Reductive C-C Coupling by Desulfurizing Gold-Catalyzed Photoreactions

Article abstract of DOI:10.1021/acscatal.9b01368

[Au₂(μ-dppm)₂]Cl₂-mediated photocatalysis reactions are usually initiated by ultraviolet A (UVA) light; herein, an unreported system using blue light-emitting diodes (LEDs) as excitation light source was found. The red shift of the absorption wavelength originates from the combination of [Au₂(μ-dppm)₂]Cl₂ and ligand (Ph₃P or mercaptan). On the basis of this finding, a gold-catalyzed reductive desulfurizing C-C coupling of electrophilic radicals and styrenes mediated by blue LEDs is presented, a coupling which cannot be efficiently accessed by previously reported methods. This mild and highly efficient C-C bond formation strategy uses mercaptans both as electron-deficient alkyl radical precursor as well as the hydrogen source. Two examples of amino acids have also been modified by using this strategy. Moreover, this methodology could be applied in polymer synthesis. Gram-scale synthesis and mechanistic insights into this transformation are also presented.

Full text of DOI:10.1021/acscatal.9b01368

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Article
Reductive C-C Coupling by Desulfurizing Gold-Catalyzed Photo-reactions
Lumin Zhang, Xiaojia Si, Yangyang Yang, Sina Witzel, Kohei Sekine,
Matthias Rudolph, Frank Rominger, and A. Stephen K. Hashmi
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.9b01368 • Publication Date (Web): 24 May 2019
Downloaded from http://pubs.acs.org on May 24, 2019
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ACS Catalysis
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Reductive C-C Coupling by Desulfurizing Gold-Catalyzed
Photoreactions
Lumin Zhang,[†] Xiaojia Si,[†] Yangyang Yang,[†] Sina Witzel,[†] Kohei Sekine,[†] Matthias Rudolph,[†]
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Frank Rominger,[†] and A. Stephen K. Hashmi[†,‡]
*
†Organisch-Chemisches Institut, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
‡ Chemistry Department, Faculty of Science, King Abdulaziz University (KAU), Jeddah 21589, Saudi Arabia
ABSTRACT: [Au2(μ-dppm)2]Cl2-mediated photocatalysis reactions are usually initiated by UVA light, herein, an unreported system
which using blue LEDs as excitation light source was found. The red shift of the absorption wavelength originates from the
combination of [Au2(μ-dppm)2]Cl2 and ligand (Ph3P or mercaptan). Based on this finding, a gold-catalyzed reductive desulfurizing
C-C coupling of electrophilic radicals and styrenes mediated by blue-LEDs is presented, a coupling which cannot be efficiently
accessed by previously reported methods. This mild and highly efficient C-C bond formation strategy uses mercaptans both as
electron-deficient alkyl radical precursor as well as the hydrogen source. Two examples of amino acids have also been modified by
using this strategy. Moreover, this methodology could be applied in polymer synthesis. Gram scale synthesis and mechanistic insights
into this transformation are also presented. KEYWORDS: photoreaction, gold catalysis, radical C-C coupling, desulfurization, blue
LEDs
Photochemistry has become one of the most dynamic and
powerful manifolds in today’s synthetic chemistry as it offers
the opportunity to induce radical chemistry under extremely
mild conditions.1-7 During the last years, our group has
dedicated considerable effort to develop novel methodologies
relying on light-driven processes.8-16 Based on our’s8,9 and
other group’s studies,5,17 the binuclear bis(diphosphine)
complex [Au2(μ-dppm)2]Cl2 (dppm = bis(diphenylphosphino)-
methane) has gradually proven to be very useful in
photocatalysis. However, the requirement of UVA light as the
light source (Scheme 1, 1a) inherently prevents its application,
especially for selectivity studies and the invention of new
reactions. Interestingly, the combination of [Au2(μ-dppm)2]Cl2
with a ligand (Ph3P or mercaptan) provides a bathochromic
shift on UV-vis absorptions (see SI), this means a novel
species is generated. Subsequently, after irradiation with blue
LEDs, if oxygen is not excluded, Ph3P is oxidized by O2, or
under an atmosphere of dinitrogen, by 4-iodoanisole in the
presence of substochiometric amount of [Au2(μ-dppm)2]Cl2
(Scheme 1, 2a and SI). In addition, disulfide and
desulfurization products are produced by irradiating the
mixture of [Au2(μ-dppm)2]Cl2 and mercaptans (stoichiometric
experiment, see SI), hypothetically forming a thiyl radical by
going through ligand to metal charge transfer (S→Au)
process.18-21 These new findings inspired us that the
combination of Ph3P or mercaptan with [Au2(μ-dppm)2]Cl2
would not only form a new species which can absorb blue
light but also offer the possibility for a use in photocatalysis.
Based on our new findings and previous studies on
radical initiator. However, that report shows only 12
examples, and a large excess of alkenes has to be used
(aliphatic olefins, 10.0 eqs) at 80 oC.
Traditionally, alkyl radicals are generated by reduction alkyl
halides, the radical initiator or hydrogen atom donor required
for a subsequent C-C coupling is toxic (organotin
compounds),24 potentially explosive (AIBN and peroxides), or
pyrophoric (trialkylboranes).25 With the rapid development of
metal-based photocatalysts in the last decade,1-7 a large
number of reactions involving alkyl radical have been
reported.26-33 However, reductive electron-deficient alkyl
radical addition with styrenes is rare, probably, because stable
benzyl radical which has been formed by radical addition on
styrene is readily oxidized to a benzyl cation, followed by a β-
H elimination to form styrene products, or nucleophilic
trapping by methanol or halogen anions. Although in some
cases, the reductive addition can proceed by introducing an
excess of a hydrogen donating reagent, such NEt3, DIPEA,
NMP, Hantzsch ester or formic acid, the reaction is still
limited to aliphatic alkenes. One distinct example was reported
by Qing’s group,34 under the same reaction conditions, for
aliphatic alkenes, reductive radical addition products were
produced. However, only alkenyl products were formed for
reaction with styrenes. The only strategy by using phosphorus
ylide as the precursor of an (alkoxycarbonyl)methyl radical
species35 has been reported recently. This reaction is a distinct
pre-functionalization strategy which needs several equivalent
of substrates and additives, only low yields are obtained (43%)
and the substrate scope is limited to ester substituents.
Furthermore, our attempts to utilize common α-bromo esters
to react with styrene by following reported photocatalysis
methodologies (Scheme 1, 1b) all failed to yield the desired
product. Given that, we now provide a novel and convenient
methodology using mercaptans as both electron-deficient alkyl
radical precursor and hydrogen source, catalyzed by a dimeric
mercaptans,22 we envisaged that mercaptans could act as the
precursor of alkyl radical and hydrogen donating group which
would possibly further react with alkenes to form a C-C bond.
The strategy of combining desulfurization and C-C coupling
has only been reported once before,23 by forming thioimidoyl
radicals through reacting tBuNC with thiols and AIBN as
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Photocatalyst
gold complex to achieve a reductive radical addition with
styrenes under blue LEDs light (Scheme 1, 2b).
Phosphine
+
1
Ph
HS
COOMe
Ph
COOMe
MeCN
2
1a
2a
3aa
Blue LED
1) Previous studies
3
4
5
6
7
8
9
a) Traditional way for activating photocatalyst [Au2(-dppm)2]Cl2
3aab
Entry
1a
+
2a
+
Phosphine
Ph3P
-
Blue LED
Photocatalyst
1
2
3
+
+
-
92%
trace
- (-)*
[Au2(-dppm)2]Cl2
[Au2(-dppm)2]Cl2
[Au2(-dppm)2]Cl2
+
+
+
+
Ph3P
b) Attempts to react methyl bromoacetate with styrene
4
5
+
+
+
+
Ph3P
Ph3P
+
-
-
-
trace
- (-)*
1) [Au2(-dppm)2]Cl2, DIPEA, UVA
2) [Ir(ppy)2(dtbbpy)]PF6, DIPEA, Blue LEDs
3) [Ir(ppy)2(dtbbpy)]PF6, DIPEA, Blue LEDS
Hantzsch ester
6
7
8
+
+
+
+
-
-
+
-
-
-
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Ph
COOMe
+
Br
COOMe
Ph
4) [Ru(bpy)3]PF6, DIPEA, Blue LEDs
- (-)*
64%
[Au2(-dppm)2]Cl2
[Ir(ppy)2(dtbbpy)]PF6
5) [Ru(bpy)3]PF6, DIPEA, Blue LEDs
Hantzsch ester
+
+
Ph3P
+
6) AIBN, n-Bu3SnH, 80 o
C
9
+
+
+
+
Ph3P
Ph3P
+
+
[Ru(bpy)3](PF6)2
Eosin Y
3%
10
20%
2) Our new concepts
-
11
+
+
+
+
Ph3P
dppm
+
+
Mes-Acr-Me+BF4
-
a) Shift the light source from traditional UVA light to Blue LEDs
12
82%
[Au2(-dppm)2]Cl2
aReactions were run with 1.0 mL of the mixture of styrene (1.0 eq)
and mercaptan (1.2 eqs) in MeCN (0.2 M), photocatalyst (2.5
mol %), phosphorous (1.3 eqs) for 24 h. bYield determined by 1H
NMR analysis using 1,3,5-trimethoxybenzene as the internal
standard. *Heating at 55 oC if no reaction without light.
With optimized conditions in hand, we next determined the
generality of the styrene components in this desulfurizing C-C
coupling reaction. As shown in Table 2, electron-rich styrenes
containing one or several alkyl or methoxy groups performed
well (3ab-3ag, 86-88% yield). A diverse array of electron-
withdrawing substituents (halogens, trifluoromethyl, boronic
esters and ketones) in the o-, m- or p-position of the styrene
derivatives (3ah-3al, 3am-3ao) gave the corresponding
desulfurized C-C coupling products in 71-95% yield. The
TMS-protected alkynyl styrene and 2-vinylnaphthalene
substrates were also coupled with high efficiency (3am and
3ap, 84% and 96% yield). Multi-substituted and cyclic styrene
derivatives also readily underwent this C-C coupling (3aq-
3au, 83-97% yield). Even heteroaromatic coupling partners,
which are notoriously problematic for many photoredox
coupling technologies, performed well under these reaction
conditions (3av-3az, 74-82% yield).
b) Reductive C-C coupling by desulfurizing gold-catalyzed photoreactions
Blue LEDs
R1
R1
[Au2(-dppm)]2Cl2
H
+
Ph3P=S
R2
+
EWG
HS
EWG
Ar
Ph3
P
Ar
R2
MeCN
Scheme 1. Previous studies and our new concepts
In our initial experiments indeed C-C coupling method
could be achieved in 92% isolated yield by using styrene and
methyl thioglycolate as coupling partners, Ph3P as the
phosphorous source, in the presence of [Au2(μ-dppm)2]Cl2,
MeCN by exposure to blue LED lights (Table 1, entry 1).
Control experiments indicated that none or only traces of
desulfurizing C-C coupling product 3aa were produced in the
absence of either phosphorous source, blue led or
photocatalyst (entry 2-7). Without light (entry 3, 5, 7), no C-C
coupling product was formed after heating at 55 oC for 24 h,
which excludes the possibility of a thermal reaction (e.g.
warming by light). The use of other photosensitizers of
[Ir(ppy)2(dtbbpy)]PF6, [Ru(bpy)3](PF6)2, Eosin Y, or Mes-Acr-
Me+BF4 instead of the [Au2(μ-dppm)2]Cl2 resulted in lower
yields or no desired product (entry 8-11). Furthermore,
decreased yields were obtained with other phosphine sources
(entry 12).
-
Table 1. Initial Studies and control experimentsa
Table 2. Scope with regard to the styrene substratesa
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Table 3. Scope with regard to the mercaptansa
Blue LEDs
[Au2(-dppm)]2Cl2
Blue LEDs
1
2
+
Ar
COOMe
Ar
HS
COOMe
2a
[Au2(-dppm)]2Cl2
Ph3P
+
Ph
HS
R
Ph
R
3
1
MeCN
Ph3P
3
3
MeCN
1a
2
4
5
6
7
8
9
COOMe
COOMe
COOMe
Ph
COOMe
COOn-Bu
O
3aa, 92%
3ab, 86%
3ac, 87%
OMe
3aa, 92%
3ba, 88%
3ca, 82%
3fa, 85%
COOMe
COOMe
COOMe
Ph
Ph
O
MeO
MeO
OMe
O
O
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3ad, 87%
3ag, 87%
3ae, 86%
3af, 88%
3ai, 90%
3da, 96%
3ea, 42%
COOMe
COOMe
COOMe
CF3
tBu
F
Br
CF3
CN
3ah, 89%
CF3
3ga, 62%
3ha, 88%
3ia, 77%
COOMe
COOMe
COOMe
F3C
Br
Cl
3aj, 84%
3ak, 91%
3al, 71%
aIsolated yields. Performed with photocatalyst (2.5 mol%), styrene
(1.0 eq), mercaptan (1.2 eqs), Ph3P (1.3 eqs), in MeCN (0.2 M) for
24-36 h. See Supporting Information.
COOMe
TMS
COOMe
COOMe
PinB
With unactivated alkenes the major product is simple
desulfuration, with 4-phenylbut-1-ene only 22% of C-C
coupling are observed.
O
3am, 84%
3an, 91%
3ao, 95%
COOMe
Furthermore, this methodology has been successfully
applied in the modification of small amino acids fragments
(Scheme 2a). Both linear amino acid 4 with free NH group and
protected proline substrate 6 has been converted to 5 and 7 in
78% and 83% yield, respectively. This application could
provide the possibility of using this novel methodology in the
modification of peptides. Our gram scale synthesis also
worked very well by extending the reaction time with 0.25
mol% of [Au2(μ-dppm)2]Cl2 (Scheme 2b).
COOMe
COOMe
3ap, 96%
3aq, 84%
3ar, 86%
COOMe
COOMe
Ph
COOMe
3as, 97%
3at, 83%
3au, 85%
COOMe
a) Modification of amino acids derivatives
COOMe
N
COOMe
Ph
Blue LED
Ph
O
O
2.5 mol% [Au2(-dppm)2]Cl2
N
N
Ph
OMe
HS
OMe
(1)
+
N
H
N
Ph
N
H
O
Ph3P (1.3 eqs)
MeCN (1.0 mL)
48 h
O
3av, 75%
3aw, 79%
3ax, 74%
5
, 78%
4
1a (0.2 mmol, 1.0 eqs)
(1.2 eqs)
S
COOMe
COOMe
S
Blue LED
O
Br
O
N
Ph
2.5 mol% [Au2(-dppm)2]Cl2
HS
N
+
Ph
3ay, 82%
3az, 77%
(2)
Ph3P (1.3 eqs)
MeCN (1.0 mL)
60 h
MeOOC
MeOOC
aIsolated yields. Performed with photocatalyst (2.5 mol%), styrene
(1.0 eq), mercaptan (1.2 eqs), Ph3P (1.3 eqs), in MeCN (0.2 M) for
24-36 h. See Supporting Information.
1a (0.2 mmol, 1.0 eqs)
6
(1.2 eqs)
7
, 83%
b) Gram scale synthesis
We next investigated the scope with regard to the
mercaptans. As shown in Table 3, α-mercaptyl ketones
containing alkyl or phenyl groups, both provided 88% and
82% yield (3ba and 3ca). Moreover, a secondary mercaptan
also reacted efficiency under these conditions (3da, 96%
yield). A tertiary mercaptan was also tolerated, albeit in
slightly diminished yield (3ea, 42% yield). A cyclic mercaptan
was also shown to be a competent substrate (3fa, 85% yield).
For α-mercaptyl-trifluoroethane and -nitrile can also couple
with styrene to obtain the desired product in good yield (3ga-
3ha, 62-88% yield). Trifluoromethyl-substituted benzyl
mercaptan generated the desulfurized C-C coupling product in
77% yield (3ia).
Blue LED
0.25 mol% [Au2(-dppm)2]Cl2
+
Ph
Ph
CO2Me
HS
CO2Me
Ph3P (1.3 eqs)
MeCN (20 mL)
1a (1.0 g)
2a
(1.2 eqs)
3aa
, 82%
72 h
Scheme 2. Modification of amino acids derivatives and
gram scale synthesis.
We further demonstrated the application of this desulfurized
C-C coupling methodology by the synthesis of polymer 13
(Scheme 3). The attempt to react both monomer 8 and 10 with
2a and 1a, respectively, are both working well. Polymer 13
has been successfully synthesized by using this strategy with
the number-average weight (Mn) is 6735 g mol-1, and the
polydispersity (Ð) is 1.5.
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Page 4 of 7
1)
1
2
3
4
Blue LEDs
COOMe
2.5 mol% [Au2(-dppm)2]Cl2
HS
COOMe
+
MeOOC
Ph3P (2.4 eqs)
MeCN (1.0 mL)
36 h
2a
, 2.2 eqs
8 (
9
, 81%
0.2 mmol, 1.0 eq)
5
2)
6
7
8
9
Blue LEDs
O
O
O
Ph
2.5 mol% [Au2(-dppm)2]Cl2
HS
O
+
Ph
O
O
+
Ph
O
Ph
O
SH
O
Ph
O
S
Ph3P (1.4 eqs)
O
O
MeCN (1.0 mL)
36 h
10
, 0.6 eq
1a
3)
(0.2 mmol, 1.0 eq)
11
12
, 38%
, 55%
10
11
12
13
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Blue LEDs
O
O
2.5 mol% [Au2(-dppm)2]Cl2
O
HS
O
+
O
O
SH
O
n
Ph3P (2.4 eqs)
O
O
O
O
S
MeCN (1.0 mL)
60 h
m
O
8
(0.2 mmol, 1.0 eq)
10
, 1.0 eq
13
Mn = 6.735E+3 g/mol
D = 1.472E+0
Scheme 3. Application for polymer synthesis.
a) Inhibition experiment
Concerning the mechanism, an inhibition experiment has
been performed by adding TEMPO as radical inhibitor, no
desired product was detected (Scheme 4a). Moreover, the
reaction of 1-phenyl-2-(1-phenylethenyl)cyclopropane 14 was
also examined (Scheme 4b), the desulfurized C-C coupling
product 15 was obtained in 92% yield through a ring-opening
process of the cyclopropane unit, thus we presumed that a
radical process is operative. Deuterium experiments have been
performed, which indicated that thiol was not the only
hydrogen source (see SI). The hydrogen would also come
from the water contained in the solvent without deteriorating
the yield of desulfurized C-C coupling which means this
reaction can be performed in water solution (see SI). Control
experiments showed that thiol addition and the desulfurized
products were also detected (Scheme 4c). Quantum yield (Ф =
19.5%) (See SI) has been measured to certify that the
photocatalyst is regenerated during the reaction. However
radical chain propagation could also be involved in this
reaction based on our control experiment that this reaction is
also performed well in the condition of AIBN as initiator at 80
oC (see SI). More details of fundamental mechanism studies
can be found in our supporting information.
Blue LEDs
2.5 mol%[Au2(-dppm)]2Cl2
Ph
COOMe
3aa, n.d.
+
Ph
HS
COOMe
Ph3P, 1.3 eqs
MeCN (1.0 mL)
TEMPO (1.2 eqs)
2a, 1.2 eqs
1a (0.2 mmol, 1.0 eq)
b) Radical clock reaction
Blue LEDs
Ph
2.5 mol%[Au2(-dppm)]2Cl2
Ph
HS
COOMe
+
MeOOC
Ph
Ph
Ph3P, 1.3 eqs
MeCN (1.0 mL)
2a, 1.2 eqs
15, 92% (Z/E=1:15)
14 (0.2 mmol, 1.0 eq)
c) Control experiments
+
O
Blue LEDs
2.5 mol%[Au2(-dppm)]2Cl2
S
Ph
Ph
Ph
(1)
(2)
Ph
HS
MeCN (1.0 mL)
O
18, 90%
1a (0.2 mmol, 1.0 eq)
2da, 1.2 eqs
Blue LEDs
2.5 mol%[Au2(-dppm)]2Cl2
Ph
Ph
Ph3PS
+
HS
Ph3P, 1.3 eqs
MeCN (1.0 mL)
O
O
19, 93%
20
2da
Scheme 4. Mechanistic experiments.
Ph3P
S
(isolated)
*{[Au2(-dppm)2](2a)}2+
20
HS
COOMe
2a
Ph
COOMe
Blue LEDs
23
LMCT
{[Au2(-dppm)2](2a)}2+
Ph
1a
Radical chain propagation
New gold complex
Photoredox catalysis
Ph
COOMe
Desulfurized C-C Coupling
3aa
Ph3P
S
COOMe
Ph3P
HS
COOMe
21
-H+
22
S
COOMe
HS
COOMe
Ph
{[Au2(-dppm)2]}+
2a
[Au2(-dppm)2]Cl2
H
H
COOMe
Ph
COOMe
Ph
COOMe
Ph3P
3aa
O2
O2
23
24
Figure 1. Proposed mechanism
Based on previous studies18-22, 42-44 and our experiments, a
possible mechanism is shown in Figure 1. This desulfurizing
C-C-coupling photoreaction is catalyzed by the combination
of [Au2(μ-dppm)2]Cl2 with mercaptan to form a three-
coordinated gold complex36-39 or the combination of [Au2(μ-
dppm)2]Cl2, Ph3P and mercaptan which would act as the
photosensitizer. Upon irradiation with Blue LEDs,
intermediate 21 is formed by going through the process of
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LMCT,20,40 this radical cation further reacts with Ph3P and
generates a phosphoranyl radical 22, which by going through a
β-scission and radical addition to styrene, provides an alkyl
radical 23. The alkyl radical further abstracts a hydrogen atom
from the thiol (S-H BDE = 87.2 Kcal/mol),41 generating the
desulfurized C-C coupling product 3aa and a thiol radical. The
reduced gold catalyst would be converted to the original
[Au2(μ-dppm)2]2+ species either by reducing radical 23 to the
anion 24 or by being oxidized by a trace amount of O2
Advances in Organic Transformations Using Photoredox Gold
Catalysis. Synlett 2016, 28, 289–305.
1
2
3
4
5
6
7
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。In conclusion, the combination of [Au2(μ-dppm)2]Cl2
with ligand (Ph3P or mercaptan) exhibited the possibility for
new reaction inventions under blue LEDs lights. Moreover a
highly efficient C-C coupling by a desulfurizing gold-
catalyzed radical reaction has been explored under blue LEDs
using inexpensive, air-stable Ph3P as the phosphorous source.
This method can be a crucial foundation for studying C-C
coupling by desulfurizing under mild and water-soluble
reaction environment in both organic synthetic chemistry,
bioorganic chemistry and also shows new options for polymer
synthesis
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ASSOCIATED CONTENT
Accession Code
CCDC 1907518 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge
Crystallographic
Data
Centre
via
https://www.ccdc.cam.ac.uk/structures/.
(14) Xie, J.; Rudolph, M.; Rominger, F.; Hashmi, A. S. K.
Photoredox-Controlled Mono-and Di-Multifluoroarylation of C(sp3)-H
Bonds with Aryl Fluorides. Angew. Chem. Int. Ed. 2017, 56, 7266–
7270.
(15) Xie, J.; Sekine, K.; Witzel, S.; Krämer, P.; Rudolph, M.;
Rominger, F.; Hashmi, A. S. K. Light-Induced Gold-Catalyzed Hiyama
Arylation: A Coupling Access to Biarylboronates. Angew. Chem. Int.
Ed. 2018, 57, 16648–16653.
(16) Zhang, L.; Si, X.; Yang, Y.; Zimmer, M.; Witzel, S.; Sekine,
K.; Rudolph, M.; Hashmi, A. S. K. The Combination of Benzaldehyde
and Nickel-Catalyzed Photoredox sp3-C-H Alkylation/Arylation.
Angew. Chem. Int. Ed. 2019, 58, 1823–1827.
(17) Kwong, H. L.; Yam, V. W. W.; Li, D. D.; Che, C. M.
Photoinduced C-C Bond Formation from Alkyl Halides Catalysed by
Luminescent Dinuclear Gold(I) and Copper(I) Complexes. J. Chem.
Soc. Dalton Trans. 1992, 23, 3325–3329.
AUTHOR INFORMATION
Corresponding Author
* hashmi@hashmi.de
ORCID
A. Stephen K. Hashmi: 0000-0002-6720-8602
Notes
The authors declare no competing financial interest.
Supporting Information.
The supporting information is available free of charge via the
Internet at http://pubs.acs.org.
Experimental procedures and compound characterization (PDF)
(18) Tiekinka, E. R.T.; Kangb, J. G. Luminescence Properties of
Phosphinegold(I) Halides and Thiolates. Coord. Chem. Rev. 2009, 253,
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S.; Back, D. F.; Flores, A. F. C.; Júnior, A. M.; Deflon, V. M.;
Casagrande, G. A. The First Gold(I) Complexes Based on
ACKNOWLEDGMENT
L.Z., X.S., and Y.Y. are grateful for PhD fellowships from the
China Scholarship Council (CSC). S.W. acknowledges the
support by the Landesgraduiertenförderung of the state of
Baden-Wügrttemberg, Germany. Also acknowledged is the
Excellence Cluster 3DMM2O of the German Excellence Strategy.
Thiocarbamoyl-Pyrazoline
Ligands:
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ACS Catalysis
Blue LEDs
R1
R1
H
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[Au ( -dppm)] Cl
2

2
2
R2
+
HS
EWG
Ar
EWG
Ar
R2
Ph3P
MeCN
40 examples
42-97% yields
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