Copper-catalyzed selective ortho-arylations of 2-naphthol and phenol derivatives with diaryliodonium salts

Article abstract of DOI:10.1016/j.tetlet.2015.12.100

The selective arylations of 2-naphthol and phenol derivatives catalyzed by Cu(OTf)₂ with using diaryliodonium(III) salts have been developed. With this method, biaryls bearing hydroxyl groups can be easily accessed in moderate to good yields. Additionally, this protocol provided an alternative for the preparation of 3-arylated binaphthalene derivatives.

Full text of DOI:10.1016/j.tetlet.2015.12.100

Tetrahedron Letters 57 (2016) 607–610
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Tetrahedron Letters
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Copper-catalyzed selective ortho-arylations of 2-naphthol and
phenol derivatives with diaryliodonium salts
a,
Xiaofei Qian a, Jianwei Han b, , Limin Wang
⇑
⇑
a Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, PR China
b Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, The Chinese Academy of Sciences, 345 Ling Ling Road, Shanghai 200237,
PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The selective arylations of 2-naphthol and phenol derivatives catalyzed by Cu(OTf)2 with using
diaryliodonium(III) salts have been developed. With this method, biaryls bearing hydroxyl groups can
be easily accessed in moderate to good yields. Additionally, this protocol provided an alternative for
the preparation of 3-arylated binaphthalene derivatives.
Received 3 November 2015
Revised 15 December 2015
Accepted 25 December 2015
Available online 28 December 2015
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Arylation
Coupling reaction
Diaryliodonium salt
2-Naphthol
Biaryls
(III)
Introduction
L
Cu(II)
O
X
I
Ph
Ph
Cu
(1)
/
L
Ph
Biaryls are vital substructures which can be found in various
biologically active compounds and functional material molecules.1
The synthesis of biaryls has been emerged as an active research
topic for more than a century by using various transition metal cat-
alysts.2 During past decades, Ar3Bi worked as an efficient arylation
reagent.3 Recently, direct C–H arylation of aromatic substrates
attracted particular attention due to the easy availability of sub-
strates, and thus significant progress was also achieved in this
field.4 However, it remains a difficulty to achieve high site selectiv-
ity,5 which generally resulted in an isomeric product mixture.
Hence, the development of new methods to access selective
arylations is highly in demand.
Phenyl Intermediate
O
Ph/
OMe(NBn2)
OMe
HN
CMe3
N
Me
OH
/
/
Ph
Ph
Ph/
A
B
D
C
Scheme 1. Samples of site-selectivity in copper catalyzed C–H arylations involved
diaryliodonium salts.
Diaryliodonium salts have appeared as powerful electrophilic
arylation reagents in a wide range of reactions with or without
metal catalysts.6 Seminal contributions from Sanford and Gaunt
groups showcased the ability of diaryliodonium salts in site-
selective arylation of indoles under palladium (C2-arylation)7 or
copper catalysis (N-8a and C3-arylation8b), respectively. Gaunt
et al. reported highly meta-selective arylation of anilides
(Scheme 1, C) in combination of copper catalysts with diaryliodo-
nium salts.9 As part of our interests of biaryl structural units as
ligands for metal-coordinating catalysts,10 these reports inspired
us to use copper catalysts and diaryliodonium salts as electrophiles
for the C–H arylation of 2-naphthol (Scheme 1, D) and 4-substi-
tuted phenol derivatives.
(Scheme 1, A) and
para-selective arylation of aniline and phenol derivatives
a-aryl carbonyl compounds (Scheme 1, B),
Results and discussion
Initially, we investigated the reaction of 2-naphthol (1a) with
diphenyliodonium triflate (Ph2IOTf, 2a) in the presence of K2CO3
as base catalyzed by copper triflate. To our delight this reaction
⇑
Corresponding authors. Tel.: +86 021 54925383 (J.H.), +86 021 64253881 (L.W.).
E-mail addresses: jianweihan@sioc.ac.cn (J. Han), wanglimin@ecust.edu.cn
(L. Wang).
http://dx.doi.org/10.1016/j.tetlet.2015.12.100
0040-4039/Ó 2015 Elsevier Ltd. All rights reserved.

608
X. Qian et al. / Tetrahedron Letters 57 (2016) 607–610
Table 2
gave the desired product of 1-phenylnaphthalen-2-ol (3a) in 44%
yield in toluene as solvents at 80 °C (Table 1, entry 1). As shown
in Table 1, after examining several bases as additives, it is surpris-
ing to find that the reaction worked well even without base addi-
tives (Table 1, entry 5), but it doesn’t work well in the absence of
copper catalysts. (Table 1, entry 6). The use of copper(II) salts of
CuSO4 and Cu(OAc)2 could give the desired products but in lower
yields (Table 1, entries 8 and 9), while CuCl2 give a similar result
as 40%. The yield was improved to 60% by using dichloroethane
(DCE) as the solvent, while other solvents can’t give the same yield
(Table 1, entries 11–13). With DCE as the optimal solvent, copper(I)
salts were screened, CuI afforded the product in 47% yield, only 38%
yield was achieved with CuBr as the catalyst (Table 1, entries 14
and 15). The yield slightly decreased when we increased the reac-
tion temperature or prolonged the reaction time (Table 1, entries
16–19). We next tried Ag2CO3 as the additive, which is a base often
used in metal-catalyzed coupling reaction, the reaction proceeds
smoothly in DCE to give a good yield of 51% (Table 1, entry 20).
An evaluation of different diphenyliodonium anions showed that
the counter-anions have an influence on the yield of respective
products. Diphenyliodonium salts with OTfꢀ, PF6ꢀ, and BF4ꢀ as
anions worked efficiently but OTsꢀ (tosylate) and Brꢀ as counter-
anions gave lower yields of 30% and 12%, respectively (Table 1,
entries 21–24).
Scope of diverse iodonium salts in arylation of 2-naphthola
Ar1
OH
OH
Cu(OTf)2 (10 mol%)
DCE, 80 oC
[Ar1IAr2]+X-
+
2
3
1a
Entry
Ar1(Ar2)
X
Product
Yieldb (%)
1
2
3
4
5
6
7
8
(4-MeC6H4)2
(4-FC6H4)2
(4-ClC6H4)2
OTf
OTf
OTf
OTf
OTf
OTf
Br
OTf
OTs
OTf
OTf
OTf
OTf
OTf
3b
3c
3d
3e
3f
3g
3h
3i
81
52
52
50
(4-BrC6H4)2
(4-tBuC6H4)2
(4-MeOC6H4)2
(3-NO2C6H4)2
(Mesityl)2
59
n.r.
n.r.
Trace
36
81
44
58
27
65
9
(2-Thienyl)2
Ph(4-MeOC6H4)
Ph(Mesityl)
Ph(2,4-F2C6H4)
Ph(4-AcNHC6H4)
Ph(2-Thienyl)
3j
10
11
12
13
14
3a
3a
3a
3a
3a
a
Unless otherwise specified, reaction conditions: 1a (0.5 mmol), iodonium salt
(0.6 mmol, 1.2 equiv), and DCE (2 mL); 80 °C, 6 h; Ar1 was transferred.
b
Isolated yield.
Subsequently, with the optimal conditions in hand, we exam-
ined various iodonium salts as the coupling partners. It was
observed that a wide variety of functionalities, such as chloro-,
bromo-, electron-donating groups, and alkyl- on the aromatic ring,
are well tolerated in arylations of 2-naphthol (Table 2, entries 1–5).
However, the diaryliodonium salts bearing either the methoxyl
Table 3
Scope of diverse naphthol derivatives in arylationa
Ph
OH
+
OH
CuOTf(10 mol%)
DCE, 80 oC
[Ph2I]+OTf-
R
R
Table 1
Screening of reaction conditions for arylation of 2-naphthola
2a
4a-i
1
Ph
Cat. (10 mol%)
OH
OH
base (1 eqiv.)
Solvent,80 oC
Entry
1
1b–j
Product
Yieldb (%)
[Ph2I]+X-
2
+
OH
1a
4a
52
3a
CO2Me
OH
Entry Cat.
X-
Base
Temp (°C) Solvent
Yieldb (%)
2
4b
58
1
2
3
4
5
6
7
8
Cu(OTf)2
OTf
OTf
OTf
OTf
OTf
OTf
OTf
K2CO3
Cs2CO3
KOAc
2,6-Lutidine 80
—
—
—
—
—
—
—
—
—
—
—
—
—
80
80
80
Toluene 44
Toluene 29
Toluene Trace
Toluene n.r.
Toluene 40
Br
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
—
CuCl2
Cu(OAc)2 OTf
CuSO4
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
CuI
OH
3
4
5
4c
4d
4e
56
63
52
80
80
80
80
80
80
80
80
80
80
80
80
60
rt
100
80
80
80
80
80
EtO2C
Toluene
—
OH
OH
Toluene 40
Toluene 38
Toluene 29
9
OTf
OTf
OTf
OTf
OTf
OTf
OTf
OTf
OTf
OTf
OTf
OTf
PF6
BF4
OTs
Br
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
DCE
THF
CH2Cl2
DMF
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
60
Trace
42
n.d.
47
Me
OH
OH
6
7
8
9
4f
55
CuBr
38
MeO
tBu
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
59c
58
4g
4h
4i
45
—
—
Trace
55
51
58
52
Ag2CO3
—
—
—
—
OH
50
Ph
30
12
OH
Trace
a
Unless otherwise specified, reaction conditions: 1a (0.5 mmol), diphenyliodo-
nium salt (0.6 mmol, 1.2 equiv), base (0.75 mmol, 1.5 equiv), and solvent (2 mL);
80 °C; 6 h. OTf = trifluoromethansulfonate; OTs = 4-toluenesulfonate.
EtO2C
a
Unless otherwise specified, reaction conditions: 1b–j (0.5 mmol), 2a (0.6 mmol,
1.2 equiv), and solvent (2 mL); 80 °C; 6 h.
b
Isolated yield.
For 10 h.
c
b
Isolated yield.

X. Qian et al. / Tetrahedron Letters 57 (2016) 607–610
609
Ph
OH
OH
O
Cu(OTf)2 (10 mol%)
+ [Ph2I]+OTf-
(1)
OH
DCE, 80 oC
32% yield
2a
5
6
Ph
Ph
OMe
OMe
OMe
OMe
OMe
OMe
Cu(OTf)2 (10 mol%)
+ [Ph2I]+OTf-
(2)
DCE, 80 oC
30% yield
Ph
2a
7
8
9
Scheme 2. ortho-Arylations of naphthol derivatives.
group or nitro substituent on the aromatic ring gave no desired
products (Table 2, entries 6 and 7). Moreover, steric bulk of iodo-
nium salts affected the reactivity, only trace amount of product
was achieved with bis-(2,4,6-trimethylphenyl)-iodonium triflate
as arylating reagent (Table 2, entry 8). When [(2-Thienyl)2)I]OTs
was employed under the standard conditions, the heteroatomic
ring of thiophene was transferred to give the desired product 3j
in 36% yield. In connection with influences of the electronic prop-
erties on the reactivity, it was worth mentioning that the unsym-
metrical salts of [PhIAr]OTf with various aryl groups including
mesityl, 2,4-difluorophenyl, 4-acetaminophenyl, and 2-thienyl
groups selectively transfer phenyl to the corresponding product
in a range of 27–65% yields (Table 2, entries 10–14).
To further investigate the scope of this reaction, a range of
2-naphthol derivatives were arylated under standard conditions.
Generally, as shown in Table 3, the conditions proved to be effec-
tive for a variety of 2-naphthol derivatives bearing substituent on
3-position or 6-poistion of naphthalene nucleus, the reactions gave
the arylated products in good yield of 52–58% (entries 1–3, Table 3).
When 5,6,7,8-tetrahydro-2-naphthol was employed, the coupling
reaction with diphenyliodonium triflate furnished a good yield of
63%. This ortho-selectivity was also observed in the Gaunt’s
pioneering report of phenol derivatives with one example.9d As
such, we extended the reaction scope with para-substituted
phenol derivatives. We found that the protocol worked well with
phenols bearing electro-donating substituent, the diphenyl
products were formed with the yields of 45–55%. However,
almost no reaction took place with 4-ester substituted phenol
(entry 9, Table 3).
binaphthalene derivatives can be obtained by this protocol. The
application of this method in preparation of valuable biaryl com-
pounds is still being actively explored, therefore, it is anticipated
that double arylations at 3,30-positions on the 2,20-dimethoxy-
1,10-binaphthalene skeleton with this procedure could be realized
in the future.
Experimental section
General information
1H NMR and 13C NMR spectra were respectively, recorded at
400 and 100 MHz, using tetramethylsilane as an internal reference.
Chemical shifts (d) and coupling constants (J) were expressed in
parts per million and hertz, respectively. Melting points were
uncorrected. High-resolution mass spectrometry (HRMS) was per-
formed on an EI-TOF spectrometer. The diaryliodonium salts were
prepared according to the literature.12 All reagents were obtained
from commercial sources without further purification.
General procedure for the synthesis of 3a–j
1a (72.1 mg, 0.5 mmol, 1 equiv), Cu(OTf)2 (18.1 mg, 0.05 mmol,
10 mol %), and 2 (0.6 mmol, 1.2 equiv) were added to Schlenk tube,
sealed with a rubber under air. Then 2 mL DCE was added using a
syringe. The reaction mixture was stirred at 80 °C for 6 h. After
cooling to room temperature, the solvent was removed in vacuo
and the residue was purified by silica gel using a proper eluent
to afford the desired products.
Finally, envisaging the potential of this ortho-selectivity in
preparation of 3,30-arylated naphthol derivatives, we sought to
investigate the arylation of chiral (S)-binaphthol derivatives.
Treatment of 5 with 2a under our conditions only gave O-pheny-
lated product 6 in 32% yields.11 Subsequently, we tried the reaction
with (S)-2,20-dimethoxy-1,10-binaphthalene 7, mono-phenylated
product of 8 was obtained in 30% yield, but no diphenylated
product of 9 was found even when 4 equiv of diphenyliodonium
triflates was used. Overall, the results proved that this protocol
could be used to prepare 3-arylated binaphthalene derivatives
(see Scheme 2).
General procedure for the synthesis of 4a–i
2a (258.1 mg, 0.6 mmol, 1.2 equiv), Cu(OTf)2 (18.1 mg,
0.05 mmol, 10 mol %), and 1b–j (0.5 mmol, 1 equiv) were added
to Schlenk tube, sealed with a rubber under air. Then 2 mL DCE
was added using a syringe. The reaction mixture was stirred at
80 °C for 6 h. After cooling to room temperature, the solvent was
removed in vacuo and the residue was purified by silica gel using
a proper eluent to afford the desired products.
Acknowledgments
Conclusion
The work was supported by the National Nature Science
Foundation of China (NSFC, 21272069, 21202186) and the
Fundamental Research Funds for the Central Universities, Key
Laboratory of Organofluorine Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences.
In summary, we have developed
a method for selective
ortho-arylations of 2-naphthol and phenol derivatives with
diaryliodonium salts catalyzed by copper triflate. The method is
suitable for a variety of substituents. More importantly, 3-arylated

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X. Qian et al. / Tetrahedron Letters 57 (2016) 607–610
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