Allylic C-H Alkynylation via Copper-Photocatalyzed Cross-Dehydrogenative Coupling

Article abstract of DOI:10.1055/s-0039-1690014

An efficient, novel photocatalyzed allylic-alkynylation methodology via copper-based cross-dehydrogenative coupling (CDC) is described. Different types of 1,4-enyne compounds were synthesized in one step at room temperature using copper(I) terpyridyl comp

Full text of DOI:10.1055/s-0039-1690014

SYNTHESIS
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©
Georg Thieme Verlag Stuttgart · New York
2019, 51, A–H
paper
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Synthesis
A. A. Almasalma, E. Mejía
Paper
Allylic C–H Alkynylation via Copper-Photocatalyzed
Cross-Dehydrogenative Coupling
Ahmad A. Almasalma
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Esteban Mejía*
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Leibniz Institute for Catalysis, Albert-Einstein-Str. 29a, 18059
Rostock, Germany
Esteban.Mejia@catalysis.de
Published as part of the Bürgenstock Special Section 2019
Future Stars in Organic Chemistry
Received: 30.04.2019
Accepted after revision: 18.07.2019
Published online: 25.07.2019
allylic C–H functionalizations avoiding the use of stoichio-
metric amounts of oxidant, leading to the direct arylation of
allylic C–H bonds under mild conditions (Scheme 1 C). An
6
DOI: 10.1055/s-0039-1690014; Art ID: ss-2019-t0252-op
important drawback of this methodology is that it relies on
the use of expensive iridium photosensitizers.
Abstract An efficient, novel photocatalyzed allylic-alkynylation meth-
odology via copper-based cross-dehydrogenative coupling (CDC) is de-
scribed. Different types of 1,4-enyne compounds were synthesized in
one step at room temperature using copper(I) terpyridyl complex as
photocatalyst/initiator. This procedure is an improvement and to some
extent complementary to previously reported thermal CDC methods.
Preliminary investigations on the reaction mechanism are also present-
ed.
A) Reiser (2015)
[Cu(dap) ]Cl or
2
O
[Cu(dpp)(binc)]BF4
(1 mol%)
O
R2
Br
R2
SiMe3
+
R
R
MeCN
blue LED455
R1
R1
B) Ollivier (2013)
Ar2I][PF6]
Key words C–C bond, copper catalyst, C–H functionalization, photo-
catalyst, allylic-alkynylation, 1,4-enyne
[
Cu(dpp)2]PF6 (0.5 mol%)
[
Ts
+
DIPEA (2 equiv)
Ar
R
MeCN, rt
R
green LED530
The search for more efficient and ‘environmentally
friendlier’ processes is one of the major tasks to be accom-
plished by chemists, in response to the growing society’s
concern about pollution, energy, and resources. Therefore,
the development of new catalytic strategies of high selec-
tivity, low energy demand, and reduced waste are of para-
mount importance. Among these strategies, photocatalysis
EWG
C) MacMillan (2015)
R2
Ir(ppy)3 (1 mol%)
organocatalyst (5 mol%)
R1
H
R4
R3
+
K2CO3
acetone, 23 °C
R2
NC
R3
R4
EWG
26 W light
R1
D) This work
L1 =
1
[Cu] (5 mol%)
L1 (5 mol%)
has been in the spotlight during the last decades. Remark-
R
R
n
ably, among the plethora of reported photocatalyzed reac-
tions, allylic functionalization represents only a small frac-
tion, in spite of the ubiquity of the allylic moiety in natural
TBHP (2 equiv)
+
n
25 °C, hν
N
N
R'
N
n = 1,2,3,4
R'
2
products and pharmaceuticals. In a pioneering report,
Scheme 1 Recent examples of photocatalyzed allylic functionaliza-
tions; dap: 2,9-bis(4-methoxyphenyl)-1,10-phenanthroline; dpp: 2,9-
diphenyl-1,10-phenanthroline; py: 2-phenylpyridine.
Reiser developed the first photocatalyzed allylation of -
halocarbonyls with allyltributylstannane using homoleptic
3
[
Cu(dpa) ] as photosensitizer. Later on, the same group im-
2
proved the reaction scope by using allylsilanes and hetero-
leptic copper(I) complexes having longer excited state life-
times and stronger reductive capabilities (Scheme 1 A). Al-
Very recently, we reported the alkynylation of underi-
vatized allylic substrates under oxidative conditions using
terminal alkynes. This is an example of a thermal cross-
4
7
kylation of allyl sulfones by aryl radicals generated from
diaryliodonium salts using [Cu(dpp) ]PF as photocatalyst
dehydrogenative coupling (CDC) reaction, which can be
described as the coupling of a pre-nucleophile and a pre-
2
6
5
was reported by Ollivier in 2013 (Scheme 1 B). Two years
later, MacMillan reported a more benign approach towards
8
electrophile, both devoid of leaving groups. CDC reactions
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2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
Synthesis
A. A. Almasalma, E. Mejía
Paper
9
have been thoroughly studied in the last decade and sever-
al photocatalyzed CDC processes either using a sacrificial
Ph
L1 =
Ph
[Cu(MeCN)4]PF6 (X mol%), L1 (Y mol%)
[O] (2 equiv), hν, rt, 24 h
10
oxidant or a proton reductant have been reported. In most
cases (thermal and photocatalyzed), the derivatization
takes place at sp carbons adjacent to nitrogen, and allylic
+
N
N
N
3
substrates have been neglected. Herein, we combine for the
first time the advantages of CDC and photocatalysis for the
alkynylation of allylic substrates, using a Cu(I) terpyridine
complex as photocatalyst and tert-butyl hydroperoxide
1
a
2a
3a
Scheme 2 Investigation on the reaction conditions for the photocata-
lyzed allylic-alkynylation
(
1
TBHP) as sacrificial oxidant at room temperature (Scheme
, D).
We began our investigation on the photocatalyzed CDC
Table 1 Screening of Optimal Reaction Conditionsa
between phenylacetylene (1a) and cyclohexene (2a) as
model reactants using white light (xenon lamp,  = 300–
Entry 2a
X
Y (mol%) [O]
Solvent
3a Yield
(%)
b
(
equiv) (mol%)
7
00 nm) at room temperature (23–26 °C) (Scheme 2). We
1
2
3
4
5
6
7
8
9
1
10
10
10
10
10
10
10
10
10
10
10
10
10
20
30
20
20
20
5
–
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
DTBP
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
MeCN
10
nd
nd
nd
55
nd
nd
nd
nd
nd
41
61
60
72
43
35
54
72
employed the reaction conditions from our previous re-
port (except the reaction temperature) using DTBP as oxi-
dant and terpyridine ligand L1 (Table 1). Terpyridines are
important chelating ligands in many applications spawning
–
DTBP
–
7
5
–
DTBP
TBHP
DDQ
BPO
air
11
5
from supramolecular and macromolecular chemistry to
12
13
luminescent devices and photoelectrical cells. However,
the low photoabsorption and quantum yield of metallic
mono- and bis-terpyridyl complexes compared to their bi-
pyridine analogues has discouraged their application as
photoredox catalysts in organic synthesis. Furthermore,
most of the studied copper terpyridine complexes are of
5
5
5
5
O
2
14
0
5
2 2
H O
14a,15
16,17
11c
12
Cu(II),
conditions, only 10% of the desired product 3a was obtained
Table 1, entry 1). No product was detected without the
with only few Cu(I) examples.
Under these
5
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
7.5
10
5
(
13
14
15
copper complex or the oxidant (entries 2 and 3). Having 1a
as the sole ligand (entry 4) was not effective in our case, in
contrast to previous reports on Sonogashira-type photoin-
5
16d
17e
18
5
18
duced coupling reactions. Using TBHP instead of DTBP
was sufficient to increase the yield to 55% (entry 5). Moti-
vated by this observation, different oxidants were tested,
but no product was produced (entries 6–10). By lowering
the amount of oxidant, a decreased yield was observed (en-
try 11, 41%). The addition of an excess of L1 (1.5 and 2 equiv
relative to Cu) resulted in an increase of product yield (en-
tries 12 and 13, 61 and 60%, respectively). An increased ex-
cess of 2a was also beneficial, giving 3a in 72% (entry 14).
Conversely, further increase on the amount of 2a or oxidant
showed to be detrimental (entries 15 and 16). At this stage,
we turned our attention to the role of the ligand, for which
different terpyridine derivatives L2–L4, 4,7-diphenyl-1,10-
phenanthroline (L6), and 2,6-bis(1H-benzo[d]imidazol-2-
yl)pyridine (L7), were tested. In all cases, either lower con-
version or no reaction was observed (Table S1, SI).
5
5
MeCN/MeOH
(
3:1)
19
20
20
20
20
20
20
20
5
5
5
5
5
5
5
5
5
5
5
5
5
5
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
MeCN
MeOH
DCM
78
43
4
20
21
22
23
2
4f
DMF
34
0
THF
MeCN
MeCN
70
30
25g
a
Reaction conditions: 1a (0.5 mmol), tert-butyl hydroperoxide (TBHP) solu-
tion in decane 5.5 M, DTBP (di-tert-butylperoxide), DDQ (2,3-dichloro-5,6-
dicyano-1,4-benzoquinone), BPO (benzoyl peroxide), temperature was
kept at 24–26 °C by flowing dry air through the reactor.
b
GC-MS yield; nd: not detected.
c
TBHP: 1 equiv.
d
TBHP: 3 equiv.
= 400–700 nm.
e

f
I
With isolated Cu -L1.
g
3 3 2
With 5 mol% [Cu(CF SO ) ].
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

C
Synthesis
A. A. Almasalma, E. Mejía
Paper
Moreover, we tested the effect of different light sources,
including LED strips and household bulbs. To our delight all
tested light sources were able to produce the desired prod-
uct, however, only in moderate yields (Table S1, SI). By re-
moving the UV radiation of the Xenon light source, that is,
using only visible light (exc = 420–600 nm), a yield of 54%
was obtained (Table 1, entry 17). This decrease can be due
to the reduction of the light intensity resulting from the use
of the long pass filter. We also investigated the solvent ef-
fect (entries 18–23) and found that MeCN gives the best re-
sults (entry 19, 78%). Interestingly, coupling by-products
results under thermal conditions. There, a variety of by-
products were always present, for instance the Glaser cou-
pling product of 1a being practically unavoidable. In this
case, only the CDC product 3 is produced.
Once we have identified a suitable set of reaction condi-
tions, we proceeded with the investigations on the sub-
strate scope. In general, all phenylacetylene derivatives 1
tested produced the CDC products with 2a in moderate to
good yields (Scheme 3, 3a–p). The highest yield was ob-
tained for the electronically enriched 1-ethynyl-4-me-
thoxy-2-methylbenzene (1n) (90% of 3n), while the lowest
was obtained for the electron-poor 1-ethynyl-4-fluoroben-
zene (1d) (44% of 3d). Interestingly, halogenated substrates
1b–f gave satisfactory results in spite of their propensity to
19
20
resulting from a reaction between 1a with DMF and THF
were produced. The nature of the copper species was brief-
I
ly investigated. By using the isolated complex [Cu -L1] (see
21
SI) as catalyst, very similar results were obtained as when it
is produced in situ (entry 24, 70%). Interestingly, and con-
form radical species by reacting with analogous catalysts.
Importantly, the presence of reactive functionalities like
thiophene and phenol did not inhibit the product forma-
tion (3o and 3p, respectively). The presence of a carboxyl
moiety at position 1 of the allyl substrate 2q resulted in
complete reaction inhibition, while the methyl-substituted
7
trary to what we observed under thermal conditions, using
II
I
Cu instead of Cu resulted in 30% yield of 3a (entry 25). Im-
portantly, high selectivity towards the allylic alkynylation
product was achieved in all cases, in strong contrast to the
R
R
[Cu(MeCN)4]PF6 (5 mol%), L1 (5 mol%)
R'
+
R'
TBHP (2 equiv), MeCN (2 mL)
n
n
hν, rt, 24 h
n = 1,2,3,4
3
1
2
F
OMe
F
OMe
F
Cl
Br
OMe
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
70%
57%
47%
44%
70%
65%
59%
54%
61%
51%
55%
COOH
OH
S
Bu
tBu
OMe
3
l
3m
3n
3o
3p
3q
0%
3r
3s
3t
3u
74% (2:5)a
7
1%
62%
90%
65%
56%
53%
80%
49%
3v
3w
3x
0%
traces
traces
Scheme 3 Substrate scope for the photocatalyzed allylic alkynylation reaction. Isolated yields are reported. a Determined by GC-MS.
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

D
Synthesis
A. A. Almasalma, E. Mejía
Paper
analogue produced the desired product 3r in moderate
yield (53%). Under the same conditions, cyclopentene and
cycloheptene produced exclusively the expected products
per catalyzes the peroxide splitting, presumably by single
electron transfer (SET) during the irradiation period (Fig-
ures S5 to S7, SI).
3
s and 3t in 80% and 49% yield, respectively. Unfortunately,
The addition of an excess of the radical-trapping reagent
TEMPO only resulted in a decrease on the reaction yield to
56%, also in strong contrast to the use if DTBP under ther-
mal conditions where the addition of the scavenger result-
the regioselectivity was not controlled in the case of cy-
clooctene, producing a mixture of isomers 3u. The lack of
regioselectivity for 3u and the high regioselectivity for 3s
are in strong contrast with the thermal method where the
7
ed in complete inhibition of the reaction. Under thermal
7
complete opposite behavior was observed. The difference
conditions, the main open-shell species formed by the per-
oxide decomposition showed to be methyl radicals, which
were presumably also responsible for the hydrogen abstrac-
tion at the allylic substrate. In the present case, the methyl
radical seems to play only a minor role, if any (a very small
amount of methylated TEMPO was detected. See Figure S8,
SI).
in selectivity between the two sets of conditions (thermal
vs photoinduced) relays on the stability and reactivity of
the metal-allyl intermediates 6 and 8, common to both
mechanism, but that can undergo different side reactions
(like thermal isomerization) before the product-forming
step (vide infra). Moreover, the use of open-chain allylic
substrates or a not-conjugated alkyne did not yield the de-
sired products 3v and 3w or 3x, respectively. We believe
that for the former, it is due to unintended photoexitation
of the substrates while for the latter, due the lower acidity
of the alkyne. The thermal method, on the other hand, was
effective for the coupling of both alkylic and open-chain
substrates. This makes, to some extent, the two approaches
complementary. Kinetic investigations of the reaction be-
tween 1a and 2a showed that the formation of product 3a is
of zero order and is not complete after 24 hours of irradia-
tion under the above-described conditions (Figure S3, SI).
Furthermore, when the reaction was irradiated for only
one hour and then further stirred in the dark, it yields 3a in
Although a detailed reaction mechanism cannot be pro-
posed with the available data, based in our preliminary ob-
7
servations and our previous report, we anticipate that the
reaction pathway might be as depicted in Scheme 4. After
I
+
photon absorption, the excited copper species [Cu ] * shall
react with TBHP via SET to produce the oxidized complex
copper(II) 5, which shall be feasible considering the en-
hanced reductive power of photoexcited copper complexes
+
{for instance, [Cu(XyBnta)(dppb)] is a very strong photore-
ductant: E* = –2.40 V vs. SCE in THF; XyBnta: N-[2-(1-ben-
ox
zyl-1H-1,2,3-triazol-4-yl)phenyl]-2,6-dimethylaniline;
dppb: 1,2-bis(diphenylphosphanyl)benzene}23 The radicals
resulting from the peroxide splitting can then abstract a hy-
drogen from the allyl substrate 2, to yield an open-shell
54% (Table S1, SI). This suggests that the active (radical)
24
species are generated during the induction (irradiation) pe-
riod and a thermal reaction follows in the dark without the
intervention of photoexcited copper species. Hence, the re-
action should be better described as ‘photoinitiated’ rather
species 4 that shall react quickly with complex 5 to pro-
duce a transient copper(III) intermediate 6.25 Under the re-
tBuOOH
R''OH
R
22
than ‘photosensitized’. To assess the role of the copper
catalyst as photoinitiator, we measured the UV absorption
of the different species and the luminescence quenching of
the complex upon addition of the different substrates.
The UV/Vis absorption spectra in acetonitrile (Figure S4,
SI) of the free ligand L1, copper(I) complex (Cu-L1), and its
mixtures with the different substrates (1a, 2a, and TBHP)
show in all cases only absorption bands below 360 nm. This
is rather puzzling, not only considering the strong maroon
color of the reaction mixture (under catalytic conditions),
but also the fact that there is considerable catalytic turn-
over even after suppression of the UV wavelengths of the ir-
radiation source (see the above discussion and SI). It is thus
very plausible, that the photoactive copper species are of
polymeric and/or multimetallic nature, although this hy-
pothesis has to be supported by experimental data (cur-
rently being collected in our laboratories). Preliminary pho-
toluminescence quenching experiments (ex = 317 nm) for
complex Cu-L1 with the three different substrates showed
that only the peroxide (TBHP) is capable of effectively
quenching the excited state emission of the copper com-
plex. This suggests that, as expected, the photoexcited cop-
R
n
t
R'' = H, Bu
n
LCuI ]*+
[
hν
2
SET
R''O
3
R
R'
[LCuI ]+
LCu OR'']+
II
[
5
n
SET
4
+
R
n
+
R
LCuIII
R'
n
LCuIII
OR''
8
6
[LCuOR'']
LCu
R'
7
R''OH
H
R'
1
Scheme 4 Proposed reaction mechanism for the photocatalyzed allylic
alkynylation
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

E
Synthesis
A. A. Almasalma, E. Mejía
Paper
action condition it is expected that organocuprates 7 are
1-(Cyclohex-2-en-1-ylethynyl)benzene (3a)
Following the general procedure, using Cu(MeCN) PF (9.4 mg, 0.024
mmol), ligand L1 (8.3 mg, 0.024 mmol), cyclohexene (2a; 788 mg, 9.6
mmol), phenylacetylene (1a; 50 mg, 0.5 mmol), and TBHP (86.5 mg,
26
formed from 1. Finally, ligand exchange between 6 and 7
followed by reductive elimination from 8 shall regenerate
the copper(I) catalyst and lead to the cross-coupling prod-
uct 3.
4
6
0.959 mmol), the pure product was obtained by flash column chro-
matography on silica gel with pentane as eluent; colorless oil; yield:
In conclusion, we have developed a new photocatalytic
method for the synthesis of substituted 1,4-enynes via
cross-dehydrogenative coupling of underivatized cyclic
alkenes and terminal alkynes under very mild conditions.
This methodology poses a dramatic improvement over our
previous reports under thermal conditions and, to some ex-
tent, is complementary to it on the substrate scope. More-
over, the use of copper complex as photocatalyst/photoini-
tiator at room temperature for this reaction poses an attrac-
tive alternative to previous CDC methodologies relaying on
precious metals. Further investigations on the underlying
reaction mechanism, the role and nature of the photocata-
lyst and the application of this methodology in asymmetric
allylic functionalization are currently under investigation
and will be the subject of a later report.
6
1 mg (70%, 0.33 mmol); R = 0.62.
f
1
H NMR (400 MHz, CDCl ):  = 7.34–7.31 (m, 2 H), 7.21–7.18 (m, 3 H),
3
5
.74–5.68 (m, 1 H), 5.65 (ddt, J = 10.0, 3.5, 1.8 Hz, 1 H), 3.22 (ddp,
J = 7.6, 5.1, 2.6 Hz, 1 H), 1.98–1.87 (m, 3 H), 1.81–1.69 (m, 2 H), 1.59–
1.49 (m, 1 H).
13
C NMR (101 MHz, CDCl ):  = 131.8, 128.3, 128.2, 127.7, 127.2,
3
124.0, 93.0, 80.4, 29.5, 28.1, 24.8, 20.8.
The NMR data matched with the previous report.28
MS: m/z = 182 (72), 167 (81), 153 (100), 128 (56), 115 (89).
+
HRMS (ESI-TOF): m/z calcd for C14H14 [M + H] : 182.10900; found:
1
82.10905.
1
-(Cyclohex-2-en-1-ylethynyl)-2-fluorobenzene (3b)
Following the general procedure, using Cu(MeCN) PF (7.8 mg, 0.02
mmol), ligand L1 (7 mg, 0.02 mmol), cyclohexene (2a; 663 mg, 8.07
mmol), 1-ethynyl-2-fluorobenzene (1b; 50 mg, 0.4 mmol), and TBHP
4
6
(72 mg, 0.8 mmol), the pure product was obtained by flash column
chromatography on silica gel with Et O/pentane (5:95) as eluent; col-
Chemicals, reagents, and solvents were purchased from commercial
2
orless oil; yield: 46 mg (57%, 0.22 mmol); R = 0.7.
suppliers and used without further purification. The ligands L2, L3,
f
27
1
and L4 were synthesized following reported procedures. TLC was
H NMR (300 MHz, CDCl ):  = 7.43–7.37 (m, 1 H), 6.87–6.78 (m, 2 H),
3
1
13
performed on silica HSGF254 plates. H and C NMR spectra were re-
6.76–6.70 (m, 1 H), 5.89–5.82 (m, 1 H), 5.73–5.66 (m, 1 H), 3.28 (tq,
corded in CDCl using a Bruker Avance 300 spectrometer with a QNP
J = 5.7, 2.4 Hz, 1 H), 1.90–1.81 (m, 4 H), 1.79–1.72 (m, 1 H), 1.45–1.35
(m, 1 H).
3
1
13
1
probe head ( H: 300 MHz, C: 75 MHz) or Bruker Avance 400 ( H:
1
3
4
00 MHz, C:1 01 MHz). The calibration of the spectra were carried
13
C NMR (75 MHz, CDCl ):  = 164.8, 161.5, 133.5, 129.0, 128.1, 127.8,
3
1
out on referenced with residual solvent shifts (CDCl , H = 7.26,
C = 77.16) and were reported as parts per million relative to SiMe4.
3
127.4, 126.8, 123.7, 115.2, 98.6, 74.1, 29.2, 28.4, 24.6, 20.5.
13
19
F NMR (282 MHz, CDCl ):  = –110.4.
3
All the NMR samples were measured at 297 K. ESI-TOF spectra were
recorded using a Waters Q-Tof micro mass spectrometer. GC analysis
was performed on Hewlett-Packard 6890 Series. Samples were dis-
solved in DCM and sampled in to the GC column. The chromatogram
peak ratios of the (cyclohex-2-en-1-ylethynyl)benzene (3a) and inter-
nal standard naphthalene (AE/AS) were used for calibration (exem-
plary calibration curve in Figure S0, SI). The GC-yields were calculated
with the corresponding calibration curve with naphthalene as an in-
ternal standard. Asahi Spectra Max-303 Xenon Light Source was used.
MS: m/z = 200 (100), 185 (49), 172 (68), 165 (39), 159 (35), 133 (48).
+
HRMS (ESI-TOF): m/z calcd for C14H13F [M + H] : 200.09958; found:
200.09983.
1-(Cyclohex-2-en-1-ylethynyl)-3-fluorobenzene (3c)
Following the general procedure, using Cu(MeCN) PF (8.1 mg, 0.02
4
6
mmol), ligand L1 (8 mg, 0.02 mmol), cyclohexene (2a; 670 mg, 8.07
mmol), 1-ethynyl-3-fluorobenzene (1c; 50 mg, 0.4 mmol), and TBHP
(
73 mg, 0.8 mmol), the pure product was obtained by flash column
Allylic C–H Alkynylation; General Procedure
chromatography on silica gel with Et O/pentane (2:98) as eluent; col-
orless oil; yield: 38 mg (47%, 0.19 mmol); R = 0.8.
2
In an oven-dried glass Schlenk tube equipped with a stirring bar,
f
Cu(MeCN) PF and ligand L1 were mixed under argon. The tube was
4
6
1
H NMR (400 MHz, CDCl ):  = 7.24–7.18 (m, 2 H), 6.84–6.78 (m, 1 H),
3
evacuated and carefully refilled with argon three times. Then anhyd
MeCN (2.0 mL) was injected into the tube through a syringe. After
stirring for 15 min at rt, TBHP, a 20-fold excess of the allyl substrate 2,
and the corresponding alkyne 1 were subsequently injected into the
reaction tube. The reaction was then irradiated with white light (Xe-
non lamp, 300–700 nm)) for 24 h (9 cm was the distance between the
light source and the Schlenk tube) while keeping the temperature
6
1
.76–6.69 (m, 1 H), 5.84 (ddt, J = 10.1, 3.6, 2.1 Hz, 1 H), 5.75–5.69 (m,
H), 3.24 (tp, J = 5.7, 2.5 Hz, 1 H), 1.90–1.81 (m, 4 H), 1.80–1.71 (m, 1
H), 1.48–1.37 (m, 1 H).
13C NMR (101 MHz, CDCl
127.5, 126.8, 118.4, 114.7, 94.1, 79.7, 29.2, 28.1, 24.6, 20.6.
19
):  = 163.8, 161.4, 129.7, 128.0, 127.8,
3
F NMR (282 MHz, CDCl ):  = –112.4.
3
(23–26 °C) by a stream of dry air. After stirring for 24 h, H O was add-
2
H]+: 200.09958;
F [M +
HRMS (ESI-TOF): m/z calcd for C14H13
found: 200.09880
ed and the product was extracted with DCM (3 × 50 mL). The pure
product 3 was obtained by flash column chromatography on silica gel.
Importantly, most of the obtained compounds were found to be un-
stable in solution under bench conditions, most probably due to po-
lymerization.
1-(Cyclohex-2-en-1-ylethynyl)-4-fluorobenzene (3d)
Following the general procedure, using Cu(MeCN) PF (7.9 mg, 0.02
6
4
mmol), ligand L1 (6.8 mg, 0.02 mmol), cyclohexene (2a; 656 mg, 8
mmol), 1-fluoro-4-ethynylbenzene (1d; 50 mg, 0.4 mmol), and TBHP
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

F
Synthesis
A. A. Almasalma, E. Mejía
Paper
(
72 mg, 0.8 mmol), the pure product was obtained by flash column
1-(Cyclohex-2-en-1-ylethynyl)-3-methoxybenzene (3h)
Following the general procedure, using Cu(MeCN) PF (7.1 mg, 0.018
mmol), ligand L1 (6.1 mg, 0.018 mmol), cyclohexene (2a; 603 mg, 7.3
mmol), 1-ethynyl-3-methoxybenzene (1h; 50 mg, 0.37 mmol), and
TBHP (66 mg, 0.73 mmol), the pure product was obtained by flash
chromatography on silica gel with Et O/pentane (5:95) as eluent; col-
orless oil; yield: 35 mg (44%, 0.18 mmol); R = 0.7.
2
4
6
f
1
H NMR (400 MHz, CDCl ):  = 7.38 (dd, J = 8.9, 5.4 Hz, 2 H), 6.99–6.94
3
(
m, 2 H), 5.79 (dtd, J = 9.3, 3.5, 2.1 Hz, 1 H), 5.71 (ddt, J = 9.9, 3.5, 2.0
Hz, 1 H), 3.28 (ddp, J = 7.9, 5.4, 2.6 Hz, 1 H), 2.06–2.01 (m, 2 H), 2.00–
.94 (m, 1 H), 1.90–1.82 (m, 1 H), 1.82–1.75 (m, 1 H), 1.66–1.55 (m, 1
H).
column chromatography on silica gel using Et O/pentane (1:99) as
2
1
eluent; colorless oil; yield: 46 mg (54%, 0.21 mmol); R = 0.7.
f
1
H NMR (300 MHz, CDCl ):  = 7.22–7.16 (m, 1 H), 7.04–7.00 (m, 1 H),
3
1
3
C NMR (101 MHz, CDCl ):  = 163.5, 161.0, 133.6, 133.5, 128.3,
6.96 (dd, J = 2.6, 1.4 Hz, 1 H), 6.86–6.81 (m, 1 H), 5.83–5.77 (m, 1 H),
5.74 (ddd, J = 9.9, 3.0, 1.6 Hz, 1 H), 3.79 (s, 3 H), 3.35–3.27 (m, 1 H),
2.07–1.95 (m, 3 H), 1.90 (ddd, J = 13.2, 5.6, 2.4 Hz, 1 H), 1.85–1.79 (m,
3
1
1
27.0, 120.1, 115.6, 115.4, 92.6, 79.4, 29.5, 28.1, 24.8, 20.8.
9
F NMR (282 MHz, CDCl ):  = –112.0.
3
1
H), 1.69–1.57 (m, 1 H).
1
3
C NMR (75 MHz, CDCl ):  = 159.3, 129.3, 128.2, 127.1, 125.0, 124.3,
1
-Chloro-4-(cyclohex-2-en-1-ylethynyl)benzene (3e)
3
1
16.5, 114.4, 92.8, 80.3, 77.2, 55.3, 29.5, 28.1, 24.8, 20.8.
Following the general procedure, using Cu(MeCN) PF (7 mg, 0.018
4
6
MS: m/z = 212 (100), 197 (65), 184 (45), 165 (41), 131 (74), 118 (57).
mmol), ligand L1 (6.1 mg, 0.018 mmol), cyclohexene (2a; 590 mg, 7.2
mmol), 1-chloro-4-ethynylbenzene (1e; 50 mg, 0.35 mmol), and
TBHP (64 mg, 0.71 mmol), the pure product was obtained by flash
column chromatography on silica gel with pentane as eluent; color-
+
HRMS (ESI-TOF): m/z calcd for C15H16O [M + H] : 212.11957; found:
212.11901.
less oil; yield: 55 mg (70%, 0.25 mmol); R = 0.76.
f
1-(Cyclohex-2-en-1-ylethynyl)-4-methoxybenzene (3i)
1
H NMR (300 MHz, CDCl ):  = 7.27 (d, J = 8.7 Hz, 2 H), 7.18 (d, J = 8.8
3
Following the general procedure, using Cu(MeCN) PF (7 mg, 0.018
4
6
Hz, 2 H), 5.77–5.70 (m, 1 H), 5.65 (ddt, J = 10.0, 3.7, 1.9 Hz, 1 H), 3.22
mmol), ligand L1 (6.3 mg, 0.018 mmol), cyclohexene (2a; 610 mg, 7.4
mmol), 1-ethynyl-4-methoxybenzene (1i; 50 mg, 0.37 mmol), and
TBHP (64 mg, 0.74 mmol), the pure product was obtained by flash
(ddp, J = 7.6, 5.2, 2.4 Hz, 1 H), 1.99–1.87 (m, 3 H), 1.79–1.68 (m, 2 H),
1.61–1.51 (m, 1 H).
13
C NMR (75 MHz, CDCl ):  = 133.6, 133.0, 128.6, 128.4, 126.9, 122.5,
column chromatography on silica gel using Et O/pentane (1:30) as
2
3
94.0, 79.4, 29.4, 28.1, 24.8, 20.7.
eluent; yellowish oil; yield: 48 mg (61%, 0.22 mmol); R = 0.56.
f
1
H NMR (300 MHz, CDCl ):  = 7.34 (d, J = 8.9 Hz, 2 H), 6.80 (d, J = 8.9
3
1-Bromo-4-(cyclohex-2-en-1-ylethynyl)benzene (3f)
Hz, 2 H), 5.81–5.69 (m, 2 H), 3.79 (s, 3 H), 3.28 (dtd, J = 7.1, 5.4, 4.8, 2.2
Hz, 1 H), 2.04–1.95 (m, 3 H), 1.85–1.74 (m, 2 H), 1.65–1.56 (m, 1 H).
Following the general procedure, using Cu(MeCN) PF (5.5 mg, 0.013
4
6
13
mmol), ligand L1 (5.1 mg, 0.013 mmol), cyclohexene (2a; 445 mg, 5.4
mmol), 1-bromo-4-ethynylbenzene (1f; 50 mg, 0.27 mmol), and
TBHP (94 mg, 0.54 mmol), the pure product was obtained by flash
column chromatography on silica gel using pentane as eluent; color-
C NMR (101 MHz, CDCl ):  = 159.1, 133.7, 133.0, 128.0, 127.4,
3
116.1, 114.0, 113.8, 91.3, 80.1, 77.2, 75.9, 55.3, 29.6, 28.1, 24.8, 20.8.
1-(Cyclohex-2-en-1-ylethynyl)-4-methylbenzene (3j)
less oil; yield: 46 mg (65%, 0.18 mmol); R = 0.54.
f
Following the general procedure, using Cu(MeCN) PF (8.4 mg, 0.021
4
6
1
H NMR (300 MHz, CDCl ):  = 7.40 (d, J = 8.6 Hz, 2 H), 7.27–7.24 (m, 2
3
mmol), ligand L1 (7.2 mg, 0.021 mmol), cyclohexene (2a; 693 mg, 8.4
mmol), 1-ethynyl-4-methylbenzene (1j; 50 mg, 0.42 mmol), and
TBHP (76 mg, 0.84 mmol), the pure product was obtained by flash
column chromatography on silica gel using pentane as eluent; color-
H), 5.82–5.75 (m, 1 H), 5.71 (ddd, J = 7.9, 4.2, 2.5 Hz, 1 H), 3.28 (ddp,
J = 7.6, 5.1, 2.4 Hz, 1 H), 2.05–2.00 (m, 2 H), 1.87 (ddd, J = 14.1, 6.2, 2.9
Hz, 1 H), 1.82–1.73 (m, 2 H), 1.67–1.58 (m, 1 H).
13
C NMR (75 MHz, CDCl ):  = 133.2, 131.5, 128.4, 126.8, 123.0, 121.8,
less oil; yield: 42 mg (51%, 0.21 mmol); R = 0.6.
f
3
94.3, 79.5, 29.4, 28.1, 24.8, 20.7.
1
H NMR (400 MHz, CDCl ):  = 7.32 (dd, J = 8.1, 1.8 Hz, 2 H), 7.10 (dd,
3
J = 8.5, 0.7 Hz, 2 H), 5.83–5.78 (m, 1 H), 5.78–5.73 (m, 1 H), 3.31 (tdt,
J = 7.2, 4.1, 2.5 Hz, 1 H), 2.35 (s, 3 H), 2.10–2.03 (m, 2 H), 2.00 (ddd,
J = 13.2, 5.1, 3.0 Hz, 1 H), 1.94–1.86 (m, 1 H), 1.85–1.78 (m, 1 H), 1.68–
1
-(Cyclohex-2-en-1-ylethynyl)-2-methoxybenzene (3g)
Following the general procedure, using Cu(MeCN) PF (7.1 mg, 0.018
4
6
1.56 (m, 1 H).
mmol), ligand L1 (6.1 mg, 0.018 mmol), cyclohexene (2a; 603 mg, 7.3
mmol), 1-ethynyl-2-methoxybenzene (1g; 50 mg, 0.37 mmol), and
TBHP (66 mg, 0.73 mmol), the pure product was obtained by flash
13
C NMR (101 MHz, CDCl ):  = 137.6, 132.5, 131.6, 129.3, 129.0,
3
128.0, 127.3, 120.9, 92.1, 80.4, 77.2, 29.6, 28.1, 24.8, 21.5, 20.8.
column chromatography on silica gel using Et O/pentane (1:30) as
2
eluent; colorless oil; yield: 42 mg (59%, 0.2 mmol); R = 0.6.
f
2-(Cyclohex-2-en-1-ylethynyl)-1,4-dimethylbenzene (3k)
1
H NMR (400 MHz, CDCl ):  = 7.39 (d, J = 9.3 Hz, 1 H), 7.23 (ddd,
3
Following the general procedure, using Cu(MeCN) PF (7.3 mg, 0.018
4
6
J = 8.3, 7.5, 1.8 Hz, 1 H), 6.88 (dd, J = 7.5, 1.1 Hz, 1 H), 6.84 (d, J = 8.7
Hz, 1 H), 5.77 (d, J = 1.4 Hz, 2 H), 3.86 (s, 3 H), 3.40–3.34 (m, 1 H),
mmol), ligand L1 (6.7 mg, 0.018 mmol), cyclohexene (2a; 612 mg, 7.4
mmol), 2-ethynyl-1,4-dimethylbenzene (1k; 50 mg, 0.37 mmol), and
TBHP (67 mg, 0.74 mmol), the pure product was obtained by flash
column chromatography on silica gel using pentane as eluent; color-
2.06–1.98 (m, 3 H), 1.91 (ddd, J = 13.2, 5.7, 2.5 Hz, 1 H), 1.87–1.80 (m,
1
H), 1.67–1.57 (m, 1 H).
13
C NMR (101 MHz, CDCl ):  = 159.9, 133.8, 129.0, 128.0, 127.3,
less oil; yield: 43 mg (55%, 0.25 mmol); R = 0.67.
f
3
1
20.4, 113.1, 110.7, 97.2, 76.5, 55.9, 29.5, 28.4, 24.8, 20.8.
1
H NMR (400 MHz, CDCl ):  = 7.23 (s, 1 H), 7.07 (d, J = 7.7 Hz, 1 H),
3
+
HRMS (ESI-TOF): m/z calcd for C15H16O [M + H] : 212.11957; found:
6.99 (d, J = 9.4 Hz, 1 H), 5.82–5.74 (m, 2 H), 3.35 (dtt, J = 6.7, 3.4, 1.9
Hz, 1 H), 2.39 (s, 3 H), 2.29 (s, 3 H), 2.07–1.98 (m, 3 H), 1.95–1.89 (m, 1
H), 1.87–1.80 (m, 1 H), 1.70–1.62 (m, 1 H).
212.11889.
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

G
Synthesis
A. A. Almasalma, E. Mejía
Paper
13
1
C NMR (101 MHz, CDCl ):  = 137.0, 134.9, 132.4, 129.3, 128.5,
H NMR (400 MHz, CDCl ):  = 7.36 (d, J = 4.1 Hz, 1 H), 7.22 (d, J = 3.0
3
3
1
28.0, 127.4, 123.5, 96.7, 79.5, 77.2, 29.7, 28.3, 24.8, 20.9, 20.8, 20.3.
Hz, 1 H), 7.09–7.07 (m, 1 H), 5.78 (dtd, J = 9.1, 3.5, 2.1 Hz, 1 H), 5.72
ddt, J = 9.9, 3.5, 1.9 Hz, 1 H), 3.28 (ddp, J = 7.8, 5.4, 2.8 Hz, 1 H), 2.05–
.94 (m, 3 H), 1.91–1.83 (m, 1 H), 1.82–1.75 (m, 1 H), 1.66–1.57 (m, 1
(
1
1
-Butyl-4-(cyclohex-2-en-1-ylethynyl)benzene (3l)
H).
Following the general procedure, using Cu(MeCN) PF (5.8 mg, 0.015
mmol), ligand L1 (5.2 mg, 0.015 mmol), cyclohexene (2a; 500 mg, 6
mmol), 1-butyl-4-ethynylbenzene (1l; 50 mg, 0.3 mmol), and TBHP
4
6
13C NMR (75 MHz, CDCl
):  = 130.2, 128.2, 127.8, 127.1, 125.0, 122.9,
3
92.5, 77.6, 77.2, 76.7, 75.4, 29.4, 28.1, 24.8, 20.8.
(55 mg, 0.61 mmol), the pure product was obtained by flash column
chromatography on silica gel using pentane as eluent; colorless oil;
2-(Cyclohex-2-en-1-ylethynyl)phenol (3p)
yield: 51 mg (71%, 0.21 mmol); R = 0.52.
f
Following the general procedure, using Cu(MeCN) PF (7.8 mg, 0.021
4
6
1
H NMR (300 MHz, CDCl ):  = 7.33 (d, J = 8.3 Hz, 2 H), 7.10 (d, J = 8.4
mmol), ligand L1 (6.7 mg, 0.021 mmol), cyclohexene (2a; 810 mg,
8.04 mmol), 2-ethynylphenol (1p; 50 mg, 0.4 mmol), and TBHP (72
mg, 0.8 mmol), the pure product was obtained by flash column chro-
matography on silica gel using pentane/EtOAc (8:2) as eluent; color-
3
Hz, 2 H), 5.82–5.70 (m, 2 H), 3.30 (dtd, J = 7.1, 5.4, 4.8, 2.0 Hz, 1 H),
2.62–2.56 (m, 2 H), 2.08–1.75 (m, 5 H), 1.66–1.53 (m, 3 H), 1.35 (dq,
J = 14.3, 7.2 Hz, 2 H), 0.93 (t, J = 7.3 Hz, 3 H).
13
less oil; yield: 45 mg (56%, 0.22 mmol); R = 0.6.
f
C NMR (75 MHz, CDCl ):  = 142.6, 132.5, 131.6, 128.7, 128.4, 128.0,
3
127.4, 121.1, 92.2, 80.5, 35.6, 33.6, 29.6, 28.2, 24.8, 22.4, 20.8, 14.1.
Note: Extensive drying of the product under high vacuum leads to de-
composition of the product.
1
1-(tert-Butyl)-4-(cyclohex-2-en-1-ylethynyl)benzene (3m)
H NMR (300 MHz, CDCl ):  = 7.14 (t, J = 7.9 Hz, 1 H), 6.98 (d, J = 7.7
3
Following the general procedure, using Cu(MeCN) PF (5.8 mg, 0.015
Hz, 1 H), 6.89–6.86 (m, 1 H), 6.75 (dd, J = 8.1, 3.5 Hz, 1 H), 5.82–5.75
(m, 1 H), 5.74–5.67 (m, 1 H), 3.28 (pt, J = 6.0, 3.2 Hz, 1 H), 2.07–2.00
(m, 2 H), 1.96 (dd, J = 11.3, 4.0 Hz, 1 H), 1.92–1.83 (m, 1 H), 1.83–1.72
(m, 1 H), 1.67–1.55 (m, 1 H).
4
6
mmol), ligand L1 (5.1 mg, 0.015 mmol), cyclohexene (2a; 500 mg, 6
mmol), 1-(tert-butyl)-4-ethynylbenzene (1m; 50 mg, 0.3 mmol), and
TBHP (54 mg, 0.6 mmol), the pure product was obtained by flash col-
umn chromatography on silica gel using pure pentane as eluent; col-
13
C NMR (75 MHz, CDCl ):  = 155.3, 129.6, 128.3, 127.1, 125.3, 124.5,
3
orless oil; yield: 564 mg (62%, 0.18 mmol); R = 0.44.
f
118.5, 115.2, 93.2, 80.1, 77.2, 29.4, 28.1, 24.8, 20.8.
1
H NMR (400 MHz, CDCl ):  = 7.37 (d, J = 8.7 Hz, 2 H), 7.32 (d, J = 6.6
3
Hz, 2 H), 5.83–5.73 (m, 2 H), 3.32 (qt, J = 5.3, 2.3 Hz, 1 H), 2.08–1.97
[(3-Methylcyclohex-2-en-1-yl)ethynyl]benzene (3r)
(
1
m, 3 H), 1.92–1.78 (m, 2 H), 1.68–1.58 (m, 1 H), 1.32 (s, 9 H).
Following the general procedure, using Cu(MeCN) PF (9.2 mg, 0.024
4
6
3
C NMR (101 MHz, CDCl ):  = 150.8, 132.4, 131.4, 128.0, 127.4,
mmol), ligand L1 (8.4 mg, 0.024 mmol), 1-methylcyclohex-1-ene (2e;
923 mg, 9.6 mmol), phenylacetylene (1a; 50 mg, 0.48 mmol), and
TBHP (86 mg, 0.96 mmol), the pure product was obtained by flash
column chromatography on silica gel using pentane as eluent; color-
3
1
25.2, 121.0, 92.2, 80.4, 77.2, 34.8, 31.3, 29.6, 28.2, 24.8, 20.8.
1
-(Cyclohex-2-en-1-ylethynyl)-4-methoxy-2-methylbenzene (3n)
less oil; yield: 50 mg (53%, 0.25 mmol); R = 0.8.
f
Following the general procedure, using Cu(MeCN) PF (6.5 mg, 0.017
4
6
1H NMR (300 MHz, CDCl
):  = 7.39–7.35 (m, 2 H), 7.23–7.20 (m, 3 H),
mmol), ligand L1 (5.9 mg, 0.017 mmol), cyclohexene (2a; 545 mg, 6.6
mmol), 1-ethynyl-4-methoxy-2-methylbenzene (1n; 50 mg, 0.33
mmol), and TBHP (60 mg, 0.66 mmol), the pure product was obtained
3
5.42 (dh, J = 3.0, 1.5 Hz, 1 H), 3.24 (dddq, J = 7.4, 5.5, 4.1, 2.1 Hz, 1 H),
1.89 (ddd, J = 10.9, 6.1, 2.8 Hz, 3 H), 1.85–1.77 (m, 1 H), 1.75–1.67 (m,
1 H), 1.65 (ddd, J = 2.2, 1.8, 0.8 Hz, 3 H), 1.57 (ddd, J = 9.0, 4.8, 2.6 Hz, 1
H).
by flash column chromatography on silica gel using Et O/pentane
2
(1:30) as eluent; colorless oil; yield: 68 mg (90%, 0.3 mmol); R = 0.5.
f
1
13C NMR (75 MHz, CDCl
H NMR (400 MHz, CDCl ):  = 7.30 (d, J = 8.5 Hz, 1 H), 6.72 (d, J = 2.7
3
):  = 135.5, 131.7, 128.2, 127.6, 124.1, 121.2,
3
Hz, 1 H), 6.65 (dd, J = 8.0, 2.7 Hz, 1 H), 5.80–5.72 (m, 2 H), 3.78 (s, 3 H),
93.5, 80.2, 77.2, 29.8, 29.3, 28.4, 23.9, 21.2.
3
1
1
.32 (dtt, J = 6.7, 3.6, 1.8 Hz, 1 H), 2.40 (s, 3 H), 2.01 (dddt, J = 20.7,
0.7, 5.4, 2.2 Hz, 3 H), 1.93–1.85 (m, 1 H), 1.84–1.77 (m, 1 H), 1.68–
.58 (m, 1 H).
(Cyclopent-2-en-1-ylethynyl)benzene (3s)
Following the general procedure, using Cu(MeCN) PF (9.2 mg, 0.024
4
6
13
C NMR (101 MHz, CDCl ):  = 159.05, 141.83, 133.07, 127.88,
mmol), ligand L1 (8.4 mg, 0.024 mmol), cyclopentene (2b; 653 mg,
9.6 mmol), phenylacetylene (1a; 50 mg, 0.48 mmol), and TBHP (86
mg, 0.96 mmol), the pure product was obtained by flash column chro-
3
1
2
27.59, 116.10, 115.02, 111.10, 95.39, 79.10, 77.16, 55.29, 29.79,
8.30, 24.84, 21.12, 20.79.
matography on silica gel using Et O/pentane (0.5:99.5) as eluent; col-
MS: m/z = 226 (100), 211 (34), 198 (70), 165 (39), 146 (68).
2
orless oil; yield: 65 mg (80%, 0.38 mmol); R = 0.8.
f
+
HRMS (ESI-TOF): m/z calcd for C16H18O [M + H] : 226.13522; found:
Note: Extensive drying of the product under high vacuum leads to de-
composition of the product.
226.13481.
1
H NMR (300 MHz, CDCl ):  = 7.35–7.31 (m, 2 H), 7.21–7.17 (m, 3 H),
.81–5.76 (m, 1 H), 5.71–5.65 (m, 1 H), 3.64 (dddt, J = 9.2, 7.1, 4.6, 2.3
3
-(Cyclohex-2-en-1-ylethynyl)thiophene (3o)
3
5
Following the general procedure, using Cu(MeCN) PF (8.7 mg, 0.022
4
6
Hz, 1 H), 2.47–2.38 (m, 1 H), 2.36–2.29 (m, 1 H), 2.29–2.21 (m, 1 H),
1
13C NMR (75 MHz, CDCl
127.7, 124.2, 92.8, 80.8, 77.2, 36.7, 32.2, 31.9, 26.0.
mmol), ligand L1 (7.8 mg, 0.022 mmol), cyclohexene (2a; 736 mg, 9
mmol), 3-ethynylthiophene (1o; 50 mg, 0.45 mmol), and TBHP (81
mg, 0.9 mmol), the pure product was obtained by flash column chro-
matography on silica gel using pentane as eluent; colorless oil; yield:
.99–1.88 (m, 1 H).
):  = 132.3, 132.0, 131.8, 131.4, 128.4, 128.3,
3
5
5 mg (65%, 0.3 mmol); R = 0.6.
f
MS: m/z = 167 (100), 153 (53), 141 (11), 128 (8), 115 (16).
©
2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H

H
Synthesis
A. A. Almasalma, E. Mejía
Paper
3-(Phenylethynyl)cyclohept-1-ene (3t)
(4) (a) Knorn, M.; Rawner, T.; Czerwieniec, R.; Reiser, O. ACS Catal.
2
015, 5, 5186. (b) Reiser, O. Acc. Chem. Res. 2016, 49, 1990.
Following the general procedure, using Cu(MeCN) PF (9.5 mg, 0.024
mmol), ligand L1 (8.4 mg, 0.024 mmol), cycloheptene (2c; 941 mg, 9.6
mmol), phenylacetylene (1a; 50 mg, 0.48 mmol), and TBHP (86 mg,
4
6
(
5) Baralle, A.; Fensterbank, L.; Goddard, J.-P.; Ollivier, C. Chem. Eur.
J. 2013, 19, 10809.
6) Cuthbertson, J. D.; MacMillan, D. W. C. Nature 2015, 519 (7541),
(
0.96 mmol), the pure product was obtained by flash column chroma-
74.
tography on silica gel using Et O/pentane (1:99) as eluent; colorless
2
(
(
7) Almasalma, A. A.; Mejia, E. Chem. Eur. J. 2018, 24, 12269.
8) Tsang, A. S.-K.; Park, S. J.; Todd, M. H. In From C-H to C-C Bonds:
Cross-Dehydrogenative-Coupling, RSC Green Chemistry Vol. 26;
Li, C.-J., Ed.; The Royal Society of Chemistry: Cambridge, 2015,
oil; yield: 50 mg (49%, 0.25 mmol); R = 0.8.
f
1
H NMR (300 MHz, CDCl ):  = 7.40–7.36 (m, 2 H), 7.26–7.23 (m, 3 H),
3
5.85–5.82 (m, 2 H), 3.50–3.43 (m, 1 H), 2.30–2.18 (m, 1 H), 2.05
(
(
1
dddd, J = 13.6, 10.1, 6.8, 3.2 Hz, 2 H), 1.94–1.86 (m, 1 H), 1.81–1.68
m, 2 H), 1.55 (ddt, J = 15.7, 8.9, 3.2 Hz, 2 H).
254–294.
(
9) (a) Li, C.-J. Acc. Chem. Res. 2009, 42, 335. (b) Girard, S. A.;
Knauber, T.; Li, C. J. Angew. Chem. Int. Ed. 2014, 53, 74. (c) Li, Z.;
Li, C. J. J. Am. Chem. Soc. 2006, 128, 56. (d) Varun, B. V.;
Dhineshkumar, J.; Bettadapur, K. R.; Siddaraju, Y.; Alagiri, K.;
Prabhu, K. R. Tetrahedron Lett. 2017, 58, 803. (e) Yoo, W.-J.; Li,
C.-J. C-H Activation, In Topics in Current Chemistry, Vol. 292; Yu,
J.-Q.; Shi, Z., Ed.; Springer: Berlin, 2010, 281–302. (f) Zheng, X.;
Li, Z. In From C-H to C-C Bonds: Cross-Dehydrogenative-Coupling,
RSC Green Chemistry Vol. 26; Li, C.-J., Ed.; The Royal Society of
Chemistry: Cambridge, 2015, 55–66.
10) Chen, B.; Wu, L. Z.; Tung, C. H. Acc. Chem. Res. 2018, 51, 2512.
11) Constable, E. C. Chem. Soc. Rev. 2007, 36, 246.
12) Harriman, A.; Ziessel, R. Coord. Chem. Rev. 1998, 171, 331.
13) Heller, M.; Schubert, U. S. Eur. J. Org. Chem. 2003, 947.
14) (a) Yan, X.; Zhang, J. Chem. Res. Chin. Univ. 2017, 33, 1.
3
C NMR (75 MHz, CDCl ):  = 133.5, 132.8, 131.7, 128.3, 127.6, 124.1,
3
93.1, 80.9, 77.2, 33.8, 32.6, 29.7, 28.5, 26.9.
3-(Phenylethynyl)cyclooct-1-ene (3u, Mixture of Isomers)
Following the general procedure, using Cu(MeCN) PF (9.3 mg, 0.024
4
6
mmol), ligand L1 (8.2 mg, 0.024 mmol), cis-cyclooctene (2d; 1 g, 9.6
mmol), phenylacetylene (1a; 50 mg, 0.48 mmol), and TBHP (86 mg,
0.96 mmol), a mixture of isomeric products was obtained. This was
purified by flash column chromatography on silica gel using pentane
as eluent. A colorless oil consisting of two main products was ob-
(
(
(
(
(
tained; yield: 75 mg (74%, 0.35 mmol); R = 0.6.
f
13
C NMR (75 MHz, CDCl ):  [for the 3-(phenylethynyl)cyclooct-1-ene
3
assigned from 2D NMR] = 131.7, 131.1, 130.2, 128.3, 127.7, 124.1,
3.7, 80.6, 37.1, 29.4, 29.1, 26.6, 26.1, 25.5.
9
(b) Huang, J.-B.; Bai, X.-F.; Li, L.; Zheng, Z.-J.; Xu, Z.; Cui, Y.-M.;
Cao, J.; Xu, L.-W. Chem. Eur. J. 2017, 23, 4055.
(
15) (a) Rajalakshmi, S.; Weyhermüller, T.; Dinesh, M.; Nair, B. U.
J. Inorg. Biochem. 2012, 117, 48. (b) Zhang, Y.; Schulz, M.;
Wächtler, M.; Karnahl, M.; Dietzek, B. Coord. Chem. Rev. 2018,
Funding Information
Financial support by the German Academic Exchange Service, DAAD
356, 127. (c) Hogg, R.; Wilkins, R. G. J. Chem. Soc. 1962, 341.
(Leadership for Syria Program) is gratefully acknowledged.()
(
16) (a) Potts, K. T.; Keshavarz-K, M.; Tham, F. S.; Raiford, K. A. G.;
Arana, C.; Abruna, H. D. Inorg. Chem. 1993, 32, 5477. (b) Potts, K.
T.; Keshavarz-K, M.; Tham, F. S.; Abruna, H. D.; Arana, C. R. Inorg.
Chem. 1993, 32, 4422. (c) Munakata, M.; Nishibayashi, S.;
Sakamoto, H. J. Chem. Soc., Chem. Commun. 1980, 219.
Acknowledgment
We thank the analytical department at LIKAT, Rostock and Prof. Udo
Kragl (University of Rostock) for the continuous support. We thank
also Dr. Nils Rockstroh for the photospectroscopy measurements in
LIKAT. Thanks to the state of Mecklenburg-West Pomerania and the
European Union (European Regional Development Fund, ERDF), for
the support to acquire the high-performance Xenon lamp used for the
photochemical reactions.
(d) Crumbliss, A. L.; Poulos, A. T. Inorg. Chem. 1975, 14, 1529.
(17) Pflaum, R. T.; Brandt, W. W. J. Am. Chem. Soc. 1955, 77, 2019.
(18) Sagadevan, A.; Hwang, K. C. Adv. Synth. Catal. 2012, 354, 3421.
(19) Wu, J. J.; Li, Y. W.; Zhou, H. Y.; Wen, A. H.; Lun, C. C.; Yao, S. Y.;
Ke, Z. F.; Ye, B. H. ACS Catal. 2016, 6, 1263.
(
(
20) Li, J.; Zhang, J.; Tan, H.; Wang, D. Z. Org. Lett. 2015, 17, 2522.
21) Ogino, K.; Kanegae, A.; Yamaguchi, R.; Sato, H.; Kurjata, J. Macro-
mol. Rapid Commun. 1999, 20, 103.
(
22) Photosensitive Metal – Organic Systems; Kutal, C.; Serpone, N.,
Ed.; In Advances in Chemistry, Vol 238; American Chemical
Society: Washington, 1993.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0039-1690014.
S
u
p
p
orti
n
g Inform ati
o
n
S
u
p
p
orit
n
g Inform ati
o
n
(23) Manbeck, G. F.; Brennessel, W. W.; Eisenberg, R. Inorg. Chem.
011, 50, 3431.
2
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2019. Thieme. All rights reserved. — Synthesis 2019, 51, A–H