In Situ Generated Gold Nanoparticles on Active Carbon as Reusable Highly Efficient Catalysts for a Csp3 ?Csp3 Stille Coupling

Article abstract of DOI:10.1002/anie.201902352

Gold nanoparticle catalysts are important in many industrial production processes. Nevertheless, for traditional C_sp2-C_sp2 cross-coupling reactions they have been rarely used and Pd catalysts usually give a superior performance. Herein we report that in situ formed gold metal nanoparticles are highly active catalysts for the cross coupling of allylstannanes and activated alkylbromides to form C_sp3-C_sp3 bonds. Turnover numbers up to 29 000 could be achieved in the presence of active carbon as solid support, which allowed for convenient catalyst recovery and reuse. The present study is a rare case where a gold metal catalyst is superior to Pd catalysts in a cross-coupling reaction of an organic halide and an organometallic reagent.

Full text of DOI:10.1002/anie.201902352

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: In-situ Generated Gold Nanoparticles on Active Carbon as
Reusable Highly Efficient Catalysts for a Csp3–Csp3 Stille
Coupling
Authors: Julia Holz, Camilla Pfeffer, Hualiang Zuo, Dennis Beierlein,
Gunther Richter, Elias Klemm, and René Peters
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201902352
Angew. Chem. 10.1002/ange.201902352
Link to VoR: http://dx.doi.org/10.1002/anie.201902352
http://dx.doi.org/10.1002/ange.201902352

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
In-situ Generated Gold Nanoparticles on Active Carbon as
Reusable Highly Efficient Catalysts for a Csp –Csp Stille Coupling
3
3
Julia Holz,[a] Camilla Pfeffer,[a] Hualiang Zuo,[b] Dennis Beierlein,[b] Gunther Richter,[c] Elias Klemm,[b]
and René Peters*[a]
Abstract: Gold nanoparticle catalysts are important in many industrial
production processes. Nevertheless, for traditional Csp2–Csp2 cross-
coupling reactions they have been rarely used and Pd catalysts
usually allow for a superior performance. Herein we report that in-situ
formed gold metal nanoparticles are highly active catalysts for the
cross coupling of allylstannanes and activated alkylbromides to form
Csp3–Csp3 bonds. Turnover numbers up to 29000 could be achieved in
the presence of active carbon as solid support, which allowed for
convenient catalyst recovery and reuse. The present study is a rare
case where a gold metal catalyst is superior to Pd catalysts in a cross
coupling reaction of an organic halide and an organometallic reagent.
catalyst could be applied as the only catalyst in an intermolecular
Stille type cross coupling.[11] Very high turnover numbers were
achieved with the AuNPs which could also be conveniently reused
by performing the coupling in the presence of commercial active
carbon (AC) as solid support.
The Pd catalyzed Stille cross coupling[1] of organostannanes and
aryl- or vinylhalides/-triflates is one of the most important and
general methods in chemical synthesis for Csp2–Csp
2
bond
formation (eq. 1).[2] The corresponding version for Csp3–Csp3 bond
formation using allylstannanes and activated alkylhalides like
benzyl and allylhalides is less developed (eq. 2), which is at least
in part due to regioselectivity issues and retarded reductive
elimination.[1d,3,4]
Au catalyzed C–C bond formations have also been intensively
investigated in the last decades.[5] Application of bulk gold metal
for C–C bond formations is not common due to low catalytic
activity.[5] The use of gold metal nanoparticles (AuNPs) on solid
support materials has allowed for a large number of attractive
catalytic applications, including many industrial production
processes.[5,6,7] Nevertheless, cross-couplings for C–C bond
formation making use of organic halides or triflates –i.e. reactions
which are typically performed with Pd-catalysts[8]– are still very
rare with AuNP catalysts (eq. 3). It has been concluded in a recent
review on AuNP catalysis that ‘‘the outcome of the available
experimental data points to a remarkably low catalytic activity of
Au compared to Pd’’ in these reactions so far.[6a] Previous studies
showed that the solid support and the way how the AuNPs were
formed is very important to achieve the desired reactivity and to
suppress homocouplings.[6] Mainly for a Suzuki-Miyaura type
coupling[9] and Sonogashira type couplings[10] AuNP catalyzed
versions could be developed so far.
Herein, we describe in-situ formed AuNPs which show excellent
activity for cross coupling of allylstannanes and benzyl or allyl
bromides (eq. 4). To our knowledge this is the first time that a gold
Besides AuNP catalysis, bisgold catalyzed cross couplings have
been described. They are likely to proceed via Au(II)–Au(II)
intermediates in order to facilitate an oxidative addition step at
Au(I).[12] Recently, we reported the synthesis of dinuclear
ferrocenyl Au(I) complexes like C1 (see Table 1) and found that
they are readily oxidized to the corresponding dinuclear Au(II)
complexes C2.[13] We were initially interested to explore this
reactivity in bimetal catalyzed C–C cross coupling reactions
studying the model reaction of benzylbromide (1a) and
allyltributylstannane (2a). In the presence of 5 mol% of C1 or C2
the coupling product 3a was formed in promising yield (Table 1,
[a]
Dr. J. Holz, M.Sc. C. Pfeffer, Prof. Dr. R. Peters
Universität Stuttgart, Institut für Organische Chemie
Pfaffenwaldring 55, D-70569 Stuttgart, Germany
E-mail: rene.peters@oc.uni-stuttgart.de
Dr. H. Zuo, M.Sc. D. Beierlein, Prof. Dr. E. Klemm
Universität Stuttgart, Institut für Technische Chemie
Pfaffenwaldring 55, D-70569 Stuttgart, Germany
Dr. Gunther Richter
[b]
[c]
MPI IS Stuttgart, Heisenbergstr. 3, D-70569 Stuttgart, Germany
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
No. 1&2). Without catalyst no product was detected under
otherwise identical conditions (No. 3).
0.01 mol% (No. 12 & 13). Monitoring by 1H-NMR using an internal
standard revealed that with 0.05 mol% of precatalyst the reaction
started sluggishly with an induction period of about 2 h (16% 3a)
and then gained momentum leading to quantitative yield within 5
h.
Table 1. Initial studies.
Whereas with 3 mol% of (Me2S)AuCl the rapid formation of Au
grains by precatalyst decomposition was observed (entry 9), with
precatalyst loadings ≤0.5 mol% suspensions containing a finely
dispersed solid were formed (entries 12&13) and the reaction
mixture adopted a blue-purple color upon addition of 2a which is
characteristic for the aggregation of AuNPs.[14]
Employing 0.25 mol% of precatalyst full conversion to 3a was
found after 3 h (Figure 1, black curve). Reusing the separated fine
solid in catalysis led to increased initial activity [e.g.: 61% conv.
after 1 h with the recycled catalyst versus 45% conv. with
(Me2S)AuCl (0.25 mol%)]. Initial induction periods are probably
caused by formation of the AuNPs as catalytically active species.
To facilitate separation and reuse of the catalyst and to prevent
aggregation to bulk gold metal, commercial active carbon (AC)
was added to the reaction as a solid support material in order to
adsorb the in-situ formed Au-nanoparticles. AuNPs –often
supported by metal oxide surfaces like TiO2– are usually
preformed prior to use by various methods like the often applied
deposition-precipitation method which consists of a sequence of
synthetic operations like reduction of Au(III) in the presence of the
support, aging, filtration, washing and drying in an oven.[6] AC is
also often used as support for AuNPs[6,15] and is attractive as a
non-toxic, cost-efficient and widely available porous adsorbent
with a relatively high surface area and a large adsorption
capacity.[16] AC is very useful as catalyst support for its stability
towards acids and bases, its chemical inertness and the ease of
recycling.
No.
[Au]
x
T [°C] solvent
yield
(%)[a]
1
2
C1
5
5
50
50
benzene
benzene
78
59
C2 (X = Cl)
3
-
C1
-
1.5
1.5
1.5
<1.5
3
50
50
50
50
50
50
50
50
50
50
50
benzene
0
4
toluene
96
90
97
94
20
99
88
2
5
C2 (X = Cl)
toluene
6
C2 (X = Br)
toluene
7
Au precipitate recovered from #6
(Me2S)AuCl
toluene
8
benzene
9
(Me2S)AuCl
3
-
-
-
-
-
10
11
12
13
Au powder
3
Au powder
1
Experiments with 0.25 mol% precatalyst showed that in the
presence of AC the reactions proceed faster (Figure 1). With
increasing amounts of AC the reactions are accelerated.
(Me2S)AuCl
0.1
0.01
99
93
(Me2S)AuCl
[a] Determined by 1H-NMR of the crude product using an internal standard.
With 1.5 mol% C1 in toluene a nearly quantitative product yield
was obtained (No. 4). Similar results were obtained with catalysts
C2 (No. 5 & 6). Whereas in benzene the formation of metallic gold
mirrors was always observed, in toluene there appeared to be
much less catalyst decomposition. However, under light it was
observed that the reaction mixtures contained a very fine dark
solid. After separation by centrifugation, washing and drying this
solid was shining golden. This material isolated from entry 6 was
reused and provided 3a in 94% yield (No. 7).
Additional experiments were conducted with mononuclear Au(I)
complexes. (Ph3P)AuCl gave no product, but with (Me2S)AuCl the
cross coupling also delivered 3a in low yield (20%, No. 8). A
nearly quantitative yield could be obtained under neat conditions
(No. 9). In the latter case, golden-brown grains (size in 1 mm
range) were formed rapidly after addition of the allyltin reagent.
Commercial Au powder (flakeshape, 90% 6-55 m; 50% 5-20 m;
10% 1.5-9 m) was used for comparison. Whereas in benzene
solution only traces of product were found, under neat conditions
88% of 3a were formed (No. 10). However, with a catalyst loading
of 1 mol%, the catalytic activity of the powder nearly completely
vanished (No. 11). In contrast, the loading could be significantly
reduced with (Me2S)AuCl, still providing high yields using 0.1 and
Figure 1. Time dependence of the formation of product 3a using 0.25 mol%
(Me2S)AuCl as precatalyst and different amounts of AC as solid support.
With a lower AC amount (13.4 wt% Au/AC) the reaction was
complete after ca. 60 min, with a higher amount (3.3 wt% Au/AC)
30 min were enough employing identical Au amounts.
This article is protected by copyright. All rights reserved.

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
Due to the enhanced activity, lower Au-loadings could be used
than in the absence of AC. Using as little as 0.005 mol% of Au
source still led to 99% yield within 6 h (Table 2, No. 2, TON =
19800, 10.2 mmol scale). With lower catalyst loadings even
higher TONs up to 29000 were possible (0.001% precatalyst, 47.5
mmol scale, No. 4), but conversions were not complete yet after
6 h. In contrast, product formation was not catalyzed by AC itself
in the absence of the Au catalyst.
substrate (S)-1a (61% ee). In the coupling with 2a under the
conditions of Table 3/No. 1 almost racemic product was formed,
but with a slight and reproducible excess for the product with
retention of configuration (5% ee). Previously, it has been
demonstrated that the rupture of carbon-halide bonds by partial
electron transfer from a AuNP to the substrate is a viable
process.[10f,19] The observed partial retention would be in
agreement with a concerted process.
Table 2. Investigation of the catalytic activity in the presence of AC.
Table 3. Investigation of the substrate scope.
No.
x
y
wt% AC per
t / [h]
scale /
[mmol]
yield /
[%][a]
TON
(mol%) (wt%)
1a
1
2
0.25 6.7
4
4
0.5
6
0.34
10.2
98
99
392
0.005 0.133
0.0025 0.067
0.001 0.027
19800
No.
product
R1
R2
R3 R4 t / [h]
yield /
[%][a]
3
4
4
4
6
6
19.0
47.5
53
29
21200
29000
[a] Determined by 1H-NMR of the crude product using an internal standard.
1
2
3
4
3a
3b
3c
3d
H
Me
Me
Me
Me
H
H
H
H
H
H
H
H
3
3
3
3
>99%
95
p-NO2
p-CF3
p-Br
97
Investigation of the substrate scope is summarized in Table 3.[17]
Next to model substrate 1a, the reaction could also be applied to
benzylic bromides carrying electron-withdrawing (No. 2-5, 14-16)
and -donating substituents (No. 6-8, 10). Substituents were well
tolerated at the ortho-, meta- and para-position. In most cases
using a secondary bromide yields were good to high. In all cases
where product yields did not reach 80% after 3 h, the reaction time
was increased to 5 h. Moderate yields with secondary bromides
were obtained only for product 3f carrying a p-OMe group (No. 6)
–probably due to the observed instability of the bromide, which
rapidly decomposes– and in the presence of Ph substituents R2
(No. 10&11) which slow down the coupling, arguably for steric
reasons. The title reaction could also be applied to primary (No.
14-17) and tertiary (No. 18) benzylbromides. As a general trend,
secondary bromides reacted faster than primary (compare No. 1-
4 and 14-17) and tertiary ones (compare No. 1 and 18). In the
latter case elimination to the styrene (24%) was found as side
reaction. A substituent R4 on the allyl moiety was also tolerated,
but the reaction was slower and not complete yet after 5 h
(compare No. 1 and 19).[18]
The reaction is also applicable to both aliphatic and aromatic
allylic bromides 4 (eq. 5). With R = n-pentyl the reaction was
accompanied by a slow partial isomerization of the double bond
(E/Z = 12:1), whereas with R = Ph this was not observed. In the
latter case the branched 1,5-diene was formed as side product
(20%).
Since secondary substrates showed a higher reactivity than
primary ones, it is unlikely that an SN2-type pathway is followed.
The formation of a carbocation intermediate is also unlikely,
because tertiary substrates were also less reactive. In control
experiments we studied the use of enantiomerically enriched
96
5
3e
3f
p-CN
p-OMe
p-Me
m-Me
o-Me
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
3
5
3
3
3
5
5
3
5
3
5
5
5
3
5
87
52
97
88
83
67
69
86
77
82
59
85
80
70
55
6
Me
7
3g
3h
3i
Me
8
Me
9
Me
10[b]
11
12
13
14
15[b]
16
17[b]
18
19
3j
Ph
3k
3l
p-Me
H
Ph
iPr
3m
3n
3o
3p
3q
3r
H
CH2CH=CH2
H
H
H
p-NO2
p-CF3
p-Br
H
H
H
Me
Me
3s
H
[a] Determined by 1H-NMR of the crude product using an internal standard. [b]
1,2-Dichloroethane was used as solvent due to a solid substrate.
Like mentioned, a major advantage of the AC support is an
improved catalyst recovery by facilitated filtration. The model
reaction was conducted 5 times with an identical catalyst batch
and nearly quantitative yields were obtained in all runs (eq. 6).
This article is protected by copyright. All rights reserved.

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
In addition, Au@AC (3.0 wt% Au/AC, average size of the AuNPs:
38.7 nm, determined by XRD) was synthesized by a previously
established protocol[24] and used in the model reaction of 1a and
2a. Under standard conditions (0.25 mol% Au@AC, 50 °C, 3 h)
the desired product was formed in 94% yield. However, under a
reduced catalyst loading of 0.005 mol% this material performed
significantly worse than the in-situ generated catalyst just forming
traces of product (6% yield). Under these conditions with the in-
situ formed Au@AC a product yield of 99% was obtained (Table
2, No. 2). This supports the assumption that smaller particles
display a higher activity.[25]
In conclusion, we have reported an efficient Au catalyzed Stille
type cross coupling of allylstannanes and activated alkylbromides
to form Csp3–Csp3 bonds – a reaction, which is often difficult with
Pd catalysts due to regioselectivity issues and retarded reductive
elimination. We found that in-situ formed gold metal nanoparticles
are highly active catalysts, which are still very efficient on a 50
ppm level loading. The presence of active carbon as solid support
was found to be beneficial for high catalytic activity of the AuNPs
and to facilitate catalyst recovery and reuse. No Au leaching was
detected. The present study is a rare case where a gold metal
catalyst is superior to Pd catalysts in a cross coupling reaction of
an organic halide and a organometallic reagent.
To get more information about the nature of the active catalyst
generated during the reaction, an XRD analysis of the Au@AC
material formed during the catalytic reaction (0.25 mol%
(Me2S)AuCl, 6.7 wt% Au/AC, 50 °C, 3 h) was performed. Nano-
crystalline Au domains were identified with an average size of 19
nm. Moreover, transmission electron microscopy (TEM) images
were taken of Au@AC with different Au loadings. For the standard
material with 6.7 wt% Au/AC, a polydispersive distribution of Au
particles typically ranging from 6.3 nm to 32.0 nm was found plus
some very large Au agglomerates around 100-130 nm were
occasionally found. For 2.3 wt% Au/AC, most of the Au particles
were ranging from 6.2 nm to 17.5 nm, still with a very broad
distribution. Also here, some large Au agglomerates around 50
nm were occasionally observed. For 0.13 wt% Au/AC, only few
particles were detected and ranged from 5.3 nm to 16.3 nm, with
most particles around 11.5 nm. Since higher AC amounts
increased the activity (see Table 2, entry 2), it seems reasonable
that these smaller particles display a particularly high activity.
Acknowledgements
This work was financially supported by the Deutsche
Forschungsgemeinschaft (DFG, PE 818/6-1). We thank the van
Aken research group at the Max Planck Institute for Solid State
Research, Stuttgart, for recording TEM images. Moreover, we
thank Heike Fingerle (Institut für Technische Chemie, Univ.
Stuttgart) for the ICP-OES determinations and Peter
Schützendübe (MPI IS Stuttgart) for the XPS measurements.
Figure 2. TEM images of Au@AC. a 0.13 wt% Au@AC; b: 6.7 wt% Au@AC.
Keywords: gold nanoparticles • heterogeneous catalysis •
stannane • solid support • Stille coupling
By Inductively Coupled Plasma Optical Emission Spectrometry
(ICP-OES) it was determined that about 93% of Au(0) atoms were
adsorbed on the AC after a catalytic run in which the AuNPs were
formed in-situ from (Me2S)AuCl (0.25 mol%, 6.7 wt% Au/AC,
50 °C, 3 h). On the other hand, no Au was detectable anymore in
the reaction solution. Gratifyingly, there was also no Au leaching
using the reisolated catalysts as judged from ICP
measurements.[20]
XPS studies of the Au@AC formed during a catalytic reaction
revealed a binding energy for Au 4f7/2 of 83.7 eV, which is
comparable to the binding energy found for Au(0) (83.8 eV).[21]
Although the Au@AC was washed several times with CH2Cl2 after
the reaction, not only gold but also tin was found with a binding
energy for Sn 3d5/2 of 486.6 eV. Compared to the binding energy
of Sn(0) (484.9 eV) or AuSn alloys (485.2 – 485.35 eV), the value
is shifted to higher energies and is comparable to the binding
energy of other organotin(IV) compounds (486.9 – 487.2 eV).[22]
Au/Sn(0) alloy NPs are thus excluded. The Sn(IV) reagent is
probably adsorbed in the pores of the active carbon. To confirm
this assumption allylstannane and active carbon were stirred
under the typical reaction conditions yet in the absence of the gold
source. After thorough washing, tin was still detected with a very
similar binding energy for Sn 3d5/2 of 486.7 eV.[23]
[1]
a) M. Kosugi, Y. Shimizu, T. Migita, Chem. Lett. 1977, 1423; b) D.
Milstein, J. K. Stille, J. Am. Chem. Soc. 1978, 100, 3636; c) J. K. Stille,
Angew. Chem. Int. Ed. 1986, 25, 508; d) P. Espinet, A. M. Echavarren,
Angew. Chem. Int. Ed. 2004, 43, 4704
[2]
[3]
V. Farina, V. Krishnamurthy, W. J. Scott, Org. React. 1997, 50, 1.
For a Pd free version using very high pressure (104 bar), see: Y.
Yamamoto, K. Maruyama, K. Matsumoto, J. Chem. Soc., Chem.
Commun. 1984, 548.
[4]
Alternative ways to construct these bonds from alcohols or derivatives
thereof and allylstannanes or -silanes have been developed requiring the
presence of Lewis acids for the formation of carbocation intermediates.
Selected examples: a) A. Hosomi, T. Imai, M. Endo, H. Sakurai, J.
Organomet. Chem. 1985, 285, 95; b) M. Yasuda, T. Saito, M. Ueba, A.
Baba, Angew. Chem. Int. Ed. 2004, 43, 1414; c) T. Saito, Y. Nishimoto,
M. Yasuda, A. Baba, J. Org. Chem. 2006, 71, 8516; d) Y. Kuninobu, E.
Ishii, K. Takai, Angew. Chem. Int. Ed. 2007, 46, 3296; e) G. Onodera, E.
Yamamoto, S. Tonegawa, M. Iezumi, R. Takeuchi, Adv. Synth. Catal.
2011, 353, 2013.
[5]
Selected reviews on gold catalysis: a) A. S. K. Hashmi, F. D. Toste (eds.),
Modern Gold Catalyzed Synthesis, Wiley-VCH, Weinheim, 2012; b) A. S.
K. Hashmi, Acc. Chem. Res. 2014, 47, 864; c) Y.-M. Wang, A. D.
Lackner, F. D. Toste, Acc. Chem. Res. 2014, 47, 889; d) C. Obradors, A.
This article is protected by copyright. All rights reserved.

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
M. Echavarren, Acc. Chem. Res. 2014, 47, 902; e) C. Obradors, A. M.
Echavarren, Chem. Commun. 2014, 50, 16; f) I. Braun, A. M. Asiri, A. S.
K. Hashmi, ACS Catal. 2013, 3, 1902; g) N. Krause in Organometallics
in Synthesis: Fourth Manual (Ed. Lipshutz, B. H.), 2013, pp. 429-540; h)
A. Gomez-Suarez, S. P. Nolan, Angew. Chem. Int. Ed. 2012, 51, 8156;
i) A. Fürstner, P. W. Davies, Angew. Chem. Int. Ed. 2007, 46, 3410; j) A.
S. K. Hashmi, Chem. Rev. 2007, 107, 3180; k) D. Gorin, B. Sherry, F. D.
Toste, Chem. Rev. 2008, 108, 3351.
[19] For related studies see e.g. also ref. 10d and a) J. Oliver-Meseguer, M.
Boronat, A. Vidal-Moya, P. Concepciꢀn, M. ꢁngel Rivero-Crespo, A.
Leyva-Pꢂrez, A. Corma, J. Am. Chem. Soc. 2018, 140, 3215; M.
Kidonakis, M. Stratakis, ACS Catal. 2018, 8, 1227.
[20] The detection limit of the ICP-OES machine employed is below 1000 ppb.
[21] M. Camalli, F. Caruso, G. Mattogno, E. Rivarola, Inorg. Chim. Acta 1990,
170, 225.
[22] a) N. H. Turner, A. M. Single, Surf. Interface Anal. 1990, 15, 215; b) J. A.
Taylor, S. M. Merchant, D. L. Perry, J. Appl. Phys. 1995, 78, 5356.
[23] Very small amounts of sulfur were also found in the recycled catalyst (see
Supporting Information).
[6]
[7]
Reviews on AuNP catalysis: a) M. Stratakis, H. Garcia, Chem. Rev.
2012, 112, 4469; b) Y. Zhang, X. Cui, F. Shi, Y. Deng, Chem. Rev. 2012,
112, 2467; c) B. S. Takale, M. Bao, Y. Yamamoto, Org. Biomol. Chem.
2014, 12, 2005; d) A. Corma, H. Garcia, Chem. Soc. Rev. 2008, 37,
2096, e) A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. Int. Ed. 2006,
45, 7896.
[24] F. Porta, L. Prati, M. Rossi, G. Scari, J. Catal. 2002, 211, 464.
[25] TiO2 (rutile, particle size <5 µM) was also studied as support for the in-
situ generated AuNPs, but gave a less active catalyst (see Supporting
Information). The choice of support is thus an important factor, as well.
Selected examples for the use of Au nanoclusters and NPs as catalysts:
a) H. Tsunoyama, N. Ichikuni, H. Sakurai, T. Tsukuda, J. Am. Chem. Soc.
2009, 131, 7086; b) H. Miyamura, R. Matsubara, Y. Miyazaki, S.
Kobayashi, Angew. Chem. Int. Ed. 2007, 46, 4151; c) A. Noujima, T.
Mitsudome, T. Mizugaki, K. Jitsukawa, K. Kaneda, Angew. Chem. Int. Ed.
2011, 50, 2986; d) Y. M. Liu, H. Tsunoyama, T. Akita, S. H. Xie, T.
Tsukuda, ACS Catal. 2011, 1, 2; e) J. Oliver-Meseguer, J. R. Cabrero-
Antonino, I. Dominguez, A. Leyva-Perez, A. Corma, Science 2012, 338,
1452; f) H. Miyamura, H. Min, J.-F. Soulé, S. Kobayashi, Angew. Chem.
Int. Ed. 2015, 54, 7564.
[8]
[9]
E.-i. Negishi, A. de Meijere (eds.), Handbook of Organopalladium
Chemistry for Organic Synthesis, Wiley-Interscience, New York, 2002.
J. Han, Y. Liu, R. Guo, J. Am. Chem. Soc. 2009, 131, 2060.
[10] a) C. Gonzalez-Arellano, A. Abad, A. Corma, H. Garcia, M. Iglesias, F.
Sanchez, Angew. Chem. Int. Ed. 2007, 46, 1536; b) V. K. Kanuru, G.
Kyriakou, S. K. Beaumont, A. C. Papageorgiou, D. J. Watson, R. M.
Lambert, J. Am. Chem. Soc. 2010, 132, 8081; c) S. K. Beaumont, G.
Kyriakou, R. M. Lambert, J. Am. Chem. Soc. 2010, 132, 12246; d) G.
Kyriakou, S. K. Beaumont, S. M. Humphrey, C. Antonetti, R. M. Lambert,
ChemCatChem 2010, 2, 1444; e) R. O. M. A. de Souza, M. S. Bittar, L.
V. P. Mendes, C. M. F. da Silva, V. T. da Silva, O. A. C. Antunes, Synlett
2008, 1777; f) A. Corma, R. Juárez, M. Boronat, F. Sánchez, M. Iglesias,
H. García, Chem. Commun. 2011, 47, 1446.
[11] Recently it was shown that a gold(I)-cocatalyst can accelerate Pd-
catalyzed Stille couplings: a) J. delPozo, D. Carrasco, M. H. Pérez-
Temprano, J. A. Casares, P. Espinet, Angew. Chem. Int. Ed. 2013, 52,
2189; b) J. delPozo, J. A. Casares, P. Espinet, Chem. Commun. 2013,
49, 7246; c) for a Au catalyzed intramolecular allyl-allyl coupling see: S.
Porcel, V. López‐Carrillo, C. García‐Yebra, A. M. Echavarren, Angew.
Chem. Int. Ed. 2008, 47, 1883.
[12] M. D. Levin, F. D. Toste, Angew. Chem. Int. Ed. 2014, 53, 6211.
[13] a) M. Ayerbe Garcia, W. Frey, M. Ringenberg, M. Schwilk, R. Peters,
Chem. Commun. 2015, 51, 16806; b) J. Holz, M. Ayerbe García, W. Frey,
F. Krupp, R. Peters, Dalton Trans. 2018, 47, 3880.
[14] X. Yang, M. Yang, B. Pang, M. Vara, Y. Xia, Chem. Rev. 2015, 115,
10410.
[15] Selected examples for AuNPs on AC: a) S. Carrettin, P. McMorn, P.
Johnston, K. Griffin, G. J. Hutchings, Chem. Commun. 2002, 696; b) G.
M. Veith, A. R. Lupini, S. J. Pennycook, A. Villa, L. Prati, N. J. Dudney,
Catalysis Today 2007, 122, 248; c) S. Yan, S. Zhang, Y. Lin, G. Liu, J.
Phys. Chem. C 2011, 115, 6986; d) M. Roosta, M. Ghaedi, N. Shokri, A.
Daneshfar, R. Sahraei, A. Asghari, Spectrochim. Acta, Part A 2014, 118,
55.
[16] See e.g.: P. Sathishkumar, M. Arulkumar, T. Palvannan, J. Clean. Prod.
2012, 22, 67.
[17] To get a realistic picture of the reaction efficiency, yields were determined
by 1H-NMR of the crude product using an internal standard, because of
loss of products during solvent removal in the rotavap after column
chromatography.
[18] γ-Substituents on the allyl reagent led to complex mixtures of various
isomers.
This article is protected by copyright. All rights reserved.

10.1002/anie.201902352
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Black gold: In-situ formed gold metal
nanoparticles are highly active catalysts
for the cross coupling of allylstannanes
and activated alkylbromides to form Csp3–
Csp3 bonds. Turnover numbers up to
29000 could be achieved in the presence
of active carbon as solid support, which
allowed for convenient catalyst recovery
and reuse. The present study is a rare
case where a gold metal catalyst is
superior to Pd catalysts in a cross
Julia Holz, Camilla Pfeffer, Hualiang Zuo,
Dennis Beierlein, Gunther Richter, Elias
Klemm, and René Peters*
Page No. – Page No.
In-situ Generated Gold Nanoparticles on
Active Carbon as Reusable Highly
Efficient Catalysts for Csp3–Csp3 Stille
Coupling
coupling reaction of an organic halide
and an organometallic reagent.
This article is protected by copyright. All rights reserved.