RETRACTED ARTICLE: Heterogeneous Titania-Photoredox/Nickel Dual Catalysis: Decarboxylative Cross-Coupling of Carboxylic Acids with Aryl Iodides

Article abstract of DOI:10.1021/acscatal.6b03687

The efficient, mild, and semiheterogeneous decarboxylative cross-coupling of a variety alkyl carboxylic acids with aryl iodides has been accomplished through a merger of TiO₂ photoredox and nickel cross-coupling chemistries. The protocol is tolerant to a wide range of substituted aryl iodides and alkyl carboxylic acids. Through replacement of the commonly employed Ir transition-metal complexes with P25 TiO₂ as photocatalyst, we show that these transformations can be heterogenized with little effect on the efficiency of these transformations, while at the same time decreasing the associated costs due to the reusability and inexpensive nature of the TiO₂ photocatalyst.

Full text of DOI:10.1021/acscatal.6b03687

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Letter
Heterogeneous Titania-Photoredox/Nickel Dual Catalysis:
Decarboxylative Cross-Coupling of Carboxylic Acids with Aryl Iodides
Christopher D McTiernan, Xavier Leblanc, and Juan C. Scaiano
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.6b03687 • Publication Date (Web): 17 Feb 2017
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ACS Catalysis
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Heterogeneous Titania-Photoredox/Nickel Dual Catalysis:
Decarboxylative Cross-Coupling of Carboxylic Acids with
Aryl Iodides
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Christopher D. McTiernan, Xavier Leblanc, and Juan. C. Scaiano*
Department of Chemistry and Biomolecular Sciences and Centre for Catalysis Research and Innovation, University of Ottawa, 10
Marie Curie, Ottawa ON K1N 6N5, Canada
ABSTRACT: The efficient, mild, and semi-heterogeneous decarboxylative cross-coupling of a variety alkyl carboxylic acids with aryl iodides
has been accomplished through a merger of TiO
of substituted aryl iodides and alkyl carboxylic acids. Through replacement of the commonly employed Ir transition metal complexes with
P25 TiO as photocatalyst we show that these transformations can be heterogenized with little effect on the efficiency of these transfor-
2
photoredox and nickel cross-coupling chemistries. The protocol is tolerant to a wide range
2
mations, while at the same time decreasing the associated costs due to the reusability and inexpensive nature of the TiO photocatalyst.
2
Keywords: Heterogeneous, Dual Catalysis, Nickel, Titania, Decarboxylative Cross-Coupling, Photoredox
When one thinks of important recent developments in synthetic
organic chemistry, probably one of the most impactful has to be the
introduction of transition-metal catalyzed cross-coupling reactions.
As a tool in forming C-C, C-N, and C-O bonds, these methods
have found applications in a variety of chemical syntheses, due to
their well-known reliability, selectivity, and predictability. While
there is currently a variety of different cross-coupling methods one
coupled product, there have been a number of reports which have
15,16
looked to both better understand and expand this chemistry.
While the end product of these dual photoredox-Ni catalytic sys-
tems are quite diverse, the actual catalytic system employed to
bring about these changes are quite conventional. That is, most
systems are derived from homogeneous Ir or Ru photocatalysts and
some type of bipyridinium functionalized homogeneous Ni com-
plex. The only criteria for the photocatalyst being that the SET
redox potentials be favorable for both in-situ generation of the de-
sired radical and for turnover of the Ni catalyst. Although the Ir and
Ru photocalysts have shown great promise in these dual catalytic
systems, we, along with other groups have demonstrated that in
many cases one can replace these relatively expensive transition-
metal photocatalysts with cheaper alternatives such as organic
1
2
3
4
can choose from (Heck, Suzuki-Miyaura, Negishi, Stille, Kuma-
5
6
7
8
da-Corriu, Sonogashira, Buchwald-Hartwig, and Hiyama ) all of
these methods require that the nucleophilic coupling partner be
functionalized with a transition-metal activated handle such as
Grignards, stannanes, and boronic acids. While many of these rea-
gents can be purchased or synthesized in few steps, they tend to be
relatively expensive, may require harsh synthesis conditions, and in
some cases be difficult to handle due to their high reactivity. For
these reasons, there has been interest in developing new techniques
and methods, which would allow the use of less expensive and read-
ily available starting materials containing non-traditional leaving
groups/handles (e.g. –COOH) as competent coupling partners in
1
7
dyes (Methylene Blue, Eosin-Y, 9-Mesityl-10-methylacridinium)
1
8
and organic/inorganic semiconductors (α-Sexithiophene,
1
9
TiO ) to generate the required radical intermediates with little or
2
no sacrifice in efficiency and in some cases these alternatives actual-
ly outperform their transition-metal counterparts.
9
a variety of different cross-coupling reactions.
As it had been previously demonstrated that TiO and Pt-
2
It has been recently shown that a merger of visible-light photore-
dox and transition-metal catalysis can create dual catalytic systems,
which can be used to forge C-C bonds between a variety of non-
conventional coupling partners. While there has been a surge in the
use of Ni in these dual catalytic systems, other transition-metals
modified TiO can be employed as heterogeneous photoredox
catalyst in the oxidative decarboxylation of carboxylic acids,
2
2
0,21
we
began to wonder whether we could substitute the highly oxidizing
Iridium (III) photocatalyst Ir[dF(CF )ppy] (dtbbpy) PF , typical-
3
2
6
ly used in the dual photoredox/Ni decarboxylative cross-couplings,
with TiO . Just as in the case of Ir, TiO will be responsible for both
10
11
12
such as Pd, Cu, and Au can also act synergistically when cou-
2
2
pled with appropriately selected photoredox systems.
generation of the alkyl radicals and turnover of the Ni catalytic
13
14
Since the work of Molander and MacMillan demonstrated
that alkyl radicals generated through photoredox mediated single-
electron transfer (SET) could be efficiently intercepted by Ni(II)
complexes and that the convergent Ni(III)(alkyl)(Ar) complex
could undergo reductive elimination to furnish the desired cross-
cycle. The proposed mechanism for the dual TiO -photoredox/Ni
2
is presented in Scheme 1. The idea being that upon excitation of
the TiO photocatalyst the highly oxidizing holes in the valence
2
band (VB) of the semiconductor would oxidatively decarboxylate
21
the carboxylic acid to furnish the alkyl radical, while the strongly
reducing electrons of the conduction band (CB) would in turn
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ACS Catalysis
Page 2 of 6
provide a site for reduction of the Ni(II) and Ni(I) complexes to formation of singlet and triplet excited states, such an enhancement
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
their active Ni(0) species.
would not be expected in our system.
Table 1. Optimization of Reaction Conditions
a
X
I
LnNiII Ar
N
R
Boc
0.5 eq. TiO2
I
O
1
0 mol% Ni Catalyst
N
N
1
5 mol% dtbbpy, 1 eq CsCO3
LnNi0
Boc OH
CO2Me
CO2Me
I
Boc
5
mL Solvent, Atm
Light Source
Ni Catalytic
Cycle
Alk NiIIILn
Boc-Pro-OH
0.6 mmol
Methyl 4-Iodobenzoate
0.4 mmol
Ar
e-
-I–
Isolated
Yield
CB
Red
Entry
Ni Catalyst
Solvent
Atm.
Time
CO2H
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
N
LnNiI
TiO2 Photocatalysis
I
1
2
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
2
2
2
2
2
2
2
2
2
2
2
2
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
Ÿglyme
DMF
Air
72 h
72 h
36 h
72 h
72 h
72 h
3 h
0%
0%
Boc
hν
N
Boc
DMF
Argon
Air
Ox
h+
VB
R
-
H+
, -CO2
3
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
56%
93%
0%b
0%c
19%
61%
4
Air
N
5
Air
Boc
6
Air
Scheme 1. Proposed Mechanism for the Dual TiO
Photoredox-Ni-Catalyzed Decarboxylative Arylation
2
-
7
Argon
Argon
Argon
Argon
Argon
Argon
Argon
Argon
Argon
Argon
Argon
8
6 h
We present here our recent findings on the semi-heterogeneous
dual TiO -photoredox/Ni mediated decarboxylative cross-
coupling of carboxylic acids with aryl-iodides. The main goal of this
work is to illustrate that one can replace the commonly employed Ir
and Ru photocatalysts utilized in these dual-catalytic systems, with
a inexpensive, reusable, easily removed and environmentally benign
photocatalyst such as P25 TiO
We began our studies on the decarboxylative cross-coupling of
carboxylic acids with aryl-iodides using a catalytic system compris-
9
18 h
72 h
72 h
18 h
18 h
18 h
18 h
18 h
18 h
95%
0%b
2
10
1
1
0%c
Traced
0%
Tracee
Tracef
8%
12
13
2
.
None
1
4
NiCl
NiCl
2
Ÿglyme
Ÿglyme
15
2
ing P25 TiO
precursor complexes, 4,4’-di-tert-butyl-2,2’-bipyridine (dtbbpy) as
ligand for the Ni complex, Cs CO as base, and a UVA-Visible light
2
as photoredox catalyst, a variety of Ni(II) and Ni(0)
1
1
6
7
Ni(acac)
2
2
3
Ni(COD)
2
>95%
source for irradiation (Luzchem Inc. Solar Simulator fitted with a
longpass λ>375 filter). Utilizing N-Boc-proline and Methyl 4-
Iodobenzoate as model coupling partners, we performed test and
control reactions under a variety of different conditions in order to
optimize the procedure (Table 1). From these initial tests it was
found that the optimal solvent for this particular catalytic system is
acetonitrile (MeCN) [Table 1, entries 1 and 4] and that while the
reaction can tolerate the presence of oxygen, its removal through a
20 minute argon purge drastically increases the efficiency of the
reaction [Table 1, entries 3 and 8]. While the drastically different
results in dimethylformamide (DMF) and MeCN may be simply
explained by interference due to readily oxidizable amine impuri-
ties in the DMF, the increase in efficiency observed in the absence
of oxygen may be due to the fact that, when present oxygen can be
readily reduced by electrons in the CB of TiO
vs. SCE) to give superoxide (O
SCE) which may disrupt the catalytic cycle directly or indirectly
as it may compete with the reduction of the Ni(I) complex to its
corresponding Ni(0) complex, a key step in the proposed mecha-
nism (Scheme 1). Although the observed effect of O
is opposite to that observed by Oderinde and co-workers for a simi-
lar transformation utilizing an Ir[dF(CF )ppy] (dtbbpy)PF , it
should be pointed out that they believe that the presence of O is
a
Reaction conditions: Boc-Pro-OH (0.6 mmol), Methyl 4-Iodobenzoate (0.4
mM), P25 TiO (0.5 eq.), dtbbpy (15 mol%), CsCO (1 eq.), solvent (5mL). Irra-
diated with solar simulator λ > 375 nm. no light. no light and 50°C. no base. no
P25 TiO no base.
2
3
b
c
d
e
f
2
,
In addition to solvent and atmosphere, we have also performed
control reactions under dark conditions at both room temperature
and 50 °C to ensure that it is excitation of the photocatalyst that
brings about the desired transformation and not just heating caused
by light absorption (Table 1, entries 5,6 10, and 11). From Table 1
it also evident that the photocatalyst, Ni complex, dttbpy ligand,
and base are all critical components of the system as their omission
results in little or no desired product even after 18 h of irradiation.
Lastly, due to the fact that the added Ni complex is only a precursor
2
2
ox
2
(E [CB] = -2.0 V
/O
for the NiCl
explored whether or not we could exchange the NiCl
other Ni sources such as Ni(acac) and Ni(COD) . As observed in
Table 1, entry 16; when Ni(acac) is used as precatalyst the effi-
2
Ÿdtbbpy complex utilized in these transformations, we
2
3
Ÿ−
red
Ÿ−
2
) (E [O
2
2
] = -0.8 V vs.
2
Ÿglyme with
2
4
2
2
2
ciency of the reaction falls drastically with only 8% of the desired
cross-coupled product obtained after 18 h of reaction. However,
when we switch to the Ni(0) precatalyst, Ni(COD) , there appears
to be no observable change in the efficiency of the transformation.
While the Ni(0) catalyst has the advantage that it does not require
2
in our system
2
3
2
6
2
assisting the intersystem crossing (ISC) process, resulting in a
an initial reduction by the TiO
that advantageous as reduction of Ni(II) to Ni(0) by the CB elec-
2
to become active, this may not be
more efficient formation of the strongly oxidizing triplet excited
*
red
*
16
red
II
0
state of Ir(III) (E1/2 [ Ir(III)/Ir(II)] = 1.21 V vs. SCE). While
trons is quite thermodynamically favorable (E1/2 [Ni /Ni ] = -1.2
25
such an explanation is plausible for transition metal and organic
V vs. SCE). The Ni(COD) precatalyst is also air sensitive and
2
based photocatalysts, as excitation of TiO does not lead to the
2
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Page 3 of 6
ACS Catalysis
appears as though some withdrawing functionalities may be toler-
therefore extra care must be taken when it is employed. For these
reasons we have preferred to utilize NiCl Ÿglyme as our precatalyst.
Table 2. TiO Photoredox/Ni Dual Catalytic Decarboxyla-
tive Cross-Coupling: Aryl-Iodide Scope
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
ated.
2
2
Table 3. TiO Photoredox/Ni Dual Catalytic Decarboxylative
2
Cross-Coupling: Carboxylic Acid Scope
0
.5 eq. TiO
2
O
0.5 eq. TiO2
10 mol% NiCl2.glyme
I
I
O
.glyme
1
0 mol% NiCl
2
R
R
N
N
15 mol% dtbbpy, 1.5 eq Cs
CH3CN, Argon
2
CO
3
R
OH
15 mol% dtbbpy, 1.5 eq Cs2CO3
OH
CO Me
CO2Me
Boc
Boc
R
2
CH CN, Argon
0.6 mmol
3
Methyl 4-Iodobenzoate
.4 mmol
hν > 375 nm, 18 h
Boc-Pro-OH
0.4 mmol
hν > 375 nm, 18 h
0
0
.6 mmol
OH
OH
O
OH
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
N
N
(
N
Ac
2
CO Et
CO
2
Me
O
Boc
O
Boc
Boc
O
Ph
17) 95%
(18) 88%
(19) 82%
(25) 62%
(26) 76%
(27) 73%
CF
3
N
N
N
OH
OH
CHO
CF
3
OH
Boc
20) 79%
Boc
Boc
(22) 77% CF
O
O
(
(21) 73%
3
Br
O
(29) 37%
(30) 44%
(28) 68%
N
N
OH
F
CN
Boc
23) 42%
Boc
O
(
(24) 68%
OH
N
OH
O
With the optimized conditions in hand, we then set out to test
our system in the cross-coupling of a variety of substituted aryl-
Iododes with our model alkyl carboxylic acid (N-Boc-pro). As illus-
trated in Table 2 our dual-catalytic system is capable of coupling a
number of electron-deficient aryl-iodides with N-Boc-proline in
moderate to excellent yields (37-95%) under relatively short irradi-
ation times (18h). Table 2 shows that our procedure is tolerant to
a variety of different functional groups, such as esters, acetyls, alde-
O
O
O
(31) 56%
(32) 48%
(33) 72%
O
OH
OH
O
O
S
O
(34) 83%
(35) 65%
Interestingly many of the phenylacetic acid derivatives are classi-
fied as Non-Steroidal Anti-Inflammatory Drugs (NSAIDs); this
protocol provides a quick and simple route to their modification
and functionalization with orthogonal handles for further modifica-
tion. For the most part derivatives substituted in the alpha position
display lower reactivity than their unsubstituted counterparts (Ta-
ble 3, entries 30-32). While it would be easy to attribute this de-
crease in reactivity to steric effects, this is complicated by the fact
that the more sterically hindered diphenylacetic acid (Table 3,
entry 33) appears to be a suitable coupling partner, giving similar
yields to the unsubstituted derivatives. However, this difference in
reactivity could possibly be related to the higher stability of the
hydes, CF , fluorine, and nitriles. However, it should be mentioned
3
that the presence of ether, alcohol, amine, or nitro functionalities
on the aryl-iodide coupling partner either slow or completely shut
down the catalytic cycle. While in some cases these may be due to
the radical trapping ability of some of these functionalities, the
electron donating nature of these substituents may be inhibiting
oxidative addition of the Ni(0) complex into the aryl-iodide pre-
venting formation of the Ni(II) intermediate, which would then
trap the alkyl radical formed upon oxidative decarboxylation. It is
important to note that while we have previously illustrated that one
can utilize TiO as photoredox catalysts in the reductive dehalo-
2
genation of aryl-iodides, we have observed no corresponding hy-
drodehalogenated products under these reaction conditions. We
do however find trace amounts of the corresponding phenol.
Once we had demonstrated that the aryl-iodide coupling partner
could be modified, we set out to do the same thing with the carbox-
26
resulting diphenyl methyl radical. Lastly, substrates containing
aromatic ketone chromophores (Table 3, entry 34 and 35) are also
exceptional coupling partners, giving moderate to good yields with
little to no background reaction.
In an attempt to broaden the applicability of this procedure we
have substituted the aryl iodide coupling partner with its bromide
and chloride analogues. However after 72 h of irradiation of N-Boc-
Proline and either Methyl 4-Bromobenzoate or Methyl 4-
Chlorobenzoate, under our optimized reaction conditions, we did
not obtain any of the desired product. A possible explanation for
the observed lack of reactivity may be that the reduction potential
of the corresponding Ni(I)Cl or Ni(I)Br species (formed after
reductive elimination) is outside the potential window attainable
red
ylic acid component. The holes produced in the VB (E [VB] =
1
.0 V vs. SCE) of TiO upon excitation make it a moderately oxidiz-
2
ing inorganic semiconductor. Considering that the oxidation po-
ox
tential of N-Boc-pro (E1/2 [N-Boc-pro] = 0.95 V vs. SCE) is just
within the potential window of the TiO photocatalyst, it was nec-
2
essary to find alkyl carboxylic acid type substrates which were more
easily oxidized to expand the scope and illustrate the procedures
broad applicability. With this in mind, we set out to cross-couple
our model aryl-iodide (Methyl 4-Iodobenzoate) with a variety of
substituted and unsubstituted phenylacetic acids. Table 3 shows
that we have successfully coupled various phenylacetic acid deriva-
tives to methyl 4-iodobenzoate under our optimized conditions. As
expected substrates bearing electron-donating substituents gave the
best results, owing to their lower oxidation potential. While the
ability to cross-couple electron deficient phenylacetic acids is ulti-
mately dependent on the oxidation potential of the substrate, it
by the TiO photocatalyst and thus the Ni(0) species required for
2
the initial transmetallation step cannot be regenerated.
While easy photocatalyst removal is one of the key advantages of
our semi-heterogeneous catalytic system, another benefit of heter-
ogeneous catalysts is that in many cases they can be reused after
isolation. While in some cases catalyst reusability has a large impact
on the economical feasibility of a given protocol or the scale up of
the reaction, the abundance and relatively low cost of TiO its reus-
2
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Page 4 of 6
ability not critical. However, environmental issues are still im-
portant and we thus explored the reusability of TiO towards our
model reaction. As shown if Figure 1, the TiO photocatalyst shows
only a slight decrease in efficiency towards the cross-coupling reac-
tion over 5 trials (approx. 15-20%), indicating that it is exceptional-
ly reusable. It is important to note that in each trial 10 mol% of
Nolley, J. P. J. Org. Chem. 1972, 37, 2320-2322;Mizoroki, T.; Mori, K.;
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2
Ozaki, A. Bull. Chem. Soc. Jpn. 1971, 44, 581-581; Mori, K.; Mizoroki, T.;
Ozaki, A. Bull. Chem. Soc. Jpn. 1973, 46, 1505-1508.
2
(2) Miyaura, N.; Suzuki, A. J. Chem. Soc., Chem. Commun. 1979, 866-
8
67.
3) King, A. O.; Okukado, N.; Negishi, E.-i. J. Chem. Soc., Chem.
fresh NiCl Ÿdtbbpy complex was added.
2
(
0
.5 eq. TiO2
I
Commun. 1977, 683-684; Negishi, E.; King, A. O.; Okukado, N. J. Org.
Chem. 1977, 42, 1821-1823; Negishi, E.-i.; Baba, S. J. Chem. Soc., Chem.
Commun. 1976, 596b-597b.
O
.
1
0 mol% NiCl2 glyme
N
N
15 mol% dtbbpy, 1.5 eq Cs2CO3
OH
CO Me
CO2Me
Boc
2
CH CN, Argon
Boc
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Methyl 4-Iodobenzoate
0.4 mmol
hν > 375 nm, 18 h
Boc-Pro-OH
0
.6 mmol
(4) Milstein, D.; Stille, J. K. J. Am. Chem. Soc. 1978, 100, 3636-3638.
1
00
(
5) Corriu, R. J. P.; Masse, J. P. J. Chem. Soc., Chem. Commun. 1972,
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1
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TiO Use Number
2
(
7) Guram, A. S.; Rennels, R. A.; Buchwald, S. L. Angew. Chem. Int. Ed.
Figure 1. TiO reusability in the photoredox/nickel dual catalytic
decarboxylative cross-coupling of N-Boc-proline with Methyl 4-
Iodobenzoate.
2
1995, 34, 1348-1350; Louie, J.; Hartwig, J. F. Tetrahedron Lett. 1995, 36,
3609-3612.
(
8) Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1988, 53, 918-920.
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3191-13195; Choi, S.; Chatterjee, T.; Choi, W. J.; You, Y.; Cho, E. J. ACS
In conclusion, we have demonstrated that P25 TiO can be uti-
2
lized as an efficient heterogeneous photoredox catalyst in the de-
carboxylative cross-coupling of carboxylic acids with aryl iodides
under dual photoredox/Ni catalysis conditions. The scope can
likely be extended to include heteroaryl iodides. While the system
has some limitations in comparison to its homogeneous counter-
parts, the inexpensive and heterogeneous nature of the TiO pho-
tocatalyst make the catalytic system quite attractive even without
(
1
Catal. 2015, 5, 4796-4802; Kalyani, D.; McMurtrey, K. B.; Neufeldt, S. R.;
Sanford, M. S. J. Am. Chem. Soc. 2011, 133, 18566-18569; Lang, S. B.;
O'Nele, K. M.; Douglas, J. T.; Tunge, J. A. Chem. Eur. J. 2015, 21, 18589-
2
considering its easy reusability.
1
8593; Lang, S. B.; O’Nele, K. M.; Tunge, J. A. J. Am. Chem. Soc. 2014, 136,
AUTHOR INFORMATION
13606-13609; Neufeldt, S. R.; Sanford, M. S. Adv. Synth. Catal. 2012, 354,
*
E-mail: titoscaiano@mac.com
ORCID
Juan C. Scaiano: 0000-0002-4838-7123
3
2
517-3522; Xu, N.; Li, P.; Xie, Z.; Wang, L. Chem. Eur. J. 2016, 22, 2236-
242; Xuan, J.; Zeng, T.-T.; Feng, Z.-J.; Deng, Q.-H.; Chen, J.-R.; Lu, L.-
Q.; Xiao, W.-J.; Alper, H. Angew. Chem. Int. Ed. 2015, 54, 1625-1628;
Zhou, C.; Li, P.; Zhu, X.; Wang, L. Org. Lett. 2015, 17, 6198-6201; Zoller,
J.; Fabry, D. C.; Ronge, M. A.; Rueping, M. Angew. Chem. Int. Ed. 2014, 53,
13264-13268.
Author Contributions
The manuscript was written through contributions of all authors. All
authors have given approval to the final version of the manuscript.
Supporting Information
(
(
11) Ye, Y.; Sanford, M. S. J. Am. Chem. Soc. 2012, 134, 9034-9037.
12) He, Y.; Wu, H.; Toste, F. D. Chem. Sci. 2015, 6, 1194-1198;
Details on reaction conditions, spectral data on products, UV-Vis
spectra, and NMR spectra. This material is available free of
charge via the Internet at http://pubs.acs.org
Hopkinson, M. N.; Sahoo, B.; Glorius, F. Adv. Synth. Catal. 2014, 356,
2
8
5
794-2800; Kim, S.; Rojas-Martin, J.; Toste, F. D. Chem. Sci. 2016, 7, 85-
8; Sahoo, B.; Hopkinson, M. N.; Glorius, F. J. Am. Chem. Soc. 2013, 135,
505-5508; Shu, X.-z.; Zhang, M.; He, Y.; Frei, H.; Toste, F. D. J. Am.
ACKNOWLEDGMENT
This work was supported by the Natural Sciences and Engineering
Research Council of Canada, the Canada Foundation for Innova-
tion, and the Canada Research Chairs Program
Chem. Soc. 2014, 136, 5844-5847; Tlahuext-Aca, A.; Hopkinson, M. N.;
Garza-Sanchez, R. A.; Glorius, F. Chem. Eur. J. 2016, 22, 5909-5913; Um,
J.; Yun, H.; Shin, S. Org. Lett. 2016, 18, 484-487.
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Table of Contents Artwork
I
1
9 examples
R
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up to 95 % yield
Ni Catalysis
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TiO2 Photocatalysis
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