Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh&at;SILP Catalyst

Article abstract of DOI:10.1002/anie.201916385

Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based supported ionic liquid phase (Rh&at;SILP(Ph₃-P-NTf₂)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO₂, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh&at;SILP(Ph₃-P-NTf₂) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non-benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh&at;SILP(Ph₃-P-NTf₂) catalyst opens the way to the production of a wide range of high-value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin-derived aromatic ketones.

Full text of DOI:10.1002/anie.201916385

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Accepted Article
Title: Selective Hydrogenation and Hydrodeoxygenation of Aromatic
Ketones to Cyclohexane Derivatives Using a Rh@SILP Catalyst
Authors: Gilles Moos, Meike Emondts, Alexis Bordet, and Walter
Leitner
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201916385
Angew. Chem. 10.1002/ange.201916385
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10.1002/anie.201916385
Angewandte Chemie International Edition
COMMUNICATION
Selective Hydrogenation and Hydrodeoxygenation of Aromatic
Ketones to Cyclohexane Derivatives Using a Rh@SILP Catalyst
Gilles Moos[a], Meike Emondts[b,c], Alexis Bordet*[a] and Walter Leitner*[a,c]
products and potential applications (Figure 1). Despite recent
efforts[9] the development of versatile catalytic systems able to
effectively hydrogenate and/or hydrodeoxygenate a large panel of
aromatic ketones remains a major challenge and constitutes the
focus of this study.
Abstract: The selective hydrogenation and hydrodeoxygenation of
aromatic ketones is achieved using rhodium nanoparticles
immobilized on an acid-free triphenylphosphonium-based supported
ionic liquid phase (Rh@SILP(Ph3-P-NTf2)). The flexible molecular
approach used to assemble the individual catalyst components (SiO2,
ionic liquid, nanoparticles) allows for the formation of a catalytic
system possessing outstanding catalytic properties. In particular, an
intimate contact between the nanoparticles and the phosphonium
ionic liquid is required to enable the deoxygenation reactivity. Using
the Rh@SILP(Ph3-P-NTf2) catalyst, benzylic ketones are
hydrodeoxygenated under mild conditions, while for non-benzylic
ketones the product distribution is controlled with high selectivity
between the hydrogenated (alcohol) and hydrodeoxygenated (alkane)
products by adjusting the reaction temperature. The Rh@SILP(Ph3-
P-NTf2) catalyst possesses excellent activity, versatility and stability,
and opens the way to the production of a wide range of high-value
cyclohexane
derivatives
via
the
hydrogenation
and/or
hydrodeoxygenation of Friedel-Crafts acylation products and lignin-
derived aromatic ketones. In addition, the catalyst’s temperature
controlled selectivity is a key feature broadening the scope of
accessible products and potential applications.
The synthesis of alkyl cyclohexane derivatives has attracted
considerable attention in the past decade due to the importance
of these compounds in the transportation sector[1] (kerosene-type
fuels) and as building blocks for the production of coating
agents,[2] liquid crystals[3] and pharmaceuticals.[4] The traditional
method for the synthesis of alkyl cyclohexanes consists in the
hydrogenation of alkyl aromatics[5] commonly produced through
Friedel-Crafts alkylation reactions. However, this pathway suffers
from the limited substrate scope and often low selectivity of
Figure 1. A) Pathways for the synthesis of cyclohexane derivatives through
temperature-controlled hydrogenation or hydrodeoxygenation of aromatic
ketones. B) Examples of applications for cyclohexane derivatives.
While in heterogeneous catalysis, hydrogenation reactions are
mainly performed in the presence of transition metal
nanoparticles (Ni,[10] Ru,[11] Rh,[12] Pt,[13] etc.), the subsequent
hydrodeoxygenation typically requires the presence of both a
metal and a strong Brønsted or Lewis acidic catalyst.[14] Metal
nanoparticles immobilized on Supported Ionic Liquid Phases
(SILPs) were demonstrated to open a molecular approach to
multifunctional catalytic systems with tailor-made reactivity.[15,16]
SILPs are suitable matrices for nanoparticle synthesis and
stabilization. The ionic liquid structure can be easily functionalized
to bring different types of actives sites in intimate contact with the
active metal. Recent studies described the synthesis of
monometallic[16a-c] and bimetallic[15f,16d] nanoparticles on
imidazolium-based SILPs to produce catalytic systems
possessing excellent catalytic properties for hydrogenation and
hydrodeoxygenation reactions. In particular, the choice of the acid,
and a close proximity between the metal and acid sites were
shown to be key factors in the development of effective
hydrodeoxygenation catalysts.[16b,c,e]
Friedel-Crafts
alkylation
(overalkylation,
carbocation
rearrangements),[6]. In this context, the hydro(deoxy)genation of
aromatic ketones obtained for example through Friedel-Crafts
acylation[7] or oxidative depolymerization of lignin[8] appears as an
attractive alternative. In addition, using aromatic ketones as
substrates gives the opportunity to access two classes of
compounds, i.e. alkyl cyclohexanes and hydroxyl containing
cyclohexane derivatives, broadening significantly the scope of
[a]
M. Sc. G. Moos, Dr. A. Bordet, Prof. Dr. W. Leitner
Max-Planck-Institut für Chemische Energiekonversion
45470 Mülheim an der Ruhr (Germany)
E-mail: alexis.bordet@cec.mpg.de / walter.leitner@cec.mpg.de
[b]
[c]
Dr. M. Emondts
DWI-Leibniz Institute for Interactive Materials
Forckenbeckstr. 50, D-52056 Aachen (Germany)
We report here the synthesis of Rh nanoparticles immobilized on
a
triphenylphosphonium-based SILP. Using the resulting
Rh@SILP(Ph3-P-NTf2) catalyst, aromatic ketones were effectively
hydrogenated and hydrodeoxygenated without the need for an
additional acid functionality. While benzylic ketones were readily
hydrodeoxygenated under mild conditions, non-benzylic ketones
could be selectively hydrogenated or hydrodeoxygenated
Dr. M. Emondts, Prof. Dr. W. Leitner
Institut für Technische und Makromolekulare Chemie
RWTH Aachen University
Worringerweg 2, 52074 Aachen (Germany)
Supporting information for this article is given via a link at the end
of the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201916385
Angewandte Chemie International Edition
COMMUNICATION
Figure 2. Schematic representation (A) and transmission electron microscopy
image (B) of Rh@SILP(Ph3-P-NTf2).
depending on the temperature applied, providing flexible access
to a wide range of substituted cyclohexanes.
The functionalized support material SILP(Ph3-P-NTf2) was
synthesized through the condensation of a triethoxysilane-
The catalytic activity of Rh@SILP(Ph3-P-NTf2) and several
reference catalysts for hydrogenation and hydrodeoxygenation
was first studied using acetophenone (1) as model substrate
(Table 1). The use of SiO2-supported Rh NPs resulted in the
hydrogenation of acetophenone (1) to form the saturated alcohol
1a in 95% yield (Entry 1). In contrast, Rh@SILP(Ph3-P-NTf2)
produced the fully hydrodeoxygenated alkane 1b in quantitative
yield (Entry 2). Since neither Rh NPs nor phosphonium salts are
known to catalyze the deoxygenation of ketones/alcohols
individually, we investigated this intriguing reactivity by
systematically modifying the catalyst’s structure.
functionalized
phosphonium
ionic
liquid,
([triphenyl(3-
(triethoxysilyl)propyl)phosphonium]NTf2), on dehydroxylated
silica following a modified established procedure[17]. Analysis by
DRIFT IR (Figure S1-S3) showed signals at 1440, 1484, 1590 cm-
1 and 2897, 2930, 2977, 3072 cm-1 characteristic of the
triphenylphosphine moiety. 29Si solid state (Figure S4) shows the
presence of two types of Si species: (1) tetra-functionalized (Q)
signals at -110 ppm (Q4 = Si(OSi)4) and -102 ppm (Q3 =
Si(OSi)3OH); and (2) tri-functionalized signals at -61 ppm (T2 =
R−Si(OSi)2OR’) and -53 ppm (T1 = R−Si(OSi)(OR’)2). The T2 and
T1 signals correspond to the Si atoms of IL bound to the SiO2
surface and thus substantiate the covalent attachment of the IL
on the silica support. 1H, 13C, 31P and 19F solid state NMR further
confirmed the presence of the desired triphenylphosphonium-
NTf2 ionic liquid in SILP(Ph3-P-NTf2) (Figure S5-8A).
Table 1. Hydrogenation and hydrodeoxygenation of acetophenone using Rh
and Ru nanoparticles immobilized on various supports.
Rhodium nanoparticles were generated on the SILP via
impregnation with a solution of [Rh(allyl)3] in dichloromethane,
followed by a reduction of the dried and impregnated SILP under
hydrogen atmosphere (100 bar H2, 100 °C, 2h) to give a black
powder.[16b] The Rh loading on Rh@SILP(Ph3-P-NTf2) was
determined to be 0.1 mmol/g by ICP-AAS, well in agreement with
the theoretical value. The BET surface area of the support
decreases slightly from 292 to 271 m2/g upon Rh-loading (Table
S2). Analysis of Rh@SILP(Ph3-P-NTf2) (illustrated schematically
in Figure 2A) by transmission electron microscopy shows that the
NPs are small (1.2 nm) and well dispersed over the SILP support
(Figure 2B).
Product Yield [%][a]
Entry
Catalyst
Temp. [°C]
Rh@SiO2
95
0
5
> 99
5
1
2
3
4
5
6
7
8
9
100
100
100
100
100
100
100
100
175
Rh@SILP(Ph3-P-NTf2)
Rh@SILP(Oct-n3-NTf2)
95
97
87
> 99
91
89
92
Rh@SILP(Oct-n3-NTf2)
+ SILP(Ph3-P-NTf2)
3
Rh@SILP(Oct3-P-NTf2)
Rh@SILP(Ph3-P-BPh4)
Rh@SILP(Ph3-P-BF4)
Ru@SILP(Ph3-P-NTf2)
Ru@SILP(Ph3-P-NTf2)
13
0
9
11
8
Reaction conditions: catalyst (20 mg, metal content: 0.002 mmol),
acetophenone (0.1 mmol, 50 eq., 12.0 mg), n-heptane (375 mg), H2 (50 bar),
18 h, 500 rpm. [a] Product distribution determined by GC-FID using tetradecane
[b]
[c]
as an internal standard, conversion > 99%. Catalyst details in SI. 20 mg
SILP(Ph3-P-NTf2) added (physical mixture).
With Rh NPs synthesized on an imidazolium-based SILP
(SILP(Oct-n3-NTf2), see SI for details and Figure S9 for TEM
characterization), the substrate was converted to the alcohol 1a
(95%) without any significant hydrodeoxygenation activity,
suggesting that SILP(Ph3-P-NTf2) plays a key role in the
deoxygenation step (Entry 3). However, a physical mixture of
Rh@SILP(Oct-n3-NTf2) and SILP(Ph3-P-NTf2) also gave 1a as
main product (97%), evidencing the importance of the intimate
contact of metal and support (Entry 4). Using Rh NPs immobilized
on a different phosphonium-based SILP (Rh@SILP(Oct3-P-NTf2),
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10.1002/anie.201916385
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see SI for synthetic details and Figure S10 for TEM
characterization) lead to a mixture of products with the alcohol 1a
as main product (87%) (Entry 5). Using a fluorine-free counter
anion (BPh4, Entry 6) resulted in the selective conversion of the
substrate to the alcohol 1a. In case of another fluorine-containing
anion (BF4, entry 7), no significant deoxygenation activity was
observed, indicating that the deoxygenation-active species was
not formed. These results demonstrate the importance of the NTf2
anion in the observed deoxygenation activity. Finally, the metal
precursor was changed to [Ru(cod)(cot)] and Ru NPs were then
synthesized on SILP(Ph3-P-NTf2) (see SI for synthetic details and
Figure S11 for TEM characterization). The Ru@SILP(Ph3-P-NTf2)
catalyst produced also the alcohol 1a, forming the
hydrodeoxygenation product 1b only in low yield, even at high
temperatures (11% at 100 °C, 8% at 175 °C) (Entry 8 and 9).
Altogether, these results demonstrate that an intimate contact
between Rh nanoparticles and the SILP(Ph3-P-NTf2) support is
necessary to constitute an efficient hydrodeoxygenation catalyst.
A time profile was recorded (Figure S12), evidencing a fast
conversion of the substrate in the first hour to give a mixture of
54% 1a and 46% 1b. After that, 1a was gradually converted to 1b,
producing quantitative yield of the fully hydrodeoxygenated
product after 18h.
spectrum after catalysis (Figure S8), indicating the partial
conversion of the NTf2 anion into other F-containing species. This
signal has been previously ascribed to decomposition of the NTf2
anion under formation of metal fluorides.[18] No signal
corresponding to silicon fluoride species[19] are visible on the 29Si
solid state NMR spectrum (Figure S4). We thus suspect the
formation of Rh fluoride species through the partial breakdown of
the NTf2 anion during the hydrogenation of the IL. The formation
of acidic Rh fluoride species at the surface of the nanoparticles
could explain the catalyst’s hydrodeoxygenation activity. This is
consistent with the observation made by Forsyth and co-workers
who evidenced the formation of magnesium fluoride species
during the decomposition of the NTf2 anion under electrochemical
conditions.[18] Interestingly, the thermal decomposition of the NTf2
anion is known to occur at high temperature (ca. 300°C).[20] This
is observed in the present case at much lower temperature,
indicating that the Rh nanoparticles promotes the process. The
absence of deoxygenation activity observed when using Ru as
metal suggests that the Ru NPs do not promote the anion
decomposition under these conditions.
To gain more insight into the mechanism of formation of the active
species – presumably rhodium fluoride – reference experiments
were carried out. Heterogeneous catalysts are known to possess
high hydrodefluorination activity, leading to the release of HF
when hydrogenating fluoroaromatic substrates.[21] Taking
advantage of this reactivity, we performed a first reaction involving
the hydrogenation of fluoroacetophenone with Rh@SiO2. This
resulted in the formation of a mixture of hydrogenated and
hydrodefluorinated products, with the release of small quantities
of HF (Table S3). The catalyst was recovered, washed carefully
and characterized by 19F solid state NMR, evidencing the
apparition of a signal at -122.3 ppm, similar to what was
previously observed for the Rh@SILP(Ph3P-NTf2) catalyst (Figure
S14). In addition, applying this recycled catalyst to the conversion
of acetophenone lead to the formation of ethylcyclohexane, thus
evidencing deoxygenation activity that the starting Rh@SiO2 did
not possess (Table S3). This demonstrates that the
deoxygenation activity is related to the formation of RhF species,
which can be generated by the action of small quantities of HF on
Rh nanoparticles. This supports that the RhF species observed
on Rh@SILP(Ph3P-NTf2) are formed through the decomposition
of the NTf2 anion, process which is known to generate HF among
other products.[20] The involvement of free HF in catalysis can
however be ruled out, as recycling experiment did not show any
decrease in activity (Figure 3). Furthermore, the supernatant
Recycling experiments showed that Rh@SILP(Ph3-P-NTf2) could
be reused at least 5 times without any loss of activity or selectivity
(Figure 3). For this assessment, the reaction conditions were
intentionally tuned to yield a roughly 50:50 mixture of 1a and 1b
in order to probe any change in performance. The catalyst could
also be reused efficiently after 18h reactions (Table S1).
Figure 3. Product distribution for the hydrodeoxygenation of acetophenone
using recycled Rh@SILP(Ph3-P-NTf2). Catalyst was washed with
1 mL
n-heptane between cycles. Reaction conditions: Cat (20 mg, metal content:
0.002 mmol Rh), acetophenone (12.0 mg, 0.1 mmol, 50 eq.), n-heptane
(375 mg), 100 °C, H2 (50 bar), 1 h, 500 rpm. Distribution determined by GC-FID
using tetradecane as an internal standard. Green: ethylcyclohexane (1b), grey:
1-cyclohexylethanol (1a). The conversion of the substrate was complete in all
cases.
No changes in the textural properties of the catalyst were
evidenced by BET surface analysis (Table S2). TEM
characterization after catalysis suggests that the nanoparticles
stay small and well-dispersed on the support with only a slight
increase of their size to 1.7 nm (Figure S13). Elemental analysis
by ICP-AAS did not evidence any leaching of the metal during the
reaction (Table S2). Small amounts of IL were removed from the
catalyst after the first cycle. After this initial loss, no further IL
leaching could be evidenced even after six consecutive runs
(Table S2). 1H, 13C and 31P solid state NMR of Rh@SILP(Ph3-P-
NTf2) measured before and after catalysis showed partial
hydrogenation of the phenyl groups of the phosphonium cation
during Rh NP synthesis and catalysis (Figure S5-7). Interestingly,
an additional peak at -122.5 ppm was observed in the 19F
obtained after
a catalytic reaction did not catalyze the
deoxygenation of 1-phenylethanol under standard conditions
(Table S1).
The hydrodeoxygenation activity of Rh@SILP(Ph3-P-NTf2) was
further studied for a wide range of acetophenone derivatives with
different steric and electronic properties (Table 2). All the
substrates considered were effectively hydrodeoxygenated under
mild reaction conditions, giving cyclohexane derivatives in high
yields. The catalyst was found tolerant to various functional
groups,
even
though
partial
ether
cleavage
and
hydrodefluorination were observed for substrates 6 and 7,
respectively. In some cases, an increase of the temperature to
175°C was necessary to reach full conversion (substrate 4 and 8)
or to limit the formation of dimers (substrates 9 and 10). To get
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more insight into the influence of the presence of electron-
withdrawing and -donating substituents on the catalytic activity,
substrates 1, 5, 6 and 8 were considered for a reaction time
reduced to 1h.
Table 2. Hydrodeoxygenation of substituted benzylic ketones using Rh@SILP(Ph3-P-NTf2).
Entry
1
Substrate
Temp. [°C]
Time [h]
Product
Yield [%]a]
100
100
1
52[b]
>99
18
100
100
18
18
>99
2
3
>99 (73) [e]
100
175
100
100
100
100
175
18
18
1
79[b]
>99
58[b]
>99
4
5
18
1
40 (6b)[c]
10% (1b)[c]
24[d] (1b)
75 (1b)
18
18
62 (6b)
25 (6b)
6
7
8
100
18
20 (7b)
80 (1b)
100
100
175
1
50[b]
91
18
18
>99
175
175
18
18
87 (1b)
13 (dimers)
9
>99
10
Reaction conditions: Rh@SILP(Ph3-P-NTf2) (20 mg, metal content: 0.002 mmol Rh), substrate (0.1 mmol, 50 eq.), n-heptane (375 mg), H2 (50
bar), 18 h, 500 rpm. [a]Determined by GC-FID using tetradecane as an internal standard, conversion > 99%. [b]Remaining product:
corresponding saturated alcohol. [c]Total hydrodeoxygenation products: 71%. 40% 6b, 22% 4-ethyl-cyclohexan-1-ol, 10% 1b, 25 % 1-(4-
methoxycyclohexyl)ethan-1-ol, 3% cyclohexylethanol. [d]Remaining: 4-ethyl-cyclohexan-1-ol (10%), cyclohexylethanol (3%), (1-
methoxyethyl)cyclohexane (2%). [e](Isolated yield)
While electron-donating substituents have been reported to
have a positive effect on the hydrodeoxygenation activity,[22]
we could not identify a clear trend in our particular case (Table
S4). Part of the substrates from Table 2 was then used to
evaluate the catalytic activity of Ru@SILP(Ph3-P-NTf2) as
comparison to Rh@SILP(Ph3-P-NTf2). In agreement with the
preliminary results shown in Table 1 for acetophenone, the
ruthenium-based catalyst was barely active for the
hydrodeoxygenation of the various aromatic ketones
Scheme 1. Temperature-controlled conversion of benzylideneacetone (11) to
either the fully hydrogenated (11a) or the completely hydrodeoxygenated
product (2b) using Rh@SILP(Ph3-P-NTf2).
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10.1002/anie.201916385
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considered even at high temperature (Table S5 and S6). The
catalytic properties of Rh@SILP(Ph3-P-NTf2) were further
studied for the conversion of non-benzylic ketones, which are
known to be more challenging to hydrodeoxygenate than
acetophenone derivatives.[23] Benzylideneacetone (11) was
used as model substrate for this class of ketones (Scheme 1).
Keeping the conditions previously used for the
hydrodeoxygenation of acetophenone derivatives led to the
almost exclusive formation of the saturated alcohol (11a).
However, the conversion of 11 to the hydrodeoxygenated
product 2b was achieved with excellent selectivity at higher
temperatures (175 °C). By adjusting the reaction temperature,
both products (hydrogenated and hydrodeoxygenated) were
produced in quantitative yields. Again, the hydrodeoxygenation
activity could not be switched on for Ru@SILP(Ph3-P-NTf2)
and 11a was the only product at both 100 °C and 175 °C (Table
S6). In order to see whether such a “temperature switch”
between hydrogenation and hydrodeoxygenation could be
more generally applied to other substrates, a selection of non-
benzylic ketones was converted at 100 °C and 175 °C using
Rh@SILP(Ph3-P-NTf2) as catalyst (Table 3). At 100 °C,
substrates 11-16 (Entries 1-6) possessing a phenyl ring in beta
or gamma position to the carbonyl group were converted to the
saturated alcohols in high yields (81-99%). Substrate 13
however, was converted into a mixture of the saturated alcohol
(13a, 32%) and partially hydrodeoxygenated product 11a
(50%).
Table 3. Temperature-controlled hydrogenation or hydrodeoxygenation of non-benzylic ketones using Rh@SILP(Ph3-P-NTf2).
Entry
1
Yield [%][a]
Product 100 °C
Substrate
Product 175 °C
Yield [%][a]
>99
>99[b] (87) [f]
>99[b]
>99
>99
2
3
4
5
6
7
8
50 (11a)
32[c] (13a)
81[d]
97
92
96 (92) [f]
-
>99
>99 (99) [f]
-
-
20 (17b)
80 (2b)
Dimerization
61 (18b)
22 (18c)[e]
Reaction conditions: Rh@SILP(Ph3-P-NTf2) (20 mg, metal content: 0.002 mmol Rh), substrate (0.1 mmol, 50 eq.), n-heptane (375 mg), 100 °C or 175 °C, H2 (50 bar),
18 h, 500 rpm. [a] Determined by GC-FID using tetradecane as an internal standard, conversion > 99%. [b] 1h. [c] Determined via protection of the diol with benzaldehyde
(see Scheme S1). [d] 80 °C, 30 eq.[e] Additional products: Octanol (10%), Octane (7%).[f] (Isolated yield)
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[1]
a) Z. Wang in Experimental and Kinetic Modeling Study of
cyclohexane and its Monoalkylated Derivatives Combustion, Vol1,
Springer, Singapore, 2018; b) C. J. Chuck, J. Donelly, Appl. Energy
2014, 118, 83-91.
As expected, the hydrodeoxygenation of the benzylic alcohol
was favored over the non-benzylic, resulting in high amounts
of 11a (50%) compared to 1-cyclohexylbutanol (8%). In the
case of substrate 17, only low mass balances were observed
indicating probably competing acid-mediated condensation
reactions of the enone substrate. All the substrates were
efficiently hydrodeoxygenated at 175°C to give the
corresponding alkanes in excellent yields (97-99%). In
agreement with what was previously observed for substrate 6,
the methoxy group of substrate 17 was partially cleaved at
175 °C (Entry 7). Using biomass derived 4-(tetrahydrofuran-2-
yl)butan-2-ol (18, obtained from the complete hydrogenation of
furfuralacetone) as substrate, only various dimers were
obtained when performing the reaction at 100°C. However, the
substrate was efficiently hydrodeoxygenated at 175°C,
producing a mixture of 2-butyltetrahydrofuran (18b), 2-
propyltetrahydro-2H-pyran (18c), octanol and octane (Entry 8).
Interestingly, these products are currently discussed as
potential alternative fuels and fuel additives.[24]
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In conclusion, we show that immobilizing Rh nanoparticles on
a
triphenylphosphonium-based
SILP
produces
a
Rh@SILP(Ph3-P-NTf2) catalyst
possessing
excellent
properties for the hydrogenation and hydrodeoxygenation of a
wide range of aromatic ketones with various substituents. The
required bifunctionality is enabled by a specific interaction
between the Rh NPs and the SILP(Ph3-P-NTf2)) support,
presumably leading to the formation of acidic Rh fluoride
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Table of content
Gilles Moos[a], Alexis Bordet*[a] and
Walter Leitner*[a,b]
Page No. – Page No.
Selective
Hydrogenation
and
Hydrodeoxygenation of Aromatic
Ketones to Cyclohexane Derivatives
Using a Rh@SILP Catalyst
Rhodium nanoparticles immobilized on an acid-free triphenylphosphonium-based
supported ionic liquid phase (Rh@SILP(Ph3-P-NTf2)) enable the easy access to high-
value cyclohexane derivatives starting from aromatic ketones. The product
distribution can be switched with high selectivity between the completely
hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by changing the
reaction temperature.
This article is protected by copyright. All rights reserved.