A Unified and Practical Method for Carbon–Heteroatom Cross-Coupling using Nickel/Photo Dual Catalysis

Article abstract of DOI:10.1002/chem.202000052

While carbon–heteroatom cross-coupling reactions have been extensively studied, many methods are specific and limited to a particular set of substrates or functional groups. Reported here is a general method that allows for C?O, C?N and C?S cross-coupling reactions under one general set of conditions. We propose that an energy transfer pathway, in which an iridium photosensitizer produces an excited nickel(II) complex, is responsible for the key reductive elimination step that couples aryl bromides, iodides, and chlorides to 1° and 2° alcohols, amines, thiols, carbamates, and sulfonamides, and is amenable to scale up via a flow apparatus.

Full text of DOI:10.1002/chem.202000052

A Journal of
Accepted Article
Title: A Unified and Practical Method for Carbon-Heteroatom Cross-
Coupling via Nickel/Photo Dual Catalysis
Authors: Randolph A. Escobar and Jeffrey Johannes
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: Chem. Eur. J. 10.1002/chem.202000052
Link to VoR: http://dx.doi.org/10.1002/chem.202000052
Supported by

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
A Unified and Practical Method for Carbon-Heteroatom Cross-
Coupling via Nickel/Photo Dual Catalysis
Randolph A. Escobar,* Jeffrey W. Johannes*
Abstract: While carbon-heteroatom cross coupling reactions
have been extensively studied, many methods are specific and
limited to a particular set of substrates or functional groups.
Reported here is a general method that allows for C-O, C-N and
C-S cross coupling reactions under one general set of conditions.
We propose that an energy transfer pathway, in which an iridium
photosensitizer produces an excited nickel (II) complex, is
responsible for the key reductive elimination step that couples
aryl bromides, iodides, and chlorides to 1° and 2° alcohols,
amines, thiols, carbamates, and sulfonamides, and is amenable
to scale up via a flow apparatus.
Carbon-heteroatom bond formation is a common disconnection
in synthetic chemistry and the pharmaceutical industry.1
Methods that furnish these bonds under mild conditions are
appealing especially for late-stage cross coupling or
functionalization of synthetic targets.2 Transition-metal catalyzed
cross-coupling reactions can facilitate C-O, C-S, and C-N bond
formation and has been extensively investigated by numerous
groups.3 While the formation of these bonds have primarily
involved the use of Pd and Cu catalysis, the advent of
photocatalysis has added Ni as a viable option in the field.4
Nickel has the ability to access more oxidation states which
allow for a wider range of chemical transformations.5 However,
Figure 1. Cross coupling reactions via nickel/photo dual catalysis.
the rate of carbon-heteroatom reductive elimination from Ni(II) in
C-O, C-N, and C-S bonds under one catalytic manifold, without
the ground state is known to be slow and several methods have
rigorous exclusion of oxygen, and under mild conditions (Figure
successfully shown that this crucial mechanistic step could be
1d).
achieved through manipulation of the oxidation states of the
After an initial screen of conditions, (See Supporting
nickel (II) complex or the excitation of the nickel (II) complex via
Information) we started our investigation with benzyl alcohol 1a
(1.0 equiv.) and aryl halide 2a (1.0 equiv.) as the model
a dual transition metal catalytic manifold.6 Our group at
AstraZeneca have enabled C-S7 and C-N8 bond formation
substrates; these were combined with 2 mol% of Ir(ppy)3 as the
(Figure
1a)
using
the
strongly
oxidizing
photocatalyst, 5 mol% of NiBr2•glyme, 10 mol% of dtbbpy 4a as
a ligand, and K2CO3 (2.0 equiv.) as a base in non-degassed DMF
(0.3 M, 2.54 mL) under air. Irradiation with blue light for 18 hours
at room temperature yielded the desired ether 3a in 46% yield.
(Table 1, entry 1) Further optimization was achieved by doing an
extensive ligand screen. (See full ligand screen in the Supporting
Information). When testing sterically demanding ligands, such as
neocuprine, ferrocene ligands, or Buchwald ligands12 4b-4d
(Table 1, entries 2-4) no desired product was observed. When
looking at the organic base TMEDA 4e as a ligand, a diminished
yield of 25% was observed (Table 1, entry 5). We next explored
the electronics of the bipyridyl ligands via substitution on the 4-4’
position (4f-4h). When going from the electron withdrawing
group, CF3 4g, to the nondonating H 4f to the donating, OCH3
4h, a dramatic increase in yield from 12% to >99% was observed
(Table 1, entries 6-8). When the most donating N(CH3)2 4i was
screened >99% yield was also observed (Table 1, entry 9). With
the optimal conditions in hand (Table 1, entry 8) various control
experiments were then performed.
[Ir(dF(CF3)ppy)3(dtbpy)]PF6 photocatalyst which is proposed to
directly oxidize the nucleophile to a radical that combines with a
Ni(II) intermediate to generate the requisite Ni(III) species.
Alternatively, the MacMillan group has employed the same
[Ir(dF(CF3)ppy)3(dtbpy)]PF6 photocatalyst to directly oxidize the
Ni(II) complex to a higher energy Ni(III) complex to enable the
reductive elimination step that couples alcohols with aryl halides
to make C-O9 bonds (Figure 1b).9 They also employed the
excitation of nickel (II) via energy transfer by an excited iridium
photocatalyst to enable the reductive elimination step to couple
carboxylic acids and sulfonamides with aryl halides to make C-O
and C-N bonds (Figure 1c).10 A number of groups have more
recently described numerous elegant methodologies using this
energy transfer transition-metal catalysis paradigm.11 However,
all of these methods have a limited substrate scope due to the
reaction conditions and possibly due to the highly oxidizing redox
potential of the photocatalyst. We believe there is still a need for
a photoexcitation method that allows for a generalized substrate
scope and the ability to readily access carbon-heteroatom bonds
stemming from one method. Here we describe a method to form
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
Table 1. Representative Ligand Screen.
Table 2. C-O coupling control experiments.
entry[a]
ligand
4a
3a % yield[b]
1
2
3
4
5
46%
4b
No Reaction
No Reaction
No Reaction
25%
entry[a]
conditions
3a (%)[b]
4c
1
2
3
4
5
as shown
99%
4d
no blue light
No Reaction
No Reaction
No Reaction
4e
no photocatalyst
no photocatalyst, no light
no photocatalyst, no light @ 70 °C
6
7
8
9
4f
27%
4g
4h
4i
12%
No Reaction
>99%
>99%
6
no nickel
No Reaction
No Reaction
20%
7
no base
[a] Conditions: reactions were performed with 1a (1 mmol, 1 equiv.), 2a (1
mmol, 1 equiv.), NiBr2•glyme (5 mol%), ligand (10 mol%), Ir(ppy)3 (2 mol%)
and K2CO3 (2 equiv.) in DMF (0.3 M) in a capped 1-dram vial under blue
LED in a Hepato-chem reactor with a Kessil lamp without a fan (~50°C) and
let stir for 18 hours. [b] Isolates yields.
8
no ligand
9
TEA instead of K2CO3
DBU instead of K2CO3
Halide 2b instead of 2a
Halide 2c instead of 2a
Halide 2b with Na2CO3 as base
Ni(COD)2 as Ni source
Doyle’s precatalyst as Ni source
[Ir(dF(CF3)ppy)2(dtbpy)]+ as PC
Benzophenone as PC
Phenoxazine as PC
No Reaction
77%
10
11
12
13
14
15
16
17
18
Control experiments showed that nickel, photocatalyst (PC),
blue light, and base were critical for the formation of the expected
ether 3a (Table 2). Additionally, organic bases such as TEA did
not give any desired product, except DBU, which gave a 77%
yield of the coupled product. Surprisingly, for aryl chloride 2b
under the optimized conditions, no reactivity was observed when
K2CO3 was used; however, when Na2CO3 was used instead a
modest yield of 61% was realized. Moreover, when Ni(COD)2
was used as the nickel source a yield of 90% was observed,
while use of Doyle’s precatalyst13 gave reduced yields. Finally, a
photocatalyst screen was performed, including those with high
No Reaction
99%
61%
90%
75%
No Reaction
10%
oxidation potentials at the excited state, compared to Ir(ppy)3
99%
red
(E1/2
Ir(III)*/Ir(II)
=
+0.31
V),3e
such
as
[Ir(dF(CF3)ppy)3(dtbpy)]PF6 (E1/2 Ir(III)*/Ir(II) = +1.21 V)3e and
red
[a] Conditions: reactions were performed with 1a (1 mmol, 1 equiv.), 2a (1
mmol, 1 equiv.), NiBr2•glyme (5 mol%), ligand (10 mol%), Ir(ppy)3 (2 mol%)
and K2CO3 (2 equiv.) in DMF (0.3 M) in a capped 1-dram vial under blue
LED in a Hepato-chem reactor with a Kessil lamp without a fan (~50°C) and
let stir for 18 hours. [b] Isolates yields.
red
[Ru(bpy)3]Cl2 (E1/2
Ru(II)*/Ru(I) = +0.77 V)3e, and it was
observed that such catalysts yielded no product. This implies that
the preferred pathway may not involve a Ni (II) to Ni (III) oxidation
that would be involved in a photoredox SET process. We then
screened other photocatalysts that are known photosensitizers,
such as other homoleptic Ir(III) catalysts, benzophenone, and a
phenoxazine based photocatalyst designed to mimic the redox
were also observed.
Supporting Information).
(See full photocatalyst screen in the
Based on our control experiments and ligand and
photocatalyst screens, we hypothesize that an energy transfer
pathway is responsible for the cross coupling reaction. Reductive
elimination from an excited nickel (II) complex is essential for the
efficiency of the catalytic cycle. With this in mind, we hypothesize
that the strong electron donating capabilities of ligand 4h and 4i
and triplet energy of Ir(ppy)3 (ET = 53.6 kcal/mol for Ir(ppy)3; (E0
ox
= +0.41 V, ET = 46.7 kcal/mol for phenoxazine).14 All of these
photocatalysts yielded the desired ether 3a, notably, when
phenoxazine was used as the photocatalyst quantitative yields
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
allows for a stabilized nickel (II) complex in the ground or excited
state that may facilitate the energy transfer between the iridium
PC and the nickel (II) complex. We believe that the donating
ligand may improve the molecular orbital overlap between the
ground state nickel (II) complex and excited iridium species
allowing for facile energy transfer. Follow-up spectroscopic and
computational studies are actively being performed exploring the
effect the ligand has on the triplet energy and frontier molecular
orbitals and mechanism of this transformation.
In order to further explore the proposed idea of a energy
transfer facilitated reductive elimination step, a stoichiometric
reaction was performed. (Figure 2a) Since the nickel (II) complex
with benzyl alcohol 6 is not bench stable, the reaction was
performed in a one-pot stepwise fashion. The reaction was
started by dissolving Doyle’s pre-catalyst 5 in DMF and left to stir
for 4 hours at room temperature with ligand 4h. After the pre-stir,
benzyl alcohol 1a was added along with Ir(ppy)3 and irradiated
with blue light for 18 hours to yield the expected ether 7 in a
satisfactory yield of 60% without any stoichiometric oxidant. It
should be noted that a reaction without the prestir and ligand 4h
was attempted and a lower yield of 35% was observed, which
is consistent with the lower yield observed with ligand 4e in our
initial ligand screen (Table 1, entry 5).
Based on the control experiments and the stoichiometric
reaction, we propose an energy transfer mechanism for this
reaction. (Figure 2b) We believe the reaction starts with the
generation of Ni(0) 8, which then undergoes an oxidative
addition with the aryl halide 9 to form the Ni(II)-aryl halide
complex 10. This complex performs a ligand exchange with the
alcohol 11 to generate the Ni(II)-aryl alcohol complex 12 as the
catalytic resting state. Irradiation of the iridium (III) photocatalyst
with blue light produces a long-lived triplet photoexcited iridium
(III). Based on our results and precedent set by MacMillan’s
previously reported methods10, we propose that the excited
iridium (III) will perform an energy transfer with the Ni(II)-aryl
alcohol complex 12 to obtain the excited Ni(II)-aryl alcohol
complex 13 and the ground state iridium (III). The excited
species 13 will readily undergo a reductive elimination to furnish
the expected ether 14 and regenerate Ni(0) 8.
With optimal conditions in hand and further understanding of
the mechanism, we set out to explore the scope of the reaction.
First, we decided to probe our photocatalytic method by varying
the electronics of the benzyl alcohol (Figure 3). Gratifyingly, both
the electron rich and electron poor benzyl alcohols gave
satisfactory yields when coupled with the model aryl halide 2a.
However, the carboxylic acid substrate 1g gave diminished
yields, possibly due to the competing coupling pathways
between the between the alcohol and the carboxylic acid.3e
Heterocycles such as thiophene 1s and furan 1t were also
tolerated under the established conditions. Aliphatic alcohols
such as ethanol 1w and trifluoroethanol 1x were also screened
and the expected ethers were isolated in moderate yields.
Additionally, secondary alcohols including isopropanol 1y,
cyclohexanol 1z and cyclobutanol 1ab yielded the desired
product, albeit, longer stir periods were necessary. Coupling of
water 1af was also observed which could explain the diminished
yield when using the hydrated nickel source (See Supporting
Information).
Figure 2. a) Reductive elimination readily occurs with blue LED and Ir(ppy)3
alone without stoichiometric oxidant. b) Proposed catalytic cycle for the
coupling of alcohols and aryl halides.
screened with varying electron donating capabilities and the
products were isolated in moderate to excellent yield.
Furthermore, the coupling of thiols under standard reaction
conditions gave the expected products in high yield. Protected
anilines were also synthesized in excellent yields from sulfonam-
ides 1aq, benzamide 1ar, and carbamates 1al-1au allowing for
the installment of protected amines that could be used for further
functionalization. Aliphatic amines and thiols were also screened
as nucleophiles and good to excellent yields were observed 1av-
1az. Coupling of ammonia 1ba was also noted to have
synthetically useful yields to make functionalized anilines.
The scope of the aryl bromides was explored with the
intention of showing a tolerability to activated and non-activated
halides (Figure 4). We were able to show that, in general, most
activated halides yielded 90% or above even when the
substitution was at the meta- position on the aryl ring 2r. It should
be noted that if the bromide is switched to the iodide the reaction
times are decreased significantly. Inversely, when the bromide is
switched to the chloride we see a dramatic decrease in reactivity.
To further demonstrate this halide selectivity, bis-halide 2o gave
90% yield of product coupled through the bromide, while bis-
halide 2p gave 95% yield of product coupled at the iodide.
Electron-rich bromides yielded moderate amounts of the
expected product only if let stir for 36 hours. Selectivity towards
the primary alcohol over aniline was also highlighted with
bromoaniline 2t, 70% yield of the product was isolated.
Halogenated hetero-arenes were also screened. Pyridine 2v,
pyrimidine 2w, and thiazole 2z coupled under the optimized
conditions and furnished the respective product in moderate
Other nucleophiles were attempted such as thiols and
amines 1ag-1ap and we were pleased to see that the respective
products were observed using the same method without further
optimization. Anilines functionalized at the 4-position were
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
Figure 3. Nucleophile scope for the nickel/iridium dual catalyzed cross-coupling reaction.
Ligand:
Photocatalyst:
H3CO
NiBr2· glyme (5 mol%)
Ir(ppy)3 (2 mol%)
N
Ir
F3C
4h (10 mol%)
CF3
R’
R’
N
N
N
K2CO3 (2 equiv.),
DMF (0.3 M),
blue LED, 18-36 hrs.
R
A
Br
R
A
H3CO
N
1a-ba
3a-ba
2a
Ir(ppy)3
4h
CF3
R
Scope of Alcohols
R
O
OH
OH
OH
OH
OH
OH
OH
O
H3C
F3C
OH
F
Cl
H3CO
OH
1e 96% yield
1f 73% yield
1g 22% yield
1a 99% yield
1b 87% yield
1c 90% yield
1d 75% yield
O
F
O
OH
O
OH
OH
F
F
OH
OH
OH
O
tBu-O
N
H
OCH3
F
H
OCH3
F
1n 93% yield
1h 89% yield
1i 90% yield
1j 87% yield
OH
1k 71% yield
1l 68% yield
1m 64% yield
H3CO
OH
OH
OH
OH
S
OH
O
OH
N
OCH3
1o 86% yield
1p 85% yield
1q 79% yield
CH3
OH
1y 74% yield
1r 74% yield
1u 87% yield
1s 77% yield
1t 62% yield
H3C
OH
OH
OH
OH
OH
OH
OH
1w 50% yield
CH3
H3C
H3C
CH3
HO
CF3
1ad 72% yield
1ac 88% yield
1v 68% yield
1x 53% yield
1z 87% yield
1aa 78% yield 1ab 69% yield
H3C
OH
H2O
CH3
CH3
Geraniol
1ae 82% yield
1af 35% yield
CF3
R
A
Scope of N and S Nucleophiles
R
A
A
A
A
A
O
O
S
tBu
H3CO
NH2
F3C
O
1ai NH2: 58% yield
1aj SH: 81% yield
1ak NH2: 50% yield
1al SH: 75% yield
1ao NH2: 31% yield
1ap SH: 92% yield
1ag NH2: 63% yield
1ah SH: 97% yield
1am NH2: 55% yield
1an SH: 91% yield
RO
NH2
1aq 99% yield
1as OtBu: 65% yield
1at OBn: 75% yield
O
CH3
NH2
SH
A
NH2
1au OAllyl: 63% yield
H3C
NH2
NH3
H3CO
1ar 83% yield
1av 99% yield
1aw 40% yield
1ay NH2: 32% yield
1az SH: 79% yield
1ax 37% yield
1ba 42% yield
Conditions: reactions were performed with (1 mmol, 1 equiv.) of the nucleophile, (1 mmol, 1 equiv.) of the aryl halide, NiBr2•glyme (5 mol%), ligand 4h (10 mol%),
Ir(ppy)3 (2 mol%) and K2CO3 (2 equiv.) in DMF (0.3 M) in a capped 1-dram vial under blue LED in a Hepatochem reactor with a Kessil lamp without a fan (~50°C)
and let stir for 18 - 36 hours. All reported yields are isolated.
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
re 4. Electrophile scope for the nickel/iridium dual catalyzed cross-coupling
Table 3. Optimization of the nickel/iridium dual catalyzed cross-coupling
reaction.
reaction in flow for scalability studies.
entry
temp
(°C)
tR (min)
flow rate
(mL/min)
scale
(mmol)
yield
(%)
1
2
3
35
50
45
15
10
15
0.33
0.50
0.33
2.5
2.5
5.0
37
NR
45
C-N, and C-S bonds without the need for any further optimization
or modification to the reaction conditions and allows for activated
and non-activated aryl halides as coupling partners. These
results along with the control experiments and the stoichiometric
reaction supports our proposed mechanism in which the iridium
performs a triplet-triplet energy transfer to facilitate the otherwise
disfavored reductive elimination to furnish the desired product.
We envision this method could be widely applied for a variety of
synthetic targets in total synthesis or in the pharmaceutical
industry due to its robustness, mild conditions and its ability to
scale when used in a flow platform.
Conditions: reactions were performed with (1 mmol, 1 equiv.) of nucleophile
1a, (1 mmol, 1 equiv.) of the aryl halide, NiBr2•glyme (5 mol%), ligand 4h (10
mol%), Ir(ppy)3 (2 mol%) and K2CO3 (2 equiv.) in DMF (0.3 M) in a capped 1-
dram vial under blue LED in a Hepatochem reactor with a Kessil lamp without
a fan (~50°C) and let stir for 18 - 36 hours. All reported yields are isolated. [a]
Na2CO3 was used as the base. [b] Reactions were let stir for 36 hours. [c]
Ligand 4i was used instead of 4h.
yields. Interestingly, when the ligand 4i was used with the
pyridine 2v a significant increase in yield is observed.
Then we turned our attention towards the scalability of the
reaction. Unfortunately, when scaling up a photochemical
reaction in batch, the light penetration in a round-bottom flask is
of concern. It was then decided to attempt optimization of our
model reaction in flow using a Vaportech flow apparatus (See
Supporting Information). Due to the heterogeneity of the
optimized conditions caused by the K2CO3, it was decided to use
the DBU as the base, which afforded a batch reaction yield of
77% at 1 mmol scale (Table 2, entry 10) and a complete
homogenized solution under the reaction conditions when using
our model substrates 1a and 2a. After doing some preliminary
optimization, it was noted that when using a retention time (tR) of
15 min, with a flow rate of 0.33 mL/min and a reactor temperature
of 45 °C, the reaction could be successfully scaled up to 5 mmol
with a synthetically useful yield of 45% (Table 3, entry 3). It
should also be noted that the catalyst loading was decreased for
both the Ir(ppy)3 and NiBr2•glyme from 2 mol% and 5 mol% to 1
mol% and 2 mol%. Due to the volume capabilities of our
photoreactor, we could not increase the residence time to allow
for higher yields but nevertheless these preliminary results
indicate that with the proper flow apparatus, this reaction could
be further scaled.
Acknowledgements
We thank Dr. Sharon Tentarelli (AstraZeneca) For HRMS
analysis.
Keywords: cross-coupling • nickel catalysis • photocatalysis •
dual catalysis • synthetic method
[1]
a) E. P. Beaumier, A. J. Pearce, X. Y. See, I. A. Tonks, Nature Rev.
Chem. 2019, 3, 15-34; b) P. Ruiz-Castillo, S. L. Buchwald, Chem. Rev.
2016, 116, 12564-12649; c) J. J. Douglas, M. J. Sevrin, C. R.
Stephenson, Org. Process Res. Dev. 2016, 20, 1134-1147. d) D. G.
Brown, J. Boström, J. Med. Chem. 2016, 59, 4443-4458. e) J. Magano,
J. R. Dunetz, Transition Metal-Catalyzed Coupling in Process
Chemistry, Ed. 1, Wiley-VCH, Weinheim, 2013; f) J. Bariwal, E. Van der
Eycken, Chem. Soc. Rev. 2013, 42, 9283-9303; (g) C. C. Johansson-
Seechurn, M. O. Kitching, T. J. Colacot, V. Snieckus, Angew. Chem.
Int. Ed. 2012, 51, 5062-5085.
Herein, we described an optimized method in which a
carbon-alcohol coupling was achieved via excitation of a nickel
(II) complex by
photocatalyst. The method was also able to successfully furnish
a
commercially available iridium (III)
[2]
a) D. T. Cohen, C. Zhang, C. M. Fadzen, A. J. Mijalis, L. Hie, K. D.
Johnson, Z. Shriver, O. Plante, S. J. Miller, S. L. Buchwald, B. L.
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
entelute, Nature Chemistry 2019, 11, 78-85; b) T. Cernak, K. D. Dykstra,
S. Tyagarajan, P. Vachal, S. W. Krska, Chem. Soc. Rev. 2016, 45, 546-
576; c) P. S. Fier, J. F. Hartwig, J. Am. Chem. Soc. 2014, 136, 28,
10139-10147.
[3]
a) M. R. Uehling, R. P. King, S. W. Krska, T. Cernak, S. L. Buchwald,
Science 2019, 363, 405-408; b) A. Wimmer, B. Kꢀnig, Org. Lett. 2019,
218, 2740-2744; c) M. O. Konev, T. A. McTeague, J. W. Johannes, ACS
Catal. 2018, 8, 9120-9124; d) T. Kim, S. J. McCarver, C. Lee, D. W. C.
MacMillan, Angew. Chem. Int. Ed., 2018, 57, 3488-3492; e) E. R. Welin,
C. Le, D. M. Arias-Rotondo, K. James, J. K. McCusker, D. W. C.
MacMillan, Science 2017, 355, 380-385; f) E. B. Corcoran, M. T. Pirnot,
S. Lin, S. D. Dreher, D. A. DiRocco, I. W. Davies, S. L. Buchwald, D. W.
C. MacMillan, Science 2016, 353, 279−283; g) J. A. Terrett, J. D.
Cuthbertson, V. W. Shurtleff, D. W. C. MacMillan, Nature 2015, 524,
330-334; h) J. F. Hartwig, Acc. Chem. Res. 2008, 41, 1534−1544.
a) S. Z. Tasker, E. A. Standley, T. F. Jamison, Nature 2014, 509, 299-
309; b) M. R. Netherton, G. C. Fu, Adv. Synth. Catal. 2004, 346, 1525-
1532.
[4]
[5]
a) S. Biswas, D. J. Weix, J. Am. Chem. Soc. 2013, 135, 16192–16197;
b) R. Han, G. L. Hillhouse, J. Am. Chem. Soc. 1997, 119, 8135–8136;
c) P. T. Matsunaga, J. C. Mavropoulos, G. L. Hillhouse, Polyhedron
1995, 14, 175–185; d) P. T. Matsunaga, G. L. Hillhouse, A. L.
Rheingold, J. Am. Chem. Soc. 1993, 115, 2075–2077.
[6]
For reviews on photocatalyzed and photoredox reactions, see: a) F.
Strieth-Kalthoff, M. J. James, M. Teders, L. Pitzera, F. Glorius, Chem.
Soc. Rev. 2018, 47, 7190-7202; b) S. A. Morris, J. Wang, N. Zheng,
Acc. Chem. Res. 2016, 49, 1957−1968; c) K. L. Skubi, T. R. Blum, T.
P. Yoon, Chem. Rev. 2016, 116, 10035−10074; d) J. Twilton, C. Le, P.
Zhang, M. H. Shaw, R. W. Evans, D. W. C. MacMillan, Nat. Rev. Chem.
2017, 1, 0052; e) N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116,
10075−10166; f) B. Kꢀnig, J. Org. Chem. 2017, 1979−1981; f) C.
Cavedon, P. H. Seeberger, B. Pieber Eur. J. Org. Chem. 2019, 1-15
(and references therein).
[7]
[8]
M. S. Oderinde, M. Frenette, D. W. Robbins, B. Aquila, J. W. Johannes,
J. Am. Chem. Soc. 2016, 138, 1760-1763.
M. S. Oderinde, N. S. Jones, A. Juneau, M. Frenette, B. Aquila, S.
Tentarelli, D. W. Robbins, J. W. Johannes, Angew. Chem., Int. Ed.
2016, 55, 13219-13223.
[9]
J. A. Terrett, J. D. Cuthbertson, V. W. Shurtleff, D. W. C. MacMillan,
Nature 2015, 524, 330-334.
[10] (a) T. Kim, S. J. McCarver, C. Lee, D. W. C. MacMillan, Angew. Chem.
Int. Ed., 2018, 57, 3488-3492; A. Wimmer, B. Kꢀnig, Org. Lett. 2019,
218, 2740-2744. (b) E. R. Welin, C. Le, D. M. Arias-Rotondo, J. K.
McCusker, D. W. C. MacMillan, Science 2017, 355, 6323, 380-385.
[11]
(a) Q. M. Kainz, C. D. Matier, A. Bartoszewicz, S. L. Zultanski, J. C.
Peters, G. C. Fu, Science 2016, 351, 681– 684 (b) B. J. Shields, A. G.
Doyle, J. Am. Chem. Soc. 2016, 138, 12719–12722. (c) S. J. Hwang,
D. C. Powers, A. G. Maher, B. L. Anderson, R. G. Hadt, S. -L. Zheng,
S. Y. -S. Chen, D. G. Nocera, J. Am. Chem. Soc. 2015, 137, 6472–
6475. (d) S. E. Creutz, K. J. Lotito, G. C. Fu, J. C. Peters, Science 2012,
338, 647-651. M. Kudisch, C-H. Lim, P. Thordarson, G. M. Miyake J.
Am. Chem. Soc. 2019, 141, 49, 19479-19486.
[12]
[13]
B. T. Ingoglia, C. C. Wagen, S. L. Buchwald, Tetrahedron 2019, In
Press.
J. D. Shields, E. E. Gray, A. G. Doyle, Org. Lett. 2015, 17, 2166−2169
[14] B. G. McCarthy, R. M. Pearson, C. -H. Lim, S. M. Sartor, N. H. Damrauer,
G. M. Miyake J. Am. Chem. Soc. 2018, 140, 5088-5101.
This article is protected by copyright. All rights reserved.

10.1002/chem.202000052
Chemistry - A European Journal
COMMUNICATION
This article is protected by copyright. All rights reserved.