Selective reductive amination of aldehydes from nitro compounds catalyzed by molybdenum sulfide clusters

Article abstract of DOI:10.1039/c7gc01603d

Secondary amines are selectively obtained from low value starting materials using hydrogen and a non-noble metal-based catalyst. The reductive amination of aldehydes from nitroarenes or nitroalkanes is efficiently catalyzed by a well-defined diamino molybdenum sulfide cluster in a one-pot homogeneous reaction. The integrity of the molecular cluster catalyst is preserved along the process.

Full text of DOI:10.1039/c7gc01603d

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Selective reductive amination of aldehydes from nitro compounds
catalyzed by molybdenum sulfide clusters
E. Pedrajas,a I. Sorribes,†,b K. Junge,b M. Beller,*,b and R. Llusar*,a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
(dmen = N,N’-dimethylethylenediamine), depicted in Figure 1,
Secondary amines are selectively obtained from low value starting
materials using hydrogen and a non-noble metal based catalyst.
performs this transformation under mild conditions and using
Reductive amination of aldehydes from nitroarenes or molecular hydrogen, the most “green” and least expensive reducing
agent.6 On this basis, we became interested in its use as catalyst for
nitroalkanes is efficiently catalyzed by a well-defined diamino
molybdenum sulfide cluster in a one-pot homogeneous reaction.
The integrity of the molecular cluster catalyst is preserved along
the process.
the related reductive amination of aldehydes with nitroarenes and
nitroalkanes to generate secondary amines in a straightforward
manner.
Introduction
Amines are the most important building blocks employed in
modern medicinal chemistry.1 Secondary amines are regularly
prepared by alkylation or reductive amination of the parent amines
through transition metal, typically precious metals, catalyzed
reactions.2,3 In the last years, the catalytic alkylation of amines with
alcohols under hydrogen-borrowing conditions4 as well as the
catalytic reductive amination of carbonyl compounds using
hydrogen as reductant have been proposed as environmentally
friendly procedures to produce N-substituted amines.5
NH
N
H
Cl
Mo
S
S
S
Cl
NH
NH
Mo
Mo
H
N
S
NH
Cl
Figure 1. Structure of the [Mo3S4Cl3(dmen)3]+ cluster catalyst.
An actual challenge in catalysis research is to take low value starting
materials and convert them to high value products using non-toxic
earth abundant materials through an atom efficient procedure.
Nitro compounds are an economic feedstock to provide primary
amines and their use in reductive amination processes is highly
attractive since it does not require prior isolation of the amine. Our
groups have recently shown that well-defined Mo3S4 cuboidal
clusters are efficient catalysts for the chemoselective reduction of
nitroarenes to anilines using different reducing agents.6–8
Interestingly, the diamino cluster of formula [Mo3S4Cl3(dmen)3]+
Domino catalytic transformations starting from nitroarenes and
carbonyl compounds directed towards the preparation of N-
alkylated aryl amines are not so common and they are usually done
in heterogeneous phase using palladium, platinum, rhodium or gold
nanocatalysts.9–16 N-alkylation of nitroarenes with aldehydes
catalyzed by palladium operates under ambient hydrogen pressure
at room temperature when alcohols are used as solvents. However,
formation of byproducts such as benzylalcohol and toluene
derivatives limits the selectivity of the process. Several cost
effective carbon-supported catalysts based on nanostructured
Fe2O3 and Co-Co3O4 partially encapsulated by nitrogen-enriched
graphene layers (Fe2O3/NGr@C and Co-Co3O4/NGr@C, respectively)
have also been recently developed by some of us for the tandem
reductive amination between nitro compounds and carbonyl
compounds using hydrogen as reductant.17–19 In general, these
heterogeneous processes employing non-noble metals require
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more demanding conditions (110-170 oC and 50-70 bar H2) and
contrary to general assumption that anhydrous conditions favor
reductive aminations, water has a positive influence on the
reaction. Lanthanide Metal Organic Frameworks have also proved
to be active catalysts for the tandem reductive amination of
nitrobenzene with heptanal to produce N-heptylaniline in moderate
yields.20
Table 1. Influence of the solvent in the reductive amination of
nitrobenzene with benzaldehyde.
Entry a Solvent
Conv.
[%]b
31
Yield [%]b
4a 5a
Although heterogeneous catalysts are usually preferred for most
industrial applications, molecularly defined complexes are still an
attractive approach in catalysis due to their higher selectivity and
easy modification. To our knowledge, the only examples of
homogeneous catalysts capable to afford secondary amines from
nitroarenes and aldehydes in the presence of hydrogen in a tandem
fashion were reported by Corma’s group. The complex IrLCl (L = (E)-
3a
0
1
2
3
4
5
6
1,4-Dioxane
7
22
0
CH3OH
99
74
99
0
23
0
THF (150-1500 ppm of H2O)
THF (molecular sieves)
THF-H2O (10:1)
>99
50
0
18 30
36 11
47
0
THF-H2O (5:1)
14
0
11
2
2-tert-Butyliminomethyl)-6-diisopropylaminomethyl-pyridine)
is
a Reaction conditions: 1a (0.1 mmol), 2a (0.12 mmol), H2 (20 bar), catalyst
able to produce N-benzylaniline in 66% yield after full conversion of
nitrobenzene under 6 bar of H2 pressure and 100 0C, while a
b
(5 mol %), solvent (2 mL), 18 h, 70 ºC. Determined by GC analysis using
trialkoxysilyl
derivative
of
the
pincer-type
complex
hexadecane as an internal standard.
[RuHClCO((NHC)NN)] ((NHC)NN = (S)-1-((6-((3-aryl-2,3-dihydro-1H-
imidazol-1-yl)methyl)pyridin-2-yl)methyl) affords 86% conversion
0
amine 3a is formed (Table 1, entry 4). Surprisingly, similar reactivity
is observed in THF-H2O mixtures (Table1, entries 5 and 6). Thus,
traces of water, approximately between 150 and 1500 ppm, are
needed to achieve a quantitative formation of 3a, while an excess
of water has a detrimental effect on the reaction outcome (Table 1,
entry 4). These results suggest a direct implication of the water
molecules in the reaction mechanism. The beneficial effect of
controlled amount of water in the reductive N-alkylation of amines
is not unprecedented.23 In contrast, larger amounts of water, up to
50%, are tolerated in the tandem reactions of nitro compounds to
secondary amines catalyzed by Co-Co3O4/NGr@C and Fe2O3/NGr@C
catalysts in THF.17–19 In this last case, water addition is believed to
promote hydrophobic association of aldehydes and amines as well
as suppress catalysts poisoning.24
and 25% yield under similar conditions (80 C and 5 bar H2).21,22
Remarkably, immobilization of these molecular complexes in MOF
architectures or mesoporous silica combines the catalytic power of
the iridium or ruthenium complex with that of the support
enhancing both conversion and selectivity.
Homogeneous catalysis by well-defined metal cluster complexes
offers the possibility of performing transformations similar to those
observed in heterogeneous phase, which are known to be difficult
to trace and control. Herein, we report the first homogeneous
catalyst based on non-noble metals for the clean and atom efficient
N-alkylation of amines starting from nitro compounds and
aldehydes using molecular hydrogen as a benign reducing agent.
The catalyst, a diamino cuboidal molybdenum sulfide cluster, is
highly selective and preserves its integrity during the process.
Next, optimization of the temperature, hydrogen pressure and
catalyst loading was addressed (Tables SI1, SI2 and SI3). Full
conversion of 1a with a quantitative yield of 3a (>99%) occurs at 70
0C, 20 bar of hydrogen pressure and 5 mol% of catalyst loading
within 18 hours. In contrast, partial conversion of 1a (48%) with
only scarce formation of 4a (7% yield) and 5a (38% yield) is
achieved after 4 h. Then, longer reaction times are needed for the
reduction of the imine intermediate, which is in good agreement
with the general tendency that imine hydrogenation is regarded as
the rate-determining step in the reductive amination sequence. It
shoud be noted that when aldehydes were replaced by ketones, the
reaction stopped at the aniline formation stage and no traces of the
iminium ion or the secondary amine could be detected.
Results and discussion
An initial evaluation of the [Mo3S4Cl3(dmen)3]+ catalyst performance
on the model reaction of nitrobenzene (1a) with benzaldehyde (2a)
was realized using different solvents motivated by the already
established solvent influence on the reactants conversion and
products selectivity.17,19 For this study, we have tentatively chosen
the optimum reaction conditions used for the hydrogenation of
nitroarenes to anilines applying this molybdenum-based complex
(18 h at 70 °C under 20 bar H2 and 5 mol% of catalyst) and 1.2
equivalents of 2a have been added to the reaction mixture.6 While
methanol appears as an optimum solvent for the hydrogenation of
nitroarenes, the best yield towards the formation of the N-
benzylaniline (3a) has been obtained in THF (Table 1, entries 1-3).
When molecular sieves are added to remove water from the
reaction mixture and tentatively shift the equilibrium towards the in
situ generated imine, conversion of 1a halved and no secondary
Our recent works on the catalytic reduction of nitroarenes to aniline
derivatives mediated by Mo3S4-based clusters decorated with
diphosphino, diamino or diimino ligands show no fragmentation of
the cluster core during the first stage of this tandem process.6–8
Here, a color change, from green to brown, occurs during the
catalytic process due to the basicity increase caused by the amine
2 | J. Name., 2012, 00, 1-3
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generation. However, analysis of the reaction mixture by
electrospray ionization mass spectrometry (ESI-MS), shows a single
chloronitrobenzene (1b). To our delight, the corresponding
secondary amines were afforded in good to excellent yields. As a
general trend, when both the aldehyde and nitroarene are
funtionalized with electron-donating groups, such as alkyl, alkoxy or
thiomethyl groups, the one-pot reductive amination reaction
proceeds smothly towards the formation of the secondary amines.
However, the presence of electron-withdrawing groups on the
aromatic ring had a high impact on the reductive amination activity
since an increased hydrogen pressure (up to 50 bar H2) is required
to avoid accumulation of the imine intermediate.
peak at m/z
= 786.9, associated to the pseudomolecular
[Mo3S4Cl3(dmen)3]+ ion on the basis of the m/z value and its
characteristic isotopic pattern (Figure SI1). Additionally, cluster
integrity was further confirmed by 1H NMR spectroscopy (Figure
SI2). Therefore, the integrity of the cluster core is also preserved
during the reductive amination stage. In addition, catalyst recycling
in the model reaction after recovering the catalyst by evaporating,
washing and drying the reaction mixture, shows full conversion and
an excellent yield of 3a (90%) in the second run (Figure SI3). In a
third run, conversion decreased to 67% and only traces of the
secondary amine 3a were formed together with N-
benzylideneaniline (5a) as a major product (46%) and aniline (4a) in
16% yield.
Gratifyingly, both halogen-substituted nitroarenes and aldehydes
react to give the corresponding halogenated-amines without any
dehalogenation processes affording the corresponding halogenated
secondary amines in moderate to excellent yields. Notably,
reductive amination of p-fluorobenzaldehyde with 1b affords a
quantitative yield of the expected alkylated amine (Table 3, entry
5). However, reaction with the ortho-isomer requires an increased
hydrogen pressure (50 bar H2) to get a moderate yield of the
corresponding secondary amine (Table 3, entry 6). Hence, it seems
that reactivity could be affected by both electronic and steric
effects.
To prove the general applicability of the Mo3S4-based catalytic
system, the reaction between various functionalized nitro
compounds and aldehydes was investigated. More specifically,
different nitro compounds were reacted with p-anisaldehyde (2b)
(Table 2), and as shown in Table 3, the reductive amination of
diverse structure aldehydes was carried out with p-
From a synthetic point of view, substrates bearing reducible
Table 2. Hydrogenation of different nitroarenes (entries 1-9)
and 1-nitrohexane with p-anisaldehyde.
Table 3. Hydrogenation of diverse benzaldehydes (entries 1-8) and
cyclohexanecarboxaldehyde with 1-chloro-4-nitrobenzene.
Entrya
Substrate
P
Conv.
[%]b
Yield
amine
3 [%]b
Entrya
Substrate
P
Conv.
[%]b
Yield
amine
3 [%]b
(bar)
(bar)
1
R = H
20
20
50
20
20
20
50
50
>99
>99
>99
>99
>99
>99
>99
>99
(98)
1
R = H
40
20
20
20
20
50
50
40
>99
>99
>99
>99
>99
>99
>99
>99
(95)
2c
3d
4
R = 3-Me
R = 3-CF3
R = 4-F
R = 4-Cl
R = 4-I
91
2c
R = 4-iPr
R = 3-OMe; 4-OEt
R = 4-SMe
R = 4-F
(90)
(97)
(95)
>99
(68)
(77)
(85)
(97)
>99
(91)
(90)
(82)
(85)
3
4
5d
5
6c,d
7c,d
8d
R = 2-F
6
7d,e
8d,e
R = 4-CN
R = 4-Br
R = 4-COOMe
R = 3-CHCH2
NO2
CHO
9d, f
50
50
>99
>99
(81)
61
9c,d
50
>99
88 (79)
N
10c, d, g
Reaction conditions: 1b (0.25 mmol), 2 (0.3 mmol), catalyst (6 mol %
a
NO2
b
related to nitroarene), solvent (2 mL). Determined by GC analysis using
hexadecane as an internal standard; yields of isolated products given in
parentheses. c 24 h. d Traces of imine as byproduct.
a
Reaction conditions: 1 (0.25 mmol), 2b (0.3 mmol), catalyst (6 mol %
b
related to nitroarene), solvent (2 mL). Determined by GC analysis using
hexadecane as an internal standard; yields of isolated products given in
parentheses. c Traces of aniline as byproduct. d Traces of imine as byproduct.
f
e 24 h. 100 ºC of temperature. g 150 ºC of temperature; Yield based on 1H
functionalities are highly attractive. In this respect, we tested some
NMR using 2,4,6-trimethylphenol as internal standard.
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General procedure for the one-pot reductive amination: A 8 mL
glass vial containing a stirring bar was sequentially charged with the
substrates functionalized with nitriles, esters or olefines. To our
delight, these moieties were well tolerated, thus furnishing the
expected amines in 82-85% isolated yields (Table 2, entries 7 and 8;
Table 3, entry 8). In addition, a nitro-substituted heteroarene was
tested and the corresponding N-heterocyclic amine was isolated in
81% yield (Table 2, entry 9).
molybdenum
catalyst
(4.4
mg,
0.005
mmol
of
[Mo3S4Cl3(dmen)3](BF4)), nitrobenzene (10 µL, 0.097 mmol),
benzaldehyde (12 µL, 0.12 mmol), n-hexadecane (15 µL; added as
an internal standard) and 2 mL of THF. Afterwards, the reaction vial
was capped with a septum equipped with a needle and set in the
alloy plate, which was then placed into a 300 mL autoclave. Once
sealed, the autoclave was purged three times with 30 bar of
hydrogen, then pressurized to 20 bar and placed into an aluminum
block, which was preheated at 70 °C. After 18 h, the autoclave was
cooled to room temperature and the hydrogen was released. Ethyl
acetate (2 mL) was then added, and a sample was taken to be
analyzed by GC. To determine the isolated yields of the anilines, the
general procedure was scaled up by the factor of 2.5, and no
internal standard was added. After completion of the reaction, the
mixture was purified by silica column chromatography (n-
heptane/ethyl acetate mixtures) to give the corresponding anilines.
In the case of the nitroalkane, 2,4,6-trimehtylphenol was added as
internal standard and the yield was calculated based on 1H NMR.
Nowadays, the reductive amination of aldehydes with aliphatic
nitrocompounds remains as an important challenge. Interestingly,
in the presence of our Mo3S4-based catalyst reaction between 2b
and 1-nitrohexane leads to the formation of the secondary amine in
61% yield (Table 2, entry 10). Moreover, our catalytic system also
works with cyclic aliphatic aldehydes. Reductive amination of
cyclohexanecarboxaldehyde with 1b affords a moderate yield (60%)
of the desired amine (Table 3, entry 9).
Finally, the preparative value of this protocol was further
demonstrated upscaling the model reaction of nitrobenzene (1a)
with benzaldehyde (2a) by a factor of 40 and using a considerable
higher concentration of reactants. As shown Scheme 1, N-
benzylaniline (3a) was obtained in 90 % yield after purification by
column chromatography.
Acknowledgements
The financial support of the Spanish Ministerio de Economía y
Competitividad (Grant CTQ2015-65207-P) and Generalitat
Valenciana (PrometeoII/2014/022) is gratefully acknowledged. The
authors also thank the Serveis Centrals d’Instrumentació Cientifica
(SCIC) of the Universitat Jaume I for providing us with mass
spectrometry and NMR techniques. E. Pedrajas thanks the
University Jaume I for a predoctoral fellowship.
Scheme 1. Up-scaled preparation of N-benzylaniline (3a)
References
Conclusions
1
2
3
4
5
6
S. D. Roughley and A. M. Jordan, J. Med. Chem., 2011, 54,
3451–3479.
In conclusion, we have developed an atom-efficient catalytic
protocol for the synthesis of secondary amines through a one-pot
reductive amination reaction from easily available nitroarenes and
aldehydes using hydrogen as reducing agent. The use of a well-
defined diamino molecular Mo3S4 cluster as catalyst allows for
successful reductive amination of aldehydes with the in situ
generated primary amines selectively affording a variety of
secondary amines in good to excellent yields. Remarkably, this
procedure applies for aromatic as well as for aliphatic nitro
compounds or aldehydes. Spectrometric and spectroscopic
techniques show no changes in cluster composition or evidences of
cluster fragmentation during the catalytic reaction. Mechanistic
investigations on the catalytic process which combine theory with
experiment are in progress.
G. Guillena, D. J. Ramón and M. Yus, Chem. Rev., 2010, 110,
1611–1641.
E. W. Baxter and A. B. Reitz, in Organic Reactions, John
Wiley & Sons, Inc., Hoboken, NJ, USA, 2002, pp. 1–714.
R. Kawahara, K. Fujita and R. Yamaguchi, Adv. Synth. Catal.,
2011, 353, 1161–1168.
S. Fleischer, S. Zhou, K. Junge and M. Beller, Chem. - An
Asian J., 2011, 6, 2240–2245.
E. Pedrajas, I. Sorribes, A. L. Gushchin, Y. A. Laricheva, K.
Junge, M. Beller and R. Llusar, ChemCatChem, 2017, 9,
1128–1134.
7
E. Pedrajas, I. Sorribes, K. Junge, M. Beller and R. Llusar,
ChemCatChem, 2015, 7, 2675–2681.
8
I. Sorribes, G. Wienhöfer, C. Vicent, K. Junge, R. Llusar and
M. Beller, Angew. Chemie Int. Ed., 2012, 51, 7794–7798.
B. Sreedhar, P. S. Reddy and D. K. Devi, J. Org. Chem., 2009,
74, 8806–8809.
Experimental section
9
Synthesis of the catalyst: The catalyst [Mo3S4Cl3(dmen)3](BF4) was
prepared starting from the [Mo3S4(tu)8(H2O)]Cl4·4H2O thiourea
precursor according to the literature.6
10
L. Li, Z. Niu, S. Cai, Y. Zhi, H. Li, H. Rong, L. Liu, L. Liu, W. He
and Y. Li, Chem. Commun., 2013, 49, 6843.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
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Please do not adjust margins
Green Chemistry
Page 5 of 6
View Article Online
DOI: 10.1039/C7GC01603D
Journal Name
COMMUNICATION
11
12
13
S. Wei, Z. Dong, Z. Ma, J. Sun and J. Ma, Catal. Commun.,
2013, 30, 40–44.
B. Sreedhar and V. S. Rawat, Synth. Commun., 2012, 42,
2490–2502.
L. Hu, X. Cao, D. Ge, H. Hong, Z. Guo, L. Chen, X. Sun, J.
Tang, J. Zheng, J. Lu and H. Gu, Chem. - A Eur. J., 2011, 17,
14283–14287.
14
15
Y. Yamane, X. Liu, A. Hamasaki, T. Ishida, M. Haruta, T.
Yokoyama and M. Tokunaga, Org. Lett., 2009, 11, 5162–
5165.
A. L. Nuzhdin, E. A. Artiukha, G. A. Bukhtiyarova, S. Y.
Zaytsev, P. E. Plyusnin, Y. V. Shubin and V. I. Bukhtiyarov,
RSC Adv., 2016, 6, 88366–88372.
16
17
18
19
20
L. Huang, Z. Wang, L. Geng, R. Chen, W. Xing, Y. Wang and
J. Huang, RSC Adv., 2015, 5, 56936–56941.
T. Stemmler, F. A. Westerhaus, A.-E. Surkus, M.-M. Pohl, K.
Junge and M. Beller, Green Chem., 2014, 16, 4535–4540.
R. V Jagadeesh, T. Stemmler, A.-E. Surkus, H. Junge, K.
Junge and M. Beller, Nat. Protoc., 2015, 10, 548–557.
T. Stemmler, A.-E. Surkus, M.-M. Pohl, K. Junge and M.
Beller, ChemSusChem, 2014, 7, 3012–3016.
R. F. D’Vries, M. Iglesias, N. Snejko, S. Alvarez-Garcia, E.
Gutiérrez-Puebla and M. A. Monge, J. Mater. Chem., 2012,
22, 1191–1198.
21
22
23
24
M. Pintado-Sierra, A. M. Rasero-Almansa, A. Corma, M.
Iglesias and F. Sánchez, J. Catal., 2013, 299, 137–145.
C. del Pozo, A. Corma, M. Iglesias and F. Sánchez, J. Catal.,
2012, 291, 110–116.
J. R. Cabrero-Antonino, R. Adam, K. Junge and M. Beller,
Catal. Sci. Technol., 2016, 6, 7956–7966.
S. Sato, T. Sakamoto, E. Miyazawa and Y. Kikugawa,
Tetrahedron, 2004, 60, 7899–7906.
This journal is © The Royal Society of Chemistry 20xx
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One-pot selective synthesis of secondary amines catalyzed
by a well-defined Mo3S4 cluster using hydrogen as benign
reductant.
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