Catalytic Availabilities of Lewis Acidic SnCl2: Ph3PAuCl–SnCl2Composite Catalyzed Successive ortho-Alkenylation/O-Alkenylation of Phenols Followed by Cyclization to 1-Benzopyrans

Article abstract of DOI:10.1002/ejoc.201601042

A Ph₃PAuCl–SnCl₂composite, prepared in situ from Ph₃PAuCl and SnCl₂, catalyzed the formation of 1-benzopyrans from phenols and phenylacetylene. The Ph₃PAuCl–SnCl₂composite catalyzed reactio

Full text of DOI:10.1002/ejoc.201601042

A Journal of
Accepted Article
Title: Catalytic Availabilities of Lewis Acidic SnCl2: Ph3PAuCl-SnCl2 Composite-
Catalyzed Successive ortho-Alkenylation/O-Alkenylation of Phenols Followed
by Cyclization to 1-Benzopyrans
Authors: Atsushi Tochigi; Kadzuoki Tsukamoto; Noriyuki Suzuki; Yoshiro Masuyama
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201601042
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Catalytic Availabilities of Lewis Acidic SnCl2: Ph3PAuCl-SnCl2
Composite-Catalyzed Successive ortho-Alkenylation/O-
Alkenylation of Phenols Followed by Cyclization to 1-
Benzopyrans
Atsushi Tochigi,[a] Kadzuoki Tsukamoto,[a] Noriyuki Suzuki,*[a] and Yoshiro Masuyama*[a]
Abstract: Ph3PAuCl-SnCl2 composite, prepared beforehand in situ
from Ph3PAuCl and SnCl2, catalyzed the preparation of 1-
benzopyrans from phenols and phenylacetylene. The Ph3PAuCl-
SnCl2 composite-catalyzed reaction was presumed to proceed via
the successive ortho-alkenylation and O-alkenylation of phenols with
phenylacetylene followed by the cyclization of prepared ortho- and
O-dialkenylated phenol derivatives. Conveniently, all reactions with
Ph3PAuCl-SnCl2 composite were established without much attention
to air and water.
Ph3PAuCl-catalyzed nucleophilic additions of phenols to
phenylacetylene with SnCl2 as a Lewis acidic auxiliary agent;
Ph3PAuCl-SnCl2
composite-catalyzed
successive
ortho-
alkenylation[9, 10] and O-alkenylation[11, 12] of phenols followed by
cyclization to 1-benzopyrans.[13,
In addition, the ortho-
14]
alkenylation catalyzed by SnCl2 itself is described, which has
been found in the course of the study of Ph3PAuCl-SnCl2
composite catalysis.
Results and Discussion
Introduction
Preparation of 1-benzopyran derivatives
The nucleophilic addition of 2-methylphenol 2a to
phenylacetylene 1 was investigated using some catalysts such
as AlCl3, FeCl3, SnCl2, Ph3PAuCl, Ph3PAuCl/AgSbF6 (1:1)
composite, and Ph3PAuCl/SnCl2 (1:1) composite, prepared
beforehand in situ by stirring a mixture of Ph3PAuCl and SnCl2 in
dichloroethane (DCE) at room temperature for 10 min (Table 1).
The nucleophilic addition scarcely proceeded with traditional
Lewis acids such as AlCl3 or FeCl3, and Ph3PAuCl, and starting
materials were almost entirely recovered (Entries 1, 2 and 5). A
weak Lewis acidic SnCl2 caused slight ortho-alkenylation of 2a
to afford only 2-methyl-6-(1-phenylethenyl)phenol 3a in an 11%
yield (Entry 3). While the reaction of 2a (0.5 mmol) and 1 (1.0
mmol) with Ph3PAuCl-SnCl2 composite produced the mixture of
3a (35%) and 2,8-dimethyl-2,4-diphenyl-1-benzopyran 4a (40%)
(Entry 7), the use of 1 increased to 2.0 mmol afforded only 4a in
62% yield (Entry 8). The reaction with SnCl2 in CH3NO2 (Entry 4)
or that with a cationic Au(I) complex that was prepared in situ
from Ph3PAuCl with AgSbF6 (Entry 6) also afforded only 4a in
31% or 9% yield respectively, but structurally unconfirmed
complex mixtures of high molecular weights were concurrently
produced. Some 1-benzopyran derivatives 4 were selectively
prepared from 1 and phenols 2 under the same conditions as
those of entry 8 in Table 1 (Table 2). Neither 2,6-bis(1-
Tin(II) chloride, which is insensitive to air and water, can be
applied as
a Lewis acid catalyst into various organic
syntheses.[1] During the development of SnCl2-mediated
carbonyl allylations by allylic alcohols, acetates or carbonates
with a catalytic amount of PdCl2(PhCN)2,[2] [RhCl(cod)]2,[3] or
[IrCl(cod)]2,[4] we had perceived that the coordination of SnCl2 to
chloride in chlorometal (M-Cl) complexes would reduce the
electron density on metals such as Pd(II), Rh(I) or Ir(I).
Therefore, the formation of metal stannate (M-SnCl3) complexes
from chlorometal complexes and SnCl2 might induce each of the
catalyst activations.[5] Our idea of activating the chlorometal
complexes with SnCl2 was realized for phosphine-free
[IrCl(cod)]2-catalyzed cyclotrimerization of terminal alkynes.[6]
We planned to apply this idea to the activation of various
chlorometal complexes.
A kind of chlorometal complex,
Ph3PAuCl, is usually converted with Ag(I) salts such as AgOTf,
AgPF6, or AgSbF6 into the corresponding active cationic Au(I)
complexes that can be applied as -Lewis acids into various
organic reactions.[7] If SnCl2 can be used instead of Ag(I) salts
for preparing an active -Lewis acidic Au(I) complex from
Ph3PAuCl,[8] -Lewis acidic Au(I)-catalyzed organic reactions will
attract much further attention, because SnCl2 is relatively
inexpensive and is easy to handle. Herein, we describe
phenylethenyl)phenols
nor
the
corresponding
8-(1-
phenylethenyl)-1-benzopyrans were detected in the reaction of
phenol 2b and 4-substituted phenols 2e–h (Entries 1 and 4–7).
Under the same conditions as those of Entry 8 in Table 1, an
electron-deficient phenol, 2,4-dichlorophenol was scarcely
consumed, and salicylaldehyde was gradually consumed with
[a]
A. Tochigi,[a] K. Tsukamoto,[a] N. Suzuki,*[a] Y. Masuyama*[a]
Department of Materials and Life Sciences,
Faculty of Science and Technology,
Sophia University,
7-1 Kioicho,Chiyoda-ku, Tokyo 102-8554, Japan
E-mail: norisuzuki@sophia.ac.jp
producing
neither
the
corresponding
ortho-(1-
phenylethenyl)phenol derivative nor 1-benzopyran derivative.
The reactivity of other alkynes was also investigated under the
same conditions as those of Entry 8 in Table 1; a terminal
aliphatic alkyne, 1-octyne resulted in a structurally unconfirmed
www.mls.sophia.ac.jp/~orgsynth/
Supporting information for this article is given via a link at the end of
the document.
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Ph
O
Ph
O
complex mixture, and an internal alkyne, 1-phenylpropyne did
not seem to react.
Ph3PAuCl/SnCl2
+
Ph
DCE
80 °C, 48 h
HO
OH
Ph
Ph
1
5
6
syn:anti = 1:1
Table 1. Nucleophilic addition of 2-methylphenol 2a to phenylacetylene 1.[a]
Ph
O
Ph
O
recrystallization
Ph
Catalyst
Ph
Ph
Ph
+
+
Ph
Ph
DCE
80 °C, 48 h
6anti
O
OH
2a
OH
1
3a
4a
Scheme 1. Preparation of a crystallized 1-benzopyran derivative 6anti from 1
and 5.
4a, Yield
Entry
Catalyst
3a, Yield [%][b]
[%][b]
0
1
2
AlCl3
FeCl3
0
0
0
3
SnCl2
SnCl2
Ph3PAuCl
11
0
0
0
31
0
4[c]
5
6
Ph3PAuCl/AgSbF6
Ph3PAuCl/SnCl2
Ph3PAuCl/SnCl2
Ph3PAuCl/SnCl2
0
35
0
9
7[d]
8
40
62
36
9[e]
27
[a] Reaction conditions: 1 (2.0 mmol), 2a (0.5 mmol), catalyst (0.05 mmol),
DCE (0.25 mL). [b] Isolated yields. [c] CH3NO2 was used as a solvent. [d] 1.0
mmol of 1 was used. [e] Toluene was used as a solvent.
Figure 1. ORTEP drawing of the molecular structure of 6anti.
Table 2. Preparation of 1-benzopyran derivatives 4.[a]
ortho-Alkenylation of Phenols
R2
Because an ortho-alkenylated product 3a was obtained from the
reaction of 1 and 2a (Entries 3, 8, and 9 in Table 1), the
selective ortho-alkenylation of phenols 2 with 1 was investigated.
The reaction of 2-t-butylphenol 2j (1.0 mmol) bearing a bulky
substituent on the 2-position with 1 (0.5 mmol) was conducted
under various conditions (Table 3). The ortho-alkenylation
proceeded smoothly with a catalytic amount of SnCl2 in CH3NO2
at 80 ºC for 3 h to afford 3j selectively (Entry 4), while no
reaction proceeded in solvents such as THF, dioxane, DMF, or
DMSO at 80 ºC for 24 h. Ph3PAuCl-SnCl2 composite catalyst
also served for the selective ortho-alkenylation in CH3NO2 (Entry
12). Even if excess 1 was used with prolonged stirring at 80 ºC
(Entry 9), the corresponding 1-benzopyran was not detected by
GC, similarly to any other conditions in Table 3. The bulky 2-t-
butyl substituent would hinder the formation of 1-benzopyran.
Next, the ortho-alkenylation of various phenols 2 bearing smaller
substituents than t-butyl on 2-position was conducted with SnCl2
catalyst in CH3NO2 at 60 ºC in Table 4. The reaction of 1 (0.5
mmol) and 2a (1.0 mmol) produced not only the ortho-
alkenylated product 3a (22%), but also the corresponding 1-
benzopyran 4a (35%) (Entry 1). Consequently, using 10
equimolar amounts of 2 to 1 made selective ortho-alkenylation
possible to afford only 3 without preparing 1-benzopyrans 4
(Entries 2-7). 2,6-Bis(1-phenylethenyl)phenol derivatives were
not detected in the reaction of 4-substituted phenols 2e–g
(Entries 4–6).
Ph
R2
Ph3PAuCl/SnCl2
+
Ph
R1
Ph
DCE
80 °C, 48 h
O
OH
R1
1
2
4
Entry
Phenol
2b
2c
2d
2e
2f
2g
2h
2i
R1
R2
Product
4b
Yield [%][b]
1
2
3
4
5
6
7
8
H
H
H
H
CH3O
CH3
t-Bu
Ph
67
73
23
81
80
84
71
62
CH3O
Ph
H
H
H
4c
4d
4e
4f
4g
H
CH3
4h
4i
CH3
[a] Reaction conditions: 1 (2.0 mmol), 2 (0.5 mmol), Ph3PAuCl/SnCl2 (0.05
mmol), DCE (0.25 mL). [b] Isolated yields.
To confirm the structure of 1-benzopyrans 4 independently, an
X-ray diffraction study was performed on colorless crystals of
6anti (mp 177–178 ºC) obtained by the slow diffusion of hexane
into a DCE solution of 6 (syn:anti = 1:1) that was produced in
73% yield by the reaction of
1 (4.0 mmol) and 1,3-
dihydroxybenzene (5, 0.5 mmol) with Ph3PAuCl-SnCl2 (0.05
mmol) in DCE (0.5 mL) at 80 ºC for 48 h (Scheme 1). The
ORTEP drawing of the molecular structure of 6anti is shown in
Figure 1. This result supported the structure of 1-benzopyrans 4
shown in Tables 1 and 2.
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European Journal of Organic Chemistry
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preparing 8 or 9 under the same conditions as those of the
reaction with the Ph3PAuCl-SnCl2 composite.[16] No reaction of
2,6-di-t-butylphenol (1.0 mmol) and 1 (0.5 mmol) with Ph3PAuCl-
SnCl2 composite catalyst (0.05 mmol) occurred even in DCE
(0.25 mL) at 80 ºC for 72 h. An ortho-alkenylated phenol, 3f (1.0
mmol) reacted with 1 (4.0 mmol) in the presence of Ph3PAuCl-
SnCl2 composite (0.1 mmol) in DCE (0.5 mL) at 80 ºC for 48 h to
produce 4f in 67% yield, although no intermediate, such as O-
Table 3. ortho-Alkenylation of 2-t-butylphenol 2b with phenylacetylene 1.[a]
Catalyst
Ph
+
Ph
t-Bu
t-Bu
Solvent
80 °C
OH
2j
OH
1
3j
Entry
1
2
3
4
Catalyst
SnCl2
SnCl2
SnCl2
SnCl2
SnCl2
SnCl2
SnCl2
SnCl2
SnCl2
AlCl3
Solvent
DCE
Time [h]
Yield [%][b]
trace
trace
28
70
74
28
65
70
58
24
24
24
3
8
72
3
3
24
8
alkenylated
derivative
of
3f,
namely
4-methyl-2-(1-
toluene
CH3CN
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
phenylethenyl)phenyl 1-phenylethenyl ether 10, or any others
was detected (Scheme 3).
5[c]
6[d]
7[e]
8[f]
9[g]
10
11
12
Ph
Ph
+
+
Ph
OH
O
0
26
58
OH
FeCl3
Ph3PAuCl/SnCl2
8
3
1
7
8
9
Ph3PAuCl-SnCl2, DCE, 80 °C, 3h
SnCl2, CH3NO2, 60 °C, 8 h
58%
16%
0%
[a] Reaction conditions: 1 (0.5 mmol), 2j (1.0 mmol), catalyst (0.05 mmol),
solvent (0.5 mL). [b] Isolated yields. [c] The reaction was carried out at 60 ºC.
[d] The reaction was carried out at 40 ºC. [e] 0.5 mmol of 2j was used. [f] 1.5
mmol of 2j was used. [g] 1.0 mmol of 1 and 0.5 mmol of 2j were used.
20%
Scheme 2. O-Alkenylation of 2,6-dimethylphenol 7.
Ph3PAuCl/SnCl2
Ph
DCE
80 °C, 48 h
Ph
Ph
+
Ph
O
OH
Table 4. ortho-Alkenylation of various phenols 2 to prepare 3.[a]
4f, 67%
1
3f
R2
R2
Ph
O
SnCl2
Ph
+
Ph
CH3NO2
60 °C, 48 h
R1
R1
OH
OH
Ph
10
1
2
3
Entry
1[c]
2
3
4
Phenol
R1
CH3
CH3
Ph
H
H
R2
H
H
H
CH3O
CH3
t-Bu
CH3
Product
Yield [%][b]
Scheme 3. Preparation of 4f from 1 and 3f with Ph3PAuCl-SnCl2 composite
catalyst.
2a
2a
2d
2e
2f
2g
2i
2k
2l
3a
3a
3d
3e
3f
3g
3i
3k
3l
22
65
45
74
68
57
52
70
76
5
6
On the basis of the ortho-alkenylation of 2, the O-alkenylation of
7 and the preparation of 1-benzopyran derivative 4f from 3f, we
propose a plausible mechanism for the preparation of 3 and 4
with Ph3PAuCl-SnCl2 composite catalyst in Scheme 4, although
no isolation of Ph3PAuCl-SnCl2 composite has been successfully
carried out and consequently its structure has not been
determined. Ph3PAuCl-SnCl2 composite catalyst, abbreviated to
[Au–Sn], was presumed to serve for the coordination of Au
moiety to alkyne and that of Sn moiety to phenolic OH. Phenols
H
7
CH3
t-Bu
t-Bu
8[d]
9[d]
t-Bu
CH3O
[a] Reaction conditions: 1 (0.5 mmol), 2 (5.0 mmol), SnCl2 (0.05 mmol),
CH3NO2 (1.5 mL). [b] Isolated yields. [c] 1.0 mmol of 2 was used. 4a was also
obtained in 35% yield. [d] The reaction of 1 (0.5 mmol) and 2 (1.0 mmol) was
carried out with SnCl2 (0.05 mmol) in CH3NO2 (0.5 mL) at 60 ºC for 4 h.
2
would be coordinated to [Au–Sn] together with
phenylacetylene 1 to cause the nucleophilic addition to 1 at the
ortho-position (intermediates A) followed by proton transfer from
the ortho-position onto Au (intermediates B). Ortho-alkenylated
products 3 would be prepared by the reductive elimination of B,
and at that time the chelated complex (intermediates C) of 3 with
regenerated [Au–Sn] species would be formed to allow the
nucleophilic addition to another molecule of 1 at the phenolic O-
position followed by a proton transfer from the O-position onto
Mechanism for Preparing 1-Benzopyrans
While 2,6-dimethylphenol 7 (1.0 mmol) reacted with 1 (0.5
mmol) in the presence of SnCl2 (0.05 mmol) in CH3NO2 (0.25
mL) at 60 ºC for 8 h to afford 2,6-dimethylphenyl 1-phenylethenyl
ether 8 (16%) and 2,6-dimethyl-3-(1-phenylethenyl)phenol 9
(20%), using Ph3PAuCl-SnCl2 composite (0.05 mmol) in DCE
(0.25 mL) at 80 ºC for 3 h selectively caused the O-alkenylation
of 7 (1.0 mmol) with 1 (0.5 mmol); in other words, it caused the
hydrophenoxylation of 1 with 7, to afford 8 in 58% yield (Scheme
2).[15] Ph3PAuCl-AgSbF6 did not function as a catalyst for
Au
(intermediates
D).
1-Phenylethenyl
2-(1-
phenylethenyl)phenyl ethers, prepared by the reductive
elimination of intermediates D, might rather be coordinated to
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European Journal of Organic Chemistry
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[Au–Sn] at the more electron-rich O-ethenyl moiety than at the
ortho-ethenyl moiety to form intermediates E that would rapidly
undergo cyclization, proton transfer, and then reductive
and water. Further applications of the Ph3PAuCl-SnCl2
composite catalyst system to synthetic methodologies are in
progress.
elimination to produce 1-benzopyran derivatives
4 while
reproducing an active [Au–Sn] species. In cases of R1 = H, the
coordination (intermediates C) of ortho-alkenyl group to [Au–Sn]
might not lead to second ortho-alkenylation, but to O-
alkenylation.
Experimental Section
General methods: Tin (II) chloride (Wako first-grade, over 97%) was
purchased from Wako Pure Chemical Industries, Ltd. and was used after
being dried at 120 °C for 5 h under vacuum. Ph3PAuCl was prepared
from Ph3P and HAuCl4 3.6H2O by the conventional method. HAuCl4
3.6H2O was purchased from Kojima Chemical Co., Ltd. and was used as
received.
GC analyses were carried out with InertCap 1 (0.25 mm x 30 m) as a GC
column on a GL Sciences GC-4000. TLC analyses were carried out with
silica gel plates (Merck 105735). Column chromatography was carried
out with silica gel (Kanto Chemical Co., Inc. Cat. No.37564). GPC
purification was carried out on a Japan Analysis Industry Co. Ltd. LC-908
or LC-9201 (JAIGEL-2H; CHCl3). 1H and 13C NMR spectra were recorded
on a JEOL JNM-ECX300 spectrometer. IR spectra were recorded on a
JASCO FT/IR-4600typeA. GC/MS spectra were recorded on a JEOL
JMS-700 instrument.
R2
Ph
O
R2
Ph3PAuCl
SnCl2
Ph
Ph
+
R1
1
R1
OH
2
4
[Au-Sn]
R2
(Ph3PAuCl/SnCl2)
Ph
R1
Ph
R1
[Au-Sn]
R2
O
O
H
H
Ph
[Au-Sn]
R2
R2
Ph
R1
Ph
+
R1
H
[Au-Sn]-
OH
+
O
A
Typical procedure for ortho-alkenylation: To a solution of tin(II)
chloride (19 mg, 0.1 mmol) in CH3NO2 (1.5 mL) were successively added
phenylacetylene (1, 51 mg, 0.5 mmol) and 2-methylphenol (2a, 0.54 g,
5.0 mmol). The mixture was stirred at 60 ºC for 48 h (discontinued times);
the disappearance of phenylacetylene mostly confirmed after 6~12 hours
by being monitored by GC. The mixture was extracted with diethyl ether
(150 mL). The extracted mixture was washed with water and saturated
aqueous NaCl solution, and then was dried over anhydrous MgSO4. After
evaporation of volatiles, purification by column chromatography (Kanto
Chemical Co., silica gel 60, 37564; hexane/EtOAc = 10/1) and GPC
(Japan Analytical Industry Co. Ltd., LC-908, JAIGEL-2H; CHCl3) afforded
68 mg (65%) of 2-methyl-6-(1-phenylethenyl)phenol (3a).
H
Ph
[Au-Sn]-
R2
R2
Ph
R1
Ph
R1
HO
[Au-Sn]
O
B
H
R2
H
R2
Ph
[Au-Sn]
E
Ph
Ph
R1
R1
O
O
H
C
[Au-Sn]
[Au-Sn]
H
Ph
Ph
D
1
Typical procedure for the preparation of 1-benzopyrans 4: After
stirring the mixture of Ph3PAuCl (25 mg, 0.05 mmol) and SnCl2 (10 mg,
0.05 mmol) in DCE (0.25 mL) at room temperature for 20 min,
phenylacetylene (1, 0.20 g, 2.0 mmol) and 2-methylphenol (2a, 54 mg,
0.5 mmol) were successively added, and the mixture was stirred at 80 ºC
for 48 h (discontinued times); the disappearance of 2 and 3 mostly
confirmed after 24~36 hours by being monitored by TLC and GC. The
mixture was extracted with diethyl ether (150 mL). The extracted mixture
was washed with water and saturated aqueous NaCl solution, and then
was dried over anhydrous MgSO4. After evaporation of volatiles,
purification by column chromatography (Kanto Chemical Co., silica gel 60,
37564; hexane/EtOAc = 10/1) and GPC (Japan Analytical Industry Co.
Ltd., LC-908, JAIGEL-2H; CHCl3) afforded 0.19 g (62%) of 2,8-dimethyl-
2,4-diphenyl-1-benzopyran (4a).
Scheme 4. Plausible mechanism for ortho-alkenylation followed by cyclization
to 1-benzopyrans 4.
Conclusions
We developed a Ph3PAuCl-SnCl2 composite catalyst system for
the preparation of 1-benzopyran derivatives from phenols and
phenylacethylene, which would proceed via the successive
ortho-alkenylation and O-alkenylation of phenols with excess
phenylacetylene followed by the cyclization of prepared ortho-
and O-dialkenylated phenol derivatives. In cases of phenol and
4-substituted phenols bearing no ortho-substituent, the
corresponding 1-benzopyrans were obtained selectively without
leading to dialkenylation at two ortho-positions. In the course of
the application of Ph3PAuCl-SnCl2 composite catalyst for
preparing 1-benzopyrans, such as the Ph3PAuCl-SnCl2
composite, SnCl2 itself was found to be an efficient catalyst for
the ortho-alkenylation in CH3NO2. This Ph3PAuCl-SnCl2
composite would be more effective than SnCl2 itself for the O-
alkenylation of a key step in the preparation of 1-benzopyrans.
Conveniently, like those with SnCl2, all reactions with Ph3PAuCl-
SnCl2 composite were established without much attention to air
10b]
2-Methyl-6-(1-phenylethenyl)phenol (3a):[10a,
Pale yellow oil. Rf =
0.57 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  2.27
(s, 3H), 5.25 (s, 1H), 5.41 (d, J = 1.0 Hz, 1H), 5.87 (d, J = 1.0 Hz, 1H),
6.83 (t, J = 7.6 Hz, 1H), 6.96 (dd, J = 7.6, 1.4 Hz, 1H), 7.12 (dd, J = 7.6,
1.4 Hz, 1H), 7.27-7.39 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  16.2,
116.6, 119.9, 124.7, 127.1, 127.9, 128.56, 128.64, 130.7, 139.5, 145.5,
151.2 ppm. IR: 3510, 3082, 3058, 2920, 2854, 1682, 1598, 1494, 1463,
1446, 1359, 1325, 1266, 1223, 1173, 1119, 1079, 1026, 1000, 957, 908,
837, 779, 746, 690, 588 cm-1. HRMS (FAB): m/z calcd for C15H14O
210.1045; found 210.1041.
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European Journal of Organic Chemistry
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2-Phenyl-6-(1-phenylethenyl)phenol (3d): Pale yellow oil. Rf = 0.27
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  5.37 (s,
1134, 1084, 911, 844, 799, 779, 748, 712, 695, 568 cm-1. HRMS (FAB):
m/z calcd for C18H20O 252.1514; found 252.1505.
1
1H), 5.46 (d, J = 1.0 Hz, 1H), 5.87 (d, J = 1.0 Hz, 1H), 7.00 (t, J = 7.6 Hz,
1H), 7.17 (dd, J = 7.6, 1.7 Hz, 1H), 7.28-7.37 (m, 5H), 7.39-7.45 (m, 4H),
7.53~7.56 (m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3):  116.8, 120.4,
126.9, 127.4, 128.33, 128.36, 128.48, 128.55, 128.63, 129.3, 130.0,
130.4, 137.7, 139.8, 145.7, 149.9 ppm. IR: 3522, 3082, 3057, 3030, 1814,
1598, 1494, 1454, 1426, 1326, 1227, 1175, 1075, 1054, 1026, 957, 913,
851, 827, 805, 780, 752, 691, 636, 602, 564 cm-1. HRMS (FAB): m/z
calcd for C20H16O 272.1201; found 272.1179.
]
2,4-Di-t-butyl-6-(1-phenylethenyl)phenol (3k):[1 Pale yellow solid. Rf
= 0.73 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3): 
1.28 (s, 9H), 1.42 (s, 9H), 5.31 (s, 1H), 5.43 (d, J = 1.0 Hz, 1H), 5.93 (d, J
= 1.0 Hz, 1H), 6.97 (d, J = 2.4 Hz, 1H), 7.29-7.40 (m, 6H) ppm. 13C NMR
(75.6 MHz, CDCl3):  29.7, 31.6, 34.2, 35.1, 116.8, 123.7, 124.7, 127.0,
127.3, 128.5, 128.6, 135.3, 139.4, 141.7, 145.9, 149.2 ppm. IR: 3503,
3077, 3054, 3025, 2956, 2904, 2874, 1802, 1598, 1443, 1389, 1361,
1326, 1266, 1237, 1201, 1167, 1146, 1119, 1087, 1027, 914, 879, 833,
806, 781, 739, 707, 684, 649, 603 cm-1. HRMS (EI): m/z calcd for
C22H28O 308.2140; found 308.2137.
７
4-Methoxy-2-(1-phenylethenyl)phenol (3e):[10a] Pale yellow solid. Rf =
0.27 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  3.73
(s, 3H), 4.83 (s, 1H), 5.41 (d, J = 1.0 Hz, 1H), 5.85 (d, J = 1.0 Hz, 1H),
6.69 (d, J = 3.1 Hz, 1H), 6.81 (dd, J = 8.9, 2.8 Hz, 1H), 6.87 (d, J = 8.9
Hz, 1H), 7.28-7.39 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  55.7,
115.0, 115.3, 116.5, 116.7, 127.0, 128.1, 128.6, 128.7, 139.1, 145.3,
147.1, 153.3 ppm. IR: 3518, 3081, 3056, 3000, 2952, 2935, 2832, 1589,
1491, 1446, 1422, 1320, 1275, 1173, 1145, 1038, 899, 807, 782, 764,
690 cm-1. HRMS (FAB): m/z calcd for C15H14O2 226.0994; found
226.0979.
2-t-Butyl-4-methoxy-6-(1-phenylethenyl)phenol (3l): Pale yellow solid.
Rf = 0.50 (hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3): 
1
1.41 (s, 9H), 3.71 (s, 3H), 5.12 (s, 1H), 5.42 (d, J = 1.0 Hz, 1H), 5.93 (d, J
= 1.0 Hz, 1H), 6.51 (d, J = 3.1 Hz, 1H), 6.89 (d, J = 3.1 Hz, 1H), 7.30-
7.39 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  29.5, 35.0, 55.6, 111.4,
114.1, 117.0, 126.9, 128.2, 128.60, 128.64, 137.7, 139.1, 145.6, 145.7,
152.4 ppm. IR: 3524, 3080, 3058, 2999, 2951, 2869, 2832, 1739, 1596,
1448, 1429, 1363, 1210, 1123, 1055, 1027, 911, 874, 850, 784, 693, 603
cm-1. HRMS (EI): m/z calcd for C19H22O2 282.1620; found 282.1616.
4-Methyl-2-(1-phenylethenyl)phenol (3f):[10b] Pale yellow oil. Rf = 0.23
1
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  2.26 (s,
3H), 5.02 (s, 1H), 5.39 (d, J = 1.0 Hz, 1H), 5.84 (d, J = 1.0 Hz, 1H), 6.84
(d, J = 8.3 Hz, 1H), 6.93 (d, J = 1.7 Hz, 1H), 7.05 (d, J = 8.3, 1.7 Hz, 1H),
7.30-7.39 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3
116.5, 127.0, 127.3, 128.5, 128.6, 129.6, 130.0, 130.7, 139.5, 145.4,
150.8 ppm. IR: 3509, 3085, 3058, 3026, 2921, 2857, 1815, 1672, 1598,
1493, 1446, 1332, 1269, 1241, 1178, 1118, 1069, 1027, 959, 903, 816,
780, 758, 698, 657, 610, 589 cm-1. HRMS (FAB): m/z calcd for C15H14O
210.1045; found 210.1033.
2,8-Dimethyl-2,4-diphenyl-1-benzopyran (4a): Pale yellow oil. Rf
=
0.67 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.81
(s, 3H), 2.34 (s, 3H), 5.94 (s, 1H), 6.67 (t, J = 7.5 Hz, 1H), 6.80 (dd, J =
7.5, 1.4 Hz, 1H), 7.00 (dd, J = 7.5, 1.4 Hz, 1H), 7.16-7.25 (m, 1H), 7.28-
7.40 (m, 7H), 7.56 (bd, J = 7.2 Hz, 2H) ppm. 13C NMR (75.6 MHz,
CDCl3):  16.0, 29.9, 78.2, 120.1, 121.9, 123.5, 125.0, 125.6, 127.2,
127.5, 127.7, 128.1, 128.3, 128.8, 130.8, 136.0, 138.6, 146.1, 151.3 ppm.
IR: 3058, 3027, 2977, 2958, 2924, 2853, 1635, 1598, 1493, 1444, 1372,
1353, 1258, 1240, 1178, 1108, 1074, 1028, 953, 921, 846, 784, 756, 744,
699, 647, 585 cm-1. HRMS (EI): m/z calcd for C23H20O 312.1514; found
312.1504.
4-t-Butyl-2-(1-phenylethenyl)phenol (3g):[10b] Pale yellow oil. Rf = 0.37
(hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3
9H), 4.99 (s, 1H), 5.41 (d, J = 1.4 Hz, 1H), 5.87 (d, J = 1.4 Hz, 1H), 6.88
(d, J = 8.6 Hz, 1H), 7.14 (d, J = 2.4 Hz, 1H), 7.28 (d, J = 8.6, 2.4 Hz, 1H),
7.32-7.40 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  31.5, 34.1, 115.2,
116.5, 126.3, 126.8, 127.0, 127.2, 128.5, 128.7, 139.4, 143.1, 145.7,
150.7 ppm. IR: 3522, 3084, 3058, 3030, 2958, 2904, 2867, 1680, 1606,
1494, 1446, 1412, 1363, 1335, 1259, 1209, 1178, 1123, 1027, 897, 824,
780, 757, 707, 691, 652, 620, 588 cm-1. HRMS (FAB): m/z calcd for
C18H20O 252.1514; found 252.1516.
2-Methyl-2,4-diphenyl-1-benzopyran (4b): Pale yellow oil. Rf = 0.67
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  1.82 (s,
1
3H), 5.96 (s, 1H), 6.78 (dt, J = 7.5, 1.4 Hz, 1H), 6.95~7.00 (m, 2H), 7.11-
7.24 (m, 2H), 7.28~7.40 (m, 7H), 7.54~7.58 (m, 2H) ppm. 13C NMR (75.6
MHz, CDCl3):  29.7, 78.3, 116.9, 120.8, 122.4, 125.2, 125.7, 127.2,
127.8, 127.9, 128.2, 128.3, 128.8, 129.4, 135.5, 138.2, 145.9, 153.4 ppm.
IR: 3057, 3027, 2978, 2926, 2859, 1627, 1600, 1573, 1481, 1446, 1371,
1352, 1305, 1263, 1243, 1179, 1117, 1091, 1072, 1053, 1028, 965, 922,
843, 813, 756, 745, 724, 695, 635, 605, 589, 575 cm-1. HRMS (EI): m/z
calcd for C22H18O 298.1358; found 298.1354.
2,4-Dimethyl-6-(1-phenylethenyl)phenol (3i): Pale yellow oil. Rf = 0.53
1
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  2.22 (s,
3H), 2.23 (s, 3H), 5.09 (s, 1H), 5.38 (d, J = 1.0 Hz, 1H), 5.83 (d, J = 1.0
Hz, 1H), 6.76 (d, J = 1.4 Hz, 1H), 6.93 (d, J = 1.4 Hz, 1H), 7.27-7.38 (m,
5H) ppm. 13C NMR (75.6 MHz, CDCl3):  16.1, 20.4, 116.4, 124.4, 126.8,
127.1, 128.1, 128.5, 128.6, 128.9, 131.4, 139.6, 145.7, 149.0 ppm. IR:
3520, 3059, 3025, 2976, 2947, 2919, 2859, 1799, 1729, 1680, 1600,
1477, 1446, 1381, 1338, 1290, 1226, 1194, 1143, 1092, 1024, 972, 911,
861, 785, 758, 697, 666, 564 cm-1. HRMS (EI): m/z calcd for C16H16O
224.1201; found 224.1163.
8-Methoxy-2-methyl-2,4-diphenyl-1-benzopyran (4c): Pale yellow solid.
Rf = 0.40 (hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3): 
1
1.85 (s, 3H), 3.90 (s, 3H), 6.05 (s, 1H), 6.56 (dd, J = 7.6, 1.4 Hz, 1H),
6.70 (t, J = 7.6 Hz, 1H), 6.78 (dd, J = 7.6, 1.4 Hz, 1H), 7.15-7.21 (m, 1H),
7.24-7.30 (m, 2H), 7.31~7.40 (m, 5H), 7.56~7.60 (m, 2H) ppm. 13C NMR
(75.6 MHz, CDCl3):  30.5, 56.2, 78.3, 112.2, 118.1, 120.3, 123.5, 124.9,
127.1, 127.8, 128.0, 128.15, 128.23, 128.7, 135.8, 138.4, 142.6, 145.9,
148.5 ppm. IR: 3082, 3055, 3026, 2981, 2958, 2925, 2851, 1625, 1598,
1572, 1490, 1476, 1458, 1442, 1371, 1353, 1261, 1209, 1176, 1113,
1066, 981, 907, 830, 811, 787, 768, 753, 735, 698, 661, 580 cm-1. HRMS
(EI): m/z calcd for C23H20O2 328.1463; found 328.1464.
2-t-Butyl-6-(1-phenylethenyl)phenol (3j): Pale yellow oil. Rf = 0.70
1
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  1.42 (s,
9H), 5.43 (d, J = 1.0 Hz, 1H), 5.50 (s, 1H), 5.94 (d, J = 1.0 Hz, 1H), 6.85
(t, J = 7.5 Hz, 1H), 6.97 (dd, J = 7.5, 1.7 Hz, 1H), 7.28 (dd, J = 7.5, 1.7
Hz, 1H), 7.31-7.38 (m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  29.6,
34.9, 117.1, 119.5, 126.6, 127.0, 128.06, 128.13, 128.58, 128.62, 136.3,
139.3, 145.4, 151.6 ppm. IR: 3510, 3084, 3058, 3027, 3004, 2956, 2908,
2871, 1739, 1610, 1483, 1430, 1391, 1362, 1329, 1267, 1230, 1189,
2-Methyl-2,4,8-triphenyl-1-benzopyran (4d): Pale yellow solid. Rf
=
0.53 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.76
(s, 3H), 6.03 (s, 1H), 6.85 (t, J = 7.6 Hz, 1H), 6.97 (dd, J = 7.6, 1.7 Hz,
1H), 7.15-7.24 (m, 4H), 7.30-7.47 (m, 10H), 7.58-7.62 (m, 2H) ppm. 13C
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European Journal of Organic Chemistry
10.1002/ejoc.201601042
FULL PAPER
NMR (75.6 MHz, CDCl3):  29.8, 78.5, 120.6, 123.1, 125.2, 126.7, 126.8,
127.1, 127.8, 128.03, 128.07, 128.36, 128.46, 128.9, 129.6, 130.3, 130.7,
136.0, 138.2, 138.5, 145.5, 150.1 ppm. IR: 3081, 3057, 3027, 2978, 2960,
2925, 2851, 1632, 1600, 1492, 1446, 1423, 1371, 1355, 1263, 1243,
1213, 1178, 1113, 1071, 1027, 917, 804, 756, 695, 590 cm-1. HRMS
(FAB): m/z calcd for C28H22O 374.1671; found 374.1662.
6.676, 6.681, 6.689 (3s, 2H), 7.15-7.40 (m, 16H), 7.47-7.60 (m, 4H) ppm.
IR: 3057, 3025, 2979, 1611, 1488, 1443, 1279, 1155, 1113, 1073, 1027,
904, 878, 755, 696 cm-1. HRMS (FAB): m/z calcd for C38H30O2 518.2246;
found 518.2234.
2,8-Dimethyl-2,4,6,8-tetraphenylbenzo[1,2-b:5,4-b’]bispyran (6anti):
Colorless crystals. Mp 177-178 ºC. Rf = 0.53 (hexane : ethyl acetate =
1
6-Methoxy-2-methyl-2,4-diphenyl-1-benzopyran (4e): Pale yellow solid.
10 : 1). H NMR (300 MHz, CDCl3):  1.79 (s, 6H), 5.80 (s, 2H), 6.68 (s,
1
Rf = 0.47 (hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3): 
1H), 6.69 (s, 1H), 7.22-7.27 (m, 12H), 7.30-7.36 (m, 4H), 7.53-7.57 (m,
4H) ppm. 13C NMR (125 MHz, CDCl3):  29.9, 78.9, 105.5, 115.5, 123.2,
125.2, 125.3, 127.2, 127.7, 128.1, 128.2, 128.5, 135.2, 138.1, 146.1,
154.9 ppm. IR: 3052, 3026, 2989, 2931, 1612, 1563, 1490, 1444, 1360,
1308, 1280, 1222, 1160, 1118, 1073, 1029, 945, 899, 878, 860, 769, 755,
725, 695, 667, 586, 577 cm-1. HRMS (FAB): m/z calcd for C38H30O2
518.2246; found 518.2251.
1.80 (s, 3H), 3.61 (s, 3H), 6.02 (s, 1H), 6.54 (d, J = 3.1 Hz, 1H), 6.70 (dd,
J = 8.6, 3.1 Hz, 1H), 6.92 (d, J = 8.6 Hz, 1H), 7.18-7.24 (m, 1H), 7.28-
7.41 (m, 7H), 7.54~7.57 (m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3): 
29.6, 55.6, 78.0, 111.4, 114.3, 117.4, 123.1, 125.3, 127.2, 127.9, 128.1,
128.4, 128.7, 128.8, 135.7, 138.1, 145.8, 147.3, 153.6 ppm. IR: 3084,
3056, 3025, 2979, 2927, 2859, 1631, 1600, 1573, 1486, 1444, 1248,
1189, 1125, 1070, 1029, 940, 815, 789, 772, 754, 696, 589, 571 cm-1.
HRMS (FAB): m/z calcd for C23H20O2 328.1463; found 328.1465.
2,6-Dimethylphenyl 1-phenylethenyl ether (8): Colorless oil. Rf = 0.80
1
(hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3):  2.21 (s,
2,6-Dimethyl-2,4-diphenyl-1-benzopyran (4f): Pale yellow solid. Rf =
0.50 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.80
(s, 3H), 2.12 (s, 3H), 5.95 (s, 1H), 6.76 (br, 1H), 6.88 (d, J = 8.3 Hz, 1H),
6.93 (brd, J = 8.3 Hz, 1H), 7.15-7.21 (m, 1H), 7.27-7.40 (m, 7H), 7.53-
7.57 (m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3):  20.7, 29.7, 78.0, 116.7,
122.1, 125.2, 126.1, 127.1, 127.7, 128.07, 128.12, 128.3, 128.8, 129.87,
129.91, 135.6, 138.4, 145.9, 151.1 ppm. IR: 3061, 3019, 2978, 1633,
1604, 1486, 1443, 1247, 1125, 1069, 818, 753, 695, 589, 572 cm-1.
HRMS (FAB): m/z calcd for C23H20O 312.1514; found 312.1513.
6H), 3.83 (d, J = 2.4 Hz, 1H), 4.70 (d, J = 2.4 Hz, 1H), 7.00-7.10 (m, 3H),
7.34-7.46 (m, 3H), 7.80-7.86 (m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3):
 16.0, 84.7, 124.9, 125.4, 128.3, 128.71, 128.75, 131.1, 135.3, 151.1,
157.6 ppm. IR: 3084, 3056, 3025, 2952, 2923, 2854, 1649, 1617, 1576,
1494, 1474, 1444, 1377, 1314, 1276, 1191, 1106, 1074, 1028, 953, 919,
816, 764, 706, 689, 606 cm-1. HRMS (EI): m/z calcd for C16H16O
224.1201; found 224.1186.
2,6-Dimethyl-3-(1-phenylethenyl)phenol (9): Pale yellow solid. Rf
=
0.30 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.96
(s, 3H), 2.28 (s, 3H), 4.66 (s, 1H), 5.18 (d, J = 1.7 Hz, 1H), 5.76 (d, J =
1.7 Hz, 1H), 6.76 (d, J = 7.6 Hz, 1H), 6.99 (d, J = 7.6 Hz, 1H), 7.20-7.36
(m, 5H) ppm. 13C NMR (75.6 MHz, CDCl3):  12.9, 16.0, 114.7, 121.2,
122.1, 122.2, 126.4, 127.5, 127.8, 128.3, 140.7, 140.9, 149.1, 152.1 ppm.
IR: 3499, 3084, 3054, 3022, 2923, 2859, 1611, 1596, 1571, 1493, 1444,
1414, 1309, 1232, 1195, 1095, 1021, 943, 912, 825, 800, 780, 746, 725,
701, 690, 651, 633 cm-1. HRMS (FAB): m/z calcd for C16H16O 224.1201;
found 224.1202.
6-t-Butyl-2-methyl-2,4-diphenyl-1-benzopyran (4g): Pale yellow solid.
Rf = 0.50 (hexane : ethyl acetate = 10 : 1). H NMR (300 MHz, CDCl3): 
1
1.17 (s, 9H), 1.81 (s, 3H), 5.94 (s, 1H), 6.92 (d, J = 8.2 Hz, 1H), 7.02 (d, J
= 2.4 Hz, 1H), 7.15-7.24 (m, 2H), 7.29-7.41 (m, 7H), 7.55-7.59 (m, 2H)
ppm. 13C NMR (75.6 MHz, CDCl3):  29.8, 31.4, 34.1, 78.1, 116.1, 121.4,
122.8, 125.2, 126.2, 127.1, 127.8, 128.2, 128.3, 128.7, 135.7, 138.4,
143.3, 146.2, 151.0 ppm. IR: 3054, 3027, 2959, 2924, 2864, 1627, 1597,
1490, 1443, 1366, 1257, 1177, 1130, 1050, 1029, 896, 823, 775, 762,
749, 699, 672, 602, 567 cm-1. HRMS (FAB): m/z calcd for C26H26O
354.1984; found 354.2001.
Acknowledgements
2-Methyl-2,4,6-triphenyl-1-benzopyran (4h): Pale yellow solid. Rf
=
0.63 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.85
(s, 3H), 6.01 (s, 1H), 7.06 (d, J = 8.3 Hz, 1H), 7.19-7.46 (m, 15H), 7.56-
7.61 (m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3):  29.7, 78.5, 117.2,
122.5, 124.4, 125.3, 126.6, 126.7, 127.3, 127.9, 128.1, 128.2, 128.3,
128.5, 128.6, 128.8, 133.9, 135.5, 138.1, 140.8, 145.8, 153.0 ppm. IR:
3058, 3029, 2981, 2927, 1600, 1477, 1445, 1409, 1371, 1257, 1180,
1124, 1093, 1072, 1045, 1028, 967, 897, 828, 756, 691, 608, 592, 579,
560 cm-1. HRMS (FAB): m/z calcd for C28H22O 374.1671; found 374.1642.
Ms. E. Okano and Ms. S. Machishima (Sophia University) are
acknowledged for their assistance in NMR, mass spectrometry
and elemental analysis.
Keywords: Homogeneous catalysis • Gold • Tin • Phenols •
Alkynes • Alkenylation • Cyclization
[1]
For selected papers on the application of tin(II) chloride as a weak
Lewis acid catalyst to organic syntheses, see: a) T. Mukaiyama, K.
Wariishi, Y. Saito, M. Hayashi, S. Kobayashi, Chem. Lett. 1988, 1101–
1104; b) K. L. Ford, E. J. Roskamp, Tetrahedron Lett. 1992, 33, 1135–
1138; c) C. S. Cho, D. T. Kim, H.-J. Choi, T.-J. Kim, S. C. Shim, Bull.
Korean Chem. Soc. 2002, 23, 539–540; d) A. Bandyopadhyay, N.
Agrawal, S. M. Mali, S. V. Jadhav, H. N. Gopi, Org. Biomol. Chem.
2010, 8, 4855–4860; e) L. Nagarapu, R. Bantu, R. G. Puligoundla, Eur.
J. Chem. 2011, 2, 260–265; f) Y. Masuyama, M. Hayashi, N. Suzuki,
Eur. J. Org. Chem. 2013, 2914–2921; g) Y. Masuyama, W. Takamura,
N. Suzuki, Eur. J. Org. Chem. 2013, 8033–8038.
2,6,8-Triimethyl-2,4-diphenyl-1-benzopyran (4i): Pale yellow solid. Rf =
0.70 (hexane : ethyl acetate = 10 : 1). 1H NMR (300 MHz, CDCl3):  1.80
(s, 3H), 2.10 (s, 3H), 2.31 (s, 3H), 5.94 (s, 1H), 6.60 (d, J = 1.4 Hz, 1H),
6.82 (d, J = 1.4 Hz, 1H), 7.18-7.23 (m, 1H), 7.28-7.40 (m, 7H), 7.54-7.58
(m, 2H) ppm. 13C NMR (75.6 MHz, CDCl3):  15.9, 20.6, 29.9, 78.0,
121.8, 123.8, 125.0, 125.3, 127.1, 127.7, 128.1, 128.3, 128.4, 128.8,
129.1, 131.5, 136.1, 138.8, 146.2, 149.1 ppm. IR: 3084, 3056, 3030,
2958, 2923, 2855, 1632, 1598, 1492, 1469, 1261, 1224, 1069, 1025, 859,
795, 744, 697 cm-1. HRMS (EI): m/z calcd for C24H22O 326.1671; found
326.1664.
[2]
[3]
Y. Masuyama, In Advances in Metal-Organic Chemistry; Liebeskind, L.
S., Ed.; JAI Press: Greenwich, CT, 1994; Vol. 3, pp 255–303.
Y. Masuyama, Y. Kaneko, Y. Kurusu, Tetrahedron Lett. 2004, 45,
8969–8971.
2,8-Dimethyl-2,4,6,8-tetraphenylbenzo[1,2-b:5,4-b']bispyran
(6)
(syn:anti = 1:1): Rf = 0.53, 0.56 (hexane : ethyl acetate = 10 : 1). 1H
NMR (300 MHz, CDCl3):  = 1.79, 1.81 (2s, 6H), 5.80, 5.81 (2s, 2H),
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European Journal of Organic Chemistry
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
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Phenols to 1-Benzpyranes
R2
Ph
O
Ph3PAuCl
SnCl2
R2
Atsushi Tochigi, Kadzuoki Tsukamoto,
Noriyuki Suzuki,* and Yoshiro
Masuyama*
Ph
+
Ph
DCE
80 °C, 48 h
R1
R1
OH
Page No. – Page No.
Ph3PAuCl-SnCl2 composite, prepared beforehand in situ from Ph3PAuCl and SnCl2,
catalyzed the preparation of 1-benzopyrans from phenols and phenylacetylene.
Catalytic Availabilities of Lewis
Acidic SnCl2: Ph3PAuCl-SnCl2
Composite-Catalyzed Successive
ortho-Alkenylation/O-Alkenylation of
Phenols Followed by Cyclization to 1-
Benzopyrans
*one or two words that highlight the emphasis of the paper or the field of the study
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