unconjugated
e
f
aldehyde (2.4%). 3-Phenyl-1-propanol only. 4-Isopropenylcyclo-
g
hexane-1-methanol only. 3,7-Dimethyl-1-octanol (0.2%), 3,7-dimethyl-
5 (a) L. G. Melean, M. Rodriguez, A. Gonzalez, B. Gonzalez, M. Rosales
and P. J. Baricelli, Catal. Lett., 2011, 141, 709; (b) E. Farnetti,
M. Pesce, J. KaSpar, R. Spogliarich and M. Graziani, J. Chem. Soc.,
Chem. Commun., 1986, 10, 746; (c) J. S. Song, D. J. Szalda and
R. M. Bullock, Angew. Chem., Int. Ed. Engl., 1992, 31, 1233;
(d) M. Schlaf, Dalton Trans., 2006, 4645; (e) H. Guan, M. Limura,
M. P. Magee, J. R. Norton and G. Zhu, J. Am. Chem. Soc., 2005,
127, 7805.
6-octen-1-ol (2.8%).
Ir–ReOx/SiO2-1 provided the corresponding allyl alcohols with
high selectivity at high aldehyde conversion (entries 1–7). Note
that cinnamyl alcohol (entry 5), peril alcohol (entry 6) and a
mixture of nerol and geraniol (entry 7), which are important
components of fragrance and flavor compounds, were obtained
in high yields. Unconjugated unsaturated aldehydes reacted to
afford the corresponding esters with high selectivity (entries 8
and 9). Furfural and 5-hydroxymethyl furfural that are important
intermediates from biomass were also hydrogenated to the
corresponding furfuryl alcohols in excellent yields (entries 10
and 11). Therefore, the present catalytic system is practically
promising in the production of important chemicals such as
fragrance or flavor compounds.
6 F. Ammari, C. Milone and R. Touroude, J. Catal., 2005, 235, 1.
7 E. Galloway, M. Arbruster, K. Kovnir, M. S. Tikhov and
R. M. Lambert, J. Catal., 2009, 261, 60.
8 (a) J. K. A. Clarke, Chem. Rev., 1975, 75, 291; (b) R. Ferrando,
J. Jellinek and R. Johnston, Chem. Rev., 2008, 108, 845.
9 (a) P. Claus, Appl. Catal., A, 2005, 291, 222; (b) A. K. Prashar,
S. Mayadevi and R. N. Devi, Catal. Commun., 2012, 28, 42.
10 (a) A. Dandekar and M. A. Vannice, J. Catal., 1999, 183, 344;
(b) M. Consonni, D. Jokic, D. Y. Murzin and R. Touroude,
J. Catal., 1999, 188, 165; (c) P. Concepcion, A. Corma, J. Silvestre-
Albero, V. Franco and J. Y. Chane-Ching, J. Am. Chem. Soc., 2004,
126, 5523.
11 P. Claus, Top. Catal., 1998, 5, 51.
To clarify the role of ReOx species, the rate dependence on 12 (a) K. Taniya, H. Jinno, M. Kishida, Y. Ichihashi and S. Nishiyama,
J. Catal., 2012, 288, 84; (b) T. Mitsudome, M. Matoba, T. Mizugaki,
K. Jitsukawa and K. Kaneda, Chem.–Eur. J., 2013, 19, 5255;
(c) E. Gebauer-Henke, J. Grams, E. Szubiakiewicz, J. Farbotko,
the substrate concentration was studied. The reaction order
with respect to crotonaldehyde concentration was +0.03 and
+0.59 for Ir–ReOx/SiO2-1 and Ir/SiO2, respectively (Fig. S5, ESI†),
indicating that the substrate is more strongly adsorbed on the
surface of Ir–ReOx/SiO2-1 and this tendency is interpreted by
ReOx as the adsorption site of substrates. Probably the substrate
was adsorbed on ReOx sites at the oxygen atom of CQO. In
addition, we reported that the Ir–ReOx/SiO2 catalyst can dissociate
H2 into H+ and HÀ on the interface between Ir metal and ReOx
species.13 Considering that ionic hydrogen species are effective in
hydrogenation of polarized double bonds,3–5 the heterolytically
dissociated hydrogen species on Ir–ReOx/SiO2 will be effective in
R. Tourude and J. Rynkowski, J. Catal., 2007, 250, 195; (d) P. G.
N. Mertens, P. Vandezande, X. Ye, H. Poelman, I. F. J. Vankelecom
and D. E. De Vos, Appl. Catal., A, 2009, 355, 176.
13 (a) Y. Amada, Y. Shinmi, S. Koso, T. Kubota, Y. Nakagawa and
K. Tomishige, Appl. Catal., B, 2011, 105, 117; (b) Y. Amada,
H. Watanabe, M. Tamura, Y. Nakagawa, K. Okumura and
K. Tomishige, J. Phys. Chem. C, 2012, 116, 23503; (c) K. Chen,
K. Mori, H. Watanabe, Y. Nakagawa and K. Tomishige, J. Catal.,
2012, 294, 171; (d) K. Chen, S. Koso, T. Kubota, Y. Nakagawa and
K. Tomishige, ChemCatChem, 2010, 2, 547; (e) Y. Nakagawa,
Y. Shinmi, S. Koso and K. Tomishige, J. Catal., 2010, 272, 191.
14 Initial TOF was estimated under the conditions under which the
conversion was below 30%.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun.