New construction of p-tolylsulfonyl-substituted naphthalenes by thermal and photochemical cyclization of 1-aryl-4-(methylthio)-2-(p-tolysulfonyl)-1,3-butadienes

Article abstract of DOI:10.1002/hc.1058

Transformation of 4-(methylthio)-1-phenyl-2-(p-tolysulfonyl)-1,3-butadiene 1a was found to give 2-(p-tolysulfonyl)naphthalene 3a either by the action of I₂ in refluxing acetonitrile or by irradiation with a high-pressure Hg lamp. An electron-wi

Full text of DOI:10.1002/hc.1058

Heteroatom Chemistry
Volume 12, Number 5, 2001
New Construction of p-Tolylsulfonyl-
Substituted Naphthalenes by Thermal and
Photochemical Cyclization of 1-Aryl-4-
(methylthio)-2-(p-tolylsulfonyl)-1,3-butadienes
Shoji Matsumoto, Shinjiro Takahashi, and Katsuyuki Ogura
Department of Materials Technology, Faculty of Engineering, Chiba University, 1-33 Yayoicho,
Inage-ku, Chiba 263-8522; E-mail: katsu@galaxy.tc.chiba-u.ac.jp
Received 9 January 2001; revised 21 February 2001
(ii) coupling reaction [2]; (iii) cycloaddition [3]; (iv)
electrocyclization [4,5]. Among them, our attention
was focused on the electrocyclization of a 1,3,5-al-
katriene accompanied by elimination of an appro-
priate moiety to give the benzene ring (Equation 1)
because it can fix the position of the substituent(s)
on the newly formed benzene ring unambiguously,
and various ways are employed for the preparation
ABSTRACT: Transformation of 4-(methylthio)-1-
phenyl-2-(p-tolylsulfonyl)-1,3-butadiene 1a was found
to give 2-(p-tolylsulfonyl)naphthalene 3a either by the
action of I2 in refluxing acetonitrile or by irradiation
with a high-pressure Hg lamp. An electron-withdraw-
ing group (p-F or p-CO2Me) on the phenyl ring retarded
the thermal reaction, but the corresponding naphtha-
lene derivative was efficiently produced by the photol-
ysis in the presence of I2. The substituent effect of an
of the starting 1,3,5-alkatriene.
electron-donating methoxyl group is also reported.
᭧ 2001 John Wiley & Sons, Inc. Heteroatom Chem
12:385–391, 2001
INTRODUCTION
(1)
Efficient methods for the construction of a benzene
ring are very important for developing a new type of
biologically active compounds and functional ma-
terials with a p-electron system. Hitherto, the ben-
zene ring has been made mainly by the following
methods: (i) an aromatic substitution reaction [1];
In this reaction sequence, it is anticipated that if a
good leaving group (Z) is introduced at the 1-posi-
tion of the triene, the irreversible elimination step
would take place so smoothly and drive the cycliza-
tion step forward. However, we had to solve the prob-
lem of how to prepare the 1,3,5-alkatrienes bearing
the central double bond with the geometry appro-
priate to the cyclization. These considerations
prompted us to investigate the ring-closure of 1-aryl-
4-(methylthio)-2-(p-tolylsulfonyl)-1,3-butadienes (1)
because the methylthio group is thought to be a
good, versatile leaving group because it is removable
Dedicated to Prof. Naoki Inamoto on the occasion of his 72nd
birthday.
Correspondence to: Katsuyuki Ogura.
Contract Grant Sponsor: Japan Society for the Promotion of
Science.
Contract Grant Number: Research for the Future Program
JSPS-RFTF96P00304.
᭧ 2001 John Wiley & Sons, Inc.
385

386 Matsumoto, Takahashi, and Ogura
as the corresponding methylsulfenyl cation, meth-
ylthio radical, or methanethiolate ion.
days, we obtained 3a in 89% yield (run 2 in Table 1).
The structure of 3a was confirmed by its spectral
data and elemental analysis. On irradiation with a
high-pressure Hg lamp under a N2 atmosphere, the
electrocyclization of 1a took place in acetonitrile. It
was followed by elimination of the methanethiol
moiety to give 3a in 89% yield (run 3). Thus, the
transformation of 1a into 3a can be attained either
by an I2-assisted thermal reaction or by photolysis.
In these reactions, a significant effect of the sub-
stituent on the phenyl ring was observed, as sum-
marized in Table 1. Introduction of an electron-with-
drawing group on the phenyl ring of 1 retarded the
thermal reaction of 1 with I2: 1b (Yסp-F) and 1c
(Yסp-CO2Me) did not react efficiently (runs 4 and 7
of Table 1). In contrast, a p-methoxyl substituent did
not retard the reaction to transform 1d into the cor-
responding 3d (Run 10). It is noteworthy that 1e
(Yסm-MeO) reacted more smoothly than 1d (Yסp-
MeO). The reaction of 1e finished within 3 hours in
refluxing acetonitrile to produce two regioisomers
(3e and 3eЈ) in a ratio of 67:33. This tendency is iden-
tical to that observed in the usual electrophilic aro-
matic substitution of anisole, in which the methoxyl
group acts as an ortho, para-directing and activating
substituent. Thus, it was suggested that this reaction
might involve an electrophilic (of the Friedel-Crafts
type) reaction on the phenyl ring [7].
Since 1 can be prepared from 1-(methylthio)-3-
(p-tolylsulfonyl)-1-propene (4) as summarized in
Scheme 1, the presence of a p-tolylsulfonyl group is
expected to force the E geometry of the central dou-
ble bond that is favorable for the cyclization. Now,
we wish to report the convenient preparation of 1
and its thermal and photochemical conversion into
the naphthalene derivatives (3) having an electron-
withdrawing sulfonyl group at a specific position.
RESULTS AND DISCUSSION
The starting compound 1 could be prepared accord-
ing to Scheme 1. Successive treatment of (E)-4 [6]
with n-butyllithium, followed by the addition of an
aromatic aldehyde and the subsequent acetylation
with acetic anhydride, gave, in a one-pot manner,
4-acetoxy-4-aryl-1-(methylthio)-3-(p-tolylsulfonyl)-1-
butene 5. Furthermore, 5 was treated with sodium
hydride in THF at room temperature to afford 1. The
overall yields of 1a, 1b, 1c, 1d, and 1e were 96%,
87%, 90%, 90%, and 85%, respectively. It should be
noted that the obtained 1 has the E geometry at the
central double bond. Since the allylic carbanion of 5
is stabilized by the adjacent sulfonyl group, the E1cb
mechanism is likely for the transformation of 5 into
1 to produce (1E,3E)-1 by the repulsive interaction
between the p-tolylsulfonyl group and the aryl (Y-
C6H4) group.
The reaction of 1a and iodine in CD3CN at 95ЊC
was examined by 1H NMR (300 MHz) spectroscopy,
showing that the reaction has an induction period in
the formation of 3a, as depicted in Figure 1. At the
initial stage of the reaction, a small amount of the
(1E, 3Z)-geometric isomer of 1a appeared. After 8
First, we examined the thermal reaction of 1a
(YסH). When a solution of 1a in acetonitrile was
refluxed for 4 days, no reaction occurred, and 1a re-
mained unchanged. However, the addition of I2 (0.5
mol equiv.) was found to initiate the reaction to form
the expected 3a in refluxing acetonitrile and, after 2
TABLE 1 Transformation of 1 into 3
Run
Methoda I2 (equiv.)
Time
Yield (%)
1
2
3
1a
1b
1c
1d
A
A
B
—
0.5
—
4 days
2 days
24 hours
No reaction
89
89
4
5
6
A
B
B
0.5
—
0.5
3 days
41 hours
41 hours
7
Trace
93
7
8
9
A
B
B
0.5
—
1.0
2 days
10 hours
10 hours
0b
33 (45)b
98
10
11
12
A
B
B
0.5
—
1.0
3 days
45 hours
45 hours
86
8 (19)c
44 (96)c
aMethod A: Refluxing a solution of 1 in acetonitrile. Method B: Irra-
diation of 1 in acetonitrile with a 100 W high-pressure Hg lamp.
bThe starting material (1a) was recovered in 99% yield.
SCHEME 1
cThe value in parenthesis is the yield based on the unrecovered 1.

New Construction of p-Tolylsulfonyl-Substituted Naphthalenes by Thermal and Photochemical Cyclization 387
FIGURE 1 The time dependence of the distributions of 3a
(solid line) and (1E, 3Z)-1a (dashed line) in the I2-assisted
thermal reaction of 1a in CD3CN at 95ЊC (bath temperature).
hours, the formation of 3a occurred and then there
was a sharp increase in the amount of 3a.
It is noteworthy that the I2-assisted reaction was
almost inhibited by the addition of aqueous NaHCO3
[8]. This indicates that any acidic component plays
an important role in the initiation of the present re-
action. In fact, p-toluenesulfonic acid was effective
for the present reaction of 1e to give 3e and 3eЈ quan-
titatively in a ratio of 67:33, though a longer reaction
time was necessitated (3 days). From these results,
it is supposed that, during the induction period, an
acidic substance is produced in the reaction of 1
with I2. Hence, one possible mechanism, depicted in
Scheme 3, can be proposed for the I2-assisted for-
mation of 3 from 1: (1) The iodine attacks the D3
double bond of 1 to form a cationic intermediate (A),
which is stabilized by the adjacent methylthio group.
It is likely that olefinic isomerization proceeds via
this intermediate. (2) The intermediate A undergoes
an intramolecular cyclization to form an interme-
diate (B), though the rate is very slow. (3) The sub-
sequent removal of iodine forms a cyclized product
(2), which is easily aromatized to give 3 along with
methanethiol. (4) The methanethiol is easily oxi-
dized with coexisting I2 to form dimethyl disulfide
and HI. (5) The thus-obtained HI (or its complex
with I2) acts as an acid to catalyze the transformation
of 1 into 3. In this process, the methanethiol is gen-
erated and, as a result, HI is formed again to amplify
the reaction rate.
SCHEME 3
the photochemical electrocyclization, we irradiated
various 1-aryl-4-(methylthio)-2-(p-tolylsulfonyl)-1,3-
butadienes 1 having p-F, p-CO2Me, p-MeO, and m-
MeO on the phenyl ring. The para-substituent of the
phenyl ring (runs 5 and 8) made the yield of the cor-
responding 3 lower. When a methoxyl group was
substituted at the meta-position of the phenyl ring,
the reaction took place to form one isomer (3eЈ) pre-
dominantly between two possible products (3e:3eЈ
ס 7:93). This seems to reflect the conservation of
orbital symmetry (the Woodward-Hoffmann rule)
[9]. Again, I2 accelerates the reaction to form the cor-
responding 3 in good yields (runs 6, 9, and 12). In
the photochemical reaction of 1e in the presence of
I2 (2.0 mol equiv. or 0.1 mol equiv.), the product dis-
tribution changed to 3e:3eЈ ס 50:50 or 55:45, re-
spectively (Scheme 2). Since even a small amount of
iodine was effective, this effect does not seem to be
attributable to the oxidative property of iodine. The
UV spectrum of 1e was not changed by the addition
of iodine, but its photoluminescence (PL) spectrum
(Figure 2) exhibited a dramatic effect: the addition
of I2 (1 mol equiv.) quenched the strong PL peak at
In order to investigate the substituent effect on

388 Matsumoto, Takahashi, and Ogura
promote the photochemical reaction. The present
procedures provide a synthetic route leading to the
naphthalenes with an electron-withdrawing sulfonyl
group, which can be utilized in the development of
useful functional materials with a p-electron system.
EXPERIMENTAL
General
Melting points were determined with a Yanaco MP-
J3 instrument, and values were uncorrected. 1H
NMR measurements were performed on JEOL JNM-
GSX 270 (270 MHz) or Varian GEMINI 300 (300
MHz) spectrometers. Chemical shifts (d) of 1H NMR
were expressed in parts per million downfield from
tetramethylsilane as an internal standard (d ס 0).
Multiplicities are indicated as br (broadened), s (sin-
glet), d (doublet), t (triplet), q (quartet), m (multi-
plet), and coupling constants (J) are reported in Hz.
IR spectra were recorded on JASCO A-202 or JASCO
FT/IR-350 spectrometers. Elemental analyses (EA)
were carried out in the Analytical Chemical Center
of Chiba University using a Perkin-Elmer 240B or
2400CHN instrument. Fluorescence spectra were
recorded with JASCO FP-750 spectrophotometer.
Tetrahydrofuran was distilled from sodium benzo-
phenone ketyl immediately prior to use. Acetonitrile
(CH3CN) was freshly distilled over CaH2.
SCHEME 2
Preparation of (1E,3E)-1-(m-Methoxyphenyl)-4-
(methylthio)-2-(p-tolylsulfonyl)-1,3-butadiene
(1e): A Typical Procedure
To a solution of (E)-1-(methylthio)-3-(p-tolylsul-
fonyl)-1-propene (469 mg, 1.9 mmol) in THF (15 mL)
was added n-butyllithium (1.63 M in hexane, 1.31
mL, 2.1 mmol) and 3-methoxybenzaldehyde (0.283
mL, 2.3 mmol) at מ78ЊC, and the resulting mixture
was stirred at the same temperature for 30 minutes
under an atmosphere of N2. Then, acetic anhydride
(0.220 mL, 2.3 mmol) was added at the same tem-
perature, and the resulting mixture was stirred for
30 minutes. The usual workup (quenching with
aqueous NH4Cl, extraction with diethyl ether, and
evaporation) gave yellow crystals (891 mg), which
were subjected to column chromatography on SiO2
(hexane:ethyl acetate ס 2:1) to give yellow crystals
(742 mg). To a solution of the crystals (684 mg) in
THF (20 mL) was added NaH (60% content, 153 mg,
3.8 mmol) at 0ЊC, and the resulting mixture was
stirred at room temperature for 5 days under an at-
mosphere of N2. Quenching with H2O (20 mL), ex-
traction with diethyl ether, and column chromatog-
raphy on SiO2 (hexane:ethyl acetate ס 2:1) gave 1e
(500 mg, 1.4 mmol, 85%) as light yellow crystals:
מ2
FIGURE 2 PL spectrum of 1e (10 M in CH3CN) in the
absence and presence of I2 (excitation at 332 nm).
420 nm. Even in the presence of 0.2 mol equiv. of I2,
the PL peak diminished drastically. Although we do
not have sufficient evidence at the present time, it is
presumed that the heavy atom effect [10] of iodine
works so as to accelerate the intersystem crossing to
a triplet excited state that brings about rate enhance-
ment in the cyclization of 1 and poor regioselectivity
in the formation of 3e and 3eЈ.
In conclusion, 1-aryl-4-(methylthio)-2-(p-tolyl-
sulfonyl)-1,3-butadienes (1) underwent the cycliza-
tion, followed by the removal of the methanethiol
moiety, to give the naphthalene derivatives (3),
which was achieved either by the I2-assisted thermal
reaction or by photolysis. The iodine was shown to

New Construction of p-Tolylsulfonyl-Substituted Naphthalenes by Thermal and Photochemical Cyclization 389
1
m.p. 106.0–107.0ЊC; H NMR (CDCl3, 300 MHz) d
2.24 (s, 3H), 2.42 (s, 3H), 3.81 (s, 3H), 5.95 (d, 1H, J
ס 15.6 Hz), 6.91 (ddd, 1H, J ס 0.9, 2.7, 8.1 Hz), 7.05
(m, 1H), 7.09 (diffused d, 1H, J ס 7.5 Hz), 7.13 (d,
1H, J ס 15.6 Hz), 7.30 (t, 1H, J ס 7.8 Hz), 7.31 (d(br),
2H, J ס 8.3 Hz), 7.66 (s, 1H), 7.76 (diffused d, 2H, J
ס 8.3 Hz); IR (KBr) 3044, 2958, 2345, 1654, 1596,
1297, 1174, 1085, 950, 934, 903, 881, 811, 778, 617
cmמ1; Anal. calcd for C19H20O3S2: C, 63.30; H, 5.59;
Found: C, 63.32; H, 5.53.
(CDCl3, 300 MHz) d 2.25 (s, 3H), 2.42 (s, 3H), 3.83 (s,
3H), 5.91 (d, 1H, J ס 15.7 Hz), 6.91 (dm, 2H, J ס 8.8
Hz), 7.08 (d, 1H, J ס 15.7 Hz), 7.30 (d, 2H, J ס 8.5
Hz), 7.49 (dm, 2H, J ס 8.8 Hz), 7.65 (s, 1H), 7.75
(diffused d, 2H, J ס 8.5 Hz); IR (KBr) 1594, 1573,
1508, 1468, 1300, 1261, 1177, 1147, 1101, 1074,
1019, 932, 846, 825, 742, 661, 594 cmמ1; Anal. calcd
for C19H20O3S2: C, 63.30; H, 5.59; Found: C, 63.27; H,
5.79.
I2-Assisted Reaction of 1a: A Typical Procedure
(1E,3E)-4-(Methylthio)-1-phenyl-2-
To a solution of (1E,3E)-1a (49.2 mg, 0.15 mmol) in
dry CH3CN (15 mL) was added iodine (17.3 mg, 0.07
mmol), and the resulting mixture was refluxed for 2
days. Then, the reaction mixture was poured into
aqueous Na2S2O3 solution and extracted with ethyl
acetate (20 mL ן 3). The extracts were combined,
dried with MgSO4, evaporated, and subjected to col-
umn chromatography on SiO2 (hexane:ethyl acetate
ס 4:1) to give 2-(p-tolylsulfonyl)naphthalene 3a
(37.6 mg: 89% yield) as white powder: m.p. 158.5–
(p-tolylsulfonyl)-1,3-butadiene (1a)
Similarly, this compound was prepared in 96% yield
(two steps): colorless crystals; m.p. 111.0–112.0ЊC;1H
NMR (CDCl3, 300 MHz) d 2.23 (s, 3H), 2.42 (s, 3H),
5.94 (d, 1H, J ס 15.6 Hz), 7.14 (d, 1H, J ס 15.6 Hz),
7.31 (d(br), 2H, J ס 7.8 Hz), 7.34–7.42 (m, 3H), 7.50
(dd, 2H, J ס 2.0, 7.8 Hz), 7.70 (s, 1H), 7.76 (diffused
d, 2H, J ס 8.4 Hz); IR (KBr) 1596, 1556, 1309, 1298,
1146, 1102, 1074, 929, 850, 819, 768, 740, 697, 666,
607 cmמ1; Anal. calcd for C18H18O2S2: C, 65.42; H,
5.49; Found: C, 65.24; H, 5.68.
1
159.5ЊC; H NMR (CDCl3, 270 MHz) d 2.39 (s, 3H),
7.29 (d, 2H, J ס 8.6 Hz), 7.56–7.66 (m, 2H), 7.83 (dd,
1H, J ס 1.6, 8.6 Hz), 7.88 (d, 2H, J ס 8.6 Hz), 7.88
(d, 1H, J ס 8.6 Hz), 7.87–7.99 (m, 2H), 8.58 (d, 1H,
J ס 1.7 Hz); IR (KBr) 3061, 2958, 1595, 1347, 1318,
1152, 1094, 1065, 909, 815, 750 cmמ1; Anal. calcd for
C17H14O2S: C, 72.31; H, 5.00; Found: C, 72.02; H,
5.18.
(1E,3E)-1-(p-Fluorophenyl)-4-(methylthio)-2-
(p-tolylsulfonyl)-1,3-butadiene (1b)
The overall yield was 87%: colorless crystals; m.p.
112.5–113.0ЊC;1H NMR (CDCl3, 300 MHz) d 2.24 (s,
3H), 2.43 (s, 3H), 5.86 (d, 1H, J ס 15.6 Hz), 7.08 (tm,
2H, J ס 8.5 Hz), 7.12 (d, 1H, J ס 15.6 Hz), 7.32 (d,
2H, J ס 8.1 Hz), 7.51 (diffused dd, 2H, J ס 9 Hz,
JH-C2-F ס 5.4 Hz), 7.65 (s, 1H), 7.75 (d, 2H, J ס 8.1
Hz); IR (KBr) 1599, 1504, 1299, 1218, 1149, 1092,
930, 845, 824, 810, 743, 660, 594 cmמ1; Anal. calcd
for C18H17FO2S2: C, 62.04; H, 4.92; Found: C, 62.00;
H, 4.67.
2-Fluoro-6-(p-tolylsulfonyl)naphthalene (3b)
Colorless crystals; m.p. 137.5–138.5ЊC; 1H NMR
(CDCl3, 300 MHz) d 2.39 (s, 3H), 7.30 (dm, 2H, J ס
8.4 Hz), 7.37 (ddd, 1H, J ס 2, 7, 8.8 Hz, JH-C2-F ס 8.8
Hz), 7.47 (dd, 1H, J ס 2.7 Hz, JH-C2-F ס 9.6 Hz), 7.86
(br, 2H), 7.89 (diffused d, 2H, J ס 8.4 Hz), 7.97 (dd,
1H, J ס 8.8 Hz, JH-C3-F ס 5.4 Hz), 8.55 (s, 1H); IR
(1E,3E)-1-(p-Methoxycarbonylphenyl)-4-(meth-
ylthio)-2-(p-tolylsulfonyl)-1,3-butadiene (1c)
(KBr) 1626, 1595, 1506, 1401, 1319, 1305, 1256,
מ1
1153, 1121, 1095, 886, 815, 745, 679, 652, 588 cm
;
Anal. calcd for C17H13FO2S: C, 67.98; H, 4.36; Found:
C, 67.79; H, 4.53.
The overall yield was 90%: light yellow crystals; m.p.
132.5–133.0ЊC; 1H NMR (CDCl3, 270 MHz) d 2.23 (s,
3H), 2.43 (s, 3H), 3.93 (s, 3H), 5.90 (d, 1H, J ס 15.5
Hz), 7.17 (d, 1H, J ס 15.5 Hz), 7.32 (d(br), 2H, J ס
7.9 Hz), 7.54 (d, 2H, J ס 8.6 Hz), 7.67 (s, 1H), 7.75
(diffused d, 2H, J ס 8.6 Hz), 8.04 (d, 2H, J ס 8.6 Hz);
IR (KBr) 1710, 1310, 1280, 1140, 1100, 740, 670, 580
cmמ1; Anal. calcd for C20H20O4S2: C, 61.83; H, 5.19;
Found: C, 61.66; H, 5.05.
2-Methoxycarbonyl-6-(p-tolylsulfonyl)-
naphthalene (3c)
White powder; m.p. 180.1–180.6ЊC; 1H NMR (CDCl3,
300 MHz) d 2.39 (s, 3H), 3.99 (s, 3H), 7.32 (d, 2H, J
ס 8.2 Hz), 7.90 (d, 2H, J ס 8.2 Hz), 7.94 (d, 1H, J ס
8.5 Hz), 8.02 (d, 1H, J ס 8.4 Hz), 8.03 (d, 1H, J ס
8.5 Hz), 8.17 (dd, 1H, J ס 1.6, 8.4 Hz), 8.59 (s(br),
1H), 8.61 (s, 1H); IR (KBr) 1724, 1433, 1315, 1287,
1232, 1184, 1160, 1135, 1097, 750, 710, 693, 658, 576
cmמ1; Anal. calcd for C19H16O4S: C, 67.04; H, 4.74;
Found: C, 66.59; H, 4.69.
(1E,3E)-1-(p-Methoxyphenyl)-4-(methylthio)-2-
(p-tolylsulfonyl)-1,3-butadiene (1d)
Compound 1d was prepared in 90% yield (two
steps): colorless crystals; m.p. 87.0–88.0ЊC; 1H NMR

390 Matsumoto, Takahashi, and Ogura
2-Methoxy-6-(p-tolylsulfonyl)naphthalene (3d)
peaks [1a: 5.96 ppm (d, 1H, J ס 15.6 Hz), (1E,3Z)-
1a: 6.39 ppm (d, 1H, J ס 8.5 Hz), 3a: 8.59 ppm (d,
1H, J ס 1.8 Hz)].
Yellow crystals; m.p. 146.0–147.5ЊC; 1H NMR (CDCl3,
300 MHz) d 2.38 (s, 3H), 3.93 (s, 3H), 7.12 (d, 1H, J
ס 1.3 Hz), 7.24 (dd, 1H, J ס 1.3, 7.6 Hz), 7.28 (d,
2H, J ס 8.2 Hz), 7.79 (d, 1H, J ס 7.6 Hz), 7.84 (d,
1H, J ס 6.6 Hz), 7.85 (d, 1H, J ס 6.6 Hz), 7.86 (dif-
fused d, 2H, J ס 8.5 Hz), 8.46 (s, 1H); IR (KBr) 1620,
1300, 1260, 1140, 1090, 1020, 810, 740, 680, 580, 520
cmמ1; Anal. calcd for C18H16O3S: C, 69.21; H, 5.16;
Found: C, 69.48; H, 5.09.
Photochemical Reaction of 1e: A Typical
Procedure
A solution of 1e (36.1 mg, 0.10 mmol) in dry CH3CN
(10 mL) was bubbled with N2 for 20 minutes and was
irradiated for 10 hours with a 100-W high-pressure
mercury lamp (Shigemi AHH-100S) through a Pyrex
filter under a N2 atmosphere. The reaction mixture
was evaporated and subjected to column chroma-
tography on SiO2 (hexane: ethyl acetate ס 4:1) to
give a 7:93 mixture of 3e and 3eЈ (31.3 mg: 100%).
2-Methoxy-7-(p-tolylsulfonyl)naphthalene (3e)
Colorless crystals; m.p. 139.5–140.0ЊC; 1H NMR
(CDCl3, 300 MHz) d 2.38 (s, 3H), 3.93 (s, 3H), 7.24
(d, 1H, J ס 2.4 Hz), 7.27 (d, 1H, J ס 8.7 Hz), 7.29
(d, 2H, J ס 8.4 Hz), 7.70 (dd, 1H, J ס 1.8, 8.7 Hz),
7.75 (d, 1H, J ס 8.7 Hz), 7.83 (dm, 1H, J ס 8.7 Hz),
7.88 (dm, 2H, J ס 8.4 Hz), 8.44 (d, 1H, J ס 1.8 Hz);
IR (KBr) 1627, 1597, 1508, 1464, 1442, 1390, 1308,
1256, 1222, 1177, 1153, 1092, 1028, 847, 813, 706,
674, 635, 553, 529 cmמ1; Anal. calcd for C18H16O3S:
C, 69.21; H, 5.16; Found: C, 69.06; H, 5.08.
Photochemical Reaction of 1e in the Presence of
Iodine: A Typical Procedure
(1E,3E)-1-(m-Methoxyphenyl)-4-(methylthio)-2-(p-
tolylsulfonyl)-1,3-butadiene (1e, 53.5 mg, 0.15
mmol) and iodine (75.8 mg, 0.30 mmol) in dry
CH3CN (15 mL) was bubbled by N2 for 20 minutes,
and then irradiated for 10 hours. The workup men-
tioned in the I2-assisted thermal reaction of 1a gave
a 50:50 mixture of 3e and 3eЈ (33.1 mg: 72% yield).
1-Methoxy-6-(p-tolylsulfonyl)naphthalene (3eЈ)
Colorless crystals; m.p. 161.8–162.4ЊC; 1H NMR
(CDCl3, 300 MHz) d 2.37 (s, 3H), 3.99 (s, 3H), 6.94
(dd, 1H, J ס 1.8, 6.9 Hz), 7.28 (dm, 2H, J ס 8.2 Hz),
7.49 (t, 1H, J ס 8.7 Hz), 7.53 (dd, 1H, J ס 1.8, 8.7
Hz), 7.82 (dd, 1H, J ס 1.8, 8.9 Hz), 7.87 (diffused d,
2H, J ס 8.2 Hz), 8.33 (d, 1H, J ס 8.9 Hz), 8.49 (d,
1H, J ס 1.8 Hz); IR (KBr) 2937, 1579, 1503, 1467,
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The Follow-Up Experiment Monitored by 1H
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A solution of 1a (5.0 mg, 0.015 mmol) in CD3CN (0.5
˚
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