Synthesis of 2-Arylphenol Derivatives through a One-Pot Suzuki-Miyaura Coupling/Dehydrogenative Aromatization Sequence with Pd/C Catalysis

Article abstract of DOI:10.1002/ejoc.201500723

One-pot synthesis of 2-arylphenols starting from 2-iodo-2-cyclohexen-1-one and arylboronic acids through sequential Suzuki-Miyaura coupling/dehydrogenative aromatization with Pd/C catalysis has been developed. A range of arylboronic acids serve as substrates, including those containing electron-donating or electron-withdrawing groups. Additionally, one-pot synthesis of di- or trisubstituted phenols bearing a phenyl group at the ortho position are also generated by using 2-iodo-2-cyclohexen-1-one derivatives as substrate. In the present method, commercially available and easily removable Pd/C was employed as a catalyst without any ligands. The operationally simple procedure and accessible conditions were used to provide modified phenols as the sole product in moderate to high yields.

Full text of DOI:10.1002/ejoc.201500723

FULL PAPER
DOI: 10.1002/ejoc.201500723
Synthesis of 2-Arylphenol Derivatives through a One-Pot Suzuki–Miyaura
Coupling/Dehydrogenative Aromatization Sequence with Pd/C Catalysis
Kotaro Kikushima*[a] and Yuta Nishina*[a,b]
Keywords: Synthetic methods / Cross-coupling / Aromatization / Palladium / Phenols
One-pot synthesis of 2-arylphenols starting from 2-iodo-2-
cyclohexen-1-one and arylboronic acids through sequential
Suzuki–Miyaura coupling/dehydrogenative aromatization
a phenyl group at the ortho position are also generated by
using 2-iodo-2-cyclohexen-1-one derivatives as substrate. In
the present method, commercially available and easily re-
with Pd/C catalysis has been developed. A range of aryl- movable Pd/C was employed as a catalyst without any li-
boronic acids serve as substrates, including those containing
electron-donating or electron-withdrawing groups. Addition-
ally, one-pot synthesis of di- or trisubstituted phenols bearing
gands. The operationally simple procedure and accessible
conditions were used to provide modified phenols as the sole
product in moderate to high yields.
ing group into the substrate in situ is required to promote
the ortho-metalation. Additionally, direct ortho-arylation
using isolated O-modified phenols as substrates, such as
phenylpivalates or O-phenylcarbamates, has been re-
ported.[8] In these cases, functional groups on the oxygen
serve as protecting and directing groups. Major drawbacks
of these direct ortho-C–H activation/arylation reactions are:
(1) multiple arylation could occur to give the corresponding
mono- and/or di-arylated phenols, and (2) expensive cata-
lysts are required in some cases.
Introduction
Phenol derivatives are important core structures that are
found in natural products, pharmaceuticals, and polymers,
and are useful precursors in synthetic chemistry.[1] In par-
ticular, 2-arylphenols exist as bioactive compounds,[2] li-
gands for homogeneous catalysts,[3,4] and substrates for the
synthesis of dibenzofurans,[5] which are the structural
motifs of optoelectronically and biologically active com-
pounds. The most commonly used approach to access 2-
arylphenols is coupling reactions starting from the 2-halo-
phenol or its derivatives as substrate (Scheme 1, a). How-
ever, 2-halophenols are difficult to prepare because the typi-
cal electrophilic halogenations of phenols produce a mix-
ture of ortho- and/or para-halogenated phenols, promoted
by the strong resonance effect of the hydroxyl group. Al-
though direct ortho-metalation of O-modified phenol such
as O-phenylcarbamates with alkyllithium followed by halo-
genation can provide 2-halophenol derivatives, multiple
steps are required and the reaction is restricted to substrates
that are tolerant of the alkyllithium reagent. Direct ortho-
arylation of phenols through transition-metal-catalyzed C–
H activation is a more straightforward approach (Scheme 1,
b). However, ortho-selective arylation of naked phenols is
limited to a few examples.[6] The ortho-arylation of phenols
in the presence of phosphinite or phosphoramidite has also
been demonstrated,[7] wherein the introduction of a direct-
Scheme 1. Access to 2-arylphenol derivatives; R = H or protecting
group, X = halogen, Y = B(OR)2, SnR3, etc. XЈ = H or halogen.
As an alternative approach to the synthesis of phenol
derivatives, the transition-metal-catalyzed oxidative aroma-
tization of 2-cyclohexenone is an attractive strategy.[9–11] By
taking this route, various phenols could be obtained, in-
cluding not only ortho- and para- but also meta-substituted
phenols without concerns about selectivity. We have re-
ported a copper-catalyzed oxidative aromatization of 2-
cyclohexenones to prepare various phenols, combined with
aqueous hydrogen bromide and molecular oxygen under
simple conditions.[9d] In the course of our study, we found
[a] Research Core for Interdisciplinary Sciences,
Okayama University,
Tsushimanaka, Kita-ku, Okayama 700-8530, Japan
E-mail: nisina-y@cc.okayama-u.ac.jp
http://www.tt.vbl.okayama-u.ac.jp/
[b] Precursory Research for Embryonic Science and Technology,
Japan Science and Technology Agency,
4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500723.
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One-Pot Synthesis of 2-Arylphenol Derivatives
that the Suzuki–Miyaura coupling reaction of 2-iodocy- When the reaction was conducted at room temperature or
clohexenone (1) and phenylboronic acid (2a) in the presence with catalytic acid, the yields were reduced (entries 9–12).
of Pd/C catalyst under air, afforded 2-phenylcyclohexenone
(3a) with a small amount of 2-phenylphenol (4a),[12] which
is considered to be generated by oxidation of the coupling
Table 1. Optimization of reaction conditions for dehydrogenative
aromatization with catalytic Pd/C.[a]
product; see Equation (1). Palladium-catalyzed aerobic de-
hydrogenative aromatization has been studied and devel-
oped by the Stahl group.[9b,9c,9e,13] We hypothesized that a
Suzuki–Miyaura coupling reaction followed by sequential
dehydrogenative aromatization under optimal conditions
could provide a one-pot synthesis of 2-arylphenols 4 from
2-iodocyclohexenone (1) and arylboronic acid 2 (Scheme 1,
c).[14] Pd/C is an attractive palladium source because of its
availability and because of the ease with which it can be
removed from the reaction media. Moreover, 2-iodocy-
clohexenone (1) and its derivatives can be prepared in a
single step from cyclohexenone derivatives[15] and boronic
acids are stable, nontoxic, and commercially available rea-
gents. With the present method, 2-arylphenols 4 could be
easily obtained without problems of regioselectivity and
multiple arylation reactions. In this report, a one-pot
Suzuki–Miyaura coupling/dehydrogenative aromatization
sequence producing 2-arylphenols 4 in the presence of
Pd/C catalyst under simple conditions is described.
Entry
Additive [mol-%]
Temp. [°C]
Yield [%][b]
1
2
3
4
5
6
7
8
–
100
100
100
100
100
100
100
100
30
2
2
27
2
Na2CO3 (200)
pTsOH (10)
CuBr2 (10)
AcOH (100)
3
CF3COOH (100)
48% HBr aq. (100)
36% HCl aq. (100)
48% HBr aq. (100)
36% HCl aq. (100)
48% HBr aq. (10)
36% HCl aq. (10)
10
90
94
12
13
4
9
10
11
12
30
100
100
3
[a] Reaction conditions: 2-phenylcyclohexen-1-one (0.25 mmol), 10
wt.-% Pd/C (10 mol-%), additive, 1,4-dioxane (1.0 mL), 20 h, O2.
[b] GC yield by using dodecane as internal standard.
Following the results mentioned above, we then carried
out a re-examination of the reaction conditions of Suzuki–
Miyaura coupling using the Pd/C catalyst (Table 2). The re-
action of 2-iodocyclohexenone (1) and phenylboronic acid
(2a) in the presence of 10 mol-% Pd/C (10 wt.-%) and
Na2CO3 in anhydrous 1,4-dioxane at room temperature for
18 h gave only a trace amount of the corresponding cou-
(1)
Table 2. Re-examination of Suzuki–Miyaura coupling under vari-
ous conditions.[a]
Results and Discussion
We commenced our study by optimizing the reaction
conditions for the dehydrogenative aromatization of 2-
phenylcyclohexenone (3a) in the presence of Pd/C catalyst
under molecular oxygen (Table 1). Initially, the reaction of
2-phenylcyclohexenone (3a) was examined in the presence
of 10 mol-% Pd/C (10 wt.-%) in 1,4-dioxane at 100 °C for
20 h under molecular oxygen to give the corresponding
phenol 4a, but only a trace amount of product was detected
(entry 1). The addition of Na2CO3 as a base proved to be
ineffective (entry 2). On the other hand, the yield was im-
proved slightly when a catalytic amount of pTsOH was
added (entry 3). Although the addition of a suitable ligand
could be effective,[9c] we chose to screen acids without any
ligands to simplify the reaction conditions. The use of cata-
lytic CuBr2 as a Lewis acid was ineffective (entry 4). Al-
though the use of stoichiometric amounts of AcOH or
CF3COOH was not helpful (entries 5 and 6), the addition
of aqueous 48% HBr or 37% HCl produced 2-phen-
Entry Base
Solvent
Temp. [°C] Yield [%][b]
1
Na2CO3
1,4-dioxane
1,4-dioxane
1,4-dioxane
30
60
60
60
60
60
60
30
40
80
100
trace
10
31
33
47
72
85
64
74
64
59
2
3
Na2CO3
K2CO3
4
Na3PO4·12H2O 1,4-dioxane
5
6
7
8
9
10
11
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
1,4-dioxane
1,4-dioxane/H2O (9:1)
1,4-dioxane/H2O (4:1)
1,4-dioxane/H2O (4:1)
1,4-dioxane/H2O (4:1)
1,4-dioxane/H2O (4:1)
1,4-dioxane/H2O (4:1)
[a] Reaction conditions: 2-iodocyclohexen-1-one (0.25 mmol),
phenylboronic acid (1.2 equiv.), 10 wt.-% Pd/C (10 mol-%), base
(2.0 equiv.), solvent (1.0 mL), 18 h, argon. [b] GC yield by using
ylphenol (4a) in 90 and 94%, respectively (entries 7 and 8). dodecane as internal standard.
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K. Kikushima, Y. Nishina
FULL PAPER
pling product 3a (entry 1). After screening of the base and Table 3. Synthesis of 2-arylphenol derivatives through one-pot Su-
zuki/Miyaura coupling/dehydrogenative aromatization.[a]
reaction temperature, we found that the desired product was
obtained in moderate yield when the reaction was con-
ducted at 60 °C with K3PO4 as base (entry 5). Additionally,
performing the reaction in a mixed solvent of 1,4-dioxane/
H2O (9:1) gave the desired product in 72% yield (entry 6);
when a 4:1 ratio was used, the product yield was improved
to 85% (entry 7). The reactivity was reduced when the reac-
tion was carried out at either lower or higher temperature
(entries 8–11).
Finally, the one-pot Suzuki–Miyaura coupling/dehydro-
genative aromatization sequence was tested (Scheme 2).
Thus, a mixture of 2-iodocyclohexenone (1) and 1.2 equiv.
phenyl boronic acid (2a) with 10 mol-% Pd/C (10 wt.-%)
and K3PO4 in 1,4-dioxane/H2O (4:1) was stirred at 60 °C
for 24 h, and then aqueous 48% HBr and 1,4-dioxane were
added[16] together with a flow of molecular oxygen, fol-
lowed by stirring at 100 °C for 24 h. After purification, the
desired 2-phenylphenol (4a) was isolated in 84% yield. In
this reaction, only 0.9% palladium (24.8 μg) leached into
the reaction mixture, based on atomic absorption analysis.
[a] Reaction conditions: i. 2-iodocyclohexen-1-one derivative
(0.25 mmol), phenylboronic acid (2.0 equiv.), 10 wt.-% Pd/C
(10 mol-%), K3PO4 (2.0 equiv.), 1,4-dioxane/H2O (4:1, 1.0 mL),
60 °C, 24 h, argon; ii. 1,4-dioxane (1.0 mL), 48% HBr aq.
(8.0 equiv.), 100 °C, 24 h, O2. Isolated yields.
Scheme 2. One-pot synthesis of 2-phenylphenol through Suzuki–
Miyaura coupling/dehydrogenative aromatization. Reaction condi-
tions: i. 2-iodocyclohexen-1-one (0.25 mmol), phenylboronic acid
(1.2 equiv.), 10 wt.-% Pd/C (10 mol-%), K3PO4 (2.0 equiv.), 1,4-di-
oxane/H2O (4:1, 1.0 mL), 60 °C, 24 h, argon; ii. 1,4-dioxane
(1.0 mL), 48% HBr aq. (8.0 equiv.), 100 °C, 24 h, O2.
aryl substituent at the ortho-positions. 2-Iodocyclohexen-1-
one derivatives were prepared from the corresponding 2-
The present one-pot system could be applied to the syn- cyclohexen-1-ones by following reported procedures.[15] 2-
thesis of various 2-arylphenols (Table 3). When (4-meth- Phenyl-3-n-butylphenol (4i) was obtained in 71% yield by
oxyphenyl)boronic acid was employed as substrate, the de- using the corresponding iodide (1i) under the standard con-
sired product 4b was obtained in 99% yield. The use of (2- ditions. The reaction with 3-phenyl-2-iodo-2-cyclohexen-1-
methylphenyl)boronic acid resulted in a moderate yield due one (1j) produced terphenyl derivative 2,3-diphenylphenol
to steric hindrance. The reaction starting from (4-chloro- (4j) in 68% yield. In these cases, substitution at the 3-posi-
phenyl)boronic acid also produced the corresponding tion of 2-iodo-2-cyclohexen-1-one is considered to decrease
phenol 4d in high yield. The present reaction system worked the yield of the first coupling step due to steric hindrance.
well even in the presence of a cyano (4e), a nitro (4f), and On the other hand, 2-iodocyclohexen-1-one 1k, bearing a
an acetyl group (4g), for which further transformations benzyl group at the 4-position, produced the corresponding
could be performed for the preparation of functionalized phenol 4k in 84% yield, wherein bromination or oxidation
phenols. Furthermore, phenol derivative 4h, bearing a at the benzyl position did not occur even under oxidative
benzofuran group, which is an important heteroaryl frame- conditions. The present reaction system could be adapted
work that is contained in a wide range of biologically active to the synthesis of trisubstituted phenol. 2-Phenyl-3-methyl-
compounds, was afforded from the corresponding boronic 6-isopropylphenol (4l) was isolated in 69% yield from the
acid, albeit in moderate yield. We then focused on the syn- reaction of the corresponding iodide 1l and phenylboronic
thesis of di- or trisubstituted phenol derivatives with the acid under similar conditions.
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Eur. J. Org. Chem. 2015, 5864–5868

One-Pot Synthesis of 2-Arylphenol Derivatives
NMR (100 MHz, CDCl3): δ = 159.22, 152.48, 130.22, 129.17,
128.73, 127.79, 120.72, 116.67, 115.63, 114.62, 55.30 ppm.
Conclusions
We have demonstrated a one-pot Suzuki–Miyaura cou-
pling/dehydrogenative aromatization sequence to give 2-ar-
ylphenols from 2-iodocyclohexenone and arylboronic acids
under Pd/C catalysis. Additionally, 2-phenylphenol deriva-
tives bearing substitution groups at the meta or para posi-
tions could be produced by using the corresponding iodide.
In this method, the generation of the regioisomers or mul-
tiple arylation products that could occur in direct C–H aryl-
ation of phenols were avoided. Moreover, the present reac-
tion system did not require any ligands and proceeded un-
der operationally simple and accessible conditions.
2Ј-Methylbiphenyl-2-ol (4c): 1H NMR (400 MHz, CDCl3): δ =
7.35–7.33 (m, 2 H), 7.32–7.21 (m, 3 H), 7.12 (dd, J = 1.6, 7.7 Hz,
1 H), 7.01–6.96 (m, 2 H), 4.74 (s, 1 H), 2.18 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 152.46, 137.39, 135.67, 130.64,
130.45, 130.11, 129.09, 128.49, 127.67, 126.42, 120.42, 115.26,
19.72 ppm.
1
4Ј-Chlorobiphenyl-2-ol (4d): H NMR (400 MHz, CDCl3): δ = 7.46
(d, J = 8.8 Hz, 2 H), 7.42 (d, J = 8.8 Hz, 2 H), 7.29–7.22 (m, 2 H),
7.00 (dt, J = 1.2, 3.5 Hz, 1 H), 6.96 (dd, J = 1.1, 8.1 Hz, 1 H), 5.09
(s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.27, 135.61,
133.79, 130.47, 130.24, 129.37, 129.23, 127.01, 121.05, 116.01 ppm.
1
4Ј-Cyanobiphenyl-2-ol (4e): H NMR (400 MHz, CDCl3): δ = 7.75
(d, J = 8.5 Hz, 2 H), 7.66 (d, J = 8.5 Hz, 2 H), 7.32–7.26 (m, 2 H),
7.04 (dt, J = 0.9, 7.7 Hz, 1 H), 6.95 (d, J = 8.1 Hz, 1 H), 5.03 (s, 1
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.35, 142.59, 132.41,
130.43, 130.07, 129.94, 126.50, 121.39, 118.82, 116.39, 110.95 ppm.
Experimental Section
General Information: All commercially available compounds were
purchased and used as received. Solvents 1,4-dioxane, THF, and
Et2O were purchased from Wako Pure Chemical Industries and
used as received. Palladium on carbon (10 wt.-%) was purchased
from Sigma–Aldrich (product number: 205699). 2-Iodo-2-cyclo-
hexen-1-one derivatives were synthesized by reported methods.
Thin-layer chromatography was performed using Merck TLC silica
gel 60 F254 Aluminum sheets and visualized by UV irradiation and
phosphomolybdic acid staining. Flash chromatography separations
were performed on Kanto Chemical Silica Gel 60 (spherical, 40–
50 mesh). Gas chromatographic analysis was conducted with a Shi-
madzu GC-2014 instrument equipped with an FID detector and
the chemical yields were determined by using dodecane as an in-
3Ј-Nitrobiphenyl-2-ol (4f): 1H NMR (400 MHz, CDCl3): δ = 8.43
(t, J = 1.9 Hz, 1 H), 8.22 (ddd, J = 1.1, 2.3, 8.3 Hz, 1 H), 7.89
(ddd, J = 1.2, 1.6, 7.7 Hz, 1 H), 7.63 (t, J = 8.0 Hz, 1 H), 7.34–
7.29 (m, 2 H), 7.06 (dt, J = 1.2, 7.2 Hz, 1 H), 6.95 (dd, J = 1.1,
8.1 Hz, 1 H), 4.96 (s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 152.31, 139.39, 135.32, 130.58, 129.98, 129.43, 125.98, 124.25,
122.16, 121.48, 116.36 ppm. HRMS (EI): m/z calcd. for C12H9O3N
[M]+ 215.0582; found 215.0578.
4Ј-Acethylbiphenyl-2-ol (4g): 1H NMR (400 MHz, CDCl3): δ = 8.05
(d, J = 8.3 Hz, 2 H), 7.63 (d, J = 8.3 Hz, 2 H), 7.31–7.27 (m, 2 H),
7.02 (t, J = 7.5 Hz, 1 H), 6.98 (d, J = 8.3 Hz, 1 H), 5.45 (s, 1 H),
2.64 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 197.92,
152.51, 142.55, 135.98, 130.31, 129.75, 129.35, 128.94, 127.12,
121.10, 116.25, 26.64 ppm.
1
ternal standard. H (400 MHz) and 13C (100 MHz) NMR spectra
were recorded with a JEOL JNM-LA400 spectrometer. Proton
chemical shifts are reported relative to residual solvent peak CDCl3
at δ = 7.26 ppm. Carbon chemical shifts are reported relative to
CDCl3 at δ = 77.00 ppm. NMR spectra are reported as: chemical
shift (multiplicity, coupling constants, relative integral). High-reso-
lution mass spectra (HRMS) was measured with a JEOL JMS-700
MStation FAB-MS.
1
2-(Benzofuran-2-yl)phenol (4h): H NMR (400 MHz, CDCl3): δ =
7.74 (dd, J = 1.6, 8.0 Hz, 1 H), 7.62 (dd, J = 1.6, 6.7 Hz, 1 H), 7.55
(dd, J = 1.6, 7.2 Hz, 1 H), 7.35–7.27 (m, 3 H), 7.18 (s, 1 H), 7.11
(d, J = 0.9 Hz, 1 H), 7.04–7.00 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 154.27, 153.95, 153.29, 130.26, 128.48, 127.14, 124.43,
123.41, 120.98, 120.76, 117.37, 116.05, 110.98, 103.31 ppm.
General Procedure for the One-Pot Synthesis of 2-Arylphenols: A
screw-capped test tube was charged with 2-iodocyclohexenone
(0.25 mmol), phenylboronic acid (2.0 equiv.), 10 wt.-% Pd/C
(10 mol-%), K3PO4 (2.0 equiv.), and 1,4-dioxane/H2O (4:1, 1 mL).
The tube was filled with nitrogen and sealed with a screw-cap and
the reaction mixture was stirred at 60 °C for 24 h. After the ad-
dition of 1,4-dioxane (1 mL) and 48% HBr aq. (8.0 equiv.), the
tube was filled with molecular oxygen and again sealed with a
screw-cap. The reaction mixture was stirred at 100 °C for 24 h, then
the insoluble materials were removed through a Celite plug and
washed with EtOAc and the mixture was transferred to separating
funnel with satd. aq Na2S2O3. The organic layer was separated and
extracted with EtOAc three times, and then washed with brine,
dried with Na2SO4, filtered, and the solvents were evaporated. The
desired product was purified by column chromatography (SiO2;
EtOAc/hexane).
6-n-Butylbiphenyl-2-ol (4i): 1H NMR (400 MHz, CDCl3): δ = 7.55–
7.46 (m, 2 H), 7.46–7.40 (m, 1 H), 7.33–7.27 (m, 2 H), 7.24–7.16
(m, 1 H), 6.91–6.81 (m, 2 H), 4.67 (s, 1 H), 2.40–2.32 (m, 2 H),
1.44–1.34 (m, 2 H), 1.22–1.12 (m, 2 H), 0.76 (t, J = 6.9 Hz, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.73, 142.03, 135.01,
130.49, 129.21, 128.54, 128.09, 127.78, 120.99, 112.43, 33.25, 32.94,
22.38, 13.73 ppm. HRMS (EI): m/z calcd. for C16H18O [M]+
226.1358; found 226.1354.
2,3-Diphenylphenol (4j): 1H NMR (400 MHz, CDCl3): δ = 7.37–
7.27 (m, 4 H), 7.20–7.12 (m, 5 H), 7.11–7.01 (m, 4 H), 5.10 (s, 1
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.87, 142.20, 141.00,
134.96, 130.90, 129.59, 128.97, 128.76, 127.67, 127.57, 126.69,
126.36, 122.32, 114.42 ppm. HRMS (EI): m/z calcd. for C18H14O
[M]+ 246.1045; found 246.1043.
Biphenyl-2-ol (4a): 1H NMR (400 MHz, CDCl3): δ = 7.52–7.48 (m,
4 H), 7.44–7.40 (m, 1 H), 7.31–7.27 (m, 2 H), 7.05–7.01 (m, 2 H),
5.28 (s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.37,
137.04, 130.21, 129.22, 129.11, 129.06, 128.09, 127.82, 120.81,
115.79 ppm.
5-Benzylbiphenyl-2-ol (4k): 1H NMR (400 MHz, CDCl3): δ = 7.47–
7.40 (m, 4 H), 7.39–7.33 (m, 1 H), 7.30–7.23 (m, 2 H), 7.22–7.16
(m, 3 H), 7.09–7.03 (m, 2 H), 6.92–6.86 (m, 1 H), 5.12 (s, 1 H),
3.93 (s, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 150.70,
141.37, 137.13, 133.45, 130.57, 129.50, 129.17, 129.04, 128.79,
4Ј-Methoxybiphenyl-2-ol (4b): 1H NMR (400 MHz, CDCl3): δ =
7.39 (d, J = 8.3 Hz, 2 H), 7.24–7.20 (m, 2 H), 7.02 (d, J = 8.3 Hz, 128.43, 127.99, 127.76, 126.00, 115.83, 41.08 ppm. HRMS (EI): m/z
2 H), 6.99–6.96 (m, 2 H), 5.15 (s, 1 H), 3.86 (s, 3 H) ppm. 13C calcd. for C19H16O [M]+ 260.1201; found 260.1201.
Eur. J. Org. Chem. 2015, 5864–5868
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K. Kikushima, Y. Nishina
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3-Isopropyl-6-methylbiphenyl-2-ol (4l): 1H NMR (400 MHz,
CDCl3): δ = 7.56–7.48 (m, 2 H), 7.47–7.40 (m, 1 H), 7.35–7.28 (m,
2 H), 7.13 (d, J = 7.7 Hz, 1 H), 6.84 (d, J = 7.7 Hz, 1 H), 4.77 (s,
1 H), 3.28 (sep, J = 6.8 Hz, 1 H), 2.03 (s, 3 H), 1.27 (d, J = 6.8 Hz, 6
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 149.86, 135.67, 134.11,
131.95, 130.39, 129.47, 128.12, 127.70, 125.22, 121.49, 27.08, 22.64,
20.13 ppm. HRMS (EI): m/z calcd. for C16H18O [M]+ 226.1358;
found 226.1359.
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Acknowledgments
Financial support for this study was provided by the Ministry of
Education, Culture, Sports, Science and Technology (MEXT)
through Special Coordination Funds for Promoting Science and
Technology.
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Received: June 3, 2015
Published Online: August 6, 2015
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