Making Copper Photocatalysis Even More Robust and Economic: Photoredox Catalysis with [CuII(dmp)2Cl]Cl

Article abstract of DOI:10.1002/ejoc.201900839

The Cu^II complex [Cu^II(dmp)₂Cl]Cl (dmp = 2,9-dimethyl-1,10-phenanthroline) is evaluated as an oxidation stable precursor for visible-light-mediated Cu^I-photoredox catalysis, being efficient and considerable more cost-effective compared to previously established copper(I) photocatalysts. Its performance and efficiency are demonstrated within a broad scope of atom transfer radical addition (ATRA) reactions, allowing the 1,2-difunctionalization of alkenes, as well as for decarboxylative coupling and an Appel reaction. Moreover, the utility of the complex is shown by various gram-scale functionalizations of styrene, thus suggesting [Cu^II(dmp)₂Cl]Cl to be a low-priced alternative precatalyst for processes run on scale. Furthermore, this study provides UV/Vis evidence on the mechanism for the visible light activation of Cu^II complexes.

Full text of DOI:10.1002/ejoc.201900839

A Journal of
Accepted Article
Title: Making Copper Photocatalysis even more robust and economic:
Photoredox Catalysis with [CuII(dmp)2Cl]Cl
Authors: Sebastian Engl and Oliver Reiser
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: Eur. J. Org. Chem. 10.1002/ejoc.201900839
Link to VoR: http://dx.doi.org/10.1002/ejoc.201900839
Supported by

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
Making Copper Photocatalysis even more robust and economic:
Photoredox Catalysis with [CuII(dmp)2Cl]Cl
Sebastian Engl[a] and Oliver Reiser*[a]
Abstract: The Cu(II)-complex [CuII(dmp)2Cl]Cl (dmp = 2,9-dimethyl-
1,10-phenanthroline) is evaluated as an oxidation stable precursor for
visible-light-mediated Cu(I)-photoredox catalysis, being efficient and
considerable more cost-effective compared to previously established
copper(I) photocatalysts. Its performance and efficiency are
demonstrated within a broad scope of atom transfer radical addition
(ATRA) reactions, allowing the 1,2-difunctionalization of alkenes, as
well as for decarboxylative coupling and an Appel reaction. Moreover,
the utility of the complex is shown by various gram-scale
functionalizations of styrene, thus suggesting [CuII(dmp)2Cl]Cl to be a
low-priced alternative precatalyst for processes run on scale.
Furthermore, this study provides UV-vis evidence on the mechanism
for the visible light activation of Cu(II) complexes.
calls for a four-step ligand synthesis including a Pd-catalyzed
cross-coupling reaction.[9–11]
Results and Discussion
Recently, we have established a visible-light-mediated vicinal
chlorosulfonylation of olefins utilizing the Cu(I) complex
[CuI(dap)2]Cl
and
the
corresponding
Cu(II)
complex
[CuII(dap)Cl2].[12] The latter proved to be highly efficient in the title
reaction, being at the same time beneficial from an economic
point of view since only half the amount of dap ligand is required
compared to [CuI(dap)2]Cl. Based on this study, we were
searching for Cu(II) complexes for photoredox catalysis utilizing
alternative ligands that would be commercially available or could
be easily accessed.
Introduction
In recent years, visible light photocatalysis has emerged as a
powerful tool for carbon-carbon and carbon-heteroatom bond
forming reactions, increasing molecular complexity under mild
and ecologically benign reaction conditions.[1,2] By now, the most
commonly employed photocatalysts are represented by transition
metal complexes based on ruthenium(II) and iridium(III), having
the desired features for photocatalysts such as photostability,
long excited state lifetimes, strong absorption in the visible region
and high redox potentials.[3] However, rather high cost, potential
toxicity and the scarcity of the corresponding metal salts are major
drawbacks of this class of catalysts.[4] Organic dye photocatalysts
provide a low-cost and metal-free alternative, but suffer in general
from lower photostability.[2,5] In this context, copper complexes are
gaining importance for visible-light-mediated transformations.
Besides the economic benefits, copper complexes, especially
copper-phenanthrolines provide strong photo-excited reducing
power, sufficient excited state lifetimes and are prone to undergo
structural redistribution and ligand exchange which open up
unique reaction pathways.[6] However, although the copper salts
are low-priced and highly economic, most copper complexes
suffer from time- and price-consuming ligand synthesis.[6-8] For
instance, [CuI(dap)2]Cl (dap = 2,9-(p-anisyl)-1,10-phenanthroline)
being the leading representative among copper photocatalysts,
Scheme 1. Comparison of Cu(II)- and the corresponding Cu(I)-complexes in
photocatalysis. [a] Ref.[13] [b] Ref.[14] [c] Ref.[15] [d] For details, see SI. [e] Ref.[16]
[f] Ref.[17] [g] Ref.[18]
.
[a]
M.Sc. Sebastian Engl and Prof. Dr. Oliver Reiser
Institute of Organic Chemistry
University of Regensburg
Universitätsstr. 31, 93053 Regensburg, Germany
E-mail: oliver.reiser@chemie.uni-regensburg.de
Homepage: http://www-oc.chemie.uni-regensburg.de/reiser
Arguably the most readily available copper(II)phenanthroline
complex would be [CuII(phen)2Cl]Cl, which can be prepared
according to the literature from CuCl2 and 1,10-phenanthroline
(phen).[13] Following the previously reported concept of visible-
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
light-induced homolysis (VLIH) of Cu(II) complexes in
photoreactions[12], [CuII(phen)2Cl]Cl should be reduced in situ to
the corresponding Cu(I) complex (vide infra), representing the
catalytically active species in the ATRA reactions studied
(Scheme 1). Upon visible-light irradiation and metal-to-ligand
charge transfer (MLCT), photoinduced “flattening” of the
geometry in the excited state occurs. However, due to the lack of
substitution in the 1,10-position of the ligand, [CuI(phen)]+ is
conformationally mobile and thus prone to rapidly return to its
electronical ground state. As a consequence, this complex shows
no luminescence.[19,20] In line with this property, no ATRA reaction
between styrene (1a) and tosyl chloride (2a) is observed when
[CuII(phen)2Cl]Cl was used as a potential precatalyst (Table 1,
entry 1), contrasting [CuII(dap)Cl2] which catalyzes the formation
of 3a in 95%[12] (entry 2). In the latter, the steric effect of the para-
aryl substitution prevents a rapid geometrical relaxation and thus
quenching of the excited state, allowing intersystem crossing
(ISC) to attain a stable triplet excited state, which then can act as
the reductant in the photoreaction.
the procedure recently reported by Kloo and co-workers[14]. The
corresponding Cu(I) complex [CuI(dmp)2]+ indeed shows
luminescence, an even higher excited state reduction potential
compared to that of [CuI(dap)2]Cl, but an excited state lifetime of
90 ns[17], being significantly shorter than that of [Cu(dap)2]Cl
(270 ns[18a]). Although these photochemical parameters of
[CuI(dmp)2]+ were reported[19,21], there have been only few
applications in photoredox catalysis reflected by a small number
of reports using [CuI(dmp)2]+ as part of screening efforts for
reaction optimization.[8,16,22] Therefore, we wondered, if
[CuII(dmp)2Cl]Cl can serve as an oxidation- and bench-stable
precursor for VLIH to [CuI(dmp)2]+ and then the excited state
lifetime of the latter is still sufficient for diffusion-controlled
photoredox catalysis. Gratifyingly, [CuII(dmp)2Cl]Cl proved indeed
to be a capable precatalyst for the aforementioned ATRA process
between styrene (1a) and tosyl chloride (2a), giving rise to 3a in
up to 92% yield (entries 3-5).Control experiments, omitting either
catalyst or light, did not lead any conversion (entries 6,7).
Employing CuCl2 or the dmp ligand as potential stand-alone
catalysts resulted in no product formation (entries 8,9). Notably,
using 2.0 mol% of [CuII(dmp)2Cl]Cl precatalyst afforded a slightly
higher yield of 92% (entry 5) of the desired product compared to
1.0 mol% (entry 2), contrasting previous conditions with
[CuI(dap)2]Cl or [CuII(dap)Cl2] for which 1.0 mol% catalyst loading
was sufficient to generally give yields >90%. Given the low cost
of [CuII(dmp)2Cl]Cl prompted us to explore the substrate scope
with best-optimized conditions (entry 5), but selected examples
were also tested with lower catalyst loading to probe the limit of
the catalytical activity and to make a better comparison with
[Cu(dap)2]Cl possible (Scheme 2).
Table 1. Optimization and Control experiments[a]
Entry
1
Conditions
[CuII(phen)2Cl]Cl (1.0 mol%)
[CuII(dap)Cl2] (1.0 mol%)
1.0 mol% catalyst; green LED
1.0 mol% catalyst; blue LED
2.0 mol% catalyst; blue LED
no catalyst
NMR-yield[b]
nr
95%
75%
86%
92% (92%)
nr
2[c]
3
4
5[d]
6
7
no light
nr
8
CuCl2 (10.0 mol%)
nr
9
dmp (10.0 mol%)
4%
10[e]
AIBN (10.0 mol%); T = 80 °C
nr
[a] Reaction conditions: styrene (1a) (0.5 mmol, 1.0 equiv), tosyl chloride
(2a) (0.5 mmol, 1.0 equiv), catalyst (2.0 mol%) in MeCN (dry, degassed,
2.0 mL); Irradiation at 455 nm (blue LED) under N2 atmosphere for 30 h at
room temperature. [b] 1H NMR yield using diphenoxymethane as an internal
standard. [c] Ref.[12] [d] Isolated yield in parenthesis. [e] Polymerization
adducts of styrene observed. nr = no reaction.
Maintaining the steric effect of the 1,10-substitution but still
simplifying the ligand, we next switched to [CuII(dmp)2Cl]Cl,
readily prepared from CuCl2 and two equivalents of dmp, following
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
Scheme 2. Scope of chlorosulfonylation reaction. Reaction conditions: olefin 1
(0.5 mmol, 1.0 equiv), sulfonyl chloride 2 (0.5 mmol, 1.0 equiv), [CuII(dmp)2Cl]Cl
(2.0 mol%) in MeCN (dry, degassed, 2.0 mL); Irradiation at 455 nm (blue LED)
under N2 atmosphere for 30 h at room temperature. Isolated yields are given.
[a] Catalyst loading 1.0 mol%, 24 h irradiation at 530 nm (green LED); results
taken from previous report[12]. [b] Reaction time 48 h. [c] Olefin 1 (1.0 mmol,
2.0 equiv), Na2CO3 (0.5 mmol, 1.0 equiv), reaction time 48 h.
(1.0 mol%) under 530 nm (green LED) irradiation; results taken from previous
report[23]
.
We next investigated trifluoromethylchlorosulfonylation of
unactivated alkenes, being unique for copper(I)-photocatalysts
such as [CuI(dap)2]Cl.[23,24] We were pleased to see that also
[CuII(dmp)2Cl]Cl is able to convert unactivated alkenes to the
desired products 4a and 4b in almost quantitative yields even
outperforming the established [CuI(dap)2]Cl catalyst (Scheme 3,
top). In the case of 4b, lowering of the catalyst loading to 0.5 mol%
still yielded the desired product in an appreciable yield of 70%.
Recently, Bissember and co-workers investigated several
homoleptic 2,9-diaryl-1,10-phen Cu(I) complexes towards the
influence of the ligand in the described trifluoromethylchloro-
sulfonylation.[16] Surprisingly, they only observed 24% of 4b under
similar reaction conditions using the corresponding Cu(I) complex
[CuI(dmp)2]Cl, presumably due to the use of an elevated
temperature (45 °C).
Furthermore, while [CuI(dap)2]Cl did not tolerate the use of
activated alkenes instead leading to mixtures of various products
(exception of para-nitrostyrene), [CuII(dmp)2Cl]Cl also enables the
conversion of styrene derivatives, however, the corresponding
products with extrusion of SO2 are observed (Scheme 3, bottom).
These findings are in accordance with two recent literature reports,
who also observed copper catalyzed chlorotrifluoromethylation
when using different styrenes.[25,26]
We were pleased to find that both electron-rich and electron-poor
styrenes with sterically or electronically differentiated aromatic
sulfonyl chlorides gave rise to the corresponding photoproducts
3a-3f in high yields comparable to [CuI(dap)2]Cl, in the case of 3f
even outperforming [CuI(dap)2]Cl. Further increase of electron
deficiency or sterically bulk was also well tolerated giving rise to
the ATRA products 3i and 3j in good yields. However, subjecting
alkyl substituted sulfonyl chlorides to the reaction conditions
resulted in a significant decrease of yield (3g, 3h) compared to
[CuI(dap)2]Cl. In our previous study[12], switching to unactivated
alkenes required the use of one equivalent of Na2CO3 preventing
the [CuI(dap)2]Cl catalyst from being poisoned. Applying this
protocol, [CuII(dmp)2Cl]Cl gave nevertheless only low yields of 6-
15% for the desired products 3l-3n. Catalyst stability tests (see
SI) concluded a significant poisoning of the catalytically active
species within one hour of irradiation presumably due to formation
of acidic traces originating from sulfonyl chloride. Contrasting the
case of [CuI(dap)2]Cl, the protective effect of Na2CO3 cannot
prevent the poisoning of [CuII(dmp)2Cl]Cl.
Scheme 4. Scope of Iodoperfluorination. Reaction conditions: olefin
1
(0.5 mmol, 1.0 equiv), C8F17
I
(7) (1.0 mmol, 2.0 equiv), [CuII(dmp)2Cl]Cl
(2.0 mol%) in MeCN (dry, degassed, 1.0 mL); Irradiation at 530 nm (green LED)
under N2 atmosphere for 30 h at room temperature. Isolated yields are given.
[a] Catalyst loading 1.0 mol%, 16-20 h irradiation; results taken from previous
report[10]. [b] DCM (dry, degassed, 1.0 mL) was used as a solvent.
Recently, our group successfully showed the iodoperfluorination
of styrene derivatives with the [CuI(dap)2]Cl catalyst, a reaction
that fails with organic dyes, iridium- or ruthenium-based
photocatalysts, emphasizing the unique character of copper
photocatalysis.[10] Gratifyingly, also [CuII(dmp)2Cl]Cl performed
well in this reaction both with activated (8a-8d) as well as with
unactivated (8e) alkenes (Scheme 4).
Scheme 3. Trifluoromethylchlorosulfonylation and Chlorotrifluoromethylation
reaction. Reaction conditions: olefin 1 (0.5 mmol, 1.0 equiv), TfCl 2b (1.0 mmol,
2.0 equiv), K2HPO4 (1.0 mmol, 2.0 equiv), [CuII(dmp)2Cl]Cl (2.0 mol%) in MeCN
(dry, degassed, 1.5 mL); Irradiation at 455 nm (blue LED) under N2 atmosphere
for 24 h at room temperature. Isolated yields are given. [a]Yield for [Cu(dap)2]Cl
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
ATRA reactions with various bromine containing radical
precursors that proved to be successful with [CuI(dap)2]Cl, were
also evaluated with [CuII(dmp)2Cl]Cl (Table 2).[9,27]
Having addressed a broad scope of different activated halides for
copper-catalyzed visible-light-mediated ATRA reaction, we
wanted next to examine mechanistically different photocatalytic
transformations. First, we targeted the visible light
decarboxylative fragmentation of N-(acyloxy)phthalimide 11 with
subsequent Csp3-Csp coupling to bromoalkyne 12 (Scheme 5).
Table 2. Scope of other ATRA reagents[a]
Entry
1
Alkene 1
Halide 9
Product 10
Yield
Scheme 5. Decarboxylative coupling reaction. Reaction conditions: 11
(0.5 mmol, 1.0 equiv), 12 (0.75 mmol, 1.5 equiv), DIPEA (1.0 mmol, 2.0 equiv),
Hantzsch ester (0.75 mmol, 1.5 equiv), [CuII(dmp)2Cl]Cl (2.0 mol%) in THF (dry,
degassed, 1.5 mL); Irradiation at 455 nm (blue LED) under N2 atmosphere for
24 h at room temperature. Isolated yield is given.
2
3[b]
Indeed, subjecting the mentioned starting materials to the
reaction conditions indicated, the desired product 13 was formed
in good yields of 62% employing 2.0 mol% of [CuII(dmp)2Cl]Cl as
precatalyst. The previously reported ruthenium catalyst only
4[b]
5[c]
yielded
13
in
28%[29]
,
whereas
heteroleptic
Cu(I)
[CuI(dq)(BINAP)]BF4 complex evaluated by Collins and co-
workers afforded 87% of coupling product[8].
[a] Reaction conditions: olefin 1 (0.5 mmol, 1.0 equiv), halide 9 (0.5 mmol,
1.0 equiv), [CuII(dmp)2Cl]Cl (2.0 mol%) in MeCN (dry, degassed, 1.0 mL);
Irradiation at 455 nm (blue LED) under N2 atmosphere for 30 h at room
temperature. Isolated yields are given. [b] Halide 9 (1.0 mmol, 2.0 equiv),
LiBr (1.0 mmol, 2.0 equiv) was added, solvent DMF/water (1:4, 1.0 mL).
[c] 5.0 equiv (2.5 mmol) of styrene (1a). [d] Catalyst loading 1.0 mol%, 24 h
Additionally, Collins[30] and co-workers showed that the
heteroleptic complex [CuI(tmp)(BINAP)]BF4 is an effective
alternative in the photocatalytic Appel-type conversion of alcohols
to the corresponding bromides developed by Stephenson[31] and
co-workers in 2011. Gratifyingly, also [CuII(dmp)2Cl]Cl was
effective in this reaction yielding (1-bromoethyl)benzene (15) in
synthetical useful yield of 73% (Scheme 6), contrasting results
previously reported for the homoleptic [CuI(dmp)2]Cl complex,
which failed to achieve these transformations.[30]
irradiation at 530 nm (green LED); results taken from previous reports[9,27]
.
Tetrabrommethane (9a) addition to styrene (1a) is a widely used
test reaction for photocatalytic activity.[28] Two previous reports
screened the corresponding Cu(I) complex [CuI(dmp)2]Cl in the
aforementioned reaction, yielding product 10a in 12%[22b]
(0.3 mol% catalyst, 525 nm irradiation) and 60%[22a] (1.0 equiv
2,6-lutidine in DCM for one hour at 400 nm irradiation),
respectively. Starting from the Cu(II) complex [CuII(dmp)2Cl]Cl
and given reaction conditions, both activated alkene 1a and
unactivated alkene 1b were cleanly transformed into the desired
products 10a and 10b in almost quantitative yields (Table 4,
entries 1-2). Next, we switched to bromomalonate 9b as ATRA
reagent affording the desired photoproduct 10c in a synthetically
useful yield of 62%, being still comparable to using [CuI(dap)2]Cl
(entry 3). A limitation of the [CuII(dmp)2Cl]Cl seems to be reached
for α-bromo acetophenone (9c) and benzyl bromide 9d, giving the
corresponding products 10d and 10e in much lower yields (12-
15%) compared to [CuI(dap)2]Cl (87-98%). In light of the stronger
reducing power of excited [CuII(dmp)2Cl]Cl, this result was
surprising and might point towards an insufficient excited state
lifetime of the former which makes single electron transfer (SET)
to 9c or 9d inefficient.
Scheme 6. Photocatalytic Appel reaction. Reaction conditions: 14 (0.5 mmol,
1.0 equiv), 9a (1.0 mmol, 2.0 equiv), NaBr (1.0 mmol, 2.0 equiv),
[CuII(dmp)2Cl]Cl (2.0 mol%) in DMF (dry, degassed, 3.0 mL); Irradiation at
455 nm (blue LED) under N2 atmosphere for 24 h at room temperature. Isolated
yield is given.
With quite a variety of different copper-catalyzed photoreactions
successfully established for [CuII(dmp)2Cl]Cl, we set out to
demonstrate the viability of the complex on larger scale. Therefore,
scale-up of three different difunctionalization reactions for styrene
(1a) were tested (Scheme 7). Chlorosulfonylation, iodoperfluor-
ination as well as CBr4-addition were performed on a 5.0 mmol
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
scale giving rise to the desired photoproducts 3a, 8a and 10a in
excellent yields (82-96%) in gram quantities of 1.38-2.67 g
highlighting the possible application of [CuII(dmp)2Cl]Cl to
produce synthetically useful quantities of product in ATRA
reactions.
Scheme 7. Gram-scale functionalization of styrene. Reaction conditions:
styrene (1a) (5.0 mmol, 1.0 equiv), halide 2 / 7 / 9 (5.0 mmol, 1.0 equiv),
[CuII(dmp)2Cl]Cl (2.0 mol%) in MeCN (dry, degassed, 15.0 mL); Irradiation at
455 nm (blue LED) under N2 atmosphere for 48 h at room temperature. Isolated
yields are given. [a] C8F17I (7) (10.0 mmol, 2.0 equiv); Irradiation at 530 nm
(green LED).
Figure 1. UV-vis monitoring of chlorosulfonylation reaction using
[CuII(dmp)2Cl]Cl (green) and [CuI(dmp)2]Cl (red). (A) Copper catalysts alone;
(B) Reaction mixture for chlorosulfonylation: styrene 1a, tosyl chloride 2a and
[CuII(dmp)2Cl]Cl (green) / [CuI(dmp)2]Cl (red); (C) Crude reaction mixture B after
irradiation at 455 nm (blue LED) under N2 atmosphere for 30 h at room
temperature. All UV-vis spectra are measured in MeCN (dry, 0.02 mM).
So far, there are only few examples that consider ligand to metal
charge transfer (LMCT) for Cu(II)-complexes resulting in visible-
light-induced homolysis (VLIH) to Cu(I) as
a conceivable
mechanistic proposal for photochemistry starting from Cu(II)
complexes,[12,15,32] based on the pioneering study by Kochi
investigating the photolysis of the Cu(II)-Cl-bond in CuCl2 upon
UV irradiation.[33] However, by now there is only scarce
experimental evidence present supporting this hypothesis. In the
case of [CuII(dmp)2Cl]Cl, the resulting Cu(I) species would be a
Cu(I) complex like [CuI(dmp)2]Cl, which would then be the active
photocatalyst being able to promote transformations as shown
above. Contrasting [CuII(dap)Cl2] and [CuI(dap)2]Cl, for which both
catalysts show similar UV-vis spectra,[15] the corresponding UV-
vis spectra of [CuII(dmp)2Cl]Cl (green line) and [CuI(dmp)2]Cl (red
line) significant differ from each other (Figure 1, A). While the
absorption measurement of [CuI(dmp)2]Cl in anhydrous MeCN
shows a distinct maximum in the blue region, the corresponding
Cu(II) complex is much less luminescent, thus enabling the
monitoring of the different species by UV-vis spectroscopy.
Therefore, we subjected the model reaction between styrene (1a)
and tosyl chloride (2a) catalyzed with both complexes to UV-vis
analysis (Figure 1). Besides the similar results in reaction yield, it
was already noticed upon visual inspection that both catalysts
showed a strong color change during irradiation (for more details
see SI).
In the first step, we added the starting materials styrene (1a) and
tosyl chloride (2a) to the respective catalyst solutions (Figure 1,
B).
No change of the UV-vis spectra in the case of
[CuII(dmp)2Cl]Cl was observed, whereas the UV-vis spectrum
showed some differences for [CuI(dmp)2]Cl, indicating an
interaction of the latter with the substrates. Further UV-vis
measurements suggest that in particular tosyl chloride (2a) is
responsible for the aforementioned change in the spectra (see SI).
Subsequently, both reaction mixtures were irradiated for 30 h at
455 nm (blue LED) and UV-vis spectra were recorded again
(Figure 1, C). Remarkably, both spectra converged and,
henceforth, show a high similarity regarding the absorption
pattern, being characteristic for the Cu(I) species. These results
indicate that both catalysts go through the same catalytic cycle,
most likely having a Cu(I) complex as the photocatalytically active
species, which then can undergo photoinduced SET to the
substrate, following our previous reported mechanistic proposal
for [CuII(dap)Cl2] and [CuI(dap)2]Cl.[12] Control UV-vis experiment
with catalyst combined with product molecule ruled out potential
interaction influencing the spectra (see SI). Thus, this study
provides experimental evidence for the initiation of photo-
catalyzed reactions with Cu(II) complexes via VLIH.[12,15,32]
However, this experimental setup relies on long-term irradiation
and steady-state UV-vis spectroscopy, hence further detailed
mechanistic investigations concentrating on the exact wavelength
and corresponding energy for the VLIH of the Cu(II)-chloride bond
are required and ongoing in our laboratories.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
relative to the signal of CHCl3 at 7.26 ppm. 13C-NMR spectra were
recorded on Bruker Avance 300 (75 MHz), Bruker Avance 400 (101 MHz)
or Bruker Avance III 400 “Nanobay” (101 MHz) Spectrometer. Chemical
shifts for 13C-NMR were reported as δ, parts per million (ppm), relative to
the center line signal of the CDCl3 triplet at 77.2 ppm. 19F-NMR spectra
were recorded on Bruker Avance 300 (282 MHz), Bruker Avance 400
(376 MHz) or Bruker Avance III 400 “Nanobay” (376 MHz) Spectrometer.
FTIR spectroscopy was carried out on a Cary 630 FTIR Spectrometer.
Solid and liquid compounds were measured neatly and the wave numbers
are reported as cm-1. UV-vis absorption measurements were performed on
an Agilent Technologies Cary Series 100 UV-vis Spectrometer. Mass
spectra were recorded using Jeol AccuTOF GCX and Agilent Q-TOF 6540
UHD Spectrometer. X-ray crystallographic analysis was performed using
an Agilent Technologies SuperNova, an Agilent Technologies Gemini R
Conclusions
In conclusion, we have evaluated the Cu(II)-complex
[CuII(dmp)2Cl]Cl as
a
visible-light-mediated photoredox
precatalyst. The complex is robust and economic compared to
other copper photocatalysts, especially to the well-established
[CuI(dap)2]Cl. The present complex does not suffer from time- and
price-consuming ligand synthesis, thus providing an abundant
alternative in copper photochemistry. The catalytic activity was
demonstrated for various ATRA reactions enabling the economic
difunctionalization of alkenes. In some cases, [CuII(dmp)2Cl]Cl
even outperformed the established [CuI(dap)2]Cl system.
Furthermore, the successful decarboxylative coupling and an
Appel reaction further broadened the scope. By various gram-
scale functionalizations of styrenes, the viability of
[CuII(dmp)2Cl]Cl for synthetic use was demonstrated, underlining
the role of a low-priced and economic alternative. Notably, both
complex [CuI(dmp)2]Cl and [CuII(dmp)2Cl]Cl show good solubility
in the examined solvents. Moreover, we provide mechanistic
evidence for visible-light-induced activation of Cu(II) complexes
for photocatalysis by UV-vis reaction monitoring.
Ultra, an Agilent GV 50 or
a Rigaku GV 50 diffractometer. The
measurement of melting point (mp) was carried out on a SRS MPA 100 –
Automated melting point system by OptiMelt using a ramp rate of 1 K/min.
Synthesis of [CuII(dmp)2Cl]Cl[14]: A round-bottom flask equipped with a
magnetic stirring bar was charged with CuCl2 (268.9 mg, 2.0 mmol) and
dissolved in ethanol (120 mL). After complete dissolution, 2,9-dimethyl-
1,10-phenanthroline (916.4 mg, 4.4 mmol, 2.2 equiv) was added to the
stirred reaction mixture resulting in a green precipitate after a few minutes.
The suspension was left to fully react by stirring at room temperature for
another 2 h. Afterwards, the green precipitate was collected by vacuum
filtration using a fritted funnel. The solid was washed with cold ethanol and
cold diethyl ether and dried under vacuum to yield 840.7 mg (1.5 mmol,
76%) [CuII(dmp)2Cl]Cl as a bright green solid. Suitable crystals for X-ray
analysis were obtained by slow evaporation of a MeCN solution containing
[CuII(dmp)2Cl]Cl. The crystals obtained were green and needle-shaped
(see SI).
Experimental Section
More detailed information, as well as characterization data, copies of NMR
spectra, detailed UV-vis studies, catalyst stability test, VLIH details for
[CuI(dap)2]Cl and product yield comparison of [CuII(dmp)2Cl]Cl and
[CuI(dmp)2]Cl can be found in the Supporting Information. This material is
available free of charge via the Internet. CCDC 1922265 contain the
supplementary crystallographic data for this paper. These data can be
obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax +44 1223 336033).
Synthesis of [CuI(dmp)2]Cl: A 100 mL round-bottom flask equipped with
a
magnetic stirring bar was charged with
2,9-dimethyl-1,10-
phenanthroline (833.1 mg, 4.0 mmol, 2.0 equiv), dissolved in chloroform
(40 mL) and stirred at room temperature for 30 min. CuCl (198.0 mg,
2.0 mmol, 1.0 equiv) was added slowly and the resulting mixture was
stirred for 2 h at room temperature followed by precipitation in diethyl ether.
Afterwards, the red precipitate was collected by vacuum filtration using a
fritted funnel. The solid was washed with cold diethyl ether and dried under
vacuum to yield 734.6 mg (1.4 mmol, 71%) [CuI(dmp)2]Cl as a red solid.
1H-NMR (300 MHz, CDCl3): δ = 8.53 (d, J = 8.2 Hz, 4H), 8.04 (s, 4H), 7.78
(d, J = 8.2 Hz, 4H), 2.41 (s, 12H); 13C-NMR (75 MHz, CDCl3): δ = 157.6,
143.1, 137.5, 127.7, 126.2, 125.7, 26.0. Suitable crystals for X-ray analysis
were obtained by slow evaporation of a MeCN solution containing
[CuI(dmp)2]Cl. The crystals obtained were red and plate-shaped.
Commercially available chemical materials were purchased in high quality
and were used without further purification. All reactions were carried out in
oven-dried glassware under atmospheric conditions unless otherwise
stated. Reactions with moisture or oxygen sensitive reagents were
performed in anhydrous solvent in flame-dried glassware under an
atmosphere of predried nitrogen. Photochemical reactions were carried
out in anhydrous solvents in flame-dried glassware applying three
consecutive freeze-pump-thaw cycles. Thereby, irradiation was performed
using a LED-stick as irradiation source (for detail setup and light sources
see SI). Reactions were monitored by thin layer chromatography (TLC)
with TLC precoated aluminum sheets (Merck) Silica gel 60 F254, 0.2 mm
layer thickness and visualized by a dual short (λ = 254 nm) / long (λ = 366
nm) wavelength UV lamp. Anhydrous solvents were prepared by
established laboratory procedures.[34] EtOAc and hexanes (40-60 °C) for
chromatography were distilled prior to use. The reported yields are referred
to isolated compounds unless otherwise stated. Column chromatography
was performed with flash silica gel (Merck, 0.040-0.063 mm particle size).
1H-NMR spectra were recorded on Bruker Avance 300 (300 MHz), Bruker
Avance 400 (400 MHz) or Bruker Avance III 400 “Nanobay” (400 MHz)
Spectrometer. Spectra were evaluated in first order and coupling
constants J are reported in Hertz (Hz). Splitting patterns for the spin
multiplicity of the signals in the spectra are given as the following: s =
singlet, bs = broad singlet, d = doublet, t = triplet, q = quartet, p = pentet,
sex = sextet, hept = heptet, m = multiplet and combinations thereof.
Chemical shifts for 1H-NMR were reported as δ, parts per million (ppm),
General procedure for “standard ATRA reactions” (GP-A): A flame-
dried Schlenk tube (10.0 mL size) equipped with a magnetic stirring bar
was charged with halide 2 / 7 / 9, [CuII(dmp)2Cl]Cl (10.0 µmol, 2.0 mol%)
and dissolved in anhydrous solvent, sealed with a screw-cap and
subsequently degassed by three consecutive freeze-pump-thaw cycles.
Afterwards, alkene 1 was added under a slight nitrogen overpressure and
the screw-cap was replaced with a Teflon sealed inlet for a glass rod,
through which irradiation with LED took place from above while the
reaction mixture was magnetically stirred in an aluminum block at room
temperature for 30 – 48 h. The reaction was monitored by TLC. Afterwards,
the reaction mixture was concentrated in vacuo and the residue was
purified by flash column chromatography on silica gel (eluent hexanes /
EtOAc).
General procedure for chlorosulfonylation of unactivated alkenes
(GP-B): A flame-dried Schlenk tube (10.0 mL size) equipped with a
magnetic stirring bar was charged with sulfonyl chloride 2 (0.5 mmol,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
1.0 equiv), Na2CO3 (53.0 mg, 0.5 mmol, 1.0 equiv), [CuII(dmp)2Cl]Cl
(5.5 mg, 10.0 µmol, 2.0 mol%) and dissolved in anhydrous MeCN (2.0 mL,
0.25 M) sealed with a screw-cap and subsequently degassed by three
consecutive freeze-pump-thaw cycles. Afterwards, alkene 1 (1.0 mmol,
2.0 equiv) was added under a slight nitrogen overpressure and the screw-
cap was replaced with a Teflon sealed inlet for a glass rod, through which
irradiation with a 455 nm high power LED (blue LED) took place from
above while the reaction mixture was magnetically stirred in an aluminum
block at room temperature for 48 h. The reaction was monitored by TLC.
Afterwards, the reaction mixture was saturated by addition of brine solution
(20 mL) and the aqueous phase was washed with EtOAc (3 x 20 mL). The
combined organic fractions were dried over anhydrous Na2SO4,
concentrated in vacuo and the crude residue was purified by flash column
chromatography on silica gel (eluent hexanes / EtOAc).
of 3b as a white solid after flash column purification (hexanes / EtOAc 10:1
to 6:1). Rf (hexanes / EtOAc 5:1) = 0.45, Staining: UV, Vanillin; 1H-NMR
(400 MHz, CDCl3): δ = 7.62 (d, J = 8.3 Hz, 2H), 7.23 (d, J = 8.0 Hz, 2H),
7.15 (d, J = 8.2 Hz, 2H), 7.06 (d, J = 8.0 Hz, 2H), 5.29 (t, J = 6.9 Hz, 1H),
3.93 (dd, J = 14.7, 6.8 Hz, 1H), 3.83 (dd, J = 14.7, 7.1 Hz, 1H), 2.41 (s,
3H), 2.31 (s, 3H); 13C-NMR (101 MHz, CDCl3): δ = 144.9, 139.3, 136.4,
135.8, 129.8, 129.6, 128.3, 127.2, 64.3, 55.2, 21.8, 21.3. Spectral data are
in accordance to literature.
Compound 3c[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 143.0 mg (447 μmol, 89%)
3c as a white solid after flash column purification (hexanes / EtOAc 1:1).
Rf (hexanes / EtOAc 5:1) = 0.18, Staining: UV, Vanillin; 1H-NMR (300 MHz,
CDCl3): δ = 7.58 (d, J = 8.3 Hz, 2H), 7.52 (d, J = 8.4 Hz, 2H), 7.39 (d, J =
8.4 Hz, 2H), 7.22 (d, J = 7.7 Hz, 2H), 5.32 (dd, J = 7.7, 6.4 Hz, 1H), 3.91
(dd, J = 14.7, 6.4 Hz, 1H), 3.83 (dd, J = 14.7, 7.7 Hz, 1H), 2.38 (s, 3H);
13C-NMR (75 MHz, CDCl3): δ = 145.3, 143.2, 135.8, 132.5, 129.9, 128.1,
128.0, 118.0, 112.7, 63.3, 53.9, 21.6. Spectral data are in accordance to
literature.
General procedure for Trifluoromethylchlorosulfonylation of
unactivated alkenes and Chlorotrifluoromethylation of activated
alkenes (GP-C): A flame-dried Schlenk tube (10.0 mL size) equipped with
a magnetic stirring bar was charged with K2HPO4 (174.2 mg, 1.0 mmol,
2.0 equiv), [CuII(dmp)2Cl]Cl (5.5 mg, 10.0 µmol, 2.0 mol%) and dissolved
in anhydrous MeCN (1.5 mL, 0.33 M) sealed with a screw-cap and
subsequently degassed by three consecutive freeze-pump-thaw cycles.
Afterwards, alkene 1 (0.5 mmol, 1.0 equiv) and trifyl chloride 2b (168.5 mg,
1.0 mmol, 2.0 equiv) was added under a slight nitrogen overpressure and
the screw-cap was replaced with a Teflon sealed inlet for a glass rod,
through which irradiation with a 455 nm high power LED (blue LED) took
place from above while the reaction mixture was magnetically stirred in an
aluminum block at room temperature for 24 h. The reaction was monitored
by TLC. Afterwards, the reaction mixture was quenched with water (5 mL)
and the crude mixture was extracted with DCM (3 x 5 mL). The combined
organic fractions were dried over anhydrous Na2SO4, concentrated in
vacuo and the residue was purified by flash column chromatography on
silica gel (eluent hexanes / EtOAc).
Compound 3d[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 136.3 mg (485 μmol, 97%)
of 3d as a white solid after flash column purification (hexanes / EtOAc 5:1).
Rf (hexanes / EtOAc 5:1) = 0.38, Staining: UV, Vanillin; 1H-NMR (400 MHz,
CDCl3): δ = 7.79 – 7.69 (m, 2H), 7.62 – 7.54 (m, 1H), 7.47 – 7.40 (m, 2H),
7.30 – 7.22 (m, 5H), 5.35 (t, J = 6.9 Hz, 1H), 3.97 (dd, J = 14.8, 6.9 Hz,
1H), 3.87 (dd, J = 14.8, 7.0 Hz, 1H); 13C-NMR (101 MHz, CDCl3): δ = 139.3,
138.5, 133.9, 129.3, 129.2, 129.0, 128.2, 127.2, 64.1, 55.2. Spectral data
are in accordance to literature.
Compound 3e[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 108.9 mg (350 μmol, 70%)
of 3d as a white solid after flash column purification (hexanes / EtOAc 5:1).
Rf (hexanes / EtOAc 5:1) = 0.38, Staining: UV, Vanillin; 1H-NMR (400 MHz,
CDCl3): δ = 7.67 (d, J = 8.9 Hz, 2H), 7.28 (s, 5H), 6.89 (d, J = 8.9 Hz, 2H),
5.32 (t, J = 6.9 Hz, 1H), 3.93 (dd, J = 14.8, 6.9 Hz, 1H), 3.87 – 3.79 (m,
4H); 13C-NMR (101 MHz, CDCl3): δ = 164.0, 138.8, 130.8, 130.5, 129.2,
129.1, 127.3, 114.5, 64.4, 55.8, 55.4. Spectral data are in accordance to
literature.
General procedure for ATRA reaction with N-Boc allylamine (GP-D):
A Schlenk tube (10.0 mL size) equipped with a magnetic stirring bar was
charged with N-Boc allylamine (1c) (78.6 mg, 0.5 mmol, 1.0 equiv), halide
9
(1.0 mmol, 2.0 equiv), LiBr (86.6 mg, 1.0 mmol, 2.0 equiv),
[CuII(dmp)2Cl]Cl (5.5 mg, 10.0 µmol, 2.0 mol%) and dissolved in a DMF
(0.2 mL)/water (0.8 mL) mixture (1:4, 1.0 mL, 0.5 M) sealed with a screw-
cap and subsequently degassed by three consecutive freeze-pump-thaw
cycles. The screw-cap was replaced with a Teflon sealed inlet for a glass
rod, through which irradiation with a 455 nm high power LED (blue LED)
took place from above while the reaction mixture was magnetically stirred
in an aluminum block at room temperature for 30 h. The reaction was
monitored by TLC. Afterwards, the reaction mixture was saturated by
addition of brine solution (20 mL) and the aqueous phase was washed with
EtOAc (3 x 20 mL). The combined organic fractions were dried over
anhydrous Na2SO4, concentrated in vacuo and the crude residue was
purified by flash column chromatography on silica gel (eluent hexanes /
EtOAc).
Compound 3f[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 48 h yielded 152.8 mg (469 μmol, 94%)
of 3f as a white solid after flash column purification (hexanes / EtOAc 5:1).
Rf (hexanes / EtOAc 5:1) = 0.38, Staining: UV, Vanillin; 1H-NMR (300 MHz,
CDCl3): δ = 8.23 (d, J = 8.9 Hz, 2H), 7.88 (d, J = 8.8 Hz, 2H), 7.33 – 7.21
(m, 5H), 5.37 (t, J = 7.1 Hz, 1H), 4.05 (dd, J = 15.1, 6.9 Hz, 1H), 3.94 (dd,
J = 15.1, 7.2 Hz, 1H); 13C-NMR (75 MHz, CDCl3): δ = 150.7, 144.8, 137.9,
129.8, 129.6, 129.2, 127.4, 124.2, 64.2, 55.0. Spectral data are in
accordance to literature.
Compound 3g[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 79.2 mg (340 μmol, 68%)
of 3g as a yellowish solid after flash column purification (hexanes / EtOAc
5:1). Rf (hexanes / EtOAc 5:1) = 0.18, Staining: UV, Vanillin; 1H-NMR
(400 MHz, CDCl3): δ = 7.46 – 7.36 (m, 5H), 5.40 (dd, J = 7.7, 5.9 Hz, 1H),
3.81 (dd, J = 15.2, 7.7 Hz, 1H), 3.59 (dd, J = 15.2, 5.9 Hz, 1H), 2.94 – 2.74
(m, 2H), 1.32 (t, J = 7.5 Hz, 3H); 13C-NMR (75 MHz, CDCl3): δ = 138.9,
129.6, 129.3, 127.2, 60.7, 55.6, 49.0, 6.6. Spectral data are in accordance
to literature.
Compound 3a[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 135.6 mg (460 μmol, 92%)
of 3a as a white solid after flash column purification (hexanes / EtOAc 10:1
to 6:1). Rf (hexanes / EtOAc 5:1) = 0.30, Staining: UV, Vanillin; 1H-NMR
(300 MHz, CDCl3): δ = 7.63 (d, J = 8.4 Hz, 2H), 7.30 – 7.19 (m, 7H), 5.33
(t, J = 6.9 Hz, 1H), 3.95 (dd, J = 14.7, 6.9 Hz, 1H), 3.84 (dd, J = 14.7,
6.9 Hz, 1H), 2.41 (s, 3H); 13C-NMR (75 MHz, CDCl3): δ = 145.0, 138.7,
136.3, 129.9, 129.2, 129.0, 128.3, 127.2, 64.2, 55.2, 21.8. Spectral data
are in accordance to literature.
Compound 3h[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 48.3 mg (196 μmol, 39%)
of 3h as colorless oil after flash column purification (hexanes / EtOAc 5:1).
Compound 3b[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 145.3 mg (471 μmol, 94%)
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
Rf (hexanes / EtOAc 5:1) = 0.25, Staining: UV, Vanillin; 1H-NMR (400 MHz,
CDCl3): δ = 7.49 – 7.36 (m, 5H), 5.42 (dd, J = 7.6, 5.9 Hz, 1H), 3.84 (dd,
J = 15.0, 7.6 Hz, 1H), 3.57 (dd, J = 15.0, 5.9 Hz, 1H), 2.98 (hept, J = 6.9 Hz,
1H), 1.34 (dd, J = 13.4, 6.8 Hz, 6H); 13C-NMR (101 MHz, CDCl3): δ = 139.1,
129.5, 129.2, 127.2, 58.3, 55.5, 54.1, 15.4, 14.8. Spectral data are in
accordance to literature.
Compound 3n[12]: Following general procedure (GP-B) using irradiation
with blue LED (λmax = 455 nm) for 48 h yielded 22.9 mg (76 μmol, 15%) of
3n as colorless oil after flash column purification (hexanes / EtOAc 9:1 to
4:1). Rf (hexanes / EtOAc 4:1) = 0.68, Staining: UV, KMnO4; 1H-NMR
(400 MHz, CDCl3): δ = 7.80 (d, J = 8.3 Hz, 2H), 7.37 (d, J = 8.0 Hz, 2H),
4.30 (dtd, J = 8.9, 6.3, 3.8 Hz, 1H), 3.56 (dd, J = 14.6, 6.2 Hz, 1H), 3.45
(dd, J = 14.6, 6.5 Hz, 1H), 2.46 (s, 3H), 1.97 (dddd, J = 14.1, 9.9, 5.8,
3.9 Hz, 1H), 1.81 – 1.69 (m, 1H), 1.54 – 1.36 (m, 2H), 1.34 – 1.22 (m, 6H),
0.92 – 0.84 (m, 3H).; 13C-NMR (101 MHz, CDCl3): δ = 145.3, 136.7, 130.1,
128.3, 63.7, 54.8, 38.1, 31.7, 28.6, 25.9, 22.7, 21.8, 14.2. Spectral data
are in accordance to literature.
Compound 3i[12]: Following general procedure (GP-A) irradiation using
with blue LED (λmax = 455 nm) for 30 h yielded 157.7 mg (425 μmol, 85%)
of 3i as white solid after flash column purification (hexanes / EtOAc 5:1).
Rf (hexanes / EtOAc 5:1) = 0.65, Staining: UV, Vanillin; 1H-NMR (300 MHz,
CDCl3): δ = 7.36 – 7.25 (m, 5H), 5.41 (t, J = 7.2 Hz, 1H), 4.11 (s, 1H), 4.09
(d, J = 1.0 Hz, 1H); 13C-NMR (75 MHz, CDCl3): δ = 146.9 – 146.4 (m),
143.4 – 143.0 (m), 139.6 – 139.0 (m), 137.4, 136.3 – 135.8 (m), 129.8,
129.1, 127.3, 64.9, 55.0; 19F-NMR (282 MHz, CDCl3): δ = 135.35 – -135.57
(m, 2F), -143.38 (tt, J = 21.0, 8.0 Hz, 1F), -158.46 – -158.78 (m, 2F).
Spectral data are in accordance to literature.
Compound 4a[23]: Following general procedure (GP-C) using irradiation
with blue LED (λmax = 455 nm) for 24 h yielded 136.8 mg (477 μmol, 95%)
of 4a as colorless oil after flash column purification (hexanes / EtOAc 9:1).
Rf (hexanes / EtOAc 9:1) = 0.73, Staining: UV, KMnO4; 1H-NMR (400 MHz,
CDCl3): δ = 7.44 – 7.32 (m, 3H), 7.30 – 7.22 (m, 2H), 4.07 (qt, J = 9.6,
4.7 Hz, 1H), 3.58 (dd, J = 14.9, 5.6 Hz, 1H), 3.27 (dd, J = 14.9, 6.9 Hz, 1H),
3.14 – 2.96 (m, 1H), 2.76 – 2.58 (m, 1H); 13C-NMR (101 MHz, CDCl3): δ =
133.9, 129.5, 129.2, 128.1, 124.8 (q, J = 278.0 Hz), 71.0 (q, J = 2.4 Hz),
36.2, 34.0 (q, J = 31.1 Hz); 19F-NMR (376 MHz, CDCl3): δ = -63.95 (s, 3F).
Spectral data are in accordance to literature.
Compound 3j[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 132.3 mg (325 μmol, 65%)
of 3j as white solid after flash column purification (hexanes / EtOAc 5:1).
Rf (hexanes / EtOAc 5:1) = 0.73, Staining: UV, Vanillin; 1H-NMR (400 MHz,
CDCl3): δ = 7.38 – 7.27 (m, 5H), 7.15 (s, 2H), 5.50 (dd, J = 7.5, 5.7 Hz,
1H), 4.11 (hept, J = 6.7 Hz, 2H), 4.01 (dd, J = 14.6, 7.5 Hz, 1H), 3.86 (dd,
J = 14.6, 5.7 Hz, 1H), 2.90 (hept, J = 6.9 Hz, 1H), 1.31 – 1.23 (m, 18H);
13C-NMR (101 MHz, CDCl3): δ = 154.2, 151.1, 139.4, 132.9, 129.2, 129.1,
127.1, 124.2, 66.2, 55.3, 34.4, 29.8, 25.2, 25.0, 23.7, 23.7. Spectral data
are in accordance to literature.
Compound 4b[23]: Following general procedure (GP-C) using irradiation
with blue LED (λmax = 455 nm) for 24 h yielded 133.4 mg (475 μmol, 95%)
of 4b as colorless oil after flash column purification (hexanes / EtOAc 9:1).
Rf (hexanes / EtOAc 9:1) = 0.34, Staining: UV, KMnO4; 1H-NMR (400 MHz,
CDCl3): δ = 3.76 (dtd, J = 8.6, 5.7, 2.8 Hz, 1H), 3.07 (dqd, J = 15.6, 10.6,
2.8 Hz, 1H), 2.59 (ddt, J = 18.3, 15.6, 9.7 Hz, 1H), 2.20 (ddt, J = 15.8, 10.2,
6.1 Hz, 1H), 2.09 – 1.94 (m, 1H), 1.57 (dddd, J = 12.1, 10.2, 6.8, 5.0 Hz,
2H), 1.41 – 1.27 (m, 6H), 0.93 – 0.86 (m, 3H); 13C-NMR (101 MHz, CDCl3):
δ = 24.92 (d, J = 277.9 Hz), 69.98 (q, J = 2.6 Hz), 34.66 (q, J = 30.8 Hz),
31.24 , 30.42, 28.78 , 25.92 , 22.44 , 13.95; 19F-NMR (376 MHz, CDCl3):
δ = -64.26 (s, 3F). Spectral data are in accordance to literature.
Compound 3k[12]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 139.4 mg (486 μmol, 97%)
of 3k as yellowish solid after flash column purification (hexanes / EtOAc
5:1). Rf (hexanes / EtOAc 5:1) = 0.33, Staining: UV, Vanillin; 1H-NMR
(300 MHz, CDCl3): δ = 7.65 (dd, J = 5.0, 1.4 Hz, 1H), 7.47 (dd, J = 3.8,
1.4 Hz, 1H), 7.35 – 7.27 (m, 5H), 7.01 (dd, J = 5.0, 3.8 Hz, 1H), 5.37 (t, J =
6.9 Hz, 1H), 4.06 (dd, J = 14.8, 6.8 Hz, 1H), 3.97 (dd, J = 14.8, 7.0 Hz,
1H); 13C-NMR (75 MHz, CDCl3): δ = 140.0, 138.5, 135.0, 134.7, 129.3,
129.1, 128.0, 127.2, 65.3, 55.2. Spectral data are in accordance to
literature.
Compound 5a[25,34,35]: Following general procedure using irradiation with
blue LED (λmax = 455 nm) for 24 h yielded 134.4 mg (467 μmol, 93%) of
5a as colorless oil after flash column purification (hexanes / EtOAc 9:1). Rf
(hexanes / EtOAc 9:1) = 0.33, Staining: UV, KMnO4; 1H-NMR (400 MHz,
CDCl3): δ = 7.60 (ddd, J = 8.2, 7.3, 1.5 Hz, 2H), 7.40 (td, J = 7.6, 1.3 Hz,
1H), 7.21 (ddd, J = 8.0, 7.4, 1.7 Hz, 1H), 5.68 (dd, J = 7.8, 5.9 Hz, 1H),
2.98 – 2.81 (m, 2H); 13C-NMR (101 MHz, CDCl3): δ = 152.2, 138.8, 133.4,
130.5, 128.6 (d, J = 32.9 Hz), 124.8 (q, J = 278.1 Hz), 122.6 , 53.4 (q, J =
3.6 Hz), 43.0 (q, J = 28.9 Hz); 19F-NMR (376 MHz, CDCl3): δ = -64.54 (s,
3F). Spectral data are in accordance to literature.
Compound 3l[12]: Following general procedure (GP-B) using irradiation
with blue LED (λmax = 455 nm) for 48 h yielded 9.9 mg (32 μmol, 6%) of 3l
as a white solid after flash column purification (hexanes / EtOAc 9:1 to 4:1).
Rf (hexanes / EtOAc 4:1) = 0.22, Staining: UV, KMnO4; 1H-NMR (300 MHz,
CDCl3): δ = 7.80 (d, J = 8.3 Hz, 2H), 7.40 – 7.19 (m, 7H), 4.50 (dq, J = 7.7,
6.3 Hz, 1H), 3.53 (d, J = 6.3 Hz, 2H), 3.29 (dd, J = 14.3, 5.5 Hz, 1H), 3.10
(dd, J = 14.3, 7.7 Hz, 1H), 2.45 (s, 3H); 13C-NMR (75 MHz, CDCl3): δ =
145.3, 136.4, 135.9, 130.1, 129.7, 128.6, 128.2, 127.4, 62.4, 54.5, 43.9,
21.8. Spectral data are in accordance to literature.
Compound 5b[25,34] and 6b[25]: Following general procedure (GP-C) using
irradiation with blue LED (λmax = 455 nm) for 24 h yielded 90.7 mg
(351 μmol, 70%) of 5b as colorless oil and 14.1 mg (49 μmol, 10%) of 6b
as white solid after flash column purification (hexanes / EtOAc 12:1 to 9:1).
Rf (5b, hexanes / EtOAc 9:1) = 0.60, Staining: UV, KMnO4; 1H-NMR (5b,
300 MHz, CDCl3): δ = 8.08 – 7.77 (m, 4H), 7.75 – 7.44 (m, 3H), 5.32 (t, J =
7.1 Hz, 1H), 3.24 – 2.89 (m, 2H); 13C-NMR (5b, 75 MHz, CDCl3): δ = 136.9,
133.5, 133.1, 129.3, 128.3, 127.9, 127.0, 126.9, 126.8 (q, J = 277.9,
277.5 Hz), 126.3, 124.0, 55.3 (q, J = 3.4 Hz), 43.8 (q, J = 28.3 Hz);
19F-NMR (5b, 282 MHz, CDCl3): δ = -64.40 (s, 3F). Spectral data are in
accordance to literature. Rf (6b, hexanes / EtOAc 9:1) = 0.35, Staining: UV,
Compound 3m[12]: Following general procedure (GP-B) using irradiation
with blue LED (λmax = 455 nm) for 48 h yielded 11.5 mg (35 μmol, 7%) of
3m as colorless oil after flash column purification (hexanes / EtOAc 9:1 to
4:1). Rf (hexanes / EtOAc 4:1) = 0.41, Staining: UV, KMnO4; 1H-NMR
(400 MHz, CDCl3): δ = 7.81 (d, J = 8.3 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H),
7.31 – 7.25 (m, 2H), 7.08 – 6.92 (m, 1H), 6.85 (dd, J = 8.8, 1.1 Hz, 2H),
4.60 (ddd, J = 11.3, 6.6, 5.5 Hz, 1H), 4.25 (dd, J = 10.3, 4.8 Hz, 1H), 4.19
(dd, J = 10.3, 5.4 Hz, 1H), 3.88 (dd, J = 14.8, 6.0 Hz, 1H), 3.58 (dd, J =
14.8, 6.7 Hz, 1H), 2.43 (s, 3H); 13C-NMR (101 MHz, CDCl3): δ = 157.8,
145.5, 136.4, 130.2, 129.7, 128.3, 121.9, 114.9, 70.2, 60.1, 51.3, 21.8.
Spectral data are in accordance to literature.
1
KMnO4; H-NMR (6b, 300 MHz, CDCl3): δ = 8.09 – 8.01 (m, 2H), 7.96 –
7.86 (m, 3H), 7.70 – 7.54 (m, 3H), 6.92 (dd, J = 15.5, 0.9 Hz, 1H); 13C-NMR
(6b, 75 MHz, CDCl3): δ = 154.0, 135.5, 133.4, 133.0, 129.6, 129.3, 129.1,
128.7, 128.1, 127.6, 123.3, 122.0 (q, J = 324.9 Hz), 116.4; 19F-NMR (6b,
282 MHz, CDCl3): δ = -79.20 (s, 3F). Spectral data are in accordance to
literature.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
Compound 5c[25,34,35] and 6c: Following general procedure (GP-C) using
irradiation with blue LED (λmax = 455 nm) for 24 h yielded 114.7 mg
(430 μmol, 86%) of 5c as white solid and 16.8 mg (57 μmol, 11%) of 6c
as white solid after flash column purification (hexanes / EtOAc 12:1 to 9:1).
Rf (5c, hexanes / EtOAc 9:1) = 0.53, Staining: UV, KMnO4; 1H-NMR (5c,
400 MHz, CDCl3): δ = 7.41 (d, J = 8.6 Hz, 2H), 7.12 (d, J = 8.6 Hz, 2H),
5.11 (t, J = 6.4 Hz, 1H), 3.06 – 2.78 (m, 2H), 2.30 (s, 3H); 13C-NMR (5c,
101 MHz, CDCl3): δ = 169.3, 151.1, 137.4, 128.1, 126.2 (q, J = 277.9 Hz),
122.3, 54.2 (q, J = 3.4 Hz), 44.0 (q, J = 28.5 Hz), 21.2; 19F-NMR (5c,
376 MHz, CDCl3): δ = -64.55 (s, 3F). Spectral data are in accordance to
literature. Rf (6c, hexanes / EtOAc 9:1) = 0.33, Staining: UV, KMnO4;
1H-NMR (6c, 400 MHz, CDCl3): δ = 7.86 (d, J = 15.5 Hz, 1H), 7.63 (d, J =
8.6 Hz, 2H), 7.24 (d, J = 8.6 Hz, 2H), 6.78 (d, J = 15.4 Hz, 1H), 2.33 (s,
3H); 13C-NMR (6c, 75 MHz, CDCl3): δ = 168.9, 154.5, 152.7, 131.0, 128.9,
123.0, 121.4 (q, J = 321.3 Hz), 116.8, 21.3; 19F-NMR (6c, 376 MHz,
CDCl3): δ = -79.23 (s, 3F). HRMS (6c, ESI) m/z calculated for C11H9F3O4S
([M+H]+) 295.0246, found 295.0247. IR (6c, neat): 3064, 1744, 1603, 1591,
1510, 1425, 1361, 1328, 1185, 1115, 1047, 1021, 988, 970, 921, 869, 823,
801, 793, 712. mp (6c): 105 °C.
Compound 8c[10]: Following general procedure (GP-A) using irradiation
with green LED (λmax = 530 nm) for 30 h yielded 298.4 mg (436 μmol, 87%)
of 8c as a white solid after flash column purification (hexanes). Rf
1
(hexanes) = 0.54, Staining: UV, KMnO4; H-NMR (400 MHz, CDCl3): δ =
7.37 (d, J = 8.6 Hz, 2H), 7.30 (d, J = 8.6 Hz, 2H), 5.41 (dd, J = 10.0, 5.0 Hz,
1H), 3.34 – 3.07 (m, 2H); 13C-NMR (101 MHz, CDCl3): δ = 141.4, 134.4,
129.3, 128.2, 121.0 – 107.4 (m), 42.7 (t, J = 20.4 Hz), 15.3. 19F-NMR
(376 MHz, CDCl3): δ = -81.23 (t, J = 9.9 Hz, 3F), -111.62 – -113.20 (m, 1F),
-114.25 – -116.01 (m, 1F), -121.83 – -122.64 (m, 6F), -123.22 (s,
2F), -123.76 – -124.13 (m, 2F), -126.47 – -126.90 (m, 2F). Spectral data
are in accordance to literature.
Compound 8d[10]: Following general procedure (GP-A) using irradiation
with green LED (λmax = 530 nm) for 30 h yielded 297.7 mg (402 μmol, 80%)
of 8d as a colorless oil after flash column purification (hexanes). Rf
1
(hexanes) = 0.90, Staining: UV, KMnO4; H-NMR (400 MHz, CDCl3): δ =
5.66 (dd, J = 11.3, 4.6 Hz, 1H), 3.56 – 3.36 (m, 1H), 3.19 – 2.99 (m, 1H);
13C-NMR (101 MHz, CDCl3): δ = 144.1 – 136.1 (m), 118.8 – 108.2 (m),
40.4 (t, J = 20.7 Hz), -3.9; 19F-NMR (376 MHz, CDCl3): δ = -81.32 (t, J =
9.8 Hz, 3F), -113.67
– -114.19 (m, 1F), -115.79 – -116.61 (m,
Compound 5d[25,34,35] and 6d: Following general procedure (GP-C) using
irradiation with blue LED (λmax = 455 nm) for 24 h yielded 99.8 mg
(427 μmol, 85%) of 5d as colorless oil and 7.7 mg (29 μmol, 6%) of 6d as
white solid after flash column purification (hexanes / EtOAc 12:1 to 9:1). Rf
(5d, hexanes / EtOAc 9:1) = 0.43, Staining: UV, KMnO4; 1H-NMR (5d,
400 MHz, CDCl3): δ = 7.69 (d, J = 8.4 Hz, 2H), 7.52 (d, J = 8.4 Hz, 2H),
5.12 (t, J = 7.1 Hz, 1H), 3.08 – 2.79 (m, 2H); 13C-NMR (5d, 101 MHz,
CDCl3): δ = 144.5, 132.9, 127.9, 125.9 (q, J = 278.5 Hz), 118.2, 113.2,
53.7 (q, J = 3.4 Hz), 43.6 (q, J = 28.7 Hz); 19F-NMR (5d, 376 MHz, CDCl3):
δ = -64.37 (s, 3F). Spectral data are in accordance to literature. Rf (6d,
hexanes / EtOAc 9:1) = 0.20, Staining: UV, KMnO4; 1H-NMR (6d, 400 MHz,
CDCl3): δ = 7.90 (d, J = 15.5 Hz, 1H), 7.79 (d, J = 8.4 Hz, 2H), 7.71 (d, J =
8.3 Hz, 2H), 6.96 (d, J = 15.6 Hz, 1H); 13C-NMR (6d, 101 MHz, CDCl3):
δ = 151.0, 135.1, 133.2, 129.9, 121.3 (q, J = 324.4 Hz), 120.9, 117.7,
116.4; 19F-NMR (6d, 376 MHz, CDCl3): δ = -78.79 (s, 3F). HRMS (6d, ESI)
m/z calculated for C10H6F3NO2S ([M+H]+) 262.0144, found 262.0143. IR
(6d, neat): 3101, 3090, 2233, 1610, 1588, 1510, 1416, 1357, 1319, 1301,
1189, 1107, 984, 865, 820, 798, 716. mp (6d): 169 °C.
1F), -122.00 – -122.53 (m, 6F), -123.25 (s, 2F), -123.98 (s, 2F), -126.65 (s,
2F), -139.69 (bs, 1F), -143.52 (bs, 1F), -153.26 (t, J = 9.8 Hz, 1F), -161.21
(td, J = 21.5, 7.9 Hz, 2F). Spectral data are in accordance to literature.
Compound 8e[10]: Following general procedure (GP-A) using irradiation
with green LED (λmax = 530 nm) for 30 h yielded 297.7 mg (402 μmol, 80%)
of 8e as a colorless oil after flash column purification (hexanes). Rf
1
(hexanes) = 0.80, Staining: UV, KMnO4; H-NMR (400 MHz, CDCl3): δ =
4.34 (tdd, J = 8.3, 5.6, 4.3 Hz, 1H), 3.01 – 2.68 (m, 2H), 1.80 (dddd, J =
21.6, 14.7, 9.7, 4.6 Hz, 2H), 1.53 (q, J = 5.9, 5.2 Hz, 1H), 1.46 – 1.26 (m,
7H), 0.90 (t, J = 6.3 Hz, 2H); 13C-NMR (101 MHz, CDCl3): δ = 118.8 –
113.5 (m), 41.9 (t, J = 20.8 Hz), 40.5 (d, J = 2.1 Hz), 31.7, 29.7, 28.3, 22.7,
21.0, 14.2; 19F-NMR (282 MHz, CDCl3): δ = -81.25 (t, J = 10.0 Hz,
3F), -111.47
–
-112.92 (m, 1F), -114.40
–
-115.89 (m,
1F), -121.80 – -122.61 (m, 6F), -123.22 (s, 2F), -123.91 – -124.32 (m, 2F),
-126.46 – -126.81 (m, 2F). Spectral data are in accordance to literature.
Compound 10a[9]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 211.4 mg (485 μmol, 97%)
of 10a as a yellowish oil after flash column purification (hexanes). Rf
Compound 8a[10]: Following general procedure (GP-A) using irradiation
with green LED (λmax = 530 nm) for 30 h yielded 308.3 mg (474 μmol, 95%)
of 8a as a white solid after flash column purification (hexanes). Rf
1
(hexanes) = 0.48, Staining: UV, Vanillin; H-NMR (300 MHz, CDCl3): δ =
7.54 – 7.46 (m, 2H), 7.42 – 7.28 (m, 3H), 5.34 (dd, J = 7.5, 4.3 Hz, 1H),
4.19 – 4.01 (m, 2H); 13C-NMR (101 MHz, CDCl3): δ = 140.9, 129.1, 129.0,
128.3, 66.6, 50.2, 35.2. Spectral data are in accordance to literature.
1
(hexanes) = 0.51, Staining: UV, KMnO4; H-NMR (400 MHz, CDCl3): δ =
7.46 – 7.41 (m, 2H), 7.35 – 7.27 (m, 3H), 5.45 (dd, J = 9.7, 5.2 Hz, 1H),
3.39 – 3.08 (m, 2H); 13C-NMR (101 MHz, CDCl3): δ = 142.9, 129.1, 128.7,
126.9, 122.9 – 107.0 (m), 42.7 (t, J = 20.8 Hz), 16.7. 19F-NMR (282 MHz,
CDCl3): δ = -81.23 (t, J = 9.9 Hz, 3F), -111.68 – -113.69 (m, 1F), -111.33 –
Compound 10b[9]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 203.1 mg (458 μmol, 92%)
of 10b as a colorless oil after flash column purification (hexanes). Rf
-115.83 (m, 1F), -121.68
–
-122.65 (m, 6F), -123.21 (s,
2F), -123.77 – -124.31 (m, 2F), -126.24 – -126.99 (m, 2F). Spectral data
are in accordance to literature.
1
(hexanes) = 0.72, Staining: UV, Vanillin; H-NMR (400 MHz, CDCl3): δ =
4.20 (dq, J = 9.0, 4.5 Hz, 1H), 3.83 (dd, J = 16.2, 4.5 Hz, 1H), 3.54 (dd, J =
16.2, 4.9 Hz, 1H), 2.08 (dddd, J = 14.2, 10.1, 6.1, 4.2 Hz, 1H), 1.97 (dtd,
J = 14.3, 9.3, 4.8 Hz, 1H), 1.66 – 1.46 (m, 2H), 1.42 – 1.26 (m, 6H), 0.93 –
0.84 (m, 2H); 13C-NMR (101 MHz, CDCl3): δ = 67.1, 52.2, 39.9, 36.5, 31.8,
28.6, 27.5, 22.7, 14.2. Spectral data are in accordance to literature.
Compound 8b[10]: Following general procedure (GP-A) using irradiation
with green LED (λmax = 530 nm) for 30 h yielded 282.4 mg (425 μmol, 85%)
of 8b as a white solid after flash column purification (hexanes). Rf
1
(hexanes) = 0.59, Staining: UV, KMnO4; H-NMR (400 MHz, CDCl3): δ =
7.32 (d, J = 8.1 Hz, 2H), 7.13 (d, J = 7.9 Hz, 2H), 5.46 (dd, J = 9.8, 5.1 Hz,
1H), 3.38 – 3.08 (m, 2H), 2.32 (s, 3H); 13C-NMR (101 MHz, CDCl3): δ =
140.0, 138.8, 129.7, 129.6 – 127.3 (m), 126.7, 42.7 (t, J = 20.6 Hz), 21.4,
17.2. 19F-NMR (376 MHz, CDCl3): δ = -81.30 (t, J = 10.0 Hz, 3F), -112.18 –
-113.42 (m, 1F), -112.05 – -115.96 (m, 1F), -114.58 – -115.78 (m,
6F), -121.93 – -122.88 (m, 2F), -123.24, -124.03 (s, 2F), -126.63 (s, 2F).
Spectral data are in accordance to literature.
Compound 10c[9,36]: Following general procedure (GP-D) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 122.0 mg (308 μmol, 62%)
of 10c as a colorless oil after flash column purification (hexanes / EtOAc
10:1 to 5:1). Rf (hexanes) = 0.30, Staining: Ninhydrin; 1H-NMR (400 MHz,
CDCl3): δ = 4.98 (bs, 1H), 4.26 – 4.15 (m, 4H), 4.14 – 4.08 (m, 1H), 3.73
(dd, J = 9.5, 5.0 Hz, 1H), 3.50 (p, J = 7.9, 6.6 Hz, 2H), 2.46 (ddd, J = 14.9,
9.5, 3.7 Hz, 1H), 2.25 (ddd, J = 15.0, 10.1, 5.0 Hz, 1H), 1.43 (s, 9H), 1.26
(td, J = 7.1, 2.2 Hz, 6H); 13C-NMR (101 MHz, CDCl3): δ = 169.0, 168.6,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
155.7, 80.0, 61.9, 61.9, 53.3, 50.3, 47.2, 34.8, 28.4, 14.2, 14.1. Spectral
data are in accordance to literature.
organic layers were washed with saturated Na2S2O3 solution (10 mL),
brine (10 mL), dried over anhydrous Na2SO4 and concentrated in vacuo.
The residue was purified by flash column chromatography on silica gel
(hexanes) to yield 67.6 mg (365 μmol, 73%) of (1-bromoethyl)benzene
(15) as a colourless oil. Rf (hexanes) = 0.58, Staining: UV, Vanillin; 1H-
NMR (400 MHz, CDCl3): δ = 7.49 – 7.41 (m, 2H), 7.40 – 7.32 (m, 2H),
7.32 – 7.26 (m, 1H), 5.23 (q, J = 6.9 Hz, 1H), 2.06 (d, J = 6.9 Hz, 3H); 13C-
NMR (101 MHz, CDCl3): δ = 143.4, 128.8, 128.5, 126.9, 49.7, 27.0.
Spectral data are in accordance to literature.
Compound 10d[9]: Following general procedure (GP-D) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 21.7 mg (61 μmol, 12%) of
10d as a white solid after flash column purification (hexanes / EtOAc 9:1
to 4:1). Rf (hexanes) = 0.43, Staining: UV, vanillin; 1H-NMR (400 MHz,
CDCl3): δ = 8.00 – 7.94 (m, 2H), 7.60 – 7.53 (m, 1H), 7.46 (dd, J = 8.4,
7.0 Hz, 2H), 5.05 (bfs, 1H), 4.23 (dq, J = 12.4, 4.2 Hz, 1H), 3.61 (dt, J =
14.9, 5.7 Hz, 1H), 3.48 (ddd, J = 14.5, 7.2, 5.9 Hz, 1H), 3.23 (qdd, J = 17.9,
8.2, 6.0 Hz, 2H), 2.36 (dddd, J = 14.9, 8.2, 6.6, 3.9 Hz, 1H), 2.17 (ddd, J =
14.6, 10.0, 5.7 Hz, 1H), 1.45 (s, 9H); 13C-NMR (101 MHz, CDCl3): δ =
198.8, 155.8, 136.8, 133.4, 128.8, 128.2, 79.9, 56.3, 47.5, 36.4, 30.2, 28.5.
Spectral data are in accordance to literature.
Acknowledgments
We thank the Studienstiftung des Deutschen Volkes, the Elite
Network of Bavaria administered by the Bavarian State Ministry
of Science and the Arts and the DFG Graduiertenkolleg 1626
“Photocatalysis” for their support.
Compound 10e[27]: Following general procedure (GP-A) using irradiation
with blue LED (λmax = 455 nm) for 30 h yielded 24.3 mg (76 μmol, 15%) of
10e as a colorless oil after flash column purification (hexanes / EtOAc 12:1
to 9:1). Rf (hexanes / EtOAc 9:1) = 0.45, Staining: UV, Vanillin; 1H-NMR
(400 MHz, CDCl3): δ = 8.16 (d, J = 8.7 Hz, 2H), 7.41 – 7.28 (m, 7H), 4.88
(dd, J = 8.7, 6.1 Hz, 1H), 2.95 (ddd, J = 14.4, 9.1, 5.6 Hz, 1H), 2.82 (ddd,
J = 13.9, 8.9, 6.6 Hz, 1H), 2.63 (dtd, J = 14.4, 8.8, 5.7 Hz, 1H), 2.45 (ddt,
J = 14.3, 9.1, 6.4 Hz, 1H); 13C-NMR (101 MHz, CDCl3): δ = 148.4, 146.8,
141.5, 129.5, 129.0, 128.8, 127.3, 123.9, 54.1, 40.9, 34.3. Spectral data
are in accordance to literature.
Keywords: ATRA reaction • copper(II) • difunctionalization •
homogenous catalysis • photocatalysis
[1]
For selected examples, see: a) M. D. Kärkäs, J. A. Porco, C. R. J.
Stephenson, Chem. Rev. 2016, 116, 9683; b) B. König, Eur. J. Org.
Chem. 2017, 2017, 1979; c) L. Marzo, S. K. Pagire, O. Reiser, B. König,
Angew. Chem. Int. Ed. 2018, 57, 10034; d) J. M. R. Narayanam, C. R. J.
Stephenson, Chem. Soc. Rev. 2011, 40, 102; e) C. K. Prier, D. A. Rankic,
D. W. C. MacMillan, Chem. Rev. 2013, 113, 5322; f) D. Ravelli, S. Protti,
M. Fagnoni, Chem. Rev. 2016, 116, 9850; g) M. H. Shaw, J. Twilton, D.
W. C. MacMillan, J. Org. Chem. 2016, 81, 6898; h) K. L. Skubi, T. R.
Blum, T. P. Yoon, Chem. Rev. 2016, 116, 10035.
Decarboxylative coupling reaction[8,29]: A flame-dried Schlenk tube
(10.0 mL size) equipped with a magnetic stirring bar was charged with 1,3-
dioxoisoindolin-2-yl cyclohexanecarboxylate (11) (136.6 mg, 0.5 mmol,
1.0 equiv), (bromoethynyl)benzene (12) (135.8 mg, 0.75 mmol, 1.5 equiv),
Hantzsch ester (190.0 mg, 0.75 mmol, 1.5 equiv), [Cu(dmp)2Cl]Cl
(10.0 µmol, 2.0 mol%) and dissolved in anhydrous THF (1.5 mL, 0.33 M),
sealed with a screw-cap and subsequently degassed by three consecutive
freeze-pump-thaw cycles. Afterwards, diisopropylethylamine (129.3 mg,
1.0 mmol, 2.0 equiv) was added under a slight nitrogen overpressure and
the screw-cap was replaced with a Teflon sealed inlet for a glass rod,
through which irradiation with blue LED (λmax = 455 nm) took place from
above while the reaction mixture was magnetically stirred in an aluminum
block at room temperature for 24 h. The reaction was monitored by TLC.
Afterwards, the reaction mixture was concentrated in vacuo and the
residue was purified by flash column chromatography on silica gel
(hexanes) to yield 57.1 mg (310 μmol, 62%) of (cyclohexylethynyl)benzene
(13) as a slightly yellow oil. Rf (hexanes) = 0.50, Staining: UV, Vanillin;
1H-NMR (400 MHz, CDCl3): δ = 7.44 – 7.38 (m, 2H), 7.32 – 7.24 (m, 3H),
2.60 (tt, J = 9.2, 3.8 Hz, 1H), 1.89 (ddt, J = 12.6, 5.8, 3.4 Hz, 2H), 1.77 (qq,
J = 6.5, 2.1 Hz, 2H), 1.55 (ddt, J = 13.7, 9.7, 4.9 Hz, 3H), 1.44 – 1.30 (m,
3H); 13C-NMR (101 MHz, CDCl3): δ = 131.7, 128.3, 127.5, 124.3, 94.6,
80.7, 32.9, 29.8, 26.1, 25.1. Spectral data are in accordance to literature.
[2]
[3]
N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116, 10075.
For selected examples, see: a) J. C. K. Chu, T. Rovis, Nature 2016, 539,
272 -275; b) J. L. Jeffrey, J. A. Terrett, D. W. C. MacMillan, Science 2015,
349, 1532; c) A. J. Musacchio, L. Q. Nguyen, G. H. Beard, R. R. Knowles,
J. Am. Chem. Soc. 2014, 136, 12217; d) Z. Zuo, D. T. Ahneman, L. Chu,
J. A. Terrett, A. G. Doyle, D. W. C. MacMillan, Science 2014, 345, 437.
M. Neumann, S. Füldner, B. König, K. Zeitler, Angew. Chem. Int. Ed.
2011, 50, 951.
[4]
[5]
a) D. Ravelli, M. Fagnoni, A. Albini, Chem. Soc. Rev. 2013, 42, 97; b) D.
P. Hari, B. König, Chem. Commun. 2014, 50, 6688; c) S. Fukuzumi, K.
Ohkubo, Org. Biomol. Chem. 2014, 12, 6059.
[6]
[7]
a) A. C. Hernandez-Perez, S. K. Collins, Acc. Chem. Res. 2016, 49,
1557; b) E. B. McLean, A.-L. Lee, Tetrahedron 2018, 74, 4881; c) S.
Paria, O. Reiser, ChemCatChem 2014, 6, 2477; d) O. Reiser, Acc. Chem.
Res. 2016, 49, 1990; e) A. Hossain, A. Bhattacharyya, O. Reiser,
Science 2019, 364, eaav9713.
a) M. Alkan-Zambada, X. Hu, J. Org. Chem. 2019, 84, 4525; b) B. M.
Hockin, C. Li, N. Robertson, E. Zysman-Colman, Catal. Sci. Technol.
2019, 9, 889; c) C. B. Larsen, O. S. Wenger, Chem. Eur. J. 2018, 24,
2039; d) O. S. Wenger, J. Am. Chem. Soc. 2018, 140, 13522.
C. Minozzi, A. Caron, J.-C. Grenier-Petel, J. Santandrea, S. K. Collins,
Angew. Chem. Int. Ed. 2018, 57, 5477.
Photocatalytic Appel reaction[30,31]: A flame-dried Schlenk tube (10.0 mL
size) equipped with
a magnetic stirring bar was charged with
perbromomethane (9a) (331.6 mg, 1.0 mmol, 2.0 equiv), sodium bromide
(102.9 mg, 1.0 mmol, 2.0 equiv), [Cu(dmp)2Cl]Cl (5.5 mg, 10.0 µmol,
2.0 mol%) and dissolved in anhydrous DMF (3.0 mL, 0.17 M), sealed with
a screw-cap and subsequently degassed by three consecutive freeze-
pump-thaw cycles. Afterwards, 1-phenylethan-1-ol (14) (61.1 mg,
0.5 mmol, 1.0 equiv) was added under a slight nitrogen overpressure and
the screw-cap was replaced with a Teflon sealed inlet for a glass rod,
through which irradiation with blue LED (λmax = 455 nm) took place from
above while the reaction mixture was magnetically stirred in an aluminum
block at room temperature for 24 h. The reaction was monitored by TLC.
Afterwards, the reaction mixture was quenched by addition of water
(10 mL) and diethyl ether (10 mL). The layers were separated, and the
aqueous phase was extracted with diethyl ether (2x 10 mL). The combined
[8]
[9]
M. Pirtsch, S. Paria, T. Matsuno, H. Isobe, O. Reiser, Chem. Eur. J. 2012,
18, 7336.
[10] T. Rawner, E. Lutsker, C. A. Kaiser, O. Reiser, ACS Catal. 2018, 8, 3950.
[11] C. O. Dietrich-Buchecker, P. A. Marnot, J. P. Sauvage, J. P. Kintzinger,
P. Maltese, Nouv. J. Chim. 1984, 8, 573.
[12] A. Hossain, S. Engl, E. Lutsker, O. Reiser, ACS Catal. 2019, 9, 1103.
[13] a) O. O. Onawumi, F. A. Adekunle, A. O. Ibrahim, M. V. Rajasekharan,
O. A. Odunola, Synth. React. Inorg. M. 2010, 40, 78; b) C. Detoni, N. M.F.
Carvalho, D. A.G. Aranda, B. Louis, O.A.C. Antunes, Appl. Catal., A 2009,
365, 281.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
[14] The synthesis of [CuII(dmp)2Cl]Cl and X-ray structure of
[CuII(dmp)2Cl]PF6 (CCDC 1819088) (V. Leandri, Q. Daniel, H. Chen, L.
Sun, J. M. Gardner, L. Kloo, Inorg. Chem. 2018, 57, 4556) as well as the
X-ray structure of [CuII(dmp)2Cl]Cl•MeOH (CCDC 1861809) have been
reported. Since we evaluated [CuII(dmp)2Cl]Cl and its catalytic
performance in MeCN, a X-ray structure of this complex crystallized from
MeCN was obtained by us (CCDC 1922265 contain the supplementary
crystallographic data for this complex. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax +44 1223 336033). (For details see SI)
Dalton Trans. 2013, 42, 14628; c) Y. Zhang, M. Schulz, M. Wächtler, M.
Karnahl, B. Dietzek, Coord. Chem. Rev. 2018, 356, 127.
[22] a) K. Matsuo, E. Yamaguchi, A. Itoh, Asian J. Org. Chem. 2018, 7, 2435;
b) M. M. Cetin, R. T. Hodson, C. R. Hart, D. B. Cordes, M. Findlater, D.
J. Casadonte, A. F. Cozzolino, M. F. Mayer, Dalton Trans. 2017, 46,
6553; c) B. Michelet, C. Deldaele, S. Kajouj, C. Moucheron, G. Evano,
Org. Lett. 2017, 19, 3576; d) V. O. Smirnov, A. S. Maslov, V. A. Kokorekin,
A. A. Korlyukov, A. D. Dilman, Chem. Commun. 2018, 54, 2236.
[23] D. B. Bagal, G. Kachkovskyi, M. Knorn, T. Rawner, B. M. Bhanage, O.
Reiser, Angew. Chem. Int. Ed. 2015, 54, 6999.
[24] a) S. K. Pagire, S. Paria, O. Reiser, Org. Lett. 2016, 18, 2106; b) M.
Knorn, T. Rawner, R. Czerwieniec, O. Reiser, ACS Catal. 2015, 5, 5186.
[25] M. Alkan-Zambada, X. Hu, Organometallics 2018, 37, 3928.
[26] W. Zhang, J.-H. Lin, J.-C. Xiao, J. Fluor. Chem. 2018, 215, 25.
[27] S. Paria, M. Pirtsch, V. Kais, O. Reiser, Synthesis 2013, 45, 2689.
[28] a) M. N. C. Balili, T. Pintauer, Dalton Trans. 2011, 40, 3060; b) A. Kaur,
E. E. Gorse, T. G. Ribelli, C. C. Jerman, T. Pintauer, Polymer 2015, 72,
246; c) J. M. Muñoz-Molina, T. R. Belderraín, P. J. Pérez, Inorg. Chem.
2010, 49, 642; d) Y. Y. Ng, L. J. Tan, S. M. Ng, Y. T. Chai, R. Ganguly,
Y. Du, E. K. L. Yeow, H. S. Soo, ACS Catal. 2018, 8, 11277; e) Y. Oe, Y.
Uozumi, Adv. Synth. Catal. 2008, 350, 1771; f) T. Pintauer, W. T.
Eckenhoff, C. Ricardo, M. N. C. Balili, A. B. Biernesser, S. J. Noonan, M.
J. W. Taylor, Eur. J. Org. Chem. 2009, 15, 38.
[15] A. Hossain, A. Vidyasagar, C. Eichinger, C. Lankes, J. Phan, J. Rehbein,
O. Reiser, Angew. Chem. Int. Ed. 2018, 57, 8288.
[16] T. P. Nicholls, C. Caporale, M. Massi, M. G. Gardiner, A. C. Bissember,
Dalton Trans. 2019.
[17] D. R. McMillin, M. T. Buckner, B. T. Ahn, Inorg. Chem. 1977, 16, 943.
[18] a) J.-M. Kern, J.-P. Sauvage, J. Chem. Soc., Chem. Commun. 1987,
546; b) M. Geoffroy, M. Wermeille, C. O. Buchecker, J.-P. Sauvage, G.
Bernardinelli, Inorg. Chim. Acta 1990, 167, 157.
[19] N. Armaroli, Chem. Soc. Rev. 2001, 30, 113.
[20] a) A. Agena, S. Iuchi, M. Higashi, Chem. Phys. Lett. 2017, 679, 60; b) L.
X. Chen, G. B. Shaw, I. Novozhilova, T. Liu, G. Jennings, K. Attenkofer,
G. J. Meyer, P. Coppens, J. Am. Chem. Soc. 2003, 125, 7022; c) D.
Felder, J.-F. Nierengarten, F. Barigelletti, B. Ventura, N. Armaroli, J. Am.
Chem. Soc. 2001, 123, 6291; d) L. Hua, M. Iwamura, S. Takeuchi, T.
Tahara, Phys. Chem. Chem. Phys. 2015, 17, 2067; e) M. Iwamura, S.
Takeuchi, T. Tahara, Acc. Chem. Res. 2015, 48, 782; f) D. R. McMillin,
K. M. McNett, Chem. Rev. 1998, 98, 1201; g) D. v. Scaltrito, D. W.
Thompson, J. A. O'Callaghan, G. J. Meyer, Coord. Chem. Rev. 2000,
208, 243.
[29] J. Yang, J. Zhang, L. Qi, C. Hu, Y. Chen, Chem. Commun. 2015, 51,
5275.
[30] C. Minozzi, J.-C. Grenier-Petel, S. Parisien-Collette, S. K. Collins,
Beilstein J. Org. Chem. 2018, 14, 2730.
[31] C. Dai, J. M. R. Narayanam, C. R. J. Stephenson, Nat. Chem. 2011, 3,
140-150.
[32]
Y. Li, K. Zhou, Z. Wen, S. Cao, X. Shen, M. Lei, L. Gong, J. Am. Chem.
Soc. 2018, 140, 15850.
[21] a) M. K. Eggleston, D. R. McMillin, K. S. Koenig, A. J. Pallenberg, Inorg.
Chem. 1997, 36, 172; b) M. Sandroni, M. Kayanuma, M. Rebarz, H.
Akdas-Kilig, Y. Pellegrin, E. Blart, H. Le Bozec, C. Daniel, F. Odobel,
[33] J. K. Kochi, J. Am. Chem. Soc. 1962, 84, 2121;
[34] W. L. F. Armarego, Purification of laboratory chemicals, Butterworth-
Heinemann, 2017.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900839
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
The Cu(II)-complex [Cu(dmp)2Cl]Cl is
introduced to visible-light photo-
catalysis, being efficient but consi-
derable more cost-effective com-
pared to previously established Cu(I)
photocatalysts within a broad scope
of different reactions. Furthermore,
this study provides UV-vis evidence
for the visible light activation of Cu(II)
complexes, suggesting an LMCT
process resulting in the visible light
homolysis of Cu(II)-Cl to give rise to
catalytically active Cu(I) species.
Copper(II) Photoredox Catalysis*
Sebastian Engl, Oliver Reiser*
Page No. – Page No.
Making Copper Photocatalysis even
more robust and economic:
Photoredox Catalysis with
[CuII(dmp)2Cl]Cl
*one or two words that highlight the emphasis of the paper or the field of the study
This article is protected by copyright. All rights reserved.