C-N Bond Formation Catalyzed by Ruthenium Nanoparticles Supported on N-Doped Carbon via Acceptorless Dehydrogenation to Secondary Amines, Imines, Benzimidazoles and Quinoxalines

Article abstract of DOI:10.1002/cctc.201801525

Ruthenium nanoparticles (NPs) supported on N-doped carbon (Ru/N?C) were prepared by the pyrolysis of cis-Ru(phen)₂Cl₂ loaded onto carbon powder (VULCAN XC72R) at 800 °C. Ru/N?C NPs (0.2 mol% Ru) selectively catalyzed either acceptorless dehydrogenation coupling (ADC) or auto-transfer-hydrogen (ATH) reactions of amines with alcohols to imines and secondary amines. Such selectivity could be controlled by the choice of alkali metal ion associated with the base. Under similar catalytic conditions, the ADC cross-coupling of diamines with primary alcohols or diols afforded the corresponding benzimidazoles and quinoxalines in good to excellent yields. This catalytic system displayed good activity, recyclability, and wide applicability to a diverse range of substrates.

Full text of DOI:10.1002/cctc.201801525

Accepted Article
Title: C-N Bond Formation Catalyzed by Ruthenium Nanoparticles
Supported on N-Doped Carbon via Acceptorless
Dehydrogenation to Secondary Amines, Imines, Benzimidazoles
and Quinoxalines
Authors: Bin Guo, Hong-Xi Li, Shi-Qi Zhang, David James Young, and
Jian-Ping Lang
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To be cited as: ChemCatChem 10.1002/cctc.201801525
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10.1002/cctc.201801525
ChemCatChem
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C-N Bond Formation Catalyzed by Ruthenium Nanoparticles
Supported
on
N-Doped
Carbon
via
Acceptorless
Dehydrogenation to Secondary Amines, Imines, Benzimidazoles
and Quinoxalines
Bin Guo,[a, b] Hong-Xi Li,*[a] Shi-Qi Zhang,[a] David James Young,[c] and Jian-Ping Lang*[a, b]
Abstract: Ruthenium nanoparticles (NPs) supported on N-doped
carbon (Ru/N-C) were prepared by the pyrolysis of cis-Ru(phen)2Cl2
loaded onto carbon powder (VULCAN XC72R) at 800 °C. Ru/N-C
NPs (0.2 mol% Ru) selectively catalyzed either acceptorless
dehydrogenation coupling (ADC) or auto-transfer-hydrogen (ATH)
reactions of amines with alcohols to imines and secondary amines.
Such selectivity could be controlled by the choice of alkali metal ion
associated with the base. Under similar catalytic conditions, the ADC
cross-coupling of diamines with primary alcohols or diols afforded
the corresponding benzimidazoles and quinoxalines in good to
excellent yields. This catalytic system displayed good activity,
recyclability, and wide applicability to a diverse range of substrates.
makes the controlled-selective catalysis is in high demand.
Scheme 1. Synthesis of N-containing compounds via ADC and ATH strategies.
ADC methodology has been used to synthesize N-
compounds[7a]
pyrazines,[9b]
including
benzimidazoles,[7d,g,12]
quinazolinones,[7f]
and
pyrroles,[7b,10]
Introduction
heteroaromatic
pyridines,[7c,11]
benzoxazoles,[12]
quinolines,[7e,11]
N-substituted amines are an important class of compounds that
can be used as pharmaceuticals, agrochemicals, dyes and other
functional materials.[1] Traditionally they have been prepared
from the nucleophilic substitution of alkyl halides with primary
amines,[2] the hydrogenation of imines,[3] the reductive amination
of carbonyl compounds[4] and the metal-catalyzed amination of
aryl halides.[5] Synthesis of N-alkylated anilines using alcohols
as the alkylation reagents can avoid the use of potentially
hazardous oxidizing or reducing reagents and the formation of
salt wastes.[6] Water is the only by-product of this reaction and
alcohols are less toxic, easier to be handled and more readily
available than alkyl halides. The N-alkylation of anilines may
involve two or three steps (Scheme 1), depending on the desired
reaction outcomes. The two-step strategy is termed as
'acceptorless dehydrogenation coupling' (ADC)[7] and involves (i)
the dehydrogenation of alcohols to aldehyde, and (ii) the
condensation of aldehyde with amine to imine. The 'auto-
transfer-hydrogen' (ATH)[8] approach has an additional step, that
is, (iii) the hydrogenation of imines to alkylated amines.
Catalysts, molar ratios of reagents, reaction temperatures and
solvents all influence the final product distribution,[9] which
quinoxalines[7g] via reaction of alcohols/diols with amines or
amino alcohols. These heteroaromatic systems are commonly
encountered species in natural products, pharmaceuticals,
agrochemicals
and
other
fine
chemicals.[13]
These
transformations normally use well-defined ruthenium or iridium
organometallic complexes as the catalysts, but these precious
organometallic catalysts have not been widely used after their
initial reports because of complicated synthesis, recycling
problems and potential metal contamination of the products.
However, heterogeneous metal nanoparticles (NPs) supported
on silica-based materials,[14] metallic oxides,[15] magnetic NPs,[16]
porous organic polymers[17] and metal-organic-frameworks
(MOFs),[18] and Ru/hydroxyapatite[19] have been successfully
employed as catalysts for the assembly of nitrogen-containing
compounds via ADC and ATH methods. Porous carbon-based
materials are effective alternatives as supports[20-22] because of
their extremely high and specific surface areas, controllable
porosity and surface chemistry with high stability at various pH
values. Some of them are even commercially available. Carbon-
supported Ru catalysts exhibit good catalytic performance in the
ammonia borane hydrolysis reaction,[20a,b] hydrogenation/transfer
hydrogenation,[20c-i] and aerobic oxidation of alcohols.[20j-l] We
herein report the preparation of Ru NPs on N-doped carbon
(Ru/N-C) and their efficient, base-controlled ADC or ATH
transformation of amines and alcohols to imines and secondary
amines. This catalytic system can also effectively catalyze the
acceptorless dehydrogenation coupling of diamines with primary
alcohols or diols, giving the corresponding benzimidazoles and
quinoxalines in good to excellent yields.
[a]
B. Guo, Prof. Dr. H.-X. Li, S.-Q. Zhang, Prof. Dr. J.-P. Lang
College of Chemistry, Chemical Engineering and Materials Science
Soochow University
Suzhou 215123 (China)
E-mail: lihx@suda.edu.cn
jplang@suda.edu.cn
[b]
[c]
B. Guo, Prof. Dr. J.-P. Lang
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry, Chinese Academy of
Sciences
Shanghai 200032 (China)
Prof. Dr. D. J. Young
Results and Discussion
Faculty of Science, Health, Education and Engineering
University of the Sunshine Coast
Maroochydore DC, Queensland 4558 (Australia)
Synthesis and characterization of catalyst
Ru NPs (1 wt%) supported onto N-doped carbon (Ru/N-C) was
prepared by loading cis-Ru(phen)2Cl2 (0.0520 g, 1 wt% Ru
Supporting information for this article can be found under
http://dx.doi.org/10.1002/cctc.xxxxxx.
1
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10.1002/cctc.201801525
ChemCatChem
FULL PAPER
loading; phen
=
1,10-phenanthroline) onto carbon powder
Teller (BET) surface areas of N-C, Ru/C and Ru/N-C were 100,
98 and 64 m2/g, which were smaller than that of C-800 (117
m2/g) (Figure S5 and Table S1). Despite its low porosity,
supported carbon material still could absorb some small
molecules like H2O.
(VULCAN XC72R, 1.0000 g) and then calcinating at 800 °C for 2
h in a N2 flow. Ru/C and N-C materials were also prepared by
the similar method by replacing cis-Ru(phen)2Cl2 with RuCl3 or
phen. C-800 was obtained by heating Vulcan XC72R at 800 °C
under N2 for 2 h. The powder X-ray diffraction (PXRD) patterns
of as-synthesized Ru/N-C, Ru/C, N-C, and C-800 materials
showed peaks at 2θ = 25.38° and 43.20°, which belonged to the
carbon-support (Figure S1). However, neither Ru NPs nor Ru
complexes on N-C or C support were detected in the PXRD
patterns, probably due to the very low loading that went beyond
the detection limit of PXRD or small particle size.[15d] The
inductively coupled plasma atomic emission spectroscopy (ICP-
AES) revealed that the as-prepared Ru/N-C and Ru/C materials
contained 0.98 and 0.89 wt% of Ru, respectively (Table S1). The
chemical identity of materials was determined by X-ray
photoelectron spectroscopy (XPS). As shown in Figures 1a and
1b, the peaks at 285.81 eV for Ru/N-C and 285.90 eV for Ru/C
were assigned to Ru0 3d3/2 of RuOx/Ru.[23] Ruthenium oxide
(RuOx) was probably formed from air oxidation of surface Ru
metal. Three distinct peaks were observed in the N 1s range of
Ru/N-C and N-C with electron-binding energies of ca. 398 eV,
400 eV and 401 eV, respectively (Figure 1c). The lowest
binding-energy was attributed to a pyridine-type N.[24] The
electron-binding energy of 400.02 eV was characteristic of a
pyrrole-type N that may contribute two electrons to the carbon
matrix. Such nitrogen species was also found after the
carbonization of N-containing organic materials.[24] Finally, the
largest one was typical of a graphite-type N. Interestingly, the
signals of pyridinic N and graphitic N in Ru/N-C composites
slightly shifted to a higher binding energy compared with the
corresponding ones in the N-C material. Such positive shifts
were probably caused by the interaction of N with Ru NPs. In
their Raman spectra, the D band at 1355 cm-1 and the G band at
1588 cm-1 were assigned as the disordered sp3-hybridized
carbon and the graphitic sp2-hybridized carbon, respectively
(Figure S2). The C, H and N contents of Ru/N-C were measured
to be 96.94 wt%, 0.55 wt%, and 0.53 wt%, respectively.
The structure and morphology of the as-synthesized samples
were examined by scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). The pristine carbon
support clearly showed typical, highly cross-linked carbon
spheres (Figure S3a). The N-C, Ru/C and Ru/N-C materials
exhibited similar surface morphology, indicating that the loaded
N and/or Ru NPs had little effect on the morphology of the
carbon-support (Figure S3b-d). The TEM images showed
homogeneous distribution of Ru NPs on N-C support (Figure 2a)
with an average particle size of 2.2 nm, which was much smaller
than that (7.8 nm) of Ru NPs on unmodified carbon support
(Figure S4). The high-resolution TEM (HRTEM) image (Figure
2b) revealed that the lattice fringes of the crystalline Ru NPs,
with an interplanar spacing of 0.206 nm, were well embedded
into the carbon materials. This observation agreed well with the
(101) lattice plane of Ru hexagonal close-packed (hcp)
structure.[25] The high-angle annular dark field scanning TEM
(HAADF-STEM) dark-field images (Figure 2c) indicated Ru NPs
(bright dots) were evenly dispersed on the surface of carbon.
Elemental mapping could determine the distribution of Ru NPs
and N doping (Figure 2d) and both were found to be evenly
dispersed throughout the carbon matrix. The Brunauer–Emmett–
Figure 1. Ru 3d XPS spectra for (a) Ru/N-C, (b) Ru/C and (c) N 1s XPS
spectra for Ru/N-C and N-C.
2
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Table 1. Optimization of reaction conditions for the condensation.
Yield (%)
Cat. (mg/mol%
Ru)
Conversion
of 1a (%)
Entry[a]
Base
3a
4a
1
2
Ru/N-C (30/0.3)
Ru/C (30/0.3)
KOH
KOH
96
94
15
14
<5
98
97
>99
>99
49
<5
<5
<5
<5
<5
<5
79
98
<5
<5
<5
<5
95
88
95
78
95
15
95
16
98
92
96
94
trace
trace
trace
trace
trace
98
3
N-C (30/0)
KOH
15
4
C-800 (30/0)
KOH
14
5
-
KOH
trace
trace
97
6
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (30/0.3)
Ru/N-C (20/0.2)
Ru/N-C (10/0.1)
Ru/N-C (20/0.2)
Ru/N-C (10/0.1)
Ru/N-C (20/0.2)
Ru/N-C (20/0.2)
Ru/N-C (20/0.2)
Ru/N-C (20/0.2)
Ru/N-C (20/0.2)
Ru/C (20/0.2)
NaOH
CsOH
C2H5ONa
t-BuOK
K3PO4
K2CO3
Na2CO3
K2HPO4
NaHCO3
KHCO3
-
7
trace
74
8
26
9
71
29
10
trace
trace
trace
trace
trace
trace
trace
trace
97
46
Figure 2. (a) TEM image of Ru NPs on Ru/N-C (inset: a histogram illustrating
the particle size distribution). (b) HRTEM image of Ru/N-C. (c) HAADF-STEM
image. (d) STEM-EDS elemental mappings of Ru/N-C.
11
trace
trace
trace
trace
trace
trace
78
12
13
Additionally, Ru/N-C (2N), Ru/N-C (5N) and Ru/N-C (10N)
NPs with different N contents were prepared by calcinating cis-
Ru(phen)2Cl2 (0.0260 g) and phen (0.0168 g, or 0.0672 g,
0.1512 g) with carbon powder (1.000 g) (see Supporting
information). Their nitrogen contents were measured to be 0.95
wt%, 2.21 wt% and 4.93 wt%, respectively. The particle sizes of
Ru NPs got decreased with an increase in the N content (Figure
S6). These results showed the doping N played a vital role in
the nucleation and growth of Ru NPs.[20d]
14
15
16
17[b]
18[b]
19[c]
20[c]
21[d]
22[d]
23
NaOH
KOH
trace
trace
trace
trace
trace
trace
trace
94
Catalysis
NaOH
KOH
trace
trace
trace
trace
95
The catalytic activity of Ru/N-C was initially examined by
using the N-alkylation of aniline (1a) with benzyl alcohol (2a)
and KOH in toluene under a nitrogen atmosphere (Table 1,
entry 1). A standard workup produced N-benzylaniline (3a) as
the primary product in 96% yield together with a trace amount of
N,1-diphenylmethanimine (4a) with 96% conversion of 1a,
detected by gas chromatography (GC). Slightly lower activity
was observed with Ru/C as the catalyst (entry 2). N-C and C-
800 exhibited much lower catalytic activity (entries 3-4), yielding
15% and 14% of 3a, respectively. A blank run confirmed that no
products were observed in the absence of catalyst (entry 5). The
screening of different bases (entries 6−15) revealed their crucial
influence on the catalytic activity and selectivity. Surprisingly, an
almost quantitative yield of 4a was achieved when NaOH (entry
6) was used as a base. The same reaction with more basic
EtONa or t-BuOK also gave complete conversion of 1a, but with
lower 3a/4a selectivity (entries 8-9). Complete selectivity of 3a
(in 97% yield) was also achieved using CsOH (entry 7).
Reaction with K3PO4 also gave imine 4a as the only product, but
in a moderate yield (entry 10). Weak bases such as K2CO3,
Na2CO3, K2HPO4, NaHCO3 and KHCO3 were not effective
(entries 11-15). No reaction was observed without the addition
of a base (entry 16). These preliminary results indicated that the
strength of the base and its alkali ion did exert a significant
NaOH
KOH
KOH
24
KOH
88
25
NaOH
NaOH
KOH
trace
trace
95
26
78
27[e]
28[f]
29[e]
30[f]
31[e],[g]
32[e]
trace
9
KOH
trace
trace
trace
25
NaOH
NaOH
KOH
94
13
72
NaOH
13
79
[a] Conditions: 1a (1 mmol), 2a (1.3 mmol), Cat., base (0.5 mmol), toluene (3
ml), at 130 ºC, 24 h, N2 and conversion and selectivity detected by GC. [b] 1,4-
dioxane as a solvent. [c] DMSO as solvent. [d] MeCN as a solvent. [e] at 110
ºC. [f] at 90 °C. [g] under slow, steady N2 flow.
3
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10.1002/cctc.201801525
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influence on the outcomes of the above-mentioned reaction. We
next investigated the influence of other reaction factors. For
selectively, 1,4-dioxane proved a good solvent generating either
3a or 4a (entries 17-18). However, these ADC and ATH
reactions did not proceed at all in either DMSO or MeCN (entries
19-22), which may be due to the fact that the coordination of the
solvent might keep the substrate molecules from accessing the
catalyst. The amount of the catalyst loading was evaluated. The
decrease of the catalyst loading from 0.3 to 0.2 mol% did not
exert any appreciable impact on the yield or the distribution of
the product when entry 1 versus entry 23 (or entry 6 versus
entry 25) was compared. However, 0.1 mol % catalyst loading
led to a relatively lower conversion when entry 23 versus entry
24 (or entry 25 versus entry 26) was compared. Decreasing the
reaction temperature from 130 °C to 110 °C did not change the
product yield when entry 23 versus entry 27 (or entry 25 versus
entry 29) was compared. A lower temperature (90 °C) could
reduce the conversion to 15-16%, but with a high selectivity
(entries 28 and 30). Under a slow, steady N2 flow, the alkylation
of 1a gave 98% conversion of 1a but with a lower selectivity
(72%) for 3a (entry 31). The use of NaOH as a base gave 92%
conversion of 1a with 86% selectivity of 4a (entry 32). The N-
doped carbon supports could be used as “solid ligands” to
improve the catalytic performance of Ru NPs. Thus the optimal
reaction conditions for preparing imines or secondary amines
were fixed to be 20 mg Ru/N-C (0.2 mol% Ru), 0.5 equiv. of
KOH (for secondary amines) or NaOH (for imines) and toluene
as a solvent at 110 °C.
catalytic performances in the N-alkylation of aniline with benzyl
alcohol using Ru/N-C and other known catalysts were listed in
Table S2. Ru/N-C presented higher catalytic activity than
Cu/Al2O3 (130 °C),[26] Ru/Al2O3 (132 °C),[27] Ru(OH)3-Fe3O4
(130 °C),[28] Ni/θ–Al2O3 (144 °C).[15c] When the crossing-coupling
reactions were performed at a higher temperature (180 °C), the
catalytic activity of Au/TiO2[15a] was higher than that of Ru/N-C.
Ar2
H
NH2
OH
N
Ru/N-C, KOH
110 oC, toluene
Ar2
Ar1
+
Ar1
2
1
3
N
H
N
N
H
H
O
3a, 90%
3b, 92%
3c, 94%
O
O
O
O
N
H
N
H
N
H
3d, 90%
3e, 92%
3f, 93%
N
H
N
H
N
H
F3C
Cl
3g, 63%/79%[a]
3h, 57%/72%[a]
3i, 89%
O
N
H
N
H
N
H
N
3j, 92%
3k, 83%
3l, 85%
A variety of alcohols and amines were employed to explore
the scope of the N-alkylation reaction under the optimized
conditions (Scheme 2). Good to excellent yields of the N-
monoalkylated products of phenylamine (1a) were obtained with
various benzyl alcohols as the alkylation reagents. The
electronic nature of the substituents on the phenyl ring of
alcohols had some influence on these yields. Benzyl alcohols
with electron-rich or electron-neutral groups (2a-2f) reacted
smoothly to produce the corresponding products 3a-3f in
excellent yields (92-94%). Substrates with an electron-
withdrawing group, including (4-chlorophenyl)methanol and (4-
(trifluoromethyl)phenyl)methanol, provided products 3g and 3h
in 62% and 55% isolated yields, respectively. These yields could
be raised up to 79% and 72% upon raising the reaction
temperature to 130 °C. Ortho- or meta-positioned substituents
did not hamper alkylation (3d and 3e). Notably, the heteroatom-
containing alcohols like pyridin-3-ylmethanol and furan-2-
ylmethanol could generate the desired secondary amines (3k
and 3l) in high yields (85% and 87%).
We also examined the cross-coupling reactions of 2b with a
variety of substituted aromatic amines. The N-alkylation of 4-
methyl or 4-methoxyaniline with p-tolylmethanol gave the
corresponding products (3m and 3n) in excellent yields. Less
nucleophilic anilines (3p-3r) with electron-withdrawing groups
gave moderate yields, which could be enhanced at a higher
reaction temperature (130 °C). The alkylation of the sterically
hindered 2,3-dimethyl-phenylamine gave the expected product
(3o) in a high yield (86%) as did the extended aromatic
substrates including naphthalen-1-ylmethanol, naphthalen-2-
ylmethanol and naphthalen-1-amine 3i-3j and 3s (87-93%).
Redox active ferrocenylmethanol proceeded the smooth
coupling with p-toluidine to generate the desired product in 85%
yield under the same conditions. The comparison on the
O
N
H
N
H
N
H
3m, 92%
3n, 94%
3o, 88%
Cl
Br
CF3
N
H
N
H
N
H
3p, 69%/83%[a]
3q, 71%/87%[a]
3r, 53%/78%[a]
H
N
N
H
Fe
3s, 89%
3t, 82%
Scheme 2. Synthesis of secondary amines from primary amines and alcohols.
Reaction conditions: 1 (1 mmol), 2 (1.3 mmol), Ru/N-C (20 mg), KOH (0.5
mmol), toluene (3 mL), at 110 ºC, 24 h, N2 and isolated yield. [a] at 130 °C.
Imines are widely employed in laboratory and industrial
synthetic processes.[29] They have usually been made by the
condensation between amines and carbonyl compounds
(ketones or aldehydes) in acidic media. Other methods include
aerobic oxidation of secondary amines and using alcohols and
amines as starting materials to prepare imines under aerobic
oxidation conditions.[30] With results from the aforementioned
optimization experiments in hand, we further examined the
substrate scope of primary amines and primary alcohols leading
to imines 4 (Scheme 3). All substrates gave the desired imines
in good to excellent yields. The nature of substituents had a
similar influence on product yields as was observed with the
corresponding ATH reactions. As displayed in Table S3, the
turnover number (TON) and turnover frequency (TOF) of Ru/N-C
(TON = 450, TOF = 18.8 h-1) were higher than those of Pd/DNA
4
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(TON = 33, TOF = 2.8 h-1; DNA = fish sperm DNA),[31] Ag/Al2O3
(TON = 15.8, TOF = 0.7 h-1),[32] Cu-Fe3O4 (TON = 75.4, TOF =
0.8 h-1),[33] and TiO2/PMHSIPN (TON = 470, TOF = 3.98 h-1;
Sterically hindered (2-methoxyphenyl)methanol (2d) afforded 2-
(2-methoxyphenyl)-1H-benzo[d]imidazole (6d) in 73% isolated
yield. Heteroatom-containing alcohols also reacted smoothly to
give the corresponding 1H-benzo[d]imidazoles in 75% yield (6k)
and 78% yield (6l). The electronic nature of the substituents on
the phenyl rings of the diamine derivatives had some effect on
product yields. Diamines with electron-rich groups reacted
smoothly to produce the desired products in 90−91% yield (6m
and 6o). By contrast, the electron-donating group had a negative
influence and 4-chlorobenzene-1,2-diamine (5e) provided
product 6p only in 55% yield. A higher yield (67%) for 6p could
be achieved by prolonging the reaction time to 36 h. 3-
Methylbenzene-1,2-diamine provided a slightly lower yield (83%)
than benzene-1,2-diamine. The catalytic acticity of Ru/N-C was
slightly higher than those of Ir/TiO2,[35] Ir/JRC-TIO-4 (A) (JRC-
TIO-4 (A) = anatase-rich Japan reference catalyst TiO2),[36]
TiO2/PMHSIPN,[34] but lower than that of MNF-L1/CNT (magnetic
nanofiber (MNF) confined in carbon nanotubes (CNTs))[37] in the
synthesis of 6a with 5a and 2a (Table S4).
PMHSIPN
=
polymethylhydrosiloxane-based
semi-
interpenetrating networks).[34]
Ar2
NH2
OH
N
Ru/N-C, NaOH
110 oC, toluene
Ar2
Ar1
+
Ar1
2
1
4
N
N
N
O
4a, 90%
4b, 92%
4c, 94%
O
O
O
O
N
N
N
4d, 90%
4e, 92%
4f, 93%
N
N
N
F3C
Cl
4g, 63%/79%[a]
4h, 57%/72%[a]
4i, 89%
O
N
N
N
N
4j, 92%
4k, 83%
4l, 85%
O
N
N
N
4m, 92%
4n, 94%
4o, 88%
Cl
Br
CF3
N
N
N
4p, 69%/83%[a]
4q, 71%/87%[a]
4r, 53%/78%[a]
N
N
Fe
4s, 89%
4t, 82%
Scheme 4. Cross-coupling reactions of diamines with alcohols to give
benzimidazoles. Reaction conditions: diamine (1.3 mmol), alcohol (1 mmol),
Ru/N-C (20 mg), KOH (50% mol), toluene (3 ml), 130 °C, 24 h, N2 and isolated
yield; [a] for 36 h.
Scheme 3. Synthesis of imines from primary amines and alcohols. Reaction
conditions: 1 (1 mmol), 2 (1.3 mmol), Ru/N-C (20 mg), NaOH (0.5 mmol),
toluene (3 mL), at 110 °C, 24 h, N2 and isolated yield. [a] at 130 °C.
Finally we turned our attention to the synthesis of quinoxalines
(Scheme 5). The cross-coupling reaction of benzene-1,2-
diamine with 1-phenylethane-1,2-diol (7a) went smoothly to
produce the desired product 2-phenylquinoxaline (8a) in 88%
yield at 110 °C. Alkylethane-1,2-diols (propane-1,2-diol, butane-
1,2-diol, pentane-1,2-diol, hexane-1,2-diol, octane-1,2-diol and
dodecane-1,2-diol) and butane-2,3-diol required higher a diol/5a
molar ratio and a higher temperature (130 °C) to complete the
reactions in 58-81% isolated yields (8c-8h). The sterically
hindered 1,2-diphenylethane-1,2-diol required the higher
temperature (up to 150 °C) and mesitylene (as a solvent) to
The efficient formation of 3 and 4 activated us to investigate
Ru/N-C-catalyzed acceptorless dehydrogenation coupling
reactions of diamines with alcohols (Scheme 4). Reaction of
benzene-1,2-diamine (5a) with 2a using Ru/N-C and KOH (or
NaOH) in toluene at 110 °C led to a complex mixture of products.
Standard workup produced 2-phenyl-1H-benzo[d]imidazole (6a)
in 53% isolated yield coupled with benzaldehyde, 2-
(benzylideneamino)aniline
and/or
2-phenyl-2,3-dihydro-1H-
benzo[d]imidazole as byproducts, determined by liquid
chromatograph-mass spectrometer (LC-MS). When the reaction
temperature was raised to 130 °C, the isolated yield of 6a got
increased to 86%. Both electron-rich (Me, OMe, OCH2O) and
electron-deficient (Cl, CF3) substituents on benzyl alcohols
yielded the desired products. Benzyl alcohols with electron-rich
and electron-neutral groups reacted smoothly in 85−92%
isolated yields (6b, 6c, 6e, 6f, 6i, 6j). A longer reaction time (36
h) was needed for moderate yields (72% and 67%) of products
using the electron-withdrawing substituted alcohols (2g and 2h).
reach
a
lower yield (53%) of 8i. This acceptorless
dehydrogenative coupling reaction was compatible with
substituted benzene-1,2-diamines. 4,5-Dimethylbenzene-1,2-
diamine gave the expected product 8j in 90% yield. Reactions
having asymmetric 1,2-diamines such as 3-methylbenzene-1,2-
diamine, 3-chlorobenzene-1,2-diamine resulted in the formation
of the regioisomers of 8-methyl-2-phenylquinoxaline/5-methyl-2-
phenylquinoxaline and 6-chloro-2-phenylquinoxaline/7-chloro-2-
5
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10.1002/cctc.201801525
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phenylquinoxaline, whose proportions depended on the
substituent itself. However, the reaction of 1-phenylethane-1,2-
diol with 3-methoxybenzene-1,2-diamine gave 7-methoxy-2-
phenylquinoxaline as the major product (in 84% yield) with only
a trace amount of 8-methoxy-2-phenylquinoxaline.
content on C-N supports also exerted a great impact on the
catalytic activity of Ru NPs. Ru/N-C (2N) showed comparable
activity to that of Ru/N-C. When the N content was further
increased from 0.95 wt% to 4.93 wt%, the catalytic activity and
selectivity got decreased with the increase of the N content
(Table S5). The interaction between Ru NPs and the doping N
species could stabilize Ru NPs. However excess N may occupy
the catalytic sites, thereby reducing the activity of Ru NPs.
R1
R2
NH2
N
N
R1
R2
HO
HO
Ru/N-C, KOH
toluene
Ar1
R1
+
NH2
8
5
7
N
N
N
N
N
N
N
N
8a, 88%
8b, 63%[a,b]
8c, 69%[a,b]
8d, 75%[a,b]
N
N
N
N
N
N
(CH2)5CH3
N
(CH2)9CH3
N
8e, 79%[a,b]
8f, 81%[a,b]
8g, 58%[a,b]
8h, 65%[a,b]
N
N
N
N
N
N
N
N
8i, 31%[a]/53%[a,c]
8j, 90%
8k, 63%
8k', 21%
Cl
N
N
N
O
N
N
O
N
Cl
N
N
8l, 84%
8l', trace
8m, 51%[a]
8m', 21%[a]
Scheme 5. Cross-coupling reactions of diamines and diols to give
quinoxalines. Reaction conditions: diamine (1 mmol), diol (1.1 mmol), Ru/N-C
(20 mg), KOH (1 mmol), toluene (3 mL), at 110 ºC, 24 h, N2, isolated yield. [a]
diol (3 mmol). [b] at 130 ºC. [c] mesitylene as a solvent, at 150 ºC.
Figure 3. Recycling of Ru/N-C catalyst for the synthesis of 3a, 4a, 6a and 8a.
In the process of secondary amine formation, each alcohol
was first dehydrogenated to generate an aldehyde, followed by
condensation with an amine to render an imine, which was
subsequently hydrogenated to afford the desired product.
Notably, we could control this subsequent hydrogenation by the
We investigated the possibility of Ru leaching from this
heterogeneous catalyst during the reaction of 1a with 2a under
standard conditions. After 4h, the yields of 3a and 4a were 45%
and 17%, respectively. At this point, the mixture was filtered to
remove the catalyst and the filtrate was heated for another 20 h
at 110 °C. No further reaction was observed, indicating that the
as-prepared Ru/N-C was necessary for this reaction and that the
leaching of catalytically active Ru was insignificant if any. The
reusability of this Ru/N-C catalyst was examined by centrifuging
and washing the catalyst at the end of a reaction and then
adding the recovered material to the second cycle of 1a/2a
condensation (or 2a/5a or 5a/7a). High activity and selectivity for
the formation of 3a, 4a, 6a and 8a were observed up to four
times with a minor drop-off at the fifth reuse (Figure 3). After five
cycles, the ICP analysis indicated that 93% Ru was remained
(Table S1). XPS spectra identified that the oxidation state and
coordination environment of Ru was unchanged (Figure S7c).
XPS revealed that the intensity of Ru peaks increased relative to
carbon, indicating that more Ru was exposed on the surface on
the recycled catalyst and/or ruthenium was agglomerated with
an average particle size of 9.7 nm (Figure S7a,b). The
recyclable performance of Ru/C catalyst was also examined. At
the second cycle, its catalytic activity went down dramatically
and the product yields decreased to 30% (3a) and 25% (4a),
respectively. After two runs, the ICP measurement revealed that
63% Ru leaked from the carbon material (Table S1). The particle
size of the Ru NPs on C support was increased to 14.6 nm,
detected by TEM image (Figure S7). Thus it can be seen that
the doped pyridinic and graphitic N played a key role in
stabilizing Ru NPs on N-C support, avoiding loss of Ru NPs and
slowing their agglomeration in the catalytic process. The N
choice
phenylmethanol 2a with Ru/N-C and KOH or NaOH in toluene at
110 °C (equation 1, Scheme 6) for 12 gave the
of
base.
Acceptorless
dehydrogenation
of
h
dehydrogenated product benzaldehyde in 88% and 91% yields,
respectively. The reaction did not work without the addition of a
base (equation 1). In the presence of NaOH or KOH, the
condensation of benzaldehyde with aniline resulted in the
formation of an imine with or without Ru/N-C (equation 2). Base
was necessary for the acceptorless dehydrogenation of alcohol
and the condensation of benzaldehyde with aniline, but the
product outcome was not dependent on the alkali ion. However,
the transfer hydrogenation reaction of imine 4a with 2a catalyzed
by Ru/N-C using KOH as base at 110 °C for 24 h gave amine 3a
in 91% yield, while the same reaction using NaOH only gave 3a
in 3% yield coupled with benzaldehyde (equation 3).
The hydrogenation reaction of 4a with 2a using only KOH
without catalyst gave 3a in less 10% yield, implying that Ru NPs
catalyst was necessary for the hydrogenation step. In the
presence of 5 equiv of H2O, the hydrogenation of 4a with 2a
yielded a trace amount of 3a, 1a and benzaldehyde (equation 4).
This result implied that H2O hindered the hydrogenation of
imines. In our system, the carbon support could absorb the in-
situ formed water. Thus the hydrogenation of imines went well
under the standard conditions. The addition of 18-crown-6 into
the reaction of 4a with 2a remarkably suppressed the formation
of amine 3a (equation 5). These results indicated that K+ ion was
engaged in the transfer hydrogenation reaction of imine to
6
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10.1002/cctc.201801525
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FULL PAPER
Scheme 7. Deuterium experiments.
secondary amine, due to its ionic radius being larger than that of
Na+ and their different coordination effects.[9d,38] The interaction
of K+ with imine might lengthen C=N bond, which could be
readily hydrogenated by Ru catalyst.
The conversion of 1a and 2a to imine 4a using NaOH as a
base was monitored over time (Figure 4a). Benzaldehyde was
produced quickly and increased significantly within the first two
hours. In a separate experiment, the reaction of 1a with 2a in the
presence of NaOH for 4 h resulted in the formation of 4a in 56%
yield, together with a byproduct (benzaldehyde) in 27% yield
(equation 6, Scheme 6), supporting the hypothesis that
benzaldehyde was an intermediate in the reaction. The
distribution of the products derived from the N-alkylation of 1a
with 2a using KOH as a base was also monitored over time
using GC analysis (Figure 4b). Benzaldehyde was formed
initially and then imine 4a was generated. Their yields was
enhanced with the increase of time and reached the maximum
within ca. 2.5 h. 4a then disappeared gradually with concomitant
formation of 3a. The ATH reaction of 1a with 2a (equation 6,
Scheme 6) under standard conditions in the presence of KOH
for 4 h gave the hydrogenated product 3a in 37% yield, together
with 4a and benzaldehyde in 17% and 28% yields, respectively.
These experiments further demonstrated that benzaldehyde and
4a were intermediates in the ATH reaction but benzaldehyde
was only the intermediate in the ADC reaction.
Ru/N-C
toluene, 110 o
OH
O
(1)
C
with KOH: 88%
with NaOH: 91%
without base: Not Detected
NH2
toluene, 110 o
C
O
+
(2)
N
(4a)
with KOH: 73%
with KOH and Ru/N-C: 76%
with NaOH: 85%
with NaOH and Ru/N-C: 88%
toluene, 110 o
C
OH
O
(3)
N
H
4a
+
+
(3a)
with KOH:
<10% (based on 4a) 57% (based on 2a)
85% (based on 2a)
with Ru/N-C and KOH: 91% (based on 4a)
with Ru/N-C and NaOH: < 5% (based on 4a) 76% (based on 2a)
NH2
Ru/N-C, H2O
O
OH
3a
(4)
4a
4a
+
+
+
toluene, 110 o
C
with KOH:
with NaOH:
<10%
Not Detected <10%
<10%
<10%
<10%
Ru/N-C
toluene, 110 o
OH
(5)
(6)
N
H
+
C
1.0 mmol
1.3 mmol
31%
with 0.5 mol KOH + 0.5 mol 18-crown-6
NH2
Ru/N-C
O
OH
+
4a
+
3a
+
toluene, 110 o
C
4 h, NaOH
4 h, KOH
56% Not Detected 27%
37% 17% 28%
Scheme 6. Verification Experiments.
In order to obtain more insights into the mechanism of the
above-mentioned transfer hydrogenation reaction, the
experiments with deuterated phenylmethanol were carried out
(Scheme 7). In the presence of Ru/N-C and KOH, the reduction
of 4a with phenylmethan-d2-ol (2a-d2) in toluene at 110 °C gave
16% 3a-d1, 23% 3a and 61% 3a-d2, calculated by 1H NMR
(Scheme S1). Reaction of 1a with 2a-d2 under the standard
conditions resulted in the formation of 6% of 3a, 1% of 3a-d1,
and 93% of 3a-d2 (Scheme S2) with an overall yield of 89%.
Deuterium experiments revealed that the process for the imine-
hydrogenation and amine-dehydrogenation was reversible, and
methylene protons of 4a might be derived from the benzylic
protons of alcohol.
Figure 4. Time-course monitoring of the reaction of aniline with benzyl alcohol
using NaOH (a) or KOH (b) as a base.
These results coupled with previous reports[7,8] might
formulate a mechanism for the alkylation of amine with alcohol:
(i) under basic conditions, Ru-catalyzed dehydrogenation of
7
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10.1002/cctc.201801525
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inductively coupled plasma atomic emission spectroscopy (ICP-AES)
using a Varian 710-ES instrument. Raman spectra were obtained using a
fully automatic microprobe Raman system (XploRA PLUS, Horiba Jobin
Yvon). GC measurements were recorded on an Agilent 7820A Gas
Chromatograph with an Agilent HP-5 chromatographic column and N2 as
mobile phase. The LC-MS was recorded using a Rapid Resolution HT-3
chromatographic column on an Agilent 1260 Infinity Liquid
Chromatograph with 6120 Quadrupole Mass Spectrometer and MeCN as
mobile phase. High resolution mass spectra (HRMS) were obtained with
a GCT Premier (Micromass UK Limited) chemical ionization time-of-flight
mass spectrometer (CI-TOF).
alcohol to carbonyl compound through the Ru-alkoxide
intermediate which may undergo the β-H elimination to afford
the Ru-H active species; (ii) base-catalyzed condensation of
carbonyl compound with amine to imine; (iii) hydrogenation of
the C=N bond by Ru-H species in the presence of KOH
(Scheme 8).
Preparation of Ru/N-C materials. Carbon powder (VULCAN XC72R,
1.0000 g) was added to an ethanol solution of cis-Ru(phen)2Cl2 (0.0520
g). The mixture was stirred at 60 °C for 12 hours and then cooled to room
temperature. Ethanol was slowly removed in vacuo. The solid was dried
at 60 °C for 12 hours, and pyrolyzed at 800 °C for 2 hours under a
nitrogen atmosphere (temperature programming from room temperature
to 800 °C at the rate of 5 °C/min).
Procedure for the synthesis of secondary amines. A glass tube
equipped with a magnetic stirring bar was charged with Ru/N-C (20 mg)
and KOH (0.50 mmol). The reaction vessel was evacuated and backfilled
with nitrogen gas three times. Aniline (1.0 mmol), benzyl alcohol (1.3
mmol) and toluene (3 mL) were added by syringe. The resulting solution
was stirred at 110 °C (or 130 °C for (4-trifluorophenyl)methanol, (4-
Scheme 8. Proposed mechanism for the ADC and ATH reactions.
chlorophenyl)methanol,
4-chloroaniline,
4-bromoaniline
and
4-
Conclusions
trifluoromethylaniline) for 24 h. After cooling to room temperature, the
catalyst was separated by filtration and washed with ethyl acetate and
water. The filtrate was extracted three times with ethyl acetate (3 × 5 mL).
The combined organic layers were washed with brine, dried over
anhydrous Na2SO4 and concentrated under reduced pressure. The crude
product was purified by flash column chromatography using petroleum
ether and ethyl acetate as the eluent.
In the work reported herein, we have demonstrated efficient
synthesis of secondary amines, imines, benzimidazoles and
quinoxalines in good to excellent yields through the tunable ADC
and ATH reactions of amines with alcohols catalyzed by Ru NPs
on N-doped carbon support. This catalytic system could
selectively produce various imines and secondary amines from
anilines and alcohols with an excellent switch in selectivity just
by controlling the choice of NaOH or KOH. This methodology is
also applicable to the synthesis of useful benzimidazoles and
quinoxalines by the ADC reactions of diamines with primary
alcohols or diols. The Ru/N-C catalyst can be recycled up to five
times without significant loss of activity. The application of this
synthetic strategy to other metallic NPs catalysts for the efficient
C-C formation is currently underway in our laboratory.
Procedure for the synthesis of imines. A glass tube equipped with a
magnetic stirring bar was charged with Ru/N-C (20 mg) and NaOH (0.50
mmol). The reaction vessel was evacuated and backfilled with N2 three
times. Aniline (1.0 mmol), benzyl alcohol (1.3 mmol) and toluene (3 mL)
were added. The resulting solution was at 110 °C (or 130 °C for (4-
trifluorophenyl)methanol, (4-chlorophenyl)methanol, 4-chloroaniline, 4-
bromoaniline and 4-trifluoromethylaniline) for 24 h. After cooling to room
temperature, the catalyst was separated by filtration and washed with
ethyl acetate and water. Then filtrate was extracted three times with ethyl
acetate (3 × 5 mL). The combined organic layers were washed with brine,
dried over anhydrous Na2SO4 and concentrated under reduced pressure.
The crude product was purified by flash column chromatography using
petroleum ether and ethyl acetate as the eluent.
Experimental Section
General Characterization. All reagents were used as purchased without
further purification. Column chromatography was performed on silica gel.
1H and 13C NMR spectra were recorded at ambient temperature on a
Varian UNITY plus-400 spectrometer. Scanning electron microscopy
Procedure for the synthesis of benzimidazoles.
A glass tube
equipped with a magnetic stirring bar was charged with Ru/N-C (20 mg)
and KOH (0.50 mmol). The reaction vessel was evacuated and backfilled
with nitrogen three times. Benzene-1,2-diamine (1.0 mmol), benzyl
alcohol (1.3 mmol) and toluene (3 mL) were added. The resulting solution
was stirred at 130 °C for 24 h (or 36 h for (4-trifluorophenyl)methanol, (4-
chlorophenyl)methanol and 4-chlorobenzene-1,2-diamine). After cooling
to room temperature, the catalyst was separated by filtration and washed
with ethyl acetate and water. Then filtrate was extracted three times with
ethyl acetate (3 × 5 mL). The combined organic layers were washed with
brine, dried over anhydrous Na2SO4 and concentrated under reduced
pressure. The crude product was purified by flash column
chromatography using petroleum ether and ethyl acetate as the eluent.
(SEM) images of the Ru/N-C morphology were obtained using
a
HITACHI S-4700 scanning electron microscope. Transmission electron
microscopy (TEM) was performed on a HITACHI HT-7700 electron
microscope operating at 120 kV. High-resolution transmission electron
microscopy (HRTEM) was performed on a FEI Tecnai G20 electron
microscope operating at 200 kV. Annular dark-field scanning TEM (ADF-
STEM) was performed on
a FEI Tecnai F20 electron microscope
operating at 200 kV, equipped with Genseis EDS detector. X-ray
diffraction (XRD) patterns were recorded on an X’Pert PRO SUPERrA
rotation anode X-ray diffractometer with Ni-filtered Cu-Ka radiation (λ =
1.5418 Å). X-ray photoelectron spectra (XPS) were recorded on an X-ray
photoelectron spectrometer (AXIS Ultra DLD) whose binding energies
were referenced to C 1s at 284.7 eV from hydrocarbon to compensate for
effects. N2 adsorption–desorption was carried out using a Micromeritics
Tristar 3000 analyzer at 77 K. The Ru contents were measured by
Procedure for the synthesis of quinoxalines. A test tube equipped
with a magnetic stirring bar was charged with Ru/N-C (20 mg) and KOH
(1.0 mmol). The reaction vessel was evacuated and backfilled with
nitrogen three times. Benzene-1,2-diamine (1.0 mmol), 1-phenylethane-
1,2-diol (1.1 mmol) (or 3 mmol for aliphatic alcohols) and toluene (or
8
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10.1002/cctc.201801525
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mesitylene for 1,2-diphenylethane-1,2-diol) (3 mL) were added. The
resulting solution was stirred at 110 °C (or 130 °C for aliphatic alcohols
and 4-chlorobenzene-1,2-diamine, 150 °C for 1,2-diphenylethane-1,2-
diol) for 24 h. After cooling to room temperature, the catalyst was
separated by filtration and washed with ethyl acetate and water. The
filtrate was extracted three times with ethyl acetate (3 × 5 mL). The
combined organic layers were washed with brine, dried over anhydrous
Na2SO4 and concentrated under reduced pressure. The crude product
was purified by flash column chromatography using petroleum ether and
ethyl acetate as the eluent.
Sci. Technol. 2015, 5, 1412-1427; j) S. M. A. H. Siddiki, T. Toyao, K.
Shimizu, Green Chem. 2018, 20, 2933-2952.
[7]
[8]
a) A. Corma, J. Navas, M. J. Sabater, Chem. Rev. 2018, 118,
1410−1459; b) T. D. Nixon, M. K. Whittlesey, J. M. J. Williams, Dalton
Trans. 2009, 753-762; c) H. Wu, J. Wu, Z. Du, Chin. J. Org. Chem.
2017, 37, 1127-1138.
a) B. Gnanaprakasam, J. Zhang, D. Milstein, Angew. Chem. Int. Ed.
2010, 49, 1468-1471; b) B. Gnanaprakasam, E. Balaraman, Y. Ben-
David, D. Milstein, Angew. Chem. Int. Ed. 2011, 50, 12240-12244. c) P.
Hu, Y. Ben-David, D. Milstein, Angew. Chem. Int. Ed. 2016, 55, 1061-
1064; d) R. Cano, D. J. Ramón, M. Yus, J. Org. Chem. 2011, 76, 5547-
5557; e) S. Demir, F. Coşkun, Ì. Özdemir, J. Organomet. Chem. 2014,
755, 134-140; f) F. E. Fernández, M. C. Puerta, P. Valerga,
Organometallics 2012, 31, 6868-6879; g) D. Srimani, Y. Ben-David, D.
Milstein, Angew. Chem. Int. Ed. 2013, 52, 4012-4015.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (Grant Nos. 21471108, 21771131,
21531006 and 21773163), the State Key Laboratory of
Organometallic Chemistry of Shanghai Institute of Organic
Chemistry (2015kf-07), the Priority Academic Program
Development of Jiangsu Higher Education Institutions, the
Natural Science Foundation of Jiangsu Province (BK20161276)
and the Project of Scientific and Technologic Infrastructure of
Suzhou (SZS201708). We are very grateful to the useful
comments and suggestions of the editor and reviewers.
[9]
a) S. Michlik, R. Kempe, Nat. Chem. 2013, 5, 140-144; b) J. Schranck,
A. Tlili, M. Beller, Angew. Chem. Int. Ed. 2013, 52, 7642-7644; c) K.
Iida, T. Miura, J. Ando, S. Saito, Org. Lett. 2013, 15, 1436-1439; d) P.
Daw, S. Chakraborty, J. A. Garg, Y. Ben-David, D. Milstein, Angew.
Chem. Int. Ed. 2016, 55, 14373-14377; e) M. Zhang, X. J. Fang, H.
Neumann, M. Beller, J. Am. Chem. Soc. 2013, 135, 11384-11388.
[10] D. Srimani, Y. Ben-David, D. Milstein, Chem. Commun. 2013, 49, 6632-
6634.
[11] a) R. Ramachandran, G. Prakash, S. Selvamurugan, P.
Viswanathamurthi, J. G. Malecki, V. Ramkumar, Dalton Trans. 2014, 43,
7889-7902; b) M. Bala, P. K. Verma, U. Sharma, N. Kumar, B. Singh,
Green Chem. 2013, 15, 1687-1693; c) T. Kondo, S. Yang, K. T. Huh, M.
Kobayashi, S. Kotachi, Y. Watanabe, Chem. Lett. 1991, 20, 1275-1278.
[12] a) M. O. Chaney, P. V. Demarco, N. D. Jones, J. L. Occolowitz, J. Am.
Chem. Soc. 1974, 96, 1932-1933; b) A. J. Battershill, L. Scott, J. Drugs
2006, 66, 51-83; c) Fungicidal Agents. Kirk-Othmer Encyclopedia of
Chemical Technology, Vol. 11, Wiley, New York, 1980, pp 490-498; d)
M. E. Mason, B. Johnson, M. Hamming, J. Agric. Food Chem. 1966, 14,
454-460; e) Y. Wang, G. A. Sotzing, R. A. Weiss, Chem. Mater. 2008,
20, 2574-2882.
Conflict of interest
The authors declare no conflict of interest.
Keywords: ADC reaction • ATH reaction • Recyclability •
[13] C. E. Song, S. G. Lee, Chem. Rev. 2002, 102, 3495-3524; b) Z. L. Lu,
E. Lindner, H. A. Mayer, Chem. Rev. 2002, 102, 3543-3578; c) M.
Lamblin, L. Nassar-Hardy, J. C. Hierso, E. Fouquet, F. X. Felpin, Adv.
Synth. Catal. 2010, 352, 33-79.
Ruthenium nanoparticles • Selectivity
[1]
[2]
a) M. B. Smith, J. March, Advanced Organic Chemistry, Wiley, New
York, 5th edn, 2001, pp. 499-501; b) R. N. Salvatore, C. H. Yoon, K. W.
Jung, Tetrahedron 2001, 57, 7785-7811.
[14] a) L. He, X. B. Lou, J. Ni, Y. M. Liu, Y. Cao, H. Y. He, K. N. Fan, Chem.
Eur. J. 2010, 16, 13965-13969; b) H. Liu, G. K. Chuah, S. Jaenicke, J.
Catal. 2012, 292, 130-137; c) K. Shimizu, N. Imaiida, K. Kon, S. M. A. H.
Siddiki, A. Satsuma, ACS Catal. 2013, 3, 998-1005; d) Y. Gao, J. Wang,
A. Han, S. Jaenicke, G. K. Chuah, Catal. Sci. Technol. 2016, 6, 3806-
3813; e) H. Yang, Y. Wang, Y. Qin, Y. Chong, Q. Yang, G. Li, L. Zhang,
W. Li, Green Chem. 2011, 13, 1352-1361.
a) K. H. Hopmanna, A. Bayer, Coord. Chem. Rev. 2014, 268, 59-82; b)
N. Fleury-Brégeot, V. Fuente, S. Castillón, C. Claver, ChemCatChem
2010, 2, 1346-1371; c) J. G. Vries, N. Mršic, Catal. Sci. Technol. 2011,
1, 727-735.
[3]
[4]
a) F. Alonso, P. Riente, M. Yus, Acc. Chem. Res. 2011, 44, 379-391; b)
C. F. Lane, Synthesis 1975, 135-146; c) G. W. Gribble, Chem. Soc.
Rev. 1998, 27, 395-404; d) A. F. Abdel-Magid, K. G. Carson, B. D.
Harris, C. A. Maryanoff, R. D. Shah, J. Org. Chem. 1996, 61, 3849-
3862; e) T. Gross, A. M. Seayad, M. Ahmad, M. Beller, Org. Lett. 2002,
4, 2055-2058; f) R. V. Jagadeesh, K. Murugesan, A. S. Alshammari, H.
Neumann, M. Pohl, J. Radnik, M. Beller, Science 2017, 358, 326-332.
a) J. F. Hartwig, Synlett 2006, 1283-1294; b) S. L. Buchwald, C.
Mauger, G. Mignani, U. Scholz, Adv. Synth. Catal. 2006, 348, 23-39; c)
O. Navarro, N. Marion, J. Mei, S. P. Nolan, Chem. Eur. J. 2006, 12,
5142-5148.
[15] S. Wittmann, A. Schätz, R. N. Grass, W. J. Stark, O. Reiser, Angew.
Chem. Int. Ed. 2010, 49, 1867-1870.
[16] a) E. R. Rangel, E. M. Maya, F. Sánchez, J. G. Campa, M. Iglesias,
Green Chem. 2015, 17, 466-473; b) E. Verde-Sesto, E. M. Maya, A. E.
Lozano, J. G. Campa, F. Sánchez, M. Iglesias, J. Mater. Chem. 2012,
22, 24637-24643; c) Q. Sun, Z. Dai, X. Meng, L. Wang, F. S. Xiao, ACS
Catal. 2015, 5, 4556-45671; d) N. B. McKeown, P. M. Budd, Chem. Soc.
Rev. 2006, 35, 675-683; e) E. Verde-Sesto, E. Merino, E. Rangel-
Rangel, A. Corma, M. Iglesias, F. Sánchez, ACS Sustainable Chem.
Eng. 2016, 4, 1078-1084; f) E. Rangel-Rangel, E. Verde-Sesto, A. M.
Rasero-Almansa, M. Iglesias, F. Sánchez, Catal. Sci. Technol. 2016, 6,
6037-6045.
[5]
[6]
a) G. E. Dobereiner, R. H. Crabtree, Chem. Rev. 2010, 110, 681-703;
b) M. H. S. A. Hamid, P. A. Slatford, J. M. J. Williams, Adv. Synth. Catal.
2007, 349, 1555-1575.
[17] a) C. D. Wu, A. Hu, L. Zhang, W. Lin, J. Am. Chem. Soc. 2005, 127,
8940-8941; b) F. Song, C. Wang, J. M. Falkowski, L. Ma, W. Lin, J. Am.
Chem. Soc. 2010, 132, 15390-15398; c) Y. Liu, W. Xuan, Y. Cui, Adv.
Mater. 2010, 22, 4112-4135; d) A. Arnanz, M. Pintado-Sierra, A. Corma,
M. Iglesias, F. Sánchez, Adv. Synth. Catal. 2012, 354, 1347-1355; e) M.
Pintado-Sierra, A. M. Rasero-Almansa, A. Corma, M. Iglesias, F.
Sánchez, J. Catal. 2013, 299, 137-145; f) A. M. Rasero-Almansa, A.
Corma, M. Iglesias, F. Sánchez, ChemCatChem 2013, 5, 3092-3100.
[18] A. Peeters, L. Claes, I. Geukens, I. Stassen, D. D. Vos, Appl. Catal. A
Gen. 2014, 469, 191-197.
a) C. Gunanathan, D. Milstein, Science 2013, 341, 249-260; b) M.
Zhang, H. Neumann, M. Beller, Angew. Chem. Int. Ed. 2013, 52, 597-
601; c) S. Michlik, R. Kempe, Angew. Chem. Int. Ed. 2013, 52, 6326-
6329; d) A. J. Blacker, M. M. Farah, M. I. Hall, S. P. Marsden, O. Saidi,
J. M. J. Williams, Org. Lett. 2009, 11, 2039-2042; e) K. Taguchi, S.
Sakaguchi, Y. Ishii, Tetrahedron Lett. 2005, 46, 4539-4542; f) F. Li, L.
Lu, P. C. Liu, Org. Lett. 2016, 18, 2580-2583; g) T. Hille, T. Irrgang, R.
Kempe, Chem. Eur. J. 2014, 20, 5569-5572; h) C. Gunanathan, Y. Ben-
David, D. Milstein, Science 2007, 317, 790-792; i) K. Shimizu, Catal.
9
This article is protected by copyright. All rights reserved.

10.1002/cctc.201801525
ChemCatChem
FULL PAPER
[19] a) Z. Li, Q. Xu, Acc. Chem. Res. 2017, 50, 1449-1458; b) G. Ji, Y. Duan,
S. Zhang, B. Fei, X. Chen, Y. Yang, ChemSusChem 2017, 10, 3427-
3434; c) J. Li, W. Chen, H. Zhao, X. Zheng, L. Wu, H. Pan, J. Zhu, Y.
Chen, J. Lu, J. Catal. 2017, 352, 371-381; d) S. Zhang, B. Jiang, K.
Jiang, W. B. Cai, ACS Appl. Mater. Interfaces 2017, 9, 24678-24687; e)
C. Zhang, Y. Leng, P. Jiang, J. Li, S. Du, ChemistrySelect 2017, 2,
5469-5474; f) Y. Kitamura, S. Sako, A. Tsutsui, Y. Monguchi, T.
Maegawa, Y. Kitade, H. Sajiki, Adv. Synth. Catal. 2010, 352, 718-730.
[20] a) J. Liu, Y. Yue, H. Liu, Z. Da, C. Liu, A. Ma, J. Rong, D. Su, X. Bao, H.
Zheng, ACS Catal. 2017, 7, 3349-3355; b) R. Rizo, D. Sebastián, J. L.
Rodríguez, M. J. Lázaro, E. Pastor, J. Catal. 2017, 348, 22-28; c) G. F.
Long, X. H. Li, K. Wan, Z. X. Liang, J. H. Piao, P. Tsiakaras, Appl. Catal.
B Environ. 2017, 203, 541-548; d) L. He, F. Weniger, H. Neumann, M.
Beller, Angew. Chem. Int. Ed. 2016, 55, 12582–12594.
[21] a) M. Navlani-García, K. Mori, A. Nozak, Y. Kuwahara, H. Yamashita,
Appl. Catal. A Gen. 2016, 527, 45-52; b) C. Crisafulli, S. Scirè, M.
Salanitri, R. Zito, S. Calamia, Int. J. Hydrogen Energy 2011, 36, 3817-
3826; c) E. P. Maris, R. J. Davis, J. Catal. 2007, 249, 328-337; d) X. Yu,
R. Nie, H. Zhang, X. Lu, D. Zhou, Q. Xia, Micropor. Mesopor. Mater.
2018, 256, 10-17; e) J. Ftouni, H. C. Genuino, A. Muñoz-Murillo, P. C.
A. Bruijnincx, B. M. Weckhuysen, ChemSusChem 2017, 10, 2891-
2896; f) J. J. Muscia, A. B. Merloa, M. L. Casella, Catal. Today 2017,
296, 43-50; g) Z. Gao, L. Yang, G. Fan, F. Li, ChemCatChem 2016, 8,
3769-3779; h) T. Miyazawa, S. Koso, K. Kunimori, K. Tomishige, Appl.
Catal. A Gen. 2007, 329, 30-35; i) H. Kobayashi, H. Matsuhashi, T.
Komanoya, K. Hara, A. Fukuoka, Chem. Commun. 2011, 47, 2366-
2368; j) J. Nie, J. Xie, H. Liu, J. Catal. 2013, 301, 83-91; k) X. Yang, X.
Wang, J. Qiu, Appl. Catal. A Gen. 2010, 382, 131-137; l) E. J. García-
Suárez, M. Tristany, A. B. García, V. Collière, K. Philippot, Micropor.
Mesopor. Mater. 2012, 153, 155-162.
[22] J. Y. Shen, A. Adnot, S. Kaliaguine, Appl. Surf. Sci. 1991, 51, 47-60.
[23] J. Long, K. Shen, L. Chen, Y. Li, J. Mater. Chem. A 2016, 4, 10254-
10262.
[24] K. K. Mohaideen, W. Kim, K. Y. Koo, W. L. Yoon, Catal. Commun. 2015,
60, 8-13.
[25] F. Santoro, R. Psaro, N. Ravasio, F. Zaccheria, RSC Adv. 2014, 4,
2596-2600.
[26] J. W. Kim, K. Yamaguchi, N. Mizuno, J. Catal. 2009, 263, 205-208.
[27] A. Peeters, L. Claes, I. Geukens, I. Stassen, D. De Vos, Appl. Catal. A
Gen. 2014, 469, 191-197.
[28] J. Gawronski, N. Wascinska, J. Gajewy, Chem. Rev. 2008, 108, 5227-
5252.
[29] a) K. Yamaguchi, N. Mizuno, Angew. Chem. Int. Ed. 2003, 42, 1480-
1483; b) F. Li, J. Chen, Q. Zhang, Y. Wang, Green Chem. 2008, 10,
553-562; c) L. Blackburn, R. J. Taylor, Org. Lett. 2001, 3, 1637-1639; d)
S. Sithambaram, R. Kumar, Y. C. Son, S. L. Suib, J. Catal. 2008, 253,
269-277.
[30] a) M. S. Kwon, S. Kim, S. Park, W. Bosco, R. K. Chidrala, J. Park, J.
Org. Chem. 2009, 74, 2877-2879; b) J. W. Kim, J. He, K. Yamaguchi, N.
Mizuno, Chem. Lett. 2009, 38, 920-921; c) H. Sun, F. Z. Su, J. Ni, Y.
Cao, H. Y. He, K. N. Fan, Angew. Chem. Int. Ed. 2009, 48, 4390-4393;
d) B. Guo, J. Y. Xue, H. X. Li, D. W. Tan, J. P. Lang, RSC Adv. 2016, 6,
51687-51693.
[31] L. Tang, H. Sun, Y. Li, Z. Zha, Z. Wang, Green Chem. 2012, 14, 3423-
3428.
[32] K. Shimizu, M. Nishimura, A. Satsuma, ChemCatChem 2009, 1, 497-
503.
[33] J. M. Pérez, R. Cano, M. Yus, D. J. Ramón, Eur. J. Org. Chem. 2012,
4548-4554.
[34] H. Wang, J. Zhang, Y. M. Cui, K. F. Yang, Z. J. Zheng, L. W. Xu, RSC
Adv. 2014, 4, 34681-34686.
[35] K. Tateyama, K. Wada, H. Miura, Catal. Sci. Technol. 2016, 6, 1677-
1684.
[36] T. Fukutake, K. Wada, G. C. Liu, S. Hosokawa, Q. Feng, Catal. Today
2018, 303, 235-240.
[37] M. Shaikh, R. Yadav, P. K. Tyagi, L. Mishra, K. V. S. Ranganath,
ChemNanoMat 2018, 4, 542-545.
[38] R. Fertig, T. Irrgang, F. Freitag, J. Zander, R. Kempe, ACS Catal. 2018,
8, 8525−8530.
10
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Entry for the Table of Contents (Please choose one layout)
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Ruthenium
nanoparticles
(NPs)
Bin Guo, Hong-Xi Li,* Shi-Qi Zhang,
David James Young, and Jian-Ping
Lang*
embedded in nitrogen-doped carbon
(Ru/N-C) were prepared by the
pyrolysis of cis-Ru(phen)2Cl2 loaded
onto carbon powder. Ru/N-C NPs
Page No. – Page No.
selectively
catalyzed
coupling
C-N Bond Formation Catalyzed by
Ruthenium Nanoparticles Supported
on N-Doped Carbon via Acceptorless
reactions of amines with alcohols to
imines and secondary amines, which
could be controlled by the choice of
alkali metal ions associated with the
base. This catalytic system also
displayed high activity towards cross-
coupling of diamines with primary
Dehydrogenation
to
Secondary
Amines, Imines, Benzimidazoles and
Quinoxalines
alcohols
or
diols
to
yield
benzimidazoles and quinoxalines.
11
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