Efficient Hydrogenation of Nitrogen Heterocycles Catalyzed by Carbon-Metal Covalent Bonds-Stabilized Palladium Nanoparticles: Synergistic Effects of Particle Size and Water

Article abstract of DOI:10.1002/adsc.201600505

We reveal here the first hydrogenation of nitrogen heterocycles catalyzed by carbon–metal covalent bonds-stabilized palladium nanoparticles in water under mild conditions. Using a one-phase reduction method, smaller metal–carbon covalent bond-stabilized Pd nanoparticles were prepared with a size distribution of 2.5±0.5 nm, which showed extraordinary synergistic effects with water in the catalytic hydrogenation of nitrogen heterocycles. Water was supposed to accelerate substrate absorption and synergistic activation of molecular hydrogen on the Pd nanoparticles surface. The nanosized Pd catalyst could be easily recovered and reused for 5 runs. (Figure presented.).

Full text of DOI:10.1002/adsc.201600505

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DOI: 10.1002/adsc.201600505
Efficient Hydrogenation of Nitrogen Heterocycles Catalyzed
by Carbon-Metal Covalent Bonds-Stabilized Palladium
Nanoparticles: Synergistic Effects of Particle Size and Water
Yu Zhang,+a Jie Zhu,+a Yun-Tao Xia,a Xiao-Tao Sun,a and Lei Wua,b,*
a
Jiangsu Key Laboratory of Pesticide Science and Department of Chemistry, College of Sciences, Nanjing Agricultural
University, Nanjing 210095, Peopleꢀs Republic of China
Fax : (+86)-25-8439-6716; phone: (+86)-25-8439-6716; e-mail: rickywu@njau.edu.cn
Beijing National Laboratory for Molecular Sciences and Institute of Chemistry, Chinese Academy of Sciences, Beijing
b
100190, Peopleꢀs Republic of China
+
These authors contributed equally to this work.
Received: May 12, 2016; Revised: July 12, 2016; Published online: && &&, 0000
Supporting information for this article can be found under: http://dx.doi.org/10.1002/adsc.201600505.
Abstract: We reveal here the first hydrogenation of
nitrogen heterocycles catalyzed by carbon–metal
covalent bonds-stabilized palladium nanoparticles
in water under mild conditions. Using a one-phase
reduction method, smaller metal–carbon covalent
bond-stabilized Pd nanoparticles were prepared
with a size distribution of 2.5Æ0.5 nm, which
showed extraordinary synergistic effects with water
in the catalytic hydrogenation of nitrogen heterocy-
cles. Water was supposed to accelerate substrate ab-
sorption and synergistic activation of molecular hy-
drogen on the Pd nanoparticles surface. The nano-
sized Pd catalyst could be easily recovered and
reused for 5 runs.
workers using a ruthenium catalyst.[4] Since then, an
extensive number of soluble metal catalysts/nanopar-
ticles based on Ni,[5] Ir,[6] Ru,[7] Rh,[8] and Pd[9] has
been introduced. As is known, despite the high activi-
ty of noble metals, homogeneous catalysts suffer from
the difficulty in separation and are difficult to be
reused. Therefore, the importance of heterogeneous
catalytic hydrogenation is highlighted.
Catalysts based on stabilized nanoparticles have
proven to be a powerful tool for the heterogeneous
reduction of quinoline, exhibiting both surprising ac-
tivity due to the large surface area and efficient reusa-
bility due to the heterogeneous nature. Several studies
have been published relating to platinum nanowires,
cobalt, gold nanoparticles and so on that could per-
form the hydrogenation process smoothly under rela-
tively mild reaction conditions.[10] Beller et al. devel-
oped a modified nano-catalyst – Co3O4-Co/NGr@a-
Keywords: carbon–metal covalent bonds; catalytic
hydrogenation; nitrogen heterocycles; stabilized
palladium nanoparticles; synergistic effects
Al2O3 (NGr=nitrogen-doped graphene layers)[11]
–
which enables activation of molecular hydrogen at
a comparably low temperature (1208C), as shown in
Scheme 1 (a-1). Another example is the chemoselec-
Since the last century, much effort have been devoted tive hydrogenation process for a wide range of quino-
to the synthesis of 1,2,3,4-tetrahydroquinoline lines using supported gold nanoparticles.[12] The trans-
(1,2,3,4-THQ) and its derivatives, due to their great formations could be performed smoothly under mild
importance in the production of fine chemicals, phar- conditions with 2 MPa H2 in a temperature range
maceuticals, agrochemicals and petrochemicals.[1] from 25–808C (Scheme 1, a-2). As for the palladium
Among various approaches developed including cata- nanocatalyst, although considerable attention has
lytic cyclization,[2] Beckman rearrangement[3] and so been paid in a broad array of organic reactions, rela-
on, an especially potential method is the controlled tive high temperatures, H2 pressures or catalyst load-
hydrogenation of quinoline and its derivatives in ings are still required to achieve the hydrogenation
terms of simplicity and atom economy. The partial hy- process efficiently.[9a,13]. Hence, from both synthetic
drogenation of polynuclear heteroaromatics with mo- and green points of view, it is still a major challenge
lecular hydrogen can be traced back to 1982 and a ho- to develop innovative catalytic processes that enable
mogeneous catalytic process reported by Fish and co-
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the first example of a metal–carbon covalent bonds-
stabilized Pd nanocatalyst for the catalytic hydrogena-
tion of nitrogen heterocycles in water under mild con-
ditions.
With Pd(OAc)2 as the palladium source, the nano-
catalyst was prepared through in-situ reduction by
sodium borohydride after the addition of 1,1’-bi-
naphthyl,-2,2’-bis(diazonium tetrafluoroborate), as
shown in Scheme 2. Interestingly, the reduction pro-
cesses dramatically affects the generation and catalyt-
ic performance of the catalyst. Initial attempts of the
two-phase reduction led to the formation of some
“palladium black” after work-up, leading to poor cat-
alytic performance for quinoline hydrogenation
(Scheme 2, Path II). To modify the preparation pro-
cess, THF and MeOH were used as mixed solvents af-
fording a homogeneous reduction (Path I). The result-
ing Pd NPs prepared by the one-phase reduction are
well soluble in common aprotic solvents, including
THF, dichloromethane and toluene; but insoluble in
alcoholic solvents and water, which facilitates further
heterogeneous catalytic investigations.
TEM and HR-TEM images of the resulting Pd NPs
(the insert graphs in Scheme 2) disclosed that they
were highly dispersed without aggregation. A narrow
distribution around the core diameter (2.5Æ0.5 nm)
was exhibited, confirming the successful grafting of
the binaphthyl moiety to stabilize the nanoparticle
through Pd–C bonds. Furthermore, the homogeneous
reduction gave catalysts of smaller particle size com-
pared with the reported two-phase reduction (3.3Æ
0.9 nm), which may also account for the different cat-
alytic performance. Further characterization of Pd
NPs including FT-IR and ICP can be found in the
Scheme 1. Studies on metal–carbon-stabilized PdNPs and
hydrogenation of quinolines.
reductive transformations to be performed under mild Supporting Information and the Experimental Sec-
and clean conditions with high efficiency. tion. The XPS spectrum in Scheme 2 shows two set of
Lately, a special Pd-C(binaphthyl) covalent bond- peaks 338.4, 332.9 eV and 340.3, 335.1 eV, which can
stabilized palladium nanocatalyst was described by be assigned to the 3d3/2 and 3d5/2 of Pd(0) and Pd(II),
Sekar et al. for cross-coupling reactions.[14] Its applica- respectively.[18] This abnormal shift of binding energy
tion was further extended to the synthesis of poly-sub- (BE) values to lower values might be attributed to
stituted olefins recently (Scheme 1, b).[15,16] Inspired the electron transfer from Pd(0) to Pd(II).[18c] The X-
by these leading results, we previously designed ray powder diffraction (XRD) pattern exhibited two
a class of modular metal–carbon-stabilized palladium board humps at 238 and 408. The particle size calculat-
nanoparticles based on binaphthyl scaffolds, with ed from the Scherrer formula was 2.3 nm, which
which the designed modular moiety bearing electron- matched well with the TEM data.
rich or electron-deficient groups regulated the catalyt-
In exploratory experiments, hydrogenation of quin-
ic hydrogenation efficiently.[9b] As part of our continu- oline to the corresponding tetrahydroquinoline was
ing interest in the synthesis and application of stabi- used as a model reaction to study the catalytic per-
lized Pd nanoparticles,[17] and to pursue clean, mild formance of Pd NP. The catalytic results under differ-
and efficient catalytic reduction methodologies for ent reaction conditions are listed in Table 1. With
sustainable chemistry, herein, we report a highly effi- green and sustainable chemistry in mind, hydrogena-
cient hydrogenation process for nitrogen heterocycles tion was first carried out in pure water with an H2 bal-
at room temperature under a hydrogen balloon in loon at room temperature. To our surprise, the reac-
water (Scheme 1, c). The Pd nanocatalyst (denoted as tion was achieved smoothly under such mild condi-
Pd NPs), which was prepared via a one-phase reduc- tions and produced a yield of over 99% in 24 hours
tion method, presents smaller particle size and im- (entry 1). The hydrogenation process was highly re-
proved activity. To the best of our knowledge, this is gioselective, producing 1,2,3,4-tetrahydroquinoline ex-
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Scheme 2. The preparation of metal–carbon-stabilized Pd NPs by one-phase and two-phase methods (top); TEM (scale
bar=50 nm), HR-TEM (scale bar=2 nm), XPS and XRD characterizations of Pd NPs via one-phase reduction method.
clusively with no trace of 5,6,7,8-tetrahydroquinoline 36 h). This finding may be attributed to the adsorp-
or decahydroquinoline being detected. Moreover, al- tion of hydrogen and substrate on the catalyst through
though neither substrate nor catalyst could be dis- hydrogen bonding, which will be discussed later in
solved in water forming a heterogeneous process, detail. As mentioned above, the prepared Pd NPs ex-
pure water as solvent gave a better result compared hibited superiority when applied in the hydrogenation
with that of an alcoholic solvent (entry 5, 53% yield) process compared with that obtained through two-
or under solvent-free conditions (entry 6, 78% yield, phase reduction (entry 7, 72% yield), thus a synergistic
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Table 1. Catalytic hydrogenation of quinoline: screening of
Table 2. Pd-NPs-catalyzed hydrogenation of quinoline deriv-
the reaction conditions.[a]
atives.[a]
R1
R2
Yield [%][b]
Entry
Solvent
Time
[h]
Catalyst
Loading [%]
Yield
[%][b]
Entry
1
H
H
98
1
2
3
4
H2O
H2O
H2O
H2O
MeOH
solvent-free
H2O
24
18
12
24
24
36
24
24
1
1
1
0
1
1
1
0.5
>99
96
77
0
53
78
72
70
2
3
4
5
6
7
8
9
H
H
H
8-Me
6-Me
6-MeO
8-NH2
8-OH
H
2-Me
3-Me
4-Me
H
2-Me
H
96
90
38 (40)
97
89
82
87
89
91
52 (56)
97
90
93
98
5
6
7[c]
8
H
H
H2O
10[c]
11[d]
12[d]
13[d]
14[d]
15[e]
3-CHO
3-Br
H
2-Me
2-Me
2-Cl
[a]
Reaction conditions: quinoline (0.417 mmol), solvent
(1 mL) and Pd NP (5.0 mg, 0.00417 mmol, 1% of sub-
strate), H2 balloon, room temperature.
H
5-Br
6-Br
8-Br
8-Cl
[b]
[c]
1
The yields were determined by H-NMR.
Pd NPs obtained through a two-phase reduction were
used, ref.[14]
[a]
Reaction conditions: quinoline (0.417 mmol), water
(1 mL) and Pd NP (5.0 mg, 0.00417 mmol, 10% of sub-
strate), H2 balloon, room temperature, 24 h.
Isolated yields, 1H-NMR yields in brackets.
–CHO was reduced to –CH2OH.
C–Br bond cleavage.
C–Cl bond cleavage on the pyridine moiety, however
intact on the benzene moiety.
effect of particle size and water was disclosed. Be-
sides, a catalyst loading of 1% (mol of substrate) was
enough to initiate the reaction and obtain good effi-
ciency. So in the view of both green chemistry and
catalytic efficiency, the optimized conditions are de-
termined as water solvent under room temperature
with an H2 balloon and 1% of catalyst loading.
[b]
[c]
[d]
[e]
After the initial promising results, subsequent ex-
periments were performed to examine the applicabili- group-substituted quinolines exhibited obvious differ-
ty of this system. Under the optimized conditions, our entiation. If bromine was the substituent, either on
study was extended to various structurally differently the benzene or the pyridine moieties, tetrahydroqui-
substituted quinolines using 1 mol% of the palladium nolines were obtained in excellent yields with C–Br
nanocatalyst for 24 hours, and the results are summar- bond being broken (entries 11–14). For quinolines
ized in Table 2. For all the substrates tested, the corre- with a chlorine group, however, the corresponding
sponding 1,2,3,4-tetrahydroquinoline was the only de- functional tetrahydroquinolines were generated with
tected product without by-products frequently formed C–Cl cleavage on the pyridine moiety. In sharp con-
in catalytic hydrogenation process such as 5,6,7,8-tet- trast, the C–Cl bond was intact on the benzene ring
rahydroquinoline or decahydroquinoline. As shown in (entries 15). The interesting chemoselective results for
Table 2, reactions of quinolines bearing a methyl chlorine substituents will be meaningful for organic
group at the 2- and 3-position on the pyridine moiety synthesis with a particular purpose.
or 5-, 8-position on the benzene moiety, all proceeded
Encouraged by these results, this attractive protocol
successfully to give the corresponding 1,2,3,4-tetrahy- was further applied to the hydrogenation of the heter-
droquinolines with excellent yields (Table 2, entries 2, ocyclic rings of some other heteroaromatic nitrogen
3, and 5). Dimethyl-substituted quinoline also per- compounds, as listed in Table 3. Excellent yield and
formed well in this system (entry 6). For 4-substituted regioselective results were obtained for all the cases.
quinoline which is sometimes difficult to be reduc- Quinoxaline and methyl- or phenyl-substituted qui-
ed,[7b] a moderate yield was obtained (entry 4). Fur- noxaline were converted to the corresponding 1,2,3,4-
thermore, quinolines with electron-donating groups tetrahydroquinoxalines without any influence on the
(OMe, NH2, OH) on the benzene ring also react benzene ring (Table 3, entries 1–4). More complex
smoothly (entries 7–9). When 3-formyl-substituted fused ring compounds, including acridine and phena-
quinoline was employed in the system, the 3-hydroxy- zine were hydrogenated to their corresponding tetra-
methylquinoline would be obtained as the formyl hydro derivatives (entries 5 and 6). Note that the gen-
group was hydrogenated simultaneously (entry 10). It eral order of individual catalytic efficiency was acri-
is worthy of note that hydrogenation of halogen dine>quinoline>quinoxaline >substituted quino-
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Table 3. Pd-NPs-catalyzed hydrogenation of nitrogen hetero-
cycles.[a]
Entry
R1
X
R2, R3
Yield [%][b]
1
2
3
4
5
6
H
5-CH3
H
H
H
N
N
N
N
H
N
H, H
H, H
H, CH3
Ph, H
3,4-Ph
3,4-Ph
89
72
85
81
90
91 (cis)
H
Scheme 3. The proposed catalytic mechanism (binaphthyl
groups are omitted for clarity).
[a]
Reaction conditions: nitrogen heterocycle (0.417 mmol),
water (1 mL) and Pd NP (5.0 mg, 0.00417 mmol, 1% of
substrate), H2 balloon, room temperature, 24 h.
Isolated yields.
[b]
quinoline was the only detected product in our work,
quinoline molecules were assumed to be adsorbed on
Pd NP catalyst through nitrogen–metal coordination
line>substituted quinoxaline, which reflects both rather than via the benzene ring. The water present
steric and electronic effects.[19]
may interact with Pd active sites leading to a relatively
The reusability of the catalyst was finally studied. high concentration of hydroxyl groups on Pd nanopar-
Once the reaction was completed, the product or any ticles (Pd–OH).[7b,13b,22] As a result, the adsorption of
substrate remaining in the mixture was extracted with pyridine onto the Pd active sites is significantly pro-
ether before analysis by 1H NMR. To recycle the moted by the formation of hydrogen bonds between
system, the aqueous phase containing water and cata- the N atom and hydroxyl groups around Pd nanopar-
lyst can be reused without further treatment after re- ticles (Scheme 3, steps a and b). Subsequently, quino-
charging with the substrates, and thus was of great op- line molecules interact with the activated H produced
erational simplicity. To recover the catalyst, CH2Cl2 by H2 over Pd nanoparticles, resulting in the forma-
could be used due to the hydrophobicity of Pd NP. tion of 1,2,3,4-tetrahydroquinolines as the exclusive
The recovered catalyst could be recycled for at least 5 product and the regeneration of Pd–OH species (step
times without obvious loss of activity or selectivity as c).
shown in the Supporting Information, Figure S3. De-
Alternatively, the hydrogenation reaction may
spite the strong coordination ability of the N atom in follow a hydrogen transfer process, in which the hy-
quinoline and its corresponding hydrogenation prod- drogen source came from the solvent water actually.
ucts,[20] the catalyst in our work was resistant against Pd–OH may dehydrogenize quinoline first to release
poisoning, which confirmed the stability as well as the the 1,2,3,4-tetrahydroquinoline product and was
strong interaction between the metal and the stabiliz- turned into a Pd–OC species itself at the same time
ers due to the covalent bonds. Thus, a green, efficient (step d).[22] Afterwards, Pd–OH is regenerated
and reusable system was achieved for the hydrogena- through hydrogenation with activated H species to
tion of quinolines.
complete the catalytic cycle (step e). To examine
To clarify the effect of water, two possible catalytic whether the solvent participated in the reaction, deu-
paths were first proposed as shown in Scheme 3. With terated water was used as solvent instead of water.
water present, the nitrogen atom in the quinoline No deuterated product was detected; however, which
molecule could adsorb on the surface of the catalyst indicated that the H source comes from the hydrogen,
via a hydrogen bond in addition to coordination with and water may promote the reaction through hydro-
the metal active sites.[7b] Meanwhile, the adsorption of gen bonding.
the phenyl ring was relatively inhibited due to the hy-
In summary, an ultra-clean, mild and efficient
drophobic phenyl ring part of the quinoline molecule, methodology for the hydrogenation of nitrfogen het-
leading to the high selectivity to tetrahydroquinoline. erocylces has been disclosed using a hydrogen balloon
Thus water as the medium played a vital role in in- at room temperature in water. Using the one-phase
creasing the opportunity of interaction between cata- reduction method, a smaller size distribution of
lyst, substrate and H2. Based on previous research metal–carbon-stabilized Pd nanoparticles was ob-
work,[21] the selectivity of the hydrogenation of quino- tained. This nanosized catalyst enabled the hydroge-
line depends on the adsorption types of quinoline nation of a wide range of quinolines and related het-
over precious metal catalysts. As 1,2,3,4-tetrahydro- eroaromatic nitrogen compounds into the correspond-
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[4] R. H. Fish, A. D. Thormodsen, G. A. Cremer, J. Am.
Chem. Soc. 1982, 104, 5234–5237.
[5] a) Y. Zhao, M. W. Xue, M. H. Cao, J. Y. Shen, Appl.
Catal. B 2011, 104, 229–233; b) G. J. Shi, J. Y. Shen, J.
Mater. Chem. 2009, 19, 2295–2297; c) Y. Zhao, Y. P.
Zhao, H. S. Feng, J. Y. Shen, J. Mater. Chem. 2011, 21,
8137–8145.
[6] a) J. John, C. Wilson-Konderka, C. Metallinos, Adv.
Synth. Catal. 2015, 357, 2071–2081; b) M. Rueping,
R. M. Koenigs, R. Borrmann, J. Zoller, T. E. Weirich, J.
Mayer, Chem. Mater. 2011, 23, 2008–2010; c) B. C. Le-
desma, V. A. Vallꢄs, L. P. Rivoira, M. L. Martꢅnez,
O. A. Anunziata, A. R. Beltramone, Catal. Lett. 2014,
144, 783–795.
ing tetrahydro derivatives with excellent efficiency
and selectivity. Water was supposed to accelerate the
adsorption of substrate through hydrogen bonding
with a synergistic effect of particle size, leading to the
high efficiency as well as selectivity. As a heterogene-
ous process, the catalyst can be easily recovered and
reused. It is believed that this procedure may have
fundamental implications for the broad field of Pd
catalysis and be of potential value for industrial pur-
poses in the view of green and sustainable organic
synthesis.
[7] a) H. Zhou, Z. Li, Z. Wang, T. Wang, L. Xu, Y. He, Q.-
H. Fan, J. Pan, L. Gu, A. S. C. Chan, Angew. Chem.
2008, 120, 8592–8595; Angew. Chem. Int. Ed. 2008, 47,
8464–8467; b) T. Wang, L.-G. Zhuo, Z. Li, F. Chen, Z.
Ding, Y. He, Q.-H. Fan, J. Xiang, Z.-X. Yu, A. S. C.
Chan, J. Am. Chem. Soc. 2011, 133, 9878–9891; c) L.
Zhang, X. Y. Wang, Y. Xue, X. J. Zeng, H. Chen, R. X.
Li, S. L. Wang, Catal. Sci. Technol. 2014, 4, 1939–1948;
d) H.-Y. Jiang, X.-X. Zheng, Catal. Sci. Technol. 2015,
5, 3728–3734.
Experimental Section
Typical Procedures for the “One-Phase Reduction”
Preparation of Metal–Carbon-Stabilized Palladium
Nanoparticles
An aqueous solution of Pd(OAc)2 (1.0 mmol in 10 mL
MeOH) was added into the solution of 1,1’-binaphthyl,-2,2’-
bis(diazoniumtetrafluoro borate) (1.0 mmol in 10 mL THF).
After stirring for 0.5 h, NaBH4 (189 mg, 5.0 mmol) in
MeOH (4 mL) was added dropwise at 08C to the reaction
mixture and the immediate color change to deep brown sig-
nified the Pd NPs formation. The reaction mixture was
stirred vigorously at 08C for another 2 h. The resulting reso-
lution was extracted by dichloromethane and washed with
0.5M aqueous H2SO4 (3ꢂ20 mL) and 0.5M aqueous
NaHCO3 (3ꢂ20 mL), respectively, to remove impurities.
The solid particles were suspended in ethanol (2ꢂ4 mL) and
sonicated for half an hour at room temperature, then the
suspension was centrifuged (3000 rpm, approx. 30 min) to
furnish the Pd NPs; yield: 835 mg (9.96 wt% Pd by ICP-
OES analysis).
[8] a) M. Niu, Y. Wang, P. Chen, D. Du, J. Jiang, Z. Jin,
Catal. Sci. Technol. 2015, 5, 4746–4749; b) C. Wang,
C. Q. Li, X. F. Wu, A. Pettman, J. L. Xiao, Angew.
Chem. 2009, 121, 6646–6650; Angew. Chem. Int. Ed.
2009, 48, 6524–6528; c) H. Y. Jiang, X. X. Zheng, Appl.
Catal. A 2015, 499, 118–123; d) N. A. Beckers, S.
Huynh, X. J. Zhang, E. J. Luber, J. M. Buriak, ACS
Catal. 2012, 2, 1524–1534; e) A. Karakulina, A. Gopa-
˙
kumar, I. AkÅok, B. L. Roulier, T. LaGrange, S. A. Kat-
syuba, S. Das, P. J. Dyson, Angew. Chem. 2016, 128,
300–304; Angew. Chem. Int. Ed. 2016, 55, 292–296.
[9] a) M. M. Dell’Anna, V. F. Capodiferro, M. Mali, D.
Manno, P. Cotugno, A. Monopoli, P. Mastrorilli, Appl.
Catal. A 2014, 481, 89–95; b) Y. Zhang, M. Mao, Y.-G.
Ji, J. Zhu, L. Wu, Tetrahedron. Lett. 2016, 57, 329–332;
c) Y. Gong, P. Zhang, X. Xu, Y. Li, H. Li, Y. Wang, J.
Catal. 2013, 297, 272–280; d) R. Rahi, M. Fang, A.
Ahmed, R. A. Sꢆnchez-Delgado, Dalton Trans. 2012,
41, 14490–14497.
[10] a) S. Lu, J. Wang, X. Cao, X. Li, H. Gu, Chem.
Commun. 2014, 50, 3512–3515; b) D. Ge, L. Hu, J.
Wang, X. Li, F. Qi, J. Lu, X. Cao, H. Gu, ChemCatCh-
em 2013, 5, 2183–2186; c) M. Yan, T. Jin, Q. Chen,
H. E. Ho, T. Fujita, L.-Y. Chen, M. Bao, M.-W. Chen,
N. Asao, Y. Yamamoto, Org. Lett. 2013, 15, 1484–1487;
d) L. Tao, Q. Zhang, S.-S. Li, X. Liu, Y.-M. Liu, Y. Cao,
Adv. Synth. Catal. 2015, 357, 753–760.
Acknowledgements
This project is supported by the National Natural Science
Foundation of China (NSFC, Grant No. 21372118), the Fun-
damental Research Funds for the Central Universities (Grant
No. KYTZ201604), and “333 high level talent project” of
JiangSu Province.
References
[11] F. Chen, A.-E. Surkus, L. He, M.-M. Pohl, J. Radnik, C.
Topf, K. Junge, M. Beller, J. Am. Chem. Soc. 2015, 137,
11718–11724.
[12] D. Ren, L. He, L. Yu, R.-S. Ding, Y.-M. Liu, Y. Cao,
H.-Y. He, K.-N. Fan, J. Am. Chem. Soc. 2012, 134,
17592–17598.
[13] a) T. He, L. Liu, G. Wu, P. Chen, J. Mater. Chem. A
2015, 3, 16235–16241; b) H. Mao, C. Chen, X. Liao, B.
Shi, J. Mol. Catal. A 2011, 341, 51–56; c) V. K. R.
Kumar, K. R. Gopidas, Tetrahedron Lett. 2011, 52,
3102–3105.
[1] a) R. T. Shuman, P. L. Ornstein, J. W. Paschal, P. D. Ge-
sellchem, J. Org. Chem. 1990, 55, 738–741; b) V. Srid-
haran, P. Suryavanshi, J. C. Menendez, Chem. Rev.
2011, 111, 7157–7259.
[2] a) R. Omar-Amrani, A. Thomas, E. Brenner, R.
Schneider, Y. Fort, Org. Lett. 2003, 5, 2311–2314; b) F.
Avemaria, S. Vanderheiden, S. Brꢃse, Tetrahedron 2003,
59, 6785–6796.
[3] K. Maruoka, T. Miyazaki, M. Ando, Y. Matsumura, S.
Sakane, K. Hattori, H. Yamamoto, J. Am. Chem. Soc.
1983, 105, 2831–2843.
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[14] D. Ganapathy, G. Sekar, Catal. Commun. 2013, 39, 50–
54.
B: Environmental 1998, 19, 261–266; c) M. Hattori, D.
Shimamoto, H. Ago, M. Tsuji, J. Mater. Chem. A 2015,
3, 10666–10670.
[15] D. Ganapathy, G. Sekar, Org. Lett. 2014, 16, 3856–3859.
[16] Just when we are compiling this manuscript, Sekar
et al. reported the reduction of aldehydes into alcohols
by binaphthyl-stabilized palladium nanocatalyst with
molecular hydrogen in water: S. S. Kotha, N. Sharma,
G. Sekar, Adv. Synth. Catal. 2016, 358, 1694–1698.
[17] a) L. Wu, J. Ling, Z. Q. Wu, Adv. Synth. Catal. 2011,
353, 1452–1456; b) L. Wu, Y. M. He, Q. H. Fan, Adv.
Synth. Catal. 2011, 353, 2915–2919; c) L. Wu, X. Zhang,
Z. M. Tao, Catal. Sci. Tech. 2012, 2, 707–710; d) L. Wu,
Y. Zhang, Y. G. Ji, Curr. Org. Chem. 2013, 17, 1288–
1302; e) Y. G. Ji, L. Wu, Q. H. Fan, Acta Chim. Sin.
2014, 72, 798–808.
[19] R. H. Fish, J. L. Tan, A. D. Thormodsen, J. Org. Chem.
1984, 49, 4500–4505.
[20] a) R. A. Sꢆnchez-Delgado, N. Machalaba, N. Ng-a-qui,
Catal. Commun. 2007, 8, 2115–2118; b) F. Alonso, M.
Yus, Adv. Synth. Catal. 2001, 343, 188–191.
[21] a) R. H. Fish, H. S. Kim, R. H. Fong, Organometallics
1989, 8, 1375–1377; b) R. H. Fish, J. N. Michaels, R. S.
Moore, H. Heinemann, J. Catal. 1990, 123, 74–85;
c) R. H. Fish, H. S. Kim, R. H. Fong, Organometallics
1991, 10, 770–777; d) E. Baralt, S. J. Smith, J. Hurwitz,
I. T. Horvath, R. H. Fish, J. Am. Chem. Soc. 1992, 114,
5187–5196.
[18] a) G.-L. Zhuang, J.-Q. Bai, L. Tan, H.-L. Huang, Y.-F.
Gao, X. Zhong, C.-L. Zhong, J.-G. Wang, RSC Adv.
2015, 5, 32714–32719; b) Y. Yazawa, H. Yoshida, N.
Takagi, S.-I. Komai, A. Satsuma, T. Hattori, App. Catal.
[22] Y. Mori, M. Seki, J. Org. Chem. 2003, 68, 1571–1574.
[23] O. Verho, T. ꢇkermark, E. V. Johnston, K. P. J. Gustaf-
son, C.-W. Tai, H. Svengren, M. D. Kꢃrkꢃs, J.-E. Bꢃck-
vall, B. ꢇkermark, Chem. Eur. J. 2015, 21, 5909–5915.
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These are not the final page numbers!

COMMUNICATIONS
8 Efficient Hydrogenation of Nitrogen Heterocycles
Catalyzed by Carbon-Metal Covalent Bonds-Stabilized
Palladium Nanoparticles: Synergistic Effects of Particle Size
and Water
Adv. Synth. Catal. 2016, 358, 1 – 8
Yu Zhang, Jie Zhu, Yun-Tao Xia, Xiao-Tao Sun, Lei Wu*
Adv. Synth. Catal. 0000, 000, 0 – 0
8
ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÞÞ
These are not the final page numbers!