Water Can Accelerate Homogeneous Gold Catalysis

Article abstract of DOI:10.1002/adsc.202100729

A selection of gold-catalyzed reactions was examined in a kinetic study on the influence of water on the rate constant. Two intramolecular reactions and one intermolecular reaction, which proceed via proton transfer and/or protodeauration steps, were inve

Full text of DOI:10.1002/adsc.202100729

COMMUNICATIONS
doi.org/10.1002/adsc.202100729
Water Can Accelerate Homogeneous Gold Catalysis
Philipp M. Stein,a Matthias Rudolph,a and A. Stephen K. Hashmia, b,*
a
Organisch-Chemisches Institut, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
E-mail: hashmi@hashmi.de
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
b
Manuscript received: June 11, 2021; Version of record online: ■■■, ■■■■
Supporting information for this article is available on the WWW under https://doi.org/10.1002/adsc.202100729
© 2021 The Authors. Advanced Synthesis & Catalysis published by Wiley-VCH GmbH. This is an open access article under the
terms of the Creative Commons Attribution Non-Commercial NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
are sufficient or whether more complex protecting gas
techniques and dry solvents have to be used in order to
Abstract: A selection of gold-catalyzed reactions
was examined in a kinetic study on the influence of
achieve an optimal reaction rate and conversion.
water on the rate constant. Two intramolecular
However, there are only a handful of publications
reactions and one intermolecular reaction, which
in literature dealing with the actual influence of water
proceed via proton transfer and/or protodeauration
on gold catalyzed reaction systems.[22] Early work on
steps, were investigated. The kinetic data was
1
nucleophilic additions of alcohols already indicated
collected by GC or H NMR spectroscopy. The
that hydroxyl groups are tolerated well,[23–25] and it was
obtained rate constants provided information about
mentioned early that no special precautions like the
the influence of water in these test reactions. On the
exclusion of humidity or air are necessary.[1–3] This led
basis of the data collected, beyond the commonly
to the ubiquitous knowledge that gold catalysis
assumed tolerance against water, a reaction-promot-
ing influence of water on gold catalysis was
identified and kinetically quantified. The results
typically tolerates water, but the coordination of water
was assumed to slow down the conversions by
competing with the coordination of the substrate.
underline that the often-mentioned water-tolerance
Of particular interest are reactions that include
of gold catalysis not only simplifies these reactions
protodeauration or proton transfer steps, since these
operationally, but in addition even provides better
steps may be even favored by the use of non-dry
results than a troublesome exclusion of water.
solvents or the addition of water. Such an example was
presented by Pernpointner in a DFT study of the
nucleophilic addition of methanol to propyne. The
Keywords: water; kinetic studies; reaction optimiza-
activation barriers indicated that the simple transfer of
tion; gold catalysis
protons via hydrogen bonds from water molecules,
with even small water clusters serving as highly
efficient proton shuttles, is a significant barrier-
In recent years, the transformation of organic sub- reducing factor. The water-assisted nucleophilic addi-
strates by gold catalysts has become increasingly tion made the chemical conversion more efficient.[26]
important and numerous new gold-catalyzed reaction With regard to the trend towards simple conditions for
types and gold catalysts have been developed.[1–13] sustainable chemistry, such research on the develop-
Especially, the latter are of crucial importance for the ment of water-tolerant catalysts represents an impor-
success of a reaction and can be optimized both by the tant contribution to catalysis research.[27]
choice of the ligand and by the counter anion.[14–20] The
Here we present the first study on the influence of
tremendous impact of the counter anion was recently well-quantified amounts of water on three prototypic
demonstrated in a strategic approach for industry.[21]
Nevertheless, classic parameters such as pressure,
gold-catalyzed reactions.
We started our kinetic investigation by selecting
temperature and choice of solvent, still play a decisive well-known and not too complex test systems in order
role in the success of a chemical reaction. In particular to precisely determine the influence of water on these
the choice of solvent raises the question whether gold-catalyzed processes. Therefore, the intramolecular
technical grade solvents with small amounts of water gold-catalyzed phenol synthesis was chosen as a first
Adv. Synth. Catal. 2021, 363, 1–9
1
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
potential test reaction.[1,3,28] This organic transformation
is a very efficient tool which enables the rapid
synthesis of highly substituted arenes from α- or β-
alkynyl furans. In addition, the corresponding catalytic
cycle involves cationic intermediates and a proton
transfer step,[29–30] which made this substrate type a
good candidate for the examination of the rate depend-
ence on the amount of added water.
Due to the high resolution in time of NMR kinetics
and the high reaction rate, this kinetic investigation
1
was conducted by in situ monitoring by H NMR
°
spectroscopy at 25 C, using a standardized procedure
to ensure the comparability (see the Supporting
Information for further details). The use of this
continuous measurement method enables the recording
Figure 1. Reaction course of the phenol synthesis in dry CD2Cl2
(Table 1; Entry 1).
1
of 512 H NMR spectra within a period of maximum
fourteen hours. For the test reactions one equivalent of
the furan-yne 1 was treated with 0.5 mol% IPrAuNTf2
in deuterated DCM containing varying amounts of
water (Scheme 1).
The choice of solvent and catalyst turned out to be
a decisive parameter. While the test reactions using
The obtained data confirmed the initially assumed AuCl3 in conventional acetonitrile reached a maximum
first order reaction by using the integration conversion of 47% after 12 hours (see the Supporting
method.[31–33] In addition, the rate constant was Information for further details), the analogous test
determined by standard kinetic methods using mathe- system with IPrAuNTf2 as catalyst led to an unselec-
matical correlations (see the Supporting Information tive reaction and only 20% of the desired phenol.
for further details). The results of the measured Changing the solvent to methylene chloride signifi-
kinetics of the phenol synthesis are listed in Table 1 cantly accelerated the reaction in the case of
and sorted by rising amount of water. An exemplary IPrAuNTf2, which is described in more detail in the
reaction progress is shown in Figure 1. In order to following experiments. First, the course of the reaction
simplify the comparison of the data, the relative rate was examined in the absence of water (Table 1;
constant krel of the test reaction under anhydrous entry 1). A comparatively high-rate constant was
conditions was normalized to krel =1.
obtained, which is also reflected by 75% conversion
within the first 12 minutes with 0.5 mol% of catalyst.
After 30 minutes 96% of starting material were
converted.
Then the water content in the test system was
gradually increased. Due to the low solubility of water
in methylene chloride, kinetic studies were carried out
for a 1.50 10À 1 wt% water content and in methylene
chloride saturated with water.
Scheme 1. Gold(I)-catalyzed phenol synthesis.
Table 1. Rate constants for phenol synthesis (CD2Cl2) depending on the water content.[a]
Entry
Water content
[wt%]
Conversion [%]
0.2 h
k1
R2
krel
0.5 h
[mL/(mmol*h)]
1
2
3
dry
75
85
89
96
96
96
8.83�0.15
12.02�0.57
17.21�0.83
0.998
0.993
0.998
1.00�0.02
1.36�0.07
1.95�0.10
1.50 10–1
Saturated
[a]
°
Reaction conditions: benzenesulfonamide alkyne (50.0 μmol, 50.0 μmol/ml), IPrAuNTf2 (0.5 mol%), in CD2Cl2 at T=25 C,
observed by 1H NMR monitoring for up to 2 h.
Adv. Synth. Catal. 2021, 363, 1–9
2
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
Furthermore, the water content of the freshly
In order to further investigate the influence of the
opened deuterated solvent and of the solvent saturated amount of water on the kinetics of gold-catalyzed
with water was determined using an internal standard reactions, an oxazoline synthesis was studied next. In
with 1H NMR spectroscopy. The freshly opened contrast to the phenol synthesis, this reaction – which
solvent showed a water content of 0.30 μl/ml and the is particularly interesting for pharmaceuticals and
saturated one a water content of 2.54 μl/ml.
materials science – has no proton transfer steps apart
With 1.50 10À 1 wt% water (0.2 μl water added to from a protodeauration.[34–40] As described above, an
1
998 μl CD2Cl2), the reaction rate was already enhanced in situ monitoring with H NMR spectroscopy was
by 36% (Table 1; entry 2). In addition, a 10% higher carried out according to a standardized procedure in
conversion was observed within the first 12 minutes order to compare the kinetic results (see the Supporting
(see Figure 2). An even more efficient reaction was Information for further details). Therefore, one equiv-
achieved by using water-saturated methylene chloride alent of N-(prop-2-yn-1-yl)benzamide was treated with
resulting in an almost doubled reaction speed com- 2.0 mol% Ph3PAuNTf2 in deuterated DCM containing
pared to the dry conditions (Table 1; entry 3). More- varying amounts of water (Scheme 2).
over, a conversion of 96% was achieved after
24 minutes instead of 30 minutes (Figure 2).
The results of the mathematical regression are
shown in Table 2. Dry conditions were chosen as the
Mixtures with a higher water content led to the reference system (exemplary reaction course: see Fig-
formation of two phases, which could not be analyzed ure 3) and the corresponding relative rate constant krel
1
by H NMR spectroscopy. However, since the organic was normalized to krel =1 (see Table 2). In addition,
conversion takes place in the organic phase, it can be the use of the integration method confirmed a first
assumed that the reactions rate would be comparable order reaction with respect to the substrate (see the
to that of a saturated solution. The use of acetonitrile, Supporting Information for further details).[31–33]
which, on the other hand, is more miscible with water,
As already observed in the phenol synthesis, an
did not lead to any further improvement (see the increasing water content of the solvent favored the
Supporting Information for further details).
product formation in the oxazoline synthesis tested
here.
First, a test reaction was examined under dry
conditions (Table 2; entry 1). Within the first 30
minutes 66%, and after 60 minutes 90% conversion of
Scheme 2. Gold(I)-catalyzed oxazoline synthesis.
Table 2. Rate constants for the oxazoline synthesis (CD2Cl2)
depending on the water content.[a]
Entry Water
content
Conversion k1
R2
krel
[%]
[mL/
[wt%]
0.2 h 0.5 h (mmol*h)]
1
2
3
dry
66
90
89
91
2.42�0.01 0.999 1.00�0.01
2.60�0.09 0.996 1.07�0.04
2.77�0.02 0.999 1.14�0.01
1.50 10–1 69
saturated 73
[a] Reaction conditions: N-(prop-2-yn-1-yl)benzamide (50 μmol,
Figure 2. Reaction course of the phenol synthesis with varying
water content in CD2Cl2: a) Decrease of reactant 1; b) Increase
of product 2.
50 μmol/ml), Ph3PAuNTf2 (2.0 mol%), in CD2Cl2 at T=
1
°
25 C, observed by H NMR monitoring for up to 2 h.
Adv. Synth. Catal. 2021, 363, 1–9
3
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
Figure 3. Reaction course of the oxazoline synthesis in dry
CD2Cl2 (Table 2; Entry 1).
the reactant was achieved. Analogous to the consid-
erations for the phenol synthesis, the amount of water
was increased to 1.50 10À 1 wt%. This led to a 7%
higher reaction rate and 69% conversion of the starting
material (Table 2; entry 2). With water-saturated meth-
ylene chloride, a further increase in the reaction rate of
7% and a reaction conversion of 73% was recorded
(Table 2; entry 3). Thus, as with the phenol synthesis
previously examined, a promoting influence of the
water addition was also confirmed for the oxazoline
synthesis. The described trends of reactant decrease, or
product increase, are shown in Figure 4.
Figure 4. Reaction course of the oxazoline synthesis with
varying water content in CD2Cl2: a) Decrease of reactant 3; b)
Increase of product 4.
After observing the influence of water on the
reaction rate of intramolecular test systems, we decided
to continue our studies on an intermolecular reaction. kinetic studies, one equivalent of phenylacetylene and
For this purpose, an oxazole synthesis was chosen, 1.3 equivalents of N-oxide 6a–c were dissolved in
which was developed by Zhang et al. and recently 3.00 ml acetonitrile with 0.0 to 5.06 wt% of distilled
examined by our group to classify the reactivity of water. As an internal standard, one equivalent of n-
various N-oxides.[41] In addition to the easy accessi- dodecane was added. The temperature was kept
°
bility of the starting materials, this reaction is also constant at 60 C and the mixture was stirred at a speed
characterized by a reaction time of a few hours and is of 400 rpm. The reaction was started by adding
therefore of great interest for homogeneous gold 5.0 mol% of the gold(I) complex Ph3PAuNTf2
catalysis.[42–43] The selection of the N-oxides was based (Scheme 3).
on our recent work.[44] For the present study, we
After specific time intervals, samples were taken
examined the efficient 8-methylquinoline N-oxide 6a from the reaction mixture and the catalyst was quickly
reagent, the fast-reacting 3,5-dibromopyridine N-oxide removed by filtration over silica gel to stop the
6b and pyridine N-oxide 6c as reference compounds.
reaction. Afterwards the solution was analyzed by gas
In contrast to the intramolecular test systems, the chromatography and the reactant and product concen-
oxazole synthesis was analyzed by GC according to a trations were determined based on the method of
standardized procedure to ensure comparability (see internal standard.[45]
the Supporting Information for further details). For the
Scheme 3. Gold(I)-catalyzed oxazole synthesis.
Adv. Synth. Catal. 2021, 363, 1–9
4
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
Analogous to the analysis of the phenol and oxazo-
As expected, the highest reaction rates were
line synthesis, the kinetic data were evaluated, and the achieved by using 8-methylquinoline N-oxide 6a and
corresponding errors determined. The use of the 3,5-dibromopyridine N-oxide 6b. A water content of
unsubstituted pyridine N-oxide 6c under dry conditions 2.55 10À 1 wt% or the use of non-dry solvents from
was chosen as the reference system and the corre- conventional solvent bottles proved to be ideal for
sponding relative rate constant krel was normalized to high-rate constants and an efficient conversion in short
krel =1.
Due to the fact that acetonitrile acts both as solvent
time.
According to Table 3, the highest reaction rate was
and reactant, it is legitimate to neglect its concentration observed in the conversion of 8-methylquinoline N-
when calculating the rate constants. The value k* oxide 6a with a water content of 2.55 10À 1 wt%
therefore represents the rate constant taking into (Table 3; entry 1). The rate of the corresponding
account the acetonitrile concentration. Furthermore, reaction in conventional non-dry solvent (acetonitrile,
the assumed pseudo second order reaction was con- �99.5% (GC): water content max. 0.1 wt%)[46] was
firmed by using the integration method (see the slightly lower (Table 3; entry 2). In both cases, almost
Supporting Information for further details).[31–33]
Based on the evaluation of the observed reactions, 150 minutes.
complete conversion was achieved within the first
the results listed in Table 3 such as reaction rate
Likewise, when using 3,5-dibromopyridine N-oxide
constants and conversions were obtained. In line with 6b, a minimal amount of water was also found to
the previous test systems, there were also clear trends promote the reaction. Thus, we obtained the highest
regarding water content recognizable in the examined rate constant of this N-oxide by using a water volume
oxazole test system. In order to clarify the trends of 2.55 10À 1 wt% in acetonitrile and the second highest
discussed, the decrease in phenylacetylene was also rate constant by using non-dry solvent (Table 3;
shown graphically (Figure 5, Supporting Information). entry 6–7). The maximum conversion under these
conditions was approximately 70% after 150 minutes
and rose to 98% after 12 hours.
Using dry solvent, the reaction rate of 8-meth-
ylquinoline N-oxide 6a was drastically reduced by
almost 50%. At the same time, the reaction conversion
achieved in the first 150 minutes dropped to 93%
(Table 3; entry 3). In addition, doubling the amount of
water from 2.54 wt% to 5.06 wt%, led to a significant
drop in reaction speed. In the latter case, the reaction
rate even dropped to only one third of the maximum
value with 2.55 10À 1 water in the solvent (Table 3;
entries 4–5). In contrast, the conversion after 150
minutes did not change notably. These results are
graphically depicted in Figure 5. Thus, in this test
reaction we observed the maximum rate at low water
concentration and a rate decrease with higher concen-
trations; still, the best rate was not observed under
anhydrous conditions.
The trend observed was also reflected in the studies
on 3,5-dibromopyridine N-oxide 6b, albeit less pro-
nounced. Thus, under dry conditions, the reaction rate
dropped by 9%, while the reaction conversion re-
mained the same (Table 3; entry 8). The rate constant,
which was 30% higher than that of 8-methylquinoline
N-oxide 6a under analogous conditions, was partic-
ularly striking. This surprisingly greater dependence of
the reaction rate on the amount of water for 8-
methylquinoline N-oxide was also confirmed for a
water content of 2.54 wt% and 5.06 wt%.
While the successive increase in water content in
reactions with 3,5-dibromopyridine N-oxide 6b hardly
Figure 5. Reaction course of the oxazole synthesis with varying
water content using 6a: a) Decrease in phenylacetylene 5, b)
Increase in oxazole 7.
influenced the reaction conversion, the rate constant
decreased by 44% at 2.54 wt% (Table 3; entry 9) and
by 53% at 5.06 wt% water content (Table 3; entry 10).
Adv. Synth. Catal. 2021, 363, 1–9
5
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
Table 3. Rate constants of varying N-oxides depending on the water content.[a]
Entry N-oxide
Water content [wt%] Conversion [%]
k1
k*
R2
krel
2.5 h
24 h
[mL/(mmol*h)] [mL2/(mmol2*h)]
1
2.55 10—1
non-dry
abs.
94
100
33.16�2.31
31.94�2.08
18.52�1.28
13.97�0.96
10.70�1.06
28.86�1.87
27.12�2.04
26.28�2.72
16.06�1.41
1.79�0.12
1.72�0.11
1.00�0.07
0.77�0.05
0.64�0.08
1.56�0.10
1.46�0.11
1.42�0.15
0.88�0.08
0.99 6.73�0.47
0.99 6.48�0.42
0.99 3.76�0.26
0.99 2.84�0.19
0.99 2.17�0.22
0.99 5.85�0.38
0.99 5.51�0.41
0.98 5.34�0.55
0.98 3.26�0.29
2[b,c]
100
93
85
83
71
68
74
69
100
100
100
100
98
3
4
2.54
5
5.06
6
2.55 10À 1
non-dry
abs.
7[b,c]
96
8
97
9
2.54
96
10
5.06
73
51
41
60
95
13.76�1.56
7.89�0.55
7.27�0.64
6.19�0.51
0.77�0.09
0.43�0.03
0.40�0.04
0.33�0.03
0.97 2.79�0.32
0.99 1.60�0.11
0.98 1.48�0.13
0.98 1.26�0.10
11
2.55 10À 1
2.54
100
88
12
13[b,c]
non-dry
100
Adv. Synth. Catal. 2021, 363, 1–9
6
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
Table 3. continued
Entry N-oxide
Water content [wt%] Conversion [%]
k1
k*
R2
krel
2.5 h
24 h
[mL/(mmol*h)] [mL2/(mmol2*h)]
14
5.06
abs.
45
75
5.49�0.58
4.92�0.39
0.31�0.03
0.27�0.02
0.98 1.12�0.12
15
49
91
0.99 1.00�0.08
[a]
°
Reaction conditions: benzenesulfonamide alkyne (50 μmol, 50 μmol/ml), IPrAuNTf2 (5.0 mol%), in CD2Cl2 at T=25 C,
observed by 1H NMR monitoring for up to 2 h.
[b] In order to compare, data were taken from reference[39]
[c] conventional solvent.[46]
.
Finally, further experiments with pyridine N-oxide arbitrarily by further increasing the amount of water.
6c were carried out. Using 2.55 10À 1 wt% water Decreasing rate constants were observed from a water
content the reaction rate was increased by approx- content of over 2.54 wt% with respect to the solvent.
imately 63% compared to dry solvent, almost reaching
Based on the kinetic data found, small amounts of
the reaction rate of 8-methylquinoline N-oxide with water proved to promote the reaction and led to
5.06 wt% of water. After 12 hours the phenylacetylene increased reaction rates in combination with good
was completely converted (Table 3; entry 11, 5). yields. Probably many reactions in the field behave
Increasing the water content to 2.54 wt% or the use of similarly, thus complex protective gas techniques and
non-dry solvents led to a decrease in the corresponding the use of dry solvents is not beneficial, time and
rate constants (Table 3; entries 12–13). Nevertheless, money can be saved and the increased rate in
in contrast to the other pyridine N-oxide 6c test series, applications significantly improves the important space
complete conversion was achieved after 24 hours under time yield. Since some of the test reactions involved
the latter conditions. The increase in the amount of protodeauration, but others did not, it is beyond the
water to 5.06 wt%, as well as the use of dry solvents scope of this manuscript to provide a detailed
resulted in the lowest measured conversions and time mechanistic model for the role of the water in the
constants (Table 3; entries 14–15).
different reactions; ongoing studies focus on this.
In conclusion, the comparison of the results for
some representative key reactions of gold catalysis
showed clear trends with regard to the influence of
water on a given reaction system. Particularly interest-
ing results were obtained for the reactions executed in
methylene chloride; the phenol synthesis and the
oxazoline synthesis. For the furan-yne reaction, a
remarkable proportionality was discovered: the higher
the water content, the higher the reaction rate.
However, the maximum amount of water was limited
by the low miscibility of water and methylene chloride
which hinders from an even higher increase in the
reaction rate.
Comparable relations were also obtained for the
intermolecular oxazole synthesis examined. Reactions
with a small amount of 2.55 10À 1 wt% of water
achieved higher rate constants than those under
completely dry conditions. The use of conventional
solvents is therefore optimal for an efficient product
synthesis. Though, this effect cannot be increased
Acknowledgements
P.M.S. and A.S.K.H. gratefully acknowledge the Hector Fellow
Academy for the generous provision of funding.
References
[1] A. S. K. Hashmi, T. M. Frost, J. W. Bats, J. Am. Chem.
Soc. 2000, 122, 11553–11554.
[2] A. S. K. Hashmi, L. Schwarz, J.-H. Choi, T. M. Frost,
Angew. Chem. Int. Ed. 2000, 39, 2285–2288; Angew.
Chem. 2000, 39, 2285–2288.
[3] A. S. K. Hashmi, T. M. Frost, J. W. Bats, Org. Lett. 2001,
3, 3769–3771.
[4] A. S. K. Hashmi, G. J. Hutchings, Angew. Chem. Int. Ed.
2006, 45, 7896–7936; Angew. Chem. 2006, 45, 7896–
7936.
[5] A. S. K. Hashmi, Chem. Rev. 2007, 107, 3180–3211.
Adv. Synth. Catal. 2021, 363, 1–9
7
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
asc.wiley-vch.de
[6] A. S. K. Hashmi, M. Rudolph, Chem. Soc. Rev. 2008, 37, [29] A. S. K. Hashmi, M. Rudolph, J. P. Weyrauch, M. Wölf-
1766–1775.
le, W. Frey, J. W. Bats, Angew. Chem. Int. Ed. 2005, 44,
2798–2801; Angew. Chem. 2005, 44, 2798–2801.
[30] A. S. K. Hashmi, M. Rudolph, H.-U. Siehl, M. Tanaka,
J. W. Bats, W. Frey, Chem. Eur. J. 2008, 14, 3703–3708.
[31] W. Bechmann, J. Schmidt, Einstieg in die Physikalische
Chemie für Nebenfächler, Vieweg Teubner, Wiesbaden,
2001.
[7] N. Marion, S. P. Nolan, Chem. Soc. Rev. 2008, 37, 1776–
1782.
[8] A. Arcadi, Chem. Rev. 2008, 108, 3266–3325.
[9] S. Sengupta, X. Shi, ChemCatChem 2010, 2, 609–619.
[10] P. Garcia, M. Malacria, C. Aubert, V. Gandon, L.
Fensterbank, ChemCatChem 2010, 2, 493–497.
[11] M. Rudolph, A. S. K. Hashmi, Chem. Commun. 2011, 47, [32] P. W. Atkins, J. Paula, Physikalische Chemie, 4th edn.,
6536–6544. Wiley-VCH, Weinheim, 2006.
[12] D.-H. Zhang, X.-Y. Tang, M. Shi, Acc. Chem. Res. 2014, [33] P. L. Houston, Chemical Kinetics and Reaction Dynam-
47, 913–924. ics, Dover Publications, Inc., Minola, New York, 2012.
[13] D. Pflästerer, A. S. K. Hashmi, Chem. Soc. Rev. 2016, [34] A. S. K. Hashmi, J. P. Weyrauch, W. Frey, J. W. Bats,
45, 1331–1367. Org. Lett. 2004, 6, 4391–4394.
[14] Z. Zhang, R. A. Widenhoefer, Org. Lett. 2008, 10, 2079– [35] A. S. K. Hashmi, A. M. Schuster, F. Rominger, Angew.
2081.
Chem. Int. Ed. 2009, 48, 8247–8249; Angew. Chem.
2009, 48, 8247–8249.
[15] P. W. Davies, N. Martin, Org. Lett. 2009, 11, 2293–2296.
[16] W. Wang, G. B. Hammond, B. Xu, J. Am. Chem. Soc. [36] J.-I. Kuroyanagi, K. Kanai, Y. Sugimoto, T. Horiuchi, I.
2012, 134, 5697–5705.
[17] Z. Lu, J. Han, G. B. Hammond, B. Xu, Org. Lett. 2015,
17, 4534–4537.
Achiwa, H. Takeshita, K. Kawakami, Bioorg. Med.
Chem. 2010, 18, 7593–7606.
[37] C.-Y. Chen, T. Andreani, H. Li, Org. Lett. 2011, 13,
6300–6303.
[18] F. Jaroschik, A. Simonneau, G. Lemière, K. Cariou, N.
Agenet, H. Amouri, C. Aubert, J.-P. Goddard, D. Lesage, [38] A. J. Morrison, J. M. Adam, J. A. Baker, R. A. Campbell,
M. Malacria, Y. Gimbert, V. Gandon, L. Fensterbank,
ACS Catal. 2016, 6, 5146–5160.
[19] Z. Lu, J. Han, O. E. Okoromoba, N. Shimizu, H. Amii,
C. F. Tormena, G. B. Hammond, B. Xu, Org. Lett. 2017,
19, 5848–5851.
J. K. Clark, J. E. Cottney, M. Deehan, A.-M. Easson, R.
Fields, S. Francis, F. Jeremiah, N. Keddie, T. Kiyoi,
D. R. McArthur, K. Meyer, P. D. Ratcliffe, J. Schulz, G.
Wishart, K. Yoshiizumi, Bioorg. Med. Chem. Lett. 2011,
21, 506–509.
[20] Z. Lu, T. Li, S. R. Mudshinge, B. Xu, G. B. Hammond, [39] F. Hamon, E. Largy, A. Guédin-Beaurepaire, M. Rou-
Chem. Rev. 2021, 121, doi.org/10.1021/acs.chem-
rev.0c00713.
[21] J. Schießl, J. Schulmeister, A. Doppiu, E. Wörner, M.
Rudolph, R. Karch, A. S. K. Hashmi, Adv. Synth. Catal.
2018, 360, 2493–2502.
[22] C. Wei, C.-J. Li, J. Am. Chem. Soc. 2003, 125, 9584–
9585.
[23] Y. Fukuda, K. Utimoto, J. Org. Chem. 1991, 56, 3729–
3731.
chon-Dagois, A. Sidibe, D. Monchaud, J.-L. Mergny, J.-
F. Riou, C.-H. Nguyen, M.-P. Teulade-Fichou, Angew.
Chem. Int. Ed. 2011, 50, 8745–8749; Angew. Chem.
2011, 50, 8745–8749.
[40] A. S. K. Hashmi, A. Littmann, Chem. Asian J. 2012, 7,
1435–1442.
[41] W. Yang, R. Zhang, F. Yi, M. Cai, J. Org. Chem. 2017,
82, 5204–5211.
[42] D. Azarifar, B. Mahmoudi, J. Iran. Chem. Soc. 2016, 13,
645–651.
[24] J. H. Teles, S. Brode, M. Chabanas, Angew. Chem. Int.
Ed. 1998, 37, 1415–1418; Angew. Chem. 1998, 37, [43] A. Biswas, U. Karmakar, A. Pal, R. Samanta, Chem. Eur.
1415–1418. J. 2016, 22, 13826–13830.
[25] E. Mizushima, K. Sato, T. Hayashi, M. Tanaka, Angew. [44] J. Schießl, P. M. Stein, J. Stirn, K. Emler, M. Rudolph, F.
Chem. Int. Ed. 2002, 41, 4563–4565; Angew. Chem.
2002, 41, 4563–4565.
Rominger, A. S. K. Hashmi, Adv. Synth. Catal. 2019,
361, 725–738.
[26] C. M. Krauter, A. S. K. Hashmi, M. Pernpointner, Chem- [45] R. L. Grob, E. F. Barry, Modern Practice of Gas
CatChem 2010, 2, 1226–1230.
[27] A. S. K. Hashmi, Catal. Today 2007, 122, 211–214.
Chromatography, 4th edn., Wiley Interscience, Hoboken,
NJ, 2005.
[28] A. S. K. Hashmi, R. Salathé, W. Frey, Chem. Eur. J. [46] Honeywell International Inc; Acetonitril 99.5% (GC)
2006, 12, 6991–6996.
2020.
Adv. Synth. Catal. 2021, 363, 1–9
8
© 2021 The Authors. Advanced Synthesis & Catalysis
published by Wiley-VCH GmbH
��
These are not the final page numbers!

COMMUNICATIONS
Water Can Accelerate Homogeneous Gold Catalysis
Adv. Synth. Catal. 2021, 363, 1–9
P. M. Stein, Dr. M. Rudolph, Prof. Dr. A. S. K. Hashmi*