Synthesis of Benzo-Fused Cyclic Compounds via Rhodium-Catalyzed Decarboxylative Coupling of Aromatic Carboxylic Acids with Alkynes

Article abstract of DOI:10.1055/a-1416-6997

The decarboxylative coupling of diversely substituted benzoic acids with internal alkynes proceeds smoothly in the presence of a [RhCl(cod)] ₂/1,2,3,4-tetraphenyl-1,3-cyclopentadiene catalyst system to selectively produce highly substituted nap

Full text of DOI:10.1055/a-1416-6997

SYNTHESIS
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Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart
2021, 53, A–H
special topic
A
Bond Activation – in Honor of Prof. Shinji
Y. Inai et al.
Special Topic
Synthesis
Synthesis of Benzo-Fused Cyclic Compounds via Rhodium-Cata-
lyzed Decarboxylative Coupling of Aromatic Carboxylic Acids with
Alkynes
Yasuhito Inai
R
Yoshinosuke Usuki
Tetsuya Satoh*
CO2H
R
R
H
+
R
cat. [RhCl(cod)]2/C5H2Ph4
oxidant
R
Department of Chemistry, Graduate School of Science,
Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku,
Osaka 558-8585, Japan
R
R
H
H
R
satoh@sci.osaka-cu.ac.jp
R
R
Ph
Ph
CO2H
Published as part of the Special Topic
Bond Activation – in Honor of Prof. Shinji Murai
S
C5H2Ph4
=
Ph
Ph
S
eTDMeetpasauiClryotsamarrtSeeoanshtpto@oohsnfcdCi.iohnsegamkAiaus-tcrhuyo.,arGc.rjapduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
wide substrate scope
24 examples
39–98% yield
Received: 17.02.2021
Accepted after revision: 08.03.2021
Published online: 08.03.2021
using [CpERhCl2]2 and [CpRhI2]2, respectively, as catalysts
[CpE = 1,3-bis(ethoxycarbonyl)-2,4,5-trimethylcyclopenta-
dienyl]. Despite this progress, the substrate scope is still
limited.
DOI: 10.1055/a-1416-6997; Art ID: ss-2021-f0071-st
Abstract The decarboxylative coupling of diversely substituted ben-
zoic acids with internal alkynes proceeds smoothly in the presence of a
[RhCl(cod)]2/1,2,3,4-tetraphenyl-1,3-cyclopentadiene catalyst system
to selectively produce highly substituted naphthalene derivatives. The
catalyst system is applicable to constructing anthracene and benzo-
[c]thiophene frameworks through reactions of naphthoic and thio-
phene-2-carboxylic acids, respectively.
During our further studies on such homologation, we
found that the catalyst system [RhCl(cod)]2/C5H2Ph4
(C5H2Ph4 = 1,2,3,4-tetraphenyl-1,3-cyclopentadiene)3b,5c,8
was effective for the reaction of diversely substituted ben-
zoic acids with alkynes to produce highly substituted naph-
thalenes selectively (Scheme 1, b). This catalyst system was
also found to be applicable to the homologation of naph-
Key words C–H functionalization, carboxylic acids, decarboxylative
coupling, homologation, rhodium catalysis
a) Previous work
O
Aromatic and heteroaromatic carboxylic acids have
been recognized as promising building blocks in the field of
organic synthesis because of their ready availability. More-
over, their carboxy function acts as a directing group1 to
bring about regioselective C–H functionalization2 at the
neighboring positions under transition-metal catalysis. Our
group has reported that benzoic acids undergo dehydroge-
native coupling with internal alkynes through ortho C–H
bond cleavage upon treatment with a [Cp*RhCl2]2 catalyst
and a copper salt oxidant to produce isocoumarins (Scheme
1, a).3 Meanwhile, treatment of the same starting materials
with a [Cp*IrCl2]2 catalyst and a silver salt oxidant induces
decarboxylative 1:2 coupling to give 1,2,3,4-tetrasubstitut-
ed naphthalene derivatives.4 The latter aromatic homologa-
tion5 is of particular interest because of its utility for con-
structing benzo-fused cyclic compounds such as acenes and
benzoheteroles. Recently, the groups of Tanaka6 and Loginov7
reported that homologation can be conducted smoothly by
cat. [Cp*RhCl2]2
Cu salt
O
R
O
H
R
R
R
R
OH
+
R
R
cat. [Cp*IrCl2]2
Ag salt
R
b) This work
R1
R1
R5
R5
R5
O
cat. [RhCl(cod)]2
cat. C5H2Ph4
R2
R5
R5
R2
OH
+
R3
Ph
Cu(OAc)2
Ph
R3
H
R4
R5
R4
C5H2Ph4
=
Ph
Ph
Scheme 1 Dehydrogenative coupling of benzoic acids with alkynes
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
Y. Inai et al.
Special Topic
Synthesis
Cu(OAc)2 (0.025 mmol) under air (1 atm) gave 3aa in a
somewhat reduced yield (entry 8). At 120 °C, the reaction
was sluggish (entry 9). Under the same conditions as those
in entry 3, 1a also reacted with 8-hexadecyne (2b) to give
1,2,3,4-tetra(n-heptyl)naphthalene (3ab) predominantly,
along with a minor amount of 3,4-di(n-heptyl)-1H-iso-
chromen-1-one (4ab) (entry 10).
Under the optimized conditions (Table 1, entry 3), the
reactions of differently substituted benzoic acids 1b–k with
2a were examined (Scheme 2). 4-Methyl- (1b) and
4-(methoxycarbonyl)benzoic acids (1c) and [1,1′-biphe-
nyl]-4-carboxylic acid (1d) coupled with 2a efficiently to
produce the corresponding 6-substituted 1,2,3,4-tetra-
phenylnaphthalenes 3ba–da in excellent yields. The reaction
Table 1 Reaction of Benzoic Acid (1a) with Diphenylacetylene (2a) or
8-Hexadecyne (2b)a
O
R
O
R
Rh-cat.
ligand
R
R
OH
O
+
+
Cu(OAc)2
R
R
R
R
1a
2a (R = Ph)
2b (R = n-C7H15
3aa (R = Ph)
4aa (R = Ph)
4ab (R = n-C7H15
)
3ab (R = n-C7H15
)
)
Entry
R
Rh-cat.
Ligand
Yield (%)b
3
4
1
2
Ph
[Cp*RhCl2]2
[Cp*RhCl2]2
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
RhCl3·3H2O
RhCl3·3H2O
[RhCl(cod)]2
[RhCl(cod)]2
[RhCl(cod)]2
–
8
92 (91)
Ph
cod
0
10
3
3
Ph
C5H2Ph4
C5HPh5
–
97 (96)
R1
Ph
R1
O
Ph
cat. [RhCl(cod)]2
cat. C5H2Ph4
R2
R3
Ph
Ph
4
Ph
0
3
1
R2
R3
OH
+
5
Ph
1
Cu(OAc)2
6c
7c
8d
9e
10
Ph
–
0
0
Ph
Ph
1
2a
3
Ph
C5H2Ph4
C5H2Ph4
C5H2Ph4
C5H2Ph4
0
0
and/or regioisomer 3'
1
Product(s)
Ph
74
23
(60)
21
1
Ph
Ph
O
Ph
Ph
n-C7H15
20
OH
a Reaction conditions: 1a (0.38 mmol), 2a (0.5 mmol), Rh-cat. (0.005
mmol), ligand (0.02 mmol), Cu(OAc)2 (1 mmol), o-xylene (2.5 mL), 160 °C,
Ar (1 atm), 24 h.
R
R
Ph
1b: R = Me
1c: R = CO2Me 3 h
1d: R = Ph 3 h
3 h
3ba: R = Me, 98%
3ca: R = CO2Me, 98%
3da: R = Ph, 95%
b GC yield based on the amount of 2a used. Value in parentheses indicates
the yield of isolated product after purification.
c RhCl3·3H2O (0.01 mmol) was used.
Ph
Ph
O
d Cu(OAc)2 (0.025 mmol) was used under air (1 atm).
e Reaction at 120 °C.
Ph
Ph
OH
+
R
Ph
Ph
R
Ph
R
Ph
thoic acids and thiophene-2-carboxylic acid to form an-
thracene and benzo[c]thiophene frameworks, respectively.
These findings are described herein.
1e: R = OMe
1f: R = F
3 h
3 h
3ea + 3'ea: R = OMe, 96% (86:14)
3fa + 3'fa: R = F, 90% (32:68)
Ph
O
Ph
Ph
Ph
Ph
In an initial attempt, benzoic acid (1a) (0.38 mmol) was
treated with diphenylacetylene (2a) (0.5 mmol) under con-
ditions similar to those described in our previous report.
Thus, in the presence of [Cp*RhCl2]2 (0.005 mmol) and
Cu(OAc)2 (1 mmol) as the catalyst and the oxidant, respec-
tively, in o-xylene (2.5 mL) at 160 °C under argon (1 atm),
3,4-diphenyl-1H-isochromen-1-one (4aa) was formed as
the major product, along with a minor amount of 1,2,3,4-
tetraphenylnaphthalene (3aa) (Table 1, entry 1). Adding cod
(cod = 1,5-cyclooctadiene) (0.02 mmol) retarded the reac-
tion (entry 2). In contrast, as described above, the catalyst
system of [RhCl(cod)]2/C5H2Ph4 effectively promoted the
decarboxylative coupling to give 3aa in 96% isolated yield
(entry 3). The use of C5HPh5 (C5HPh5 = 1,2,3,4,5-pentaphe-
nyl-1,3-cyclopentadiene) in place of C5H2Ph4 (entry 4) or
the absence of any Cp ligand (entries 5 and 6) led to poor
results. It is possible that sterically more hindered C5HPh5
did not act as a ligand effectively.9 The system comprising
RhCl3·3H2O/C5H2Ph4 also showed no activity for the cou-
pling (entry 7). The reaction using a catalytic amount of
OH
Ph
1g
3 h
3ga (= 3da), 94%
Ph
R
O
R
Ph
OH
Ph
Ph
1h: R = Ph
1i: R = Me
3 h
24 h
3'ha (= 3da): R = Ph, 91%
3'ia (= 3ba): R = Me, 81%
R
Ph
Ph
Ph
R
O
Ph
Ph
R
Ph
Ph
OH
+
Ph
1j: R = OMe
1k: R = F
24 h 3ja (= 3'ea) + 3'ja (= 3ea): R = OMe, 92% (14:86)
24 h 3ka (= 3'fa) + 3'ka (= 3fa): R = F, 81% (78:22)
Scheme 2 Reactions of benzoic acids 1 with 2a. Reagents and condi-
tions: 1 (0.38 mmol), 2a (0.5 mmol), [RhCl(cod)]2 (0.005 mmol),
C5H2Ph4 (0.02 mmol), Cu(OAc)2 (1 mmol), o-xylene (2.5 mL), 160 °C, Ar
(1 atm). Yields of isolated products are given. Values in parentheses in-
dicate product ratios determined by 1H NMR.
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

C
Y. Inai et al.
Special Topic
Synthesis
of 4-methoxybenzoic acid (1e) also proceeded smoothly to
give a mixture of regioisomers 3ea and 3′ea (86:14, 96% to-
tal yield). In the reaction of 4-fluorobenzoic acid (1f), the
sterically hindered 5-fluoro-1,2,3,4-tetraphenylnaphtha-
lene (3′fa) was formed predominantly over the less crowd-
ed regioisomer 3fa. We previously observed the similar
predominant formation of a 5-substituted naphthalene de-
rivative in the iridium-catalyzed decarboxylative coupling
of 4-hydroxybenzoic acid.4a [1,1′-Biphenyl]-3-carboxylic
acid (1g), [1,1′-biphenyl]-2-carboxylic acid (1h), and 2-
methylbenzoic acid (1i) also underwent the reaction with
2a to selectively afford 6-substituted 1,2,3,4-tetraphenyl-
naphthalenes 3ga, 3′ha, and 3′ia, respectively, in good
yields. The reactions of 2-methoxy- (1j) and 2-fluorobenzo-
ic acids (1k) gave similar mixtures of regioisomers 3ja/3′ja
and 3ka/3′ka, as in cases with 1e and 1f.
ated from [RhCl(cod)]2, C5H2Ph4, and the Cu salt oxidant.
The reaction of 4-substituted benzoic acids appears to pro-
ceed in a similar way to that proposed for the previously re-
ported iridium-catalyzed reaction,4b through carboxy-
group-directed C–H bond cleavage to form A, alkyne inser-
tion to form B, decarboxylation to form C, a second alkyne
insertion, and reductive elimination steps to release 6-sub-
stituted 1,2,3,4-tetraphenylnaphthalene 3. The LRhI species
generated in the final step appears to be reoxidized by the
copper salt oxidant to regenerate the active LRhIIIX2 species.
In the reactions of 4-methoxy- and 4-fluorobenzoic acids,
at least some of C may isomerize into E through D to afford
5-substituted 1,2,3,4-tetraphenylnaphthalenes 3′ along
with 3. On the other hand, the reaction of 2-substituted
benzoic acids proceeds through ortho C–H bond cleavage,
alkyne insertion, and decarboxylation to form intermediate
E. In the cases with 2-phenyl- and 2-methylbenzoic acids (R
= Ph, Me), E undergoes isomerization into C due to steric
hindrance, to exclusively form 6-substituted 1,2,3,4-tetra-
phenylnaphthalene 3′. The reactions of 2-methoxy- and 2-
fluorobenzoic acids gave similar mixtures of 5- and 6-sub-
stituted 1,2,3,4-tetraphenylnaphthalene regioisomers as in
the cases with 4-methoxy- and 4-fluorobenzoic acids,
showing the existence of an equilibrium between interme-
diates C and E. The ratio of C/E may be determined by the
electronic and steric properties of these substituents.
It was confirmed that the present decarboxylative cou-
pling could be scaled up to mmol scale. Thus, the reaction of
1c (1.5 mmol) with 2a (2 mmol) gave the desired product
3ca in a reasonable yield (456 mg, 93%) (Scheme 3).
[RhCl(cod)]2
(0.02 mmol)
C5H2Ph4
(0.08 mmol)
O
Ph
Ph
Ph
Ph
Ph
OH
+
oxidant
(4 mmol)
o-xylene
MeO2C
MeO2C
Ph
160 °C, 6 h
It is known that hydroxy- and alkoxy-substituted ben-
zoic acids are widely distributed in plants and are therefore
readily available from biomass.3a,10 We next examined their
utilization as promising building blocks for constructing
highly substituted naphthalene derivatives (Scheme 5). Un-
der our standard conditions, 3,4,5-trimethoxybenzoic acid
(1l) reacted with 2a smoothly to produce 5,6,7-trimethoxy-
1c (1.5 mmol)
2a (2 mmol)
3ca, 93% (456 mg)
Scheme 3 A large-scale synthesis of 3ca
Plausible pathways for the reactions of 4- and 2-substi-
tuted benzoic acids with 2a are depicted in Scheme 4. An
active LRhIIIX2 species (L = η5-C5HPh4) appears to be gener-
L
CO2
O
O
Rh
2a
O
Ph
O
Rh
Rh
L
Ph
Ph
R
R
R
Ph
Ph
Ph
HX
L
C
A
Ph
2a
B
Ph
2 HX
HX
R
CO2H
H
L
R
X
Rh
LRhX2 (L = η5-C5HPh4)
LRhI
R
Ph
D
Ph
R
H
CO2H
Ph
Ph
HX
R
HX
2 HX
Ph
CO2
Ph
2a
Ph
2a
R
Ph
R
L
R
Rh
O
Ph
Rh
O
Rh
O
L
Ph
O
L
E
Scheme 4 Plausible pathways for the reactions of 4- and 2-substituted benzoic acids with 2a
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

D
Y. Inai et al.
Special Topic
Synthesis
1,2,3,4-tetraphenylnaphthalene (3la) in 73% yield. 4-Meth-
yl- (2c), 4-methoxy- (2d), 4-fluoro- (2e), and 4-(trifluoro-
methyl)- (2f) substituted diphenylacetylenes also under-
went the coupling with 1l to give products 3lc–lf in 64–82%
yields. The coupling of 3,4-dimethoxybenzoic acid (1m)
with 2a gave separable 6,7-dimethoxy-1,2,3,4-tetraphenyl-
naphthalene (3ma) and 5,6-dimethoxy-1,2,3,4-tetra-
phenylnaphthalene (3′ma) in 73% and 10% yields, respec-
tively. Benzo[d][1,3]dioxole-5-carboxylic acid (1n) is
known to be readily available from piperonal. Interestingly,
the homologation of this acid proceeded regioselectively to
afford 6,7,8,9-tetraphenylnaphtho[1,2-d][1,3]dioxole (3na)
in 83% yield.11
form 1,2,3,4-tetraphenylanthracene (6aa) in 39% yield
(Scheme 6, a). No phenanthrene isomer could be detected.12
As an oxidant, the use of AgOAc in place of Cu(OAc)2 im-
proved the yield of 6aa up to 62%. Under similar conditions,
6-methoxy-2-naphthoic acid (5b) underwent the reaction
with 2a to produce 6-methoxy-1,2,3,4-tetraphenylanthra-
cene (6ba) in 37% yield. The yield of 6ba was improved to
55% by increasing the temperature of the reaction bath to
170 °C. The anthracene 6aa could also be obtained in 64%
yield from the reaction of 1-naphthoic acid (5′a) with 2a
under conditions using AgOAc at 160 °C (Scheme 6, b).
Thiophene-2-carboxylic acid (7) underwent the coupling
with 2a in the presence of the [RhCl(cod)]2/C5H2Ph4 catalyst
system and AgOAc as the oxidant in t-AmOH at 120 °C to
predominantly produce 4,5,6,7-tetraphenylbenzo[c]thio-
phene (8a) in a moderate yield (Scheme 6, c).13 A similar
tetraarylbenzo[c]thiophene derivative 8g could also be pre-
pared by the reaction of 7 with bis(4-t-butylphenyl)acety-
lene (2g).
Ar
O
cat. [RhCl(cod)]2
cat. C5H2Ph4
Ar
R1
R2
Ar
Ar
R1
R2
OH
+
Cu(OAc)2
Ar
R3
Ar
R3
1
2
3
and/or regioisomer 3'
1
2
Product(s)
Ar
Ar
O
Ar
MeO
MeO
MeO
a)
[RhCl(cod)]2
(0.01 mmol)
C5H2Ph4
OH
O
Ph
Ph
Ph
Ar
MeO
Ph
Ph
Ar
(0.04 mmol)
OH
OMe Ar
OMe
1l
+
2a: Ar = Ph
3la: Ar = Ph, 73%
oxidant
(2 mmol)
R
R
2c: Ar = 4-MeC6H4
2d: Ar = 4-MeOC6H4
2e: Ar = 4-FC6H4
2f: Ar = 4-F3CC6H4
3lc: Ar = 4-MeC6H4, 76%
3ld: Ar = 4-MeOC6H4, 65%
3le: Ar = 4-FC6H4, 76%
3lf: Ar = 4-F3CC6H4, 82%
Ph
o-xylene
0.75 mmol
1 mmol
5a (R = H)
5b (R = OMe)
2a
6aa (R = H)
6ba (R = OMe)
Ph
O
Ph
R
H
H
OMe
OMe
Oxidant
Temp (°C)
Time (h)
24
24
24
48
Yield of 6 (%)
MeO
MeO
Ph
Ph
MeO
MeO
OH
Cu(OAc)2
AgOAc
AgOAc
AgOAc
160
160
160
170
39
62
37
55
Ph
Ph
1m
2a
3ma, 73%
+
OMe Ph
b)
[RhCl(cod)]2
(0.01 mmol)
C5H2Ph4
O
OH
Ph
Ph
Ph
MeO
Ph
Ph
Ph
(0.04 mmol)
+
AgOAc
(2 mmol)
o-xylene
Ph
Ph
Ph
3'ma, 10%
160 °C, 24 h
5'a (0.75 mmol) 2a (1 mmol)
6aa, 64%
Ph
O
O
Ph
O
Ph
Ph
c)
O
O
[RhCl(cod)]2
(0.01 mmol)
C5H2Ph4
OH
Ar
Ar
Ar
Ar
Ar
Ph
(0.04 mmol)
OH
+
Ph
1n
2a
3na, 83%
AgOAc
(2 mmol)
t-AmOH
S
O
Ar
S
Scheme 5 Reactions of alkoxy-substituted benzoic acids 1 with
alkynes 2. Reagents and conditions: 1 (0.38 mmol), 2 (0.5 mmol),
[RhCl(cod)]2 (0.005 mmol), C5H2Ph4 (0.02 mmol), Cu(OAc)2 (1 mmol),
o-xylene (2.5 mL), 160 °C, Ar (1 atm), 24 h. Yields of isolated products
are given.
0.75 mmol
1 mmol
120 °C, 4 h
7
2a (Ar = Ph)
8a (Ar = Ph)
8g (Ar = 4-t-BuC6H4)
2g (Ar = 4-t-BuC6H4)
Ar
Ph
Yield of 8 (%)
40
39
a
4-t-BuC6H4
Besides naphthalene synthesis, homologation for con-
structing other benzo-fused cyclic systems was also exam-
ined. The reaction of 2-naphthoic acid (5a) with 2a pro-
ceeded regioselectively under our standard conditions to
Scheme 6 Reactions of naphthoic acids 5 and thiophene-2-carboxylic
acid (7) with 2a. a Thiophene-2-carboxylic acid (7) (0.38 mmol), 2g (0.5
mmol), [RhCl(cod)]2 (0.005 mmol), C5H2Ph4 (0.02 mmol), and AgOAc
(1 mmol) were used.
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

E
Y. Inai et al.
Special Topic
Synthesis
In conclusion, we have developed the decarboxylative
coupling of aromatic carboxylic acids with internal alkynes.
For the homologation reactions, the [RhCl(cod)]2/C5H2Ph4
catalyst system was found to be effective. The procedure
provides straightforward routes not only to highly substi-
tuted naphthalenes, but also to anthracene and benzo-
[c]thiophene derivatives.
13C NMR (100 MHz, CDCl3):  = 136.9, 134.2, 131.1, 124.5, 124.4,
31.93, 31.91, 31.6, 31.3, 30.53, 30.48, 30.3 (overlapped), 29.2, 29.1,
22.7 (overlapped), 14.1 (overlapped).
HRMS (ESI): m/z [M + H]+ calcd for C38H65: 521.50863; found:
521.50870.
6-Methyl-1,2,3,4-tetraphenylnaphthalene (3ba)
Yield: 109.1 mg (98%); white solid; mp 220–221 °C (Lit.5b 216–217
°C).
1H NMR (400 MHz, CDCl3):  = 7.54 (d, J = 8.6 Hz, 1 H), 7.40 (s, 1 H),
7.27–7.16 (m, 11 H), 6.88–6.78 (m, 10 H), 2.39 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 140.7, 140.6, 139.73, 139.72, 138.9,
138.2, 138.0, 137.7, 135.6, 132.1, 131.4, 131.33, 131.31, 131.27, 130.2,
128.1, 127.46 (overlapped), 127.45, 126.9, 126.5 (overlapped), 126.31,
126.29, 125.8, 125.2, 21.8.
Chemicals were either purchased or were purified by standard tech-
niques. Diarylacetylenes 2c–g were prepared according to published
procedures.14 Column chromatography was performed using silica gel
60 (40–50 m). GPC (gel permeation chromatography) was per-
formed using a JASCO HPLC system EXTREMA composed of a PU-4086
pump, a UV-4075 detector, and a RV-2002-02 recycle valve unit with
a YMC-GPC-T2000 column. Melting points were obtained using a MP-
J3 Micro Melting Point Apparatus or a MPA100 OptiMelt Automated
Melting Point System. 1H (400 MHz) and 13C NMR (100 MHz) spectra
were recorded at room temperature on a Bruker AV400N spectrome-
ter using CDCl3 as the solvent and tetramethylsilane (TMS) as an in-
ternal standard. Chemical shifts () are quoted relative to TMS, and
the coupling constants (J) are given in Hz. 19F NMR (282 MHz) spectra
were recorded on a Bruker AV 300N spectrometer. Chemical shifts ()
are quoted relative to external trifluoroacetic acid (TFA) ( = –76.5).
GC analysis was carried out using a silicon OV-17 column (i.d. 2.6 mm
× 1.5 m). GC-MS analysis was carried out using a Shimadzu GC-MS-
QP2010 Plus mass spectrometer with a CBP-1 capillary column (i.d.
0.25 mm × 25 m). High-resolution mass spectrometry was performed
using a JEOL AccuTOF LC-plus 4G mass spectrometer.
HRMS (ESI): m/z [M + H]+ calcd for C35H27: 447.21128; found:
447.21113.
6-(Methoxycarbonyl)-1,2,3,4-tetraphenylnaphthalene (3ca)
Yield: 120.2 mg (98%); pale yellow solid; mp 296–297 °C (Lit.5b 296–
297 °C).
1H NMR (400 MHz, CDCl3):  = 8.42 (d, J = 1.4 Hz, 1 H), 7.95 (dd, J = 8.9,
1.8 Hz, 1 H), 7.69 (d, J = 8.9 Hz, 1 H), 7.29–7.18 (m, 10 H), 6.90–6.80
(m, 10 H), 3.86 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 167.3, 141.2, 140.08, 140.06, 139.9,
139.8, 139.0, 138.7, 138.4, 134.2, 131.3, 131.19, 131.15 (overlapped),
131.0, 130.0, 127.7, 127.6, 127.31, 127.29, 126.8, 126.6 (overlapped),
125.53, 125.48, 125.1, 52.1.
HRMS (ESI): m/z [M + H]+ calcd for C36H27O2: 491.20110; found:
491.20107.
Decarboxylative Coupling of 1 with 2; General Procedure
A mixture of benzoic acid 1 (0.38 mmol), alkyne 2 (0.5 mmol),
[Rh(cod)Cl2]2 (2.5 mg, 0.005 mmol), C5H2Ph4 (7.4 mg, 0.02 mmol),
Cu(OAc)2 (181.6 mg, 1.0 mmol) and 1-methylnaphthalene (ca. 50 mg)
as an internal standard in o-xylene (2.5 mL) was stirred at 160 °C un-
der Ar (1 atm) for 3–24 h. After the reaction was complete, the mix-
ture was diluted with dichloromethane (100 mL). The organic layer
was washed with water (2 × 100 mL) and brine (100 mL), and then
dried over Na2SO4. After evaporation of the solvents under vacuum,
products 3 (and 3′) were isolated by column chromatography on silica
gel using hexane–ethyl acetate as eluent. Further purification by GPC
(gel permeation chromatography) was performed, if needed.
1,2,3,4,6-Pentaphenylnaphthalene (3da)
Yield: 120.8 mg (95%); white solid; mp 268–269 °C (Lit.4b 268–271
°C).
1H NMR (400 MHz, CDCl3):  = 7.86 (d, J = 1.7 Hz, 1 H), 7.72 (d, J = 8.8
Hz, 1 H), 7.65 (dd, J = 8.8, 1.8 Hz, 1 H), 7.53 (dd, J = 7.8, 1.4 Hz, 2 H),
7.39 (dd, J = 7.5, 7.2 Hz, 2 H), 7.30 (t, J = 7.3 Hz, 1 H), 7.27–7.16 (m, 10
H), 6.90–6.80 (m, 10 H).
13C NMR (100 MHz, CDCl3):  = 141.2, 140.51, 140.48, 139.5, 139.4,
139.0, 138.7, 138.4, 138.3, 132.3, 131.3 (overlapped), 131.2, 128.8,
127.57 (overlapped), 127.56, 127.4, 127.2, 126.6 (overlapped), 126.49,
126.46, 125.5, 125.3, 124.9.
1,2,3,4-Tetraphenylnaphthalene (3aa)
Yield: 103.6 mg (96%); white solid; mp 206–207 °C (Lit.5b 205–206
HRMS (ESI): m/z [M + H]+ calcd for C40H29: 509.22684; found:
°C).
509.22684.
1H NMR (400 MHz, CDCl3):  = 7.67–7.61 (m, 2 H), 7.41–7.36 (m, 2 H),
6-Methoxy-1,2,3,4-tetraphenylnaphthalene (3ea) and 5-Methoxy-
7.27–7.16 (m, 10 H), 6.88–6.80 (m, 10 H).
1,2,3,4-tetraphenylnaphthalene (3′ea)
Yield: 111.4 mg (96%); white solid; mp 274–275 °C (Lit.6b 272.8–274.8
°C).
13C NMR (100 MHz, CDCl3):  = 140.5, 139.6, 138.9, 138.4, 132.0, 131.3
(overlapped), 127.5, 127.0, 126.5, 126.4, 125.8, 125.3.
HRMS (ESI): m/z [M + H]+ calcd for C34H25: 433.19563; found:
433.19472.
1H NMR (400 MHz, CDCl3):  = 7.54 (d, J = 9.2 Hz, 1 H, 3ea), 7.27–7.15
(m, 10 H, 3ea), 7.06 (dd, J = 9.3, 2.6 Hz, 1 H, 3ea), 6.95 (d, J = 2.5 Hz, 1
H, 3ea), 6.88–6.75 (m, 10 H, 3ea), 3.69 (s, 3 H, 3ea), 3.37 (s, 3 H, 3′ea).
13C NMR (100 MHz, CDCl3):  = 157.5 (3ea), 143.8 (3′ea), 140.7 (3ea),
140.6 (3ea), 140.1 (3′ea), 139.8 (3ea), 139.7 (3ea), 139.4 (3ea), 138.3
(3ea), 138.2 (3′ea), 137.3 (3ea), 136.8 (3ea), 133.3 (3ea), 131.4 (3ea),
131.25 (3ea), 131.23 (3ea), 131.18 (3ea), 131.1 (3′ea), 129.8 (3′ea),
128.7 (3ea), 127.6 (3ea), 127.5 (overlapped) (3ea), 126.5 (3ea), 126.4
1,2,3,4-Tetraheptylnaphthalene (3ab)5c
Yield: 78.6 mg (60%); colorless oil.
1H NMR (400 MHz, CDCl3):  = 8.03–7.94 (m, 2 H), 7.43–7.35 (m, 2 H),
3.07–2.95 (m, 4 H), 2.80–2.69 (m, 4 H), 1.71–1.26 (m, 40 H), 0.96–0.87
(m, 12 H).
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

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(3′ea), 126.37 (3ea), 126.36 (3ea), 126.3 (3′ea), 126.2 (3′ea), 126.0
(3′ea), 125.23 (3ea), 125.17 (3ea), 125.0 (3′ea), 124.7 (3′ea), 120.1
(3′ea), 118.0 (3ea), 106.9 (3′ea), 105.7 (3ea), 55.8 (3′ea), 55.1 (3ea).
HRMS (ESI): m/z [M + H]+ calcd for C35H27O: 463.20619; found:
13C NMR (100 MHz, CDCl3):  = 157.8, 157.0, 156.7, 156.6, 152.2,
150.1, 142.4, 139.3, 139.1, 137.1, 135.7, 135.6, 133.6, 133.4, 132.6,
132.4, 132.11, 132.05, 131.0, 130.6, 122.9, 113.1, 112.0, 111.8, 111.7,
102.6, 60.9, 60.8, 55.5, 55.10, 55.06, 54.86, 54.85.
463.20549.
HRMS (ESI): m/z [M + H]+ calcd for C41H39O7: 643.26958; found:
643.26961.
6-Fluoro-1,2,3,4-tetraphenylnaphthalene (3fa) and 5-Fluoro-
1,2,3,4-tetraphenylnaphthalene (3′fa)
Yield: 101.3 mg (90%); white solid; mp 254–255 °C (Lit.6b 253.4–256.7
5,6,7-Trimethoxy-1,2,3,4-tetrakis(4-fluorophenyl)naphthalene
(3le)
°C).
Yield: 112.2 mg (76%); white solid; mp 267–268 °C.
1H NMR (400 MHz, CDCl3):  = 7.63 (dd, J = 9.3, 5.9 Hz, 1 H, 3′fa), 7.43
(d, J = 8.5 Hz, 1 H, 3fa), 7.33–7.02 (m, 12 H, 3fa), 6.88–6.76 (m, 10 H,
3fa).
1H NMR (400 MHz, CDCl3):  = 7.12 (dd, J = 8.3, 5.5 Hz, 2 H), 7.06 (dd,
J = 8.3, 5.6 Hz, 2 H), 6.95 (dd, J = 8.6, 8.6 Hz, 2 H), 6.82 (dd, J = 8.7, 8.7
Hz, 2 H), 6.73–6.63 (m, 5 H), 6.61–6.51 (m, 4 H), 3.87 (s, 3 H), 3.71 (s, 3
H), 3.27 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 161.5 (d, J = 244.7 Hz), 160.8 (d, J =
242.5 Hz), 160.6 (d, J = 243.9 Hz), 160.5 (d, J = 243.5 Hz), 152.8, 149.9,
142.8, 138.5 (d, J = 3.5 Hz), 138.05, 137.99, 136.7, 136.3 (d, J = 3.5 Hz),
136.2 (d, J = 3.5 Hz), 135.6 (d, J = 3.4 Hz), 135.4, 132.7 (d, J = 7.9 Hz),
132.4 (d, J = 8.2 Hz), 132.3 (d, J = 8.2 Hz), 131.1 (d, J = 8.2 Hz), 130.3,
122.8, 114.9 (d, J = 21.2 Hz), 113.8 (d, J = 21.0 Hz), 113.6 (d, J = 22.3
Hz), 113.3 (d, J = 21.1 Hz), 102.3, 60.9, 60.6, 55.5.
13C NMR (100 MHz, CDCl3):  = 162.0, 160.8, 159.5, 158.3, 141.71,
141.67, 140.7, 140.3, 140.2, 140.1, 140.0, 139.93, 139.91, 139.8, 139.5,
139.3, 139.1, 138.5, 138.37, 138.35, 138.2, 137.93, 137.88, 134.89,
134.86, 134.4, 134.3, 133.3, 133.2, 131.3, 131.24, 131.15, 131.12,
131.10, 131.0, 130.00, 129.96, 129.7, 129.6, 129.1, 127.7, 127.6,
126.69, 126.65, 126.59, 126.56, 126.4, 125.9, 125.8, 125.7, 125.44,
125.39, 125.3, 123.42, 123.37, 122.1, 122.0, 116.1, 115.8, 111.6, 111.4,
110.4, 110.2.
19F NMR (282 MHz, CDCl3):  = –105.8 (3′fa);  = –114.3 (3fa).
19F NMR (282 MHz, CDCl3):  = –115.3, –116.6, –117.0, –117.7.
HRMS (ESI): m/z [M + H]+ calcd for C34H24F: 451.18620; found:
HRMS (ESI): m/z [M + H]+ calcd for C37H27F4O3: 595.18963; found:
451.18544.
595.18928.
5,6,7-Trimethoxy-1,2,3,4-tetraphenylnaphthalene (3la)15
5,6,7-Trimethoxy-1,2,3,4-tetrakis[4-(trifluoromethyl)-
phenyl]naphthalene (3lf)
Yield: 95.0 mg (73%); white solid; mp 285–286 °C.
Yield: 163.1 mg (82%); white solid; mp 295–296 °C.
1H NMR (400 MHz, CDCl3):  = 7.23–7.13 (m, 7 H), 7.12–7.06 (m, 2 H),
7.04–6.99 (m, 1 H), 6.84–6.73 (m, 11 H), 3.86 (s, 3 H), 3.68 (s, 3 H),
3.25 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 152.5, 150.1, 142.9, 142.5, 140.7,
140.6, 140.1, 138.9, 138.8, 137.2, 135.9, 131.5, 131.13, 131.10, 130.2,
130.1, 127.6, 126.4 (overlapped), 126.2, 126.1, 125.1, 125.0, 124.9,
122.7, 102.5, 60.8, 60.6, 55.5.
1H NMR (400 MHz, CDCl3):  = 7.54 (d, J = 8.1 Hz, 2 H), 7.39 (d, J = 8.1
Hz, 2 H), 7.31 (d, J = 8.0 Hz, 2 H), 7.24 (d, J = 8.1 Hz, 2 H), 7.13 (d, J = 8.2
Hz, 2 H), 7.10 (d, J = 8.3 Hz, 2 H), 6.88 (d, J = 8.0 Hz, 2 H), 6.84 (d, J = 8.0
Hz, 2 H), 6.62 (s, 1 H), 3.88 (s, 3 H), 3.71 (s, 3 H), 3.24 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 151.6, 149.8, 143.4, 143.3, 143.2,
143.0, 140.06, 140.05, 136.8, 136.7, 136.4, 135.3, 131.5, 131.2, 131.1,
129.9, 129.4 (q, J = 32.7 Hz), 128.3 (q, J = 32.7 Hz), 128.1 (q, J = 32.7
Hz), 127.9 (q, J = 32.5 Hz), 125.0 (q, J = 3.2 Hz), 124.3 (q, J = 271.9 Hz),
123.98 (q, J = 272.1 Hz), 123.97 (q, J = 3.3 Hz), 123.82 (q, J = 271.9 Hz),
123.79 (q, J = 272.1 Hz), 123.5 (q, J = 3.4 Hz), 123.3 (q, J = 3.3 Hz),
122.7, 102.0, 60.9, 60.5, 55.6.
HRMS (ESI): m/z [M + H]+ calcd for C37H31O3: 523.22732; found:
523.22725.
5,6,7-Trimethoxy-1,2,3,4-tetrakis(4-methylphenyl)naphthalene
(3lc)
19F NMR (282 MHz, CDCl3):  = –62.5, –62.6, –62.85, –62.87.
HRMS (ESI): m/z [M + H]+ calcd for C41H27F12O3: 795.17686; found:
Yield: 109.7 mg (76%); white solid; mp 297–298 °C.
1H NMR (400 MHz, CDCl3):  = 7.07–6.98 (m, 6 H), 6.89 (d, J = 7.8 Hz, 2
H), 6.76 (s, 1 H), 6.66–6.58 (m, 8 H), 3.85 (s, 3 H), 3.68 (s, 3 H), 3.23 (s,
3 H), 2.29 (s, 3 H), 2.24 (s, 3 H), 2.061 (s, 3 H), 2.057 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 152.1, 150.1, 142.4, 140.0, 139.2,
139.0, 138.0, 137.8, 137.22, 137.18, 135.8, 135.5, 134.1, 134.0, 133.8,
131.3, 131.0 (overlapped), 130.4, 129.9, 128.3, 127.1, 126.9, 126.8,
122.8, 102.7, 60.9, 60.8, 55.5, 21.3, 21.2, 21.0 (overlapped).
795.17667.
6,7-Dimethoxy-1,2,3,4-tetraphenylnaphthalene (3ma)
Yield: 89.3 mg (73%); white solid; mp 333–334 °C (Lit.16 324 °C).
1H NMR (400 MHz, CDCl3):  = 7.27–7.15 (m, 10 H), 6.94 (s, 2 H), 6.89–
6.78 (m, 10 H), 3.73 (s, 6 H).
HRMS (ESI): m/z [M + H]+ calcd for C41H39O3: 579.28992; found:
13C NMR (100 MHz, CDCl3):  = 149.2, 140.8, 139.9, 137.3, 137.0,
579.28933.
131.4, 131.1, 127.8, 127.6, 126.4, 126.3, 125.1, 105.8, 55.6.
HRMS (ESI): m/z [M + H]+ calcd for C36H29O2: 493.21675; found:
493.21718.
5,6,7-Trimethoxy-1,2,3,4-tetrakis(4-methoxyphenyl)naphthalene
(3ld)
Yield: 104.1 mg (65%); white solid; mp 292–293 °C.
5,6-Dimethoxy-1,2,3,4-tetraphenylnaphthalene (3′ma)
1H NMR (400 MHz, CDCl3):  = 7.07 (d, J = 8.6 Hz, 2 H), 7.03 (d, J = 8.6
Hz, 2 H), 6.80–6.75 (m, 3 H), 6.69–6.60 (m, 6 H), 6.41–6.35 (m, 4 H),
3.86 (s, 3 H), 3.78 (s, 3 H), 3.74 (s, 3 H), 3.69 (s, 3 H), 3.60 (s, 6 H), 3.26
(s, 3 H).
Yield: 11.7 mg (10%); pale yellow solid; mp 229–230 °C.
1H NMR (400 MHz, CDCl3):  = 7.41 (d, J = 9.3 Hz, 1 H), 7.24–7.15 (m, 8
H), 7.11–7.05 (m, 2 H), 7.04–6.98 (m, 1 H), 6.85–6.74 (m, 10 H), 3.90
(s, 3 H), 3.17 (s, 3 H).
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

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13C NMR (100 MHz, CDCl3):  = 150.2, 144.5, 142.7, 141.1, 140.6 (over-
lapped), 139.9, 138.4, 137.3, 135.3, 131.4, 131.24, 131.19, 130.3,
129.0, 127.5, 127.3, 126.42, 126.36, 126.2, 126.1, 125.1, 125.0 (over-
lapped), 123.8, 114.5, 60.4, 56.6.
HRMS (ESI): m/z [M + H]+ calcd for C36H29O2: 493.21675; found:
493.21676.
1H NMR (400 MHz, CDCl3):  = 8.11 (s, 1 H), 8.03 (s, 1 H), 7.71 (d, J =
9.2 Hz, 1 H), 7.33–7.22 (m, 10 H), 7.09–7.02 (m, 2 H), 6.90–6.80 (m, 10
H), 3.87 (s, 3 H).
13C NMR (100 MHz, CDCl3):  = 157.3, 140.7, 140.6, 140.0, 139.8,
138.6, 138.2, 137.6, 137.5, 132.5, 131.5, 131.42, 131.35, 131.3 (over-
lapped), 130.0, 129.5, 128.0, 127.60, 127.58, 126.52 (overlapped),
126.46, 126.4, 125.9, 125.3, 125.2, 123.8, 120.6, 103.8, 55.2.
HRMS (ESI): m/z [M + H]+ calcd for C39H29O: 513.22184; found:
6,7,8,9-Tetraphenylnaphtho[1,2-d][1,3]dioxole (3na)
513.22145.
Yield: 99.2 mg (83%); yellow solid; mp 313–314 °C.
1H NMR (400 MHz, CDCl3):  = 7.24–7.07 (m, 12 H), 7.85–6.77 (m, 10
H), 5.77 (s, 2 H).
4,5,6,7-Tetraphenylbenzo[c]thiophene (8a)
Yield: 87.7 mg (40%); pale yellow solid; mp 237–238 °C.
1H NMR (400 MHz, CDCl3):  = 7.44 (s, 2 H), 7.29–7.15 (m, 10 H), 6.90–
6.81 (m, 10 H).
13C NMR (100 MHz, CDCl3):  = 140.1, 139.7, 138.6, 136.4, 132.9,
131.5, 130.5, 127.7, 126.6, 126.5, 125.4, 118.2.
13C NMR (100 MHz, CDCl3):  = 144.4, 142.0, 140.49, 140.47, 140.1,
140.0, 139.9, 138.7, 137.3, 133.6, 131.3 (overlapped), 131.1, 130.8,
129.2, 127.5, 126.5, 126.44 (overlapped), 126.38, 126.0, 125.23,
125.22, 121.8, 119.1, 110.3, 100.8.
HRMS (ESI): m/z [M + H]+ calcd for C35H25O2: 477.18545; found:
477.18564.
HRMS (ESI): m/z [M + H]+ calcd for C32H23S: 439.15205; found:
439.15265.
3,4-Diphenyl-1H-isochromen-1-one (4aa)
Yield: 101.3 mg (91%); white solid; mp 171–172 °C (Lit.4b 172–174
4,5,6,7-Tetrakis[4-(1,1-dimethylethyl)phenyl]benzo[c]thiophene
°C).
(8g)
1H NMR (400 MHz, CDCl3):  = 8.41 (dd, J = 7.9, 1.1 Hz, 1 H), 7.64 (td,
J = 8.1, 1.4 Hz, 1 H), 7.52 (td, J = 7.7, 1.1 Hz, 1 H), 7.44–7.39 (m, 3 H),
7.36–7.32 (m, 2 H), 7.29–7.16 (m, 6 H).
13C NMR (100 MHz, CDCl3):  = 162.2, 150.9, 138.9, 134.6, 134.3,
132.9, 131.2, 129.5, 129.2, 129.0, 128.9, 128.10, 128.06, 127.8, 125.3,
120.5, 116.9.
Yield: 65.3 mg (39%); pale yellow solid; mp 239–240 °C.
1H NMR (400 MHz, CDCl3):  = 7.50 (s, 2 H), 7.19 (q, J = 8.2 Hz, 8 H),
6.82 (d, J = 8.4 Hz, 4 H), 6.67 (d, J = 8.2 Hz, 4 H), 1.27 (s, 18 H), 1.11 (s,
18 H).
13C NMR (100 MHz, CDCl3):  = 148.9, 147.7, 138.7, 137.3, 136.9 (over-
lapped), 132.5, 131.2, 130.2, 124.3, 123.1, 118.0, 34.4, 34.1, 31.3, 31.2.
HRMS (ESI): m/z [M + H]+ calcd for C21H15O2: 299.10720; found:
299.10711.
HRMS (ESI): m/z [M + H]+ calcd for C48H55S: 663.40245; found:
663.40252.
Decarboxylative Coupling of 5 or 7 with 2; General Procedure
Conflict of Interest
A mixture of carboxylic acid 5 or 7 (0.75 mmol), alkyne 2 (1 mmol),
[Rh(cod)Cl2]2 (5 mg, 0.01 mmol), C5H2Ph4 (14.8 mg, 0.04 mmol),
AgOAc (334 mg, 2 mmol) and 1-methylnaphthalene (ca. 80 mg) as an
internal standard in o-xylene or t-AmOH (5 mL) was stirred at 120–
170 °C under Ar (1 atm) for 4–24 h. After the reaction was complete,
the mixture was diluted with dichloromethane (100 mL). The organic
layer was washed with water (2 x 100 mL) and brine (100 mL), and
then dried over Na2SO4. After evaporation of the solvents under vacu-
um, product 6 or 8 was isolated by column chromatography on silica
gel using hexane–ethyl acetate as eluent. Further purification by GPC
(gel permeation chromatography) was performed, if needed.
The authors declare no conflict of interest.
Funding Information
This work was partly supported by the Japan Society for the Promo-
tion of Science (JSPS) (KAKENHI) (Grant Nos. 20H02745 and
18K19083), and by Osaka City University (OCU) Strategic Research
Grant 2020 for basic research to T.S. and the JSPS (KAKENHI) (Grant
No. 18H04627) to Y.U. Japa
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1,2,3,4-Tetraphenylanthracene (6aa)
Yield: 149.7 mg (62%); yellow solid; mp 295–296 °C (Lit.5b 295–296
°C).
1H NMR (400 MHz, CDCl3):  = 8.19 (s, 2 H), 7.85–7.79 (m, 2 H), 7.39–
7.34 (m, 2 H), 7.33–7.23 (m, 10 H), 6.90–6.81 (m, 10 H).
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/a-1416-6997. Su
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13C NMR (100 MHz, CDCl3):  = 140.6, 139.7, 138.5, 138.1, 131.5,
131.4, 131.3, 130.9, 128.3, 127.6, 126.6, 126.5, 125.9, 125.4, 125.3.
HRMS (ESI): m/z [M + H]+ calcd for C38H27: 483.21128; found:
References
(1) For representative reviews, see: (a) Wei, Y.; Hu, P.; Zhang, M.;
Su, W. Chem. Rev. 2017, 117, 8864. (b) Font, M.; Quibell, J. M.;
Perry, G. J. P.; Larrosa, I. Chem. Commun. 2017, 53, 5584.
(c) Drapeau, M. P.; Gooßen, L. J. Chem. Eur. J. 2016, 23, 18654.
(d) Satoh, T.; Miura, M. Synthesis 2010, 3395.
483.21029.
6-Methoxy-1,2,3,4-tetraphenylanthracene (6ba)
Yield: 141.0 mg (55%); yellow solid; mp 283–284 °C (Lit.5b 284–285
°C).
© 2021. Thieme. All rights reserved. Synthesis 2021, 53, A–H

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Y. Inai et al.
Special Topic
Synthesis
(2) For pioneering work, see: (a) Murai, S.; Kakiuchi, F.; Sekine, S.;
Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani, N. Nature 1993,
366, 529. See also selected reviews on C–H functionalization:
(b) Sambiagio, C.; Schönbauer, D.; Blieck, R.; Dao-Huy, T.;
Pototschnig, G.; Schaaf, P.; Wiesinger, T.; Farooq Zia, M.;
Wencel-Delord, J.; Besset, T.; Maes, B. U. W.; Schnürch, M. Chem.
Soc. Rev. 2018, 47, 6603. (c) Gulías, M.; Mascareñas, J. L. Angew.
Chem. Int. Ed. 2016, 55, 11000. (d) Chen, Z.; Wang, B.; Zhang, J.;
Yu, W.; Liu, Z.; Zhang, Y. Org. Chem. Front. 2015, 2, 1107.
(e) Song, G.; Li, X. Acc. Chem. Res. 2015, 48, 1007. (f) Ye, J.;
Lautens, M. Nat. Chem. 2015, 7, 863. (g) Miura, M.; Satoh, T.;
Hirano, K. Bull. Chem. Soc. Jpn. 2014, 87, 751. (h) De Sarkar, S.;
Liu, W.; Kozhushkov, S. I.; Ackermann, L. Adv. Synth. Catal. 2014,
356, 1461. (i) Wencel-Delord, J.; Glorius, F. Nat. Chem. 2013, 5,
369. (j) Colby, D. A.; Tsai, A. S.; Bergman, R. G.; Ellman, J. A. Acc.
Chem. Res. 2012, 45, 814. (k) Engle, K. M.; Mei, T.-S.; Wasa, M.;
Yu, J.-Q. Acc. Chem. Res. 2012, 45, 788. (l) Cho, S. H.; Kim, J. Y.;
Kwak, J.; Chang, S. Chem. Soc. Rev. 2011, 40, 5068. (m) Giri, R.;
Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem. Soc. Rev. 2009,
38, 3242.
(3) (a) Unoh, Y.; Hirano, K.; Satoh, T.; Miura, M. Tetrahedron 2013,
69, 4454. (b) Shimizu, M.; Hirano, K.; Satoh, T.; Miura, M. J. Org.
Chem. 2009, 74, 3478. (c) Ueura, K.; Satoh, T.; Miura, M. Org.
Lett. 2007, 9, 1407.
(4) (a) Hirosawa, K.; Usuki, Y.; Satoh, T. Adv. Synth. Catal. 2019, 361,
5253. (b) Ueura, K.; Satoh, T.; Miura, M. J. Org. Chem. 2007, 72,
5362.
(5) For homologation reactions of readily available mono-substi-
tuted aromatic substrates, see: (a) Wang, H.; Wang, Y.; Yang, H.;
Tan, C.; Jiang, Y.; Zhao, Y.; Fu, H. Adv. Synth. Catal. 2015, 357,
489. (b) Fukutani, T.; Hirano, K.; Satoh, T.; Miura, M. J. Org.
Chem. 2011, 76, 2867. (c) Uto, T.; Shimizu, M.; Ueura, K.;
Tsurugi, H.; Satoh, T.; Miura, M. J. Org. Chem. 2008, 73, 298.
(d) Yasukawa, T.; Satoh, T.; Miura, M.; Nomura, M. J. Am. Chem.
Soc. 2002, 124, 12680. (e) Kawasaki, S.; Satoh, T.; Miura, M.;
Nomura, M. J. Org. Chem. 2003, 68, 6836. (f) Wu, G.; Rheingold,
A. L.; Feib, S. L.; Heck, R. F. Organometallics 1987, 6, 1941.
(g) Sakakibara, T.; Tanaka, Y.; Yamasaki, T.-I. Chem. Lett. 1986,
797.
(7) (a) Molotkov, A. P.; Arsenov, M. A.; Kapustin, D. A.; Muratov, D.
V.; Shepel’, N. E.; Fedorov, Y. V.; Smol’yakov, A. F.; Knyazeva, E.
I.; Lypenko, D. A.; Dmitriev, A. V.; Aleksandrov, A. E.; Maltsev, E.
I.; Loginov, D. A. ChemPlusChem 2020, 85, 334. (b) Datsenko, V.
P.; Nelyubina, Y. V.; Smol’yakov, A. F.; Loginov, D. A.
J. Organomet. Chem. 2018, 874, 7. (c) Loginov, D. A.; Konoplev, V.
E. J. Organomet. Chem. 2018, 867, 14. (d) Loginov, D. A.; Belova,
A. O.; Kudinov, A. R. Russ. Chem. Bull. 2014, 63, 983.
(8) The catalyst system of [RhCl(cod)]2/C5H2Ph4 has been employed
for various dehydrogenative couplings, see: (a) Shimizu, M.;
Tsurugi, H.; Satoh, T.; Miura, M. Chem. Asian J. 2008, 3, 881.
(b) Umeda, N.; Tsurugi, H.; Satoh, T.; Miura, M. Angew. Chem. Int.
Ed. 2008, 47, 4019. (c) Mochida, S.; Shimizu, M.; Hirano, K.;
Satoh, T.; Miura, M. Chem. Asian J. 2010, 5, 847.
(9) In contrast, C5H2Ph4 is known to readily coordinate to rhodium,
see: Davies, D. L.; Ellul, C. E.; Singh, K. J. Organomet. Chem. 2019,
879, 151.
(10) For example, see: (a) Chávez-González, M.; Rodríguez-Durán, L.
V.; Balagurusamy, N.; Prado-Barragán, A.; Rodríguez, R.;
Contreras, J. C.; Aguilar, C. N. Food Bioprocess Technol. 2012, 5,
445. (b) Moodley, B.; Mulholland, D. A.; Brookes, H. C. Water SA
2012, 38, 1. (c) van Haveren, J.; Scott, E. L.; Sanders, J. Biofuels
Bioprod. Bioref. 2008, 2, 41. (d) Xu, Y.; Hanna, M. A.; Isom, L.
Open Agric. J. 2008, 2, 54. (e) Kambourakis, S.; Draths, K. M.;
Frost, J. W. J. Am. Chem. Soc. 2000, 122, 9042.
(11) A similar regioselective annulation has been observed in the
ruthenium-catalyzed 1:1 coupling of 1n with alkynes, see:
Chinnagolla, R. K.; Jeganmohan, M. Chem. Commun. 2012, 48,
2030.
(12) For related selective anthracene construction from 2-naphtha-
leneboronic acids, see ref. 5b.
(13) For the related synthesis of benzo[c]thiophenes from thio-
phene-2-carbamides, see: Fukuzumi, K.; Unoh, Y.; Nishii, Y.;
Satoh, T.; Hirano, K.; Miura, M. J. Org. Chem. 2016, 81, 2474.
(14) (a) Novák, Z.; Nemes, P.; Kotschy, A. Org. Lett. 2004, 6, 4917.
(b) Moon, J.; Jang, M.; Lee, S. J. Org. Chem. 2008, 74, 1403.
(c) Hein, S. J.; Arslan, H.; Keresztes, I.; Dichtel, W. R. Org. Lett.
2014, 16, 4416.
(15) Peng, S.; Sun, Z.; Zhu, H.; Chen, N.; Sun, X.; Gong, X.; Wang, J.;
Wang, L. Org. Lett. 2020, 22, 3200.
(16) Wu, Y. T.; Huang, K.-H.; Shin, C.-C.; Wu, T.-C. Chem. Eur. J. 2008,
14, 6697.
(6) (a) Honjo, Y.; Shibata, Y.; Tanaka, K. Chem. Eur. J. 2019, 25, 9427.
(b) Honjo, Y.; Shibata, Y.; Kudo, E.; Namba, T.; Masutomi, K.;
Tanaka, K. Chem. Eur. J. 2018, 24, 317.
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