Colloid and nanodimensional catalysts in organic synthesis: VI.1 Hydrogenation and hydrogenolysis of carbonyl compounds

Article abstract of DOI:10.1134/S1070363214090023

Aldehydes and ketones are found to be hydrogenated to alcohols with hydrogen at atmospheric pressure under the catalysis with nickel nanoparticles. The reaction under study may be used as technologically available and cheap method for hydrogenation of carbonyl groups. It is found that in the case of aromatic ketones hydrogenolysis of C=O bond with partial hydrogenation of aromatic groups takes place.

Full text of DOI:10.1134/S1070363214090023

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 9, pp. 1656–1661. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © V.M. Mokhov, Yu.V. Popov, D.N. Nebykov, 2014, published in Zhurnal Obshchei Khimii, 2014, Vol. 84, No. 9, pp. 1414–1419.
Colloid and Nanodimensional Catalysts
in Organic Synthesis: VI.1 Hydrogenation
and Hydrogenolysis of Carbonyl Compounds
V. M. Mokhov, Yu. V. Popov, and D. N. Nebykov
Volgograd State Technical University, pr. Lenina 28, Volgograd, 400131 Russia
e-mail: tons@vstu.ru
Received April 7, 2014
Abstract—Aldehydes and ketones are found to be hydrogenated to alcohols with hydrogen at atmospheric
pressure under the catalysis with nickel nanoparticles. The reaction under study may be used as technologically
available and cheap method for hydrogenation of carbonyl groups. It is found that in the case of aromatic
ketones hydrogenolysis of C=O bond with partial hydrogenation of aromatic groups takes place.
Keywords: catalysis, nickel nanoparticles, hydrogenation, carbonyl bond, hydrogenolysis
DOI: 10.1134/S1070363214090023
Hydrogenation processes are widely used in
organic chemistry and chemical technology. Reduction
(hydrogenation) of carbonyl group is one of the widely
used methods for preparation of compounds containing
a hydroxy group. A series of methods of laboratory
and industrial reduction of carbonyl group is known. It
includes using of metal complex hydrides [2], hydro-
gen in the presence of catalysts [3], transfer hydrogena-
tion with lower alcohols [4–6]. Most technologically
convenient and suitable for industry are methods, using
gaseous hydrogen as the most cheap and available
hydrogenating agent. But use of hydrogen requires the
presence of catalysts, the reactions proceed as a rule at
the elevated hydrogen pressure. For example, synthesis
of secondary alcohols by hydrogenation of ketones
with hydrogen at 11 bar pressure using the Raney
nickel and nickel applied on the magnesium oxide [7]
and hydrogenation of ketones with isopropanol in the
presence of ruthenium complexes and potassium tert-
butylate [6] are described.
alcohols by hydrogenation of ketones with hydrogen at
48 bar on the chiral ruthenium complexes applied on
the magnetite nanoparticles [9], and also hydrogena-
tion of ketones with hydrogen at 4 bar and 75°C in the
presence of iridium nanoparticles [10] are described.
The drawback of the above-mentioned methods is the
use of expensive and difficultly availabile catalysts.
Hence, the investigation of possibility of carbonyl
group hydrogenation using available highly disperse
catalytic systems is topical.
We have used nickel nanoparticles which were
prepared by the reduction of anhydrous nickel(II)
chloride with metal complex hydrides. Nickel nanopar-
ticles were used as a colloid solution without their
isolation or stabilization in the 5–10 mol % amounts
with respect to the hydrogenated substrate. Use of
nickel nanoparticles prepared in THF solution by the
reduction of nickel chloride with lithium aluminum
hydride proved to be inapplicable to the hydrogenation
of carbonyl group because only the carbon–carbon
multiple bonds of α,β-unsaturated ketones were
involved in the reaction. On the other hand, use of ultra-
disperse nickel obtained by the reaction of nickel(II)
chloride with sodium borohydride in isopropanol lead
to formation of alcohols. Reaction proceeded at simple
bubbling of hydrogen through the colloid solution of
catalyst in isopropanol and ketone to be hydrogenated
in the course of 6–8 h at 60–80°C. The difference in
In a number of works the application of nano-
particles and nanoclusters as catalysts for
hydrogenation of carbonyl compounds is reported. The
synthesis of isopropanol by catalytic hydrogenation of
acetone with hydrogen in the presence of iridium nano-
clusters, synthetic procedure for preparing secondary
1
For communication V, see [1].
1656

COLLOID AND NANODIMENSIONAL CATALYSTS IN ORGANIC SYNTHESIS: VI.
1657
Scheme 1.
O
H2 (1 atm), 60oC
Ni0, THF
O
IIа
OH
H2 (1 atm), 60oC
Iа
Ni0, i-PrOH
IIb
O
H2 (1 atm), 60oC
Ni0, THF
O
IIc
OH
H2 (1 atm), 60oC
Ib
Ni0, i-PrOH
IId
Scheme 2.
O
OH
H2 (1 atm), 70oC
Ni0, i-PrOH
IIe
OH
Ic
O
H2 (1 atm), 60−70oC
Ni0, i-PrOH (t-BuOH)
(CH2)n
(CH2)n
Id, Ie
IIf, IIg
O
OH
H2 (1 atm), 65oC
Ni0, i-PrOH
If
IIh
H2 (1 atm), 70oC
OH
O
Ni0, i-PrOH
Ig
IIi
n = 1 (Id, IIf), 2 (Ie, IIg).
the hydrogenation chemoselectivity of α,β-unsaturated
ketones Ia, Ib while using the above-mentioned
catalytic systems is presented in the Scheme 1.
target hydrogenation either of the unsaturated bond or
the C=C bond together with the carbonyl group.
It is found that nickel nanoparticles prepared by the
reduction of nickel(II) chloride with sodium boro-
hydride successively catalyze the hydrogenation of
This difference in selectivity of the colloid nickel
catalyst obtained in different ways may be used for the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 9 2014

1658
MOKHOV et al.
It was shown that the developed catalytic system is
Scheme 3.
suitable also for hydrogenation of aromatic aldehydes.
For example, unsubstituted benzaldehyde Ij within 6 h
at 65–70°C forms benzyl alcohol IIk in about 80%
yield. On the other hand, the hydrogenation of m-
nitrobenzalhehyde under these conditions provided 3-
nitrobenzyl alcohol IIl in a small amount (28%).
CHO
H2 (1 atm), 65oC
OH
Ni0, i-PrOH
R
R
IIj, IIk
R = H (Ih, IIj), NO2 (Ii, IIk).
Ih, Ii
The hydrogenation of ketones containing the
carbonyl group at the aromatic ring proceeds
differently. It is established that in this case the main
reaction pathway is hydrogenolysis of the C=O bond
to the methylene group though the successful synthesis
of secondary alcohols with aromatic substituent by
means of catalytic hydrogenation of ketones with
hydrogen at 5–8 bar in the presence of ruthenium
acyclic Ic and cyclic Id–If ketones to the correspond-
ing alcohols in 70–84% yields (Scheme 2).
As is known, metal nanoparticles catalyze the reac-
tion of transfer hydrogenation [4] while using secondary
alcohols as reagents. For the confirmation that just
hydrogen and not isopropanol is the hydrogenation
agent in the above-presented reactions we have used
tert-butanol as a solvent for hydrogenation of
cyclohexanone Ie because this alcohol cannot take part
in transfer hydrogenation. It was shown that cyclo-
hexanol is formed disregarding the alcohol used as a
solvent. Hence, just hydrogen at atmospheric pressure
is the hydrogenating agent. It was found that the ability
of hydrogenation of the carbonyl group by means of
this catalytic system is somewhat lower than the
hydrogenation of the C=C bond.
complex and potassium isopropylate has
reported [11].
been
Results of hydrogenation of acetophenone III were
unexpected. The reaction was carried out in the
presence of nickel nanoparticles obtained by the reduc-
tion of anhydrous nickel chloride with sodium
borohydride in isopropanol. The hydrogenation tem-
perature was 60–70°C, and hydrogen was bubbled
through the reaction mixture for 8 h. But instead of the
expected 1-hydroxyethylbenzene according to the
chromatomass spectrometry a mixture of hydrocarbons
was obtained. It consisted mainly of styrene IVa
(56 wt %), and ethylbenzene IVb (28 wt %). Beside
these substances vinylcyclohexane IVc (14 wt %),
three isomeric ethylcyclohexenes IVf–IVg, and
ethylcyclohexane IVh were found (Scheme 4).
The composition and structure of alkanols IIe–IIi
was confirmed by the 1H NMR spectroscopy. Properties
of the known compounds agree with the reported data.
Hence, the procedure for hydrogenation of aliphatic
and alicyclic carbonyl compounds with hydrogen at
atmospheric pressure and 69–70°C on the available
catalyst is developed. It may be used in the laboratory
as well (Scheme 3).
Therefore acetophenone suffered not hydrogenation
but hydrogenolysis of the carbonyl bond. Besides it
was found that the presence of water formed in the
reaction decreased the activity of catalyst towards
Scheme 4.
+
+
+
+
+
O
Ni0, H2 (1 atm)
O
IVd, 1.5%
IVc, 14%
IVа, 56%
IVb, 28%
60−70oC, i-PrOH
+
+
III
IVe
IVf
IVg
IVh, <1%
<1%
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COLLOID AND NANODIMENSIONAL CATALYSTS IN ORGANIC SYNTHESIS: VI.
1659
Scheme 5.
OH
+
+
O
Ni0, H2 (1 atm)
VIb, 13%
VIc, 0.2%
VIа, 47%
60−70oC, i-PrOH
O
O
O
V
+
+
+
VId, 0.8%
VIe, 0.8%
VIf, 0.1%
OH
O
+
+
+
+
O
VIIIc, 9%
Ni0, H2 (1 atm)
VIIIа, 55%
VIIIb, 22%
O
60−70oC, i-PrOH
O
+
VII
O
VIIIe, 4%
VIIId, 7%
VIIIf, 3%
hydrogenation of the multiple carbon–carbon bond
because significant amount of styrene was obtained. At
the same time the hydrogenation of aromatic ring
started, and the total amount of compounds with
partially or completely hydrogenated benzene ring
reached 16%. This fact requires further study due to
the importance of establishing the conditions of
aromatic compounds hydrohenation at mild conditions
on available catalysts. Up till now only the hydro-
genation of benzene with hydrogen at atmospheric
pressure and room temperature on the ruthenium or
rhodium nanoparticles was described [12, 13].
found that in this case alcohols also were not the main
reaction products. The conversion of benzophenone
was 65%. The main reaction product was diphenyl-
methane VIa. Its amount permitted to isolate it pure by
fractional distillation. Similarly to the reduction of
acetophenone the products of partial hydrogenation of
aromatic rings VIc, VId, VIf were found. In the case
of anthraquinone the product of partial hydrogenolysis,
anthrone VIIIa, was formed. It is interesting that the
preferred hydrogenation of the side ring of anthrax-
quinone takes place (conversion 82%). Quinone VIIId,
phenol VIIIc, and hydrocarbon VIIIe are mainly
formed. It shows the independence of pathways of
hydrogenation of the carbonyl group and aromatic rings.
For the confirmation of established rules we have
carried out hydrogenation of two other aromatic
ketones, benzophenone V and anthraquinone VII under
the same conditions (Scheme 5).
If in the hydrogenation of acetophenone III the
mechanism of formation of the mixture obtained
through the stage of dehydration leading to phenyl-
acetylene which is completely hydrogenated to styrene
and the other products is possible, for compounds V,
VII dehydration as well as hydrogenation of the enol
form is impossible. Hence, the mechanism of the
After the completion of the reactions and separation
of catalyst and solvent the reaction mixtures were
analyzed by the chromatomass spectrometry. The
majority of products were identified by coincidence of
their spectra with the database of spectrometer. It was
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1660
MOKHOV et al.
above-presented reactions should be specially studies.
The reactions described are not only interesting from
the theoretical point of view, but after optimization of
conditions may have certain preparative use. Besides
the fact of the change in selectivity of the catalytic
system under investigation in the presence of water it
is interesting because it may probably permit a
development of a convenient procedure for hydrogena-
tion of aromatic compounds under relatively mild
conditions.
1H NMR spectrum, δ, ppm: 1.19–1.93 m (6H, 3CH2),
2.19–2.30 m (2H, CH2–Ar), 2.34 t [2H, CH2C(O),
J 13.2 Hz], 2.71 t [1H, CHC(O), J 12.6 Hz], 6.98–7.30
m (5H, C6H5).
2-Benzylcyclohexanol (IId). Analogously to IIa
from 0.5 g (0.014 mol) of NaBH4 in 20 mL of
isopropanol, 0.9 g (0.007 mol) of NiCl2 and 18.6 g
(0.1 mol) of ketone Ib after bubbling of hydrogen at
60°C for 10 h 12.7 g (0.067 mol, 67%) of alkanol IId
was obtained, bp 195–198°C (20 mmHg), {bp 90–93°C
(0.15 mmHg) [16]}. 1H NMR spectrum, δ, ppm: 0.93–
1.57 m (8H, 4CH2), 2.19 t (1H, CH, J 22 Hz), 2.38–
EXPERIMENTAL
-
1H NMR spectra were taken on a Varian Mercury-
300 (300 MHz) spectrometer in carbon tetrachloride,
internal references HMDS or TMS. Chromatomass
spectral analysis was carried out on a Saturn 2100T/
GC3900 instrument.
2.68 m (2H, CH2 Ar), 3.15 m (1H, CH–O), 4.32 br.s
(1H, OH), 6.99–7.08 m (5H, C6H5).
Hexan-2-ol (IIe). Analogously to IIa from the
suspension of 0.72 g (0.02 mol) of NaBH4 in 20 mL of
isopropanol, 1.3 g (0.01 mol) of NiCl2 and 20 g
(0.2 mol) of ketone Ib after bubbling of hydrogen at
55°C for 8 h 14.9 g (0.146 mol, 73%) of alkanol IIe
was obtained, bp 138–140°C, nD20 1.4140 (bp 140°C,
nD20 1.4144 [14]).
Cyclopentanol (IIf). Analogously to IIa from the
suspension of 0.5 g (0.014 mol) of NaBH4 in 20 mL of
isopropanol, 0.9 g (0.007 mol) of NiCl2 and 15.8 g
(0.2 mol) of cyclopentanone Id after bubbling of
hydrogen at 60°C for 8 h 10.4 g (0.14 mol, 69%) of
cyclopentanol IIf was obtained, bp 140–142°C, nD20
1.4532 (bp 139–141°C, nD20 1.4530 [14]).
Cyclohexanol (IIg). a. Analogously to IIa from the
suspension of 0.58 g (0.016 mol) of NaBH4 in 20 mL
of isopropanol, 1 g (0.008 mol) of NiCl2 and 19.6 g
(0.2 mol) of cyclohexanone Ie after bubbling of
hydrogen at 60°C for 8 h 15.8 g (0.158 mol, 79%) of
cyclohexanol IIg was obtained, mp 23–25°C, bp 159–
161°C, nD20 1.4639 (mp 25.2°C, bp 161.1°C, nD20
1.4641 [14]).
b. Analogously to IIa from the suspension of 0.4 g
(0.011 mol) of NaBH4 in 15 mL of tert-butanol, 0.65g
(0.005 mol) of NiCl2 and 14.7 g (0.15 mol) of ketone
Ie after bubbling of hydrogen at 60°C for 9 h 11.7 g
(0.117 mol, 78%) of cyclohexanol IIg was obtained.
Benzylacetone (IIa). To a suspension of 0.5 g
(0.014 mol) of lithium aluminum hydride in 20 mL of
anhydrous THF 3.6 g (0.028 mol) of anhydrous NiCl2
was added in portions under bubbling of hydrogen.
After the formation of black colloid solution 22 g
(0.151 mol) of ketone Ia was added. The reaction
mixture was maintained under stirring and bubbling of
hydrogen (30–35 mL/min) for 6 h at 60°C. After that
the mixture was cooled and 1 mL of water was added
for coagulation of catalyst. The mixture was filtered,
and THF was distilled off from the filtrate. The residue
was distilled to give 13.2 g (0.116 mol, 77%) of ketone
IIa, bp 233–236°C, nD20 1.5121 (bp 234°C, nD20 1.5124
1
[14]). H NMR spectrum, δ, ppm: 1.90 s (3H, CH3),
2.53 t [2H, CH2C(O), J 14.4 Hz], 2.70 t (2H, CH2,
J 14.2 Hz), 6.92–7.08 m (5H, C6H5).
4-Phenylbutanol-2 (IIb). Analogously to IIa from
0.5 g (0.014 mol) of NaBH4 in 20 mL of isopropanol,
0.9 g (0.007 mol) of NiCl2 and 14.6 g (0.1 mol) of
ketone Ia after bubbling of hydrogen at 60°C for 8 h
10.4 g (0.071 mol, 71%) of ketone IIb was obtained,
bp 155–157°C (25 mmHg), nD20 1.5153 {bp 124°C
(12 mmHg), nD20 1.5159 [14]}. H NMR spectrum, δ,
1
ppm: 1.09 t (3H, CH3, J 10 Hz), 1.59 m (2H, CH2CO),
2.52 m (2H, CH2-Ar), 3.62 m (1H, CH–O), 4.36 s (1H,
OH), 6.91–7.12 m (5H, C6H5).
Adamantan-2-ol (IIh). Analogously to IIa from
the suspension of 0.25 g (0.007 mol) of NaBH4 in
20 mL of isopropanol, 0.45 g (0.0035 mol) of NiCl2
and 7.5 g (0.05 mol) of ketone Ib after bubbling of
hydrogen at 65°C for 9 h 6.75 g (0.045 mol, 90%) of
alkanol IIh was obtained, mp 260–262°C, (mp 258–
2-Benzylcyclohexanone (IIc). Analogously to IIa
from 0.5 g (0.014 mol) of LiAlH4 in 20 mL of dry
THF, 3.6 g (0.028 mol) of NiCl2 and 20 g (0.11 mol)
of ketone Ib after bubbling of hydrogen at 60°C for 7 h
15.7 g (0.082 mol, 75%) of ketone IIc was obtained,
bp 185–187°C/20 mm, {bp 160°C (12 mmHg) [15]}.
1
262°C [16]). H NMR spectrum, δ, ppm: 0.83–2.05 m
(14H), 3.72 br.s (1H, OH), 3.86 m (1H, CH–O).
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COLLOID AND NANODIMENSIONAL CATALYSTS IN ORGANIC SYNTHESIS: VI.
1661
1,7,7-Trimethylbicyclo[2.2.1]heptan-2-ol
(IIi).
10.4 g (0.05 mol) of anthraquinone VII after bubbling
of hydrogen at 60–70°C for 10 h 8.1 g of a mixture of
hydrogenolysis products VIIIa–VIIIg was obtained.
Analogously to IIa from the suspension of 0.25 g
(0.007 mol) of NaBH4 in 20 mL of isopropanol, 0.45 g
(0.0035 mol) of NiCl2 and 7.7 g (0.05 mol) of D,L-
camphor Ig after bubbling of hydrogen at 70°C for
10 h 6.3 g (0.04 mol, 82%) of alkanol IIi was obtained,
mp 209–210°C, (mp 208-209oC [16]). 1H NMR
spectrum, δ, ppm: 0.74–0.79 m (9H, 3CH3), 0.88–1.84
m (6H, 3CH2), 2.10 m (1H, CH) 3.45 br.s (1H, OH),
3.81–3.85 m (1H, CH).
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