Simple H2-free hydrogenation of unsaturated monoterpenoids catalyzed by Raney nickel

Article abstract of DOI:10.1016/j.mencom.2019.07.006

A series of monoterpenoids (citral, carvone, menthone, camphor) as well as cyclohexanone and hex-5-en-2-one were subjected to transfer hydrogenation with PrⁱOH/Raney nickel system at 82 or 150 °C. Among monoterpenoids, citral and carvone underwent full conversion at 82 °C within 5 h.

Full text of DOI:10.1016/j.mencom.2019.07.006

Mendeleev
Communications
Mendeleev Commun., 2019, 29, 380–381
Simple H2-free hydrogenation of unsaturated
monoterpenoids catalyzed by Raney nickel
Alexey A. Philippov,*a,b Andrey M. Chibiryaeva,b and Oleg N. Martyanova,b
a G. K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences,
630090 Novosibirsk, Russian Federation. E-mail: philippov@catalysis.ru
b Novosibirsk State University, 630090 Novosibirsk, Russian Federation
DOI: 10.1016/j.mencom.2019.07.006
A series of monoterpenoids (citral, carvone, menthone,
camphor) as well as cyclohexanone and hex-5-en-2-one were
subjected to transfer hydrogenation with PriOH/Raney nickel
system at 82 or 150 °C. Among monoterpenoids, citral and
carvone underwent full conversion at 82 °C within 5 h.
Nickel based heterogeneous catalysts including Raney nickel are
widely used in many reductive transformations.1,2 A wide range
of the Raney nickel applications continues to grow in aspect of
transfer hydrogenation (TH) reactions,3–5 mostly reduction of
carbonyl compounds to alcohols6,7 and olefins to alkanes.8,9
However, the heterogeneous TH of complex multifunctional
molecules is still a challenge for chemists due to their special
reactivity and stereo/chemo/regioselectivity problems. This study
aimed to demonstrate our results of TH of some monoterpenoids
(including low-reactive ones) catalyzed by Raney nickel in PriOH
medium. High H-donor activity of secondary PriOH compared
to primary alcohols was recently reported for reduction of
menthone.10
40% within 10 h at 80°C in the case of Pt/SiO2.16 Thus, the
simple synthetic procedure of reduction under hydrogen-free mild
conditions is in high demand.
Here, substrates 1–6 were tested under H2-free TH in the
presence of Raney nickel (Scheme 1). Among them there were
terpenoids, menthone 3, carvone 4, camphor 5 and citral 6, while
trivial hex-5-en-2-one 1 and cyclohexanone 2 served as the
Me
Me
OH
Me
Me
Me
+
O
O
1
7
8
Me
Me
O
OH
Raney nickel was previously used in conventional hydro-
genation of monoterpenoids.1,11 The heterogeneous TH of mono-
terpenoids with alcohols was also described.12–14 However, we
failed to find the Raney nickel applications for TH of any mono-
terpenoids. The TH is usually processed at elevated temperature
(95–120°C) and long time is often needed for the full conversion.
For example, the selectivity in TH of carbonyl group in citral and
carvone catalyzed by zirconium-based metal-organic framework
UiO-66 or its modified versions was studied.13 Despite the well-
known high reactivity of aldehydes and simple alkenes, the
conversion of citral (2,6-dienal) was not complete, namely, only
80% within 24 h at 120°C in PriOH. Under the same conditions,
the conversion of unsaturated carvone (2,7-dienone) was only 15%.
Better results were achieved12 when other Zr-MOF catalyst
(Zr-MOF-808-P) was used. The C=O group of citral and carvone
was converted in 100 and 50% extent, respectively, for 8 h at
120°C in PriOH. Similar results were reported for reduction of
camphor,14 namely, 75% yield of borneol was achieved for 5 h
at 25°C using nickel nanoparticles as a catalyst.
O
OH
2
9
Me
Me
Me
Me
10
3
Me
Me
Me
Me
O
OH
O
OH
+
+
Me
Me
Me
Me
Me
Me
Me
4
11
12
13
Me
Me
Me
Me
OH
Me
O
Me
5
14
Me
Me
Me
Me
Conventional hydrogenation of aldehydes usually proceeds
under milder conditions compared to TH. For example, citral can
be totally transformed to 3,7-dimethyloctan-1-ol within 1 h with
Raney nickel at 40°C.15 Nevertheless, it is difficult to perform
conventional hydrogenation of sterically hindered carbonyl substrates
such as menthone or camphor. The hydrogenation of menthone
with molecular hydrogen catalyzed by Raney nickel is effective
only at 180–200°C,11, while the conversion of camphor was
CHO
Me
Me
+
+
OH
OH
Me
Me
Me
Me
Me
Me
Me
6
15
16
17
Scheme 1 Reagents and conditions: PriOH, Raney nickel, 82 or 150°C, 5 h.
© 2019 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 380 –

Mendeleev Commun., 2019, 29, 380–381
Table 1 Transfer hydrogenation of carbonyl compounds in PriOH catalyzed
entries 11, 12). At 82°C for 5 h, the main product was citronellol
15 (73%), while the yield of fully hydrogenated dihydrocitronellol
16 was 25% only. Apparently, conjugated enal moiety of citral is
reduced faster than remote C=C bond that makes contribution in
selectivity of TH. Expectedly, dihydrocitronellol 16 becomes the
main product (94%) at 150°C when nothing of citronellol 15 is
detected. Obviously, decrease in reaction time and/or reaction
temperature can help to control the reaction selectivity from
partial to full hydrogenation. Another feature of this reaction is
a little decarbonylation of citral3 followed by fast reduction of
thus formed C9-hydrocarbon to fully hydrogenated 2,6-dimethyl-
heptane 17 (2% at 82°C vs. 6% at 150°C).
In conclusion, the TH reaction catalyzed by Raney nickel
at boiling point of PriOH demonstrates the synthetic potential
for reduction of unsaturated monoterpenoids or other olefins/
aldehydes/ketones. The method is simple and does not require
the use of flammable gaseous H2 or corrosive strong bases. The
reaction is carried out in standard laboratory glassware without
special equipment. The procedure is applicable for reduction of
sterically hindered or low-reactive substrates.
by Raney nickel.a
Entry Substrate T/°C
Conversion (%) Product compositionb (%)
1
2
1
1
2
2
3
3
4
4
5
5
6
6
82
150
82
> 98
>98
>98
>98
65
7 (2) + 8 (98)
7 (4) + 8 (96)
9 (>98)
9 (>98)
10 (>98)
3
4
150
82
5
6
150
82
98
10 (>98)
7
>98
98
11 (97) + 12 (3)
11 (98) + 12 (1) + 13 (1)
14 (>98)
14 (>98)
15 (25) + 16 (73) + 17 (2)
15 (94) + 17 (6)
8
150
82
9
27
10
11
12
150
82
53
>98
>98
150
a Conditions: substrate (0.3–0.5 g, 3.2 mmol), PriOH (120 ml, 1.5 mol),
Raney nickel (0.25 g, ~3.8 mmol of nickel), 5 h at specified temperature.
b GC–MC data, the starting substrate is excluded.
reference substrates.† All reaction courses were monitored by
GC–MS.
This work was performed within the framework of the budget
project at G. K. Boreskov Institute of Catalysis.
Under the reaction conditions, both C=C and C=O bonds
underwent hydrogenation. Conversion of hex-5-en-2-one 1, cyclo-
hexanone 2, carvone 4, and citral 6 achieved ca. 100% at both
temperatures 82 and 150°C (Table 1, entries 1–4, 7, 8, 11, 12).
Due to steric and electronic hindrances, the reduction of menthone 3
and camphor 5 occurred slower than that of cyclohexanone 2.16
Conversion of menthone 3 reached 67 and 98% for 5 h at 82 and
150°C, respectively (entries 5, 6). Since reactivity of camphor 5
is lower, only 27 and 53% of it was converted under the same
conditions (entries 9, 10). The process was chemoselective as
diastereomeric menthols 10 or borneols 14 were the only products.
Unlike menthone 3, the conversion of structurally similar
carvone 4 was higher (~100%) at both reference temperatures
(see Table 1, entries 7,8) to provide the same fully hydrogenated
carvomenthol 11 (as a mixture of diastereomers) with selectivity
of 97–98%. The possible reason could be difference in adsorption of
menthone 3 and carvone 4 on the catalyst surface, the conjugated
enone moiety of carvone 4 having facilitated its adsorption and
subsequent reduction. A small amount of carvone 4 was also
isomerized to carvacrol 13 at 150 °C. This reaction can be
accelerated at high temperatures using many catalysts including
Raney nickel.17
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi: 10.1016/j.mencom.2019.07.006.
References
1 F. Devred, B. W. Hoffer, W. G. Sloof, P. J. Kooyman, A. D. van Langeveld
and H. W. Zandbergen, Appl. Catal., A, 2003, 244, 291.
2 E. V. Shuvalova, O. A. Kirichenko and L. M. Kustov, Russ. Chem. Bull.,
Int. Ed., 2017, 66, 34 (Izv. Akad. Nauk, Ser. Khim., 2017, 34).
3 G. Calvaruso, J. A. Burak, M. T. Clough, M. Kennema, F. Meemken and
R. Rinaldi, ChemCatChem, 2017, 9, 2627.
4 C. Chesi, I. B. D. de Castro, M. T. Clough, P. Ferrini and R. Rinaldi,
ChemCatChem, 2016, 8, 2079.
5 M. J. Gilkey and B. Xu, ACS Catal., 2016, 6, 1420.
6 R. C. Mebane and A. J. Mansfield, Synth. Commun., 2005, 35, 3083.
7 R. C. Mebane, K. L. Holte and B. H. Gross, Synth. Commun., 2007, 37,
2787.
8 J. Li, S. Cheng, T. Du, N. Shang, S. Gao, C. Feng, C. Wang and Z. Wang,
New J. Chem., 2018, 42, 9324.
9 F. Alonso, P. Riente and M. Yus, Acc. Chem. Res., 2011, 44, 379.
10 A. A. Philippov, A. M. Chibiryaev and O. N. Martyanov, J. Supercrit.
Fluids, 2018, 145, 162.
ˇ
11 P. Kukula and L. Cervený, Res. Chem. Intermed., 2000, 26, 913.
Citral 6 (as a mixture of neral and geranial) demonstrates
high activity in TH at both reaction temperatures (see Table 1,
12 E. Plessers, G. Fu, C. T. Y. Xiang, D. E. De Vos and M. B. J. Roeffaers,
Catalysts, 2016, 6, 104.
13 E. Plessers, D. E. DeVos and M. B. J. Roeffaers, J. Catal., 2016, 340, 136.
14 G. P. Boldrini, D. Savoia, E. Tagliavini, C. Trombini andA. Umani-Ronchi,
J. Org. Chem., 1985, 50, 3082.
15 F. Devred, A. H. Gieske, N. Adkins, U. Dahlborg, C. M. Bao, M. Calvo-
Dahlborg, J. W. Bakker and B. E. Nieuwenhuys, Appl. Catal., A, 2009,
356, 154.
16 M. L. Casella, G. F. Santori, A. Moglioni, V. Vetere, J. F. Ruggera,
G. M. Iglesias and O. A. Ferretti, Appl. Catal., A, 2007, 318, 1.
17 E. C. Horning, J. Chem. Soc., 1945, 10, 263.
†
The reactions were carried out at 82°C (the boiling point of PriOH)
in standard laboratory glassware or at 150°C in 300 ml autoclave with
magnetic stirring for 5 h under argon atmosphere. The temperature of
150°C was reasoned by low reactivity of monoterpenoids in the TH
reaction.13,16 Monoterpene compound (0.3–0.5 g, 3.2 mmol) dissolved in
PriOH (120 ml, 1.5 mol) was mixed with Raney nickel catalyst (0.250 g,
~3.8 mmol of nickel) freshly prepared by well-known method based on
leaching with aq. NaOH at 50°C from Raney alloy (Al:Ni = 50:50).18
Physicochemical properties of prepared Raney nickel were in good
agreement with reported data.18 BET surface area of the catalyst was
50–70 m2 g–1 and did not change dramatically during the reactions. Thus,
despite the high nickel-to-substrate molar ratio (1.2:1), only about 5% of
all Ni atoms were located on the surface of the catalyst. According to
XPS method, the residual aluminum content in the catalyst was 10.3%.
X-ray powder diffraction demonstrated the phase of metallic nickel formed
from Al3Ni and Al3Ni2 intermetallics of initial alloy.
18 J. Freel, W. J. M. Pieters and R. B. Anderson, J. Catal., 1969, 14, 247.
Received: 4th February 2019; Com. 19/5816
– 381 –