Synthesis of isothiochromenes and 1,3-dihydrobenzo[c]thiophenes by iodine- and hydrobromic acid-mediated cyclizations of o-[(tert-butylsulfanyl)methyl)]styrenes

Article abstract of DOI:10.3987/COM-17-13803

Methods for the syntheses of 4-substituted isothiochromenes and 1,1-disubstituted 1,3-dihydrobenzo[c]thiophenes have been developed. Thus, treatment of α-substituted o-[(tert-butylsulfanyl)methyl]styrenes, derived from α-substituted o-bromostyrenes using

Full text of DOI:10.3987/COM-17-13803

HETEROCYCLES, Vol. 94, No. 11, 2017
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HETEROCYCLES, Vol. 94, No. 11, 2017, pp. 2065 - 2079. © 2017 The Japan Institute of Heterocyclic Chemistry
Received, 29th August, 2017, Accepted, 27th September, 2017, Published online, 3rd October, 2017
DOI: 10.3987/COM-17-13803
SYNTHESIS
DIHYDROBENZO[c]THIOPHENES BY IODINE- AND HYDROBROMIC
ACID-MEDIATED CYCLIZATIONS OF o-[(tert-
BUTYLSULFANYL)METHYL)]STYRENES
OF
ISOTHIOCHROMENES
AND
1,3-
Kazuhiro Kobayashi,* Takuma Ueyama, and Mai Horiuchi
Applied Chemistry Field, Chemistry and Biotechnology Course, Department of
Engineering, Graduate School of Sustainability Science, Tottori University, 4-101
Koyama-minami, Tottori 680-8552, Japan; E-mail: kkoba@chem.tottori-u.ac.jp
Abstract – Methods for the syntheses of 4-substituted isothiochromenes and
1,1-disubstituted 1,3-dihydrobenzo[c]thiophenes have been developed. Thus,
treatment of -substituted o-[(tert-butylsulfanyl)methyl]styrenes, derived from
-substituted o-bromostyrenes using an easily operated four-step sequence, with
iodine in the presence of sodium hydrogencarbonate gave isothiochromene
derivatives. These tert-butyl sulfides were treated with concentrated hydrobromic
acid to give 1,3-dihydrobenzo[c]thiophene derivatives.
INTRODUCTION
Some compounds with the isothiochromene (1H-2-benzothiopyran) structure have been reported to
exhibit biological activity.1 To date, construction of this skeleton has been commonly performed via the
reaction of isothiochroman-4-one with Grignard reagents followed by dehydration with concentrated
sulfuric acid.2 This method, however, suffers from low yields and limited generality. Therefore, some
different methods have recently been reported.3 On the other hand, previous studies in our laboratory have
revealed that -substituted 2-lithiostyrenes serve, through reactions with a variety of electrophile
followed by cyclizations of the resulting precursors, as versatile intermediates for the preparation of
heterocyclic derivatives.4-8 In the present paper, we wish to describe a convenient synthesis of
4-substituted isothiochromenes (8) by iodine-mediated cyclization of -substituted o-[(tert-
butylsulfanyl)methyl]styrenes (5), derived through formylation of -substituted 2-lithiostyrenes. We also
report that 1,1-disubstituted 1,3-dihydrobenzo[c]thiophenes (13) can be prepared by hydrobromic

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HETEROCYCLES, Vol. 94, No. 11, 2017
acid-mediated cyclization of 5. 1,3-Dihydrobenzo[c]thiophene 2,2-dioxide, prepared by oxidation of
1,3-dihydrobenzo[c]thiophene, has been used as a precursor for the generation of o-quinone dimethides,
which has been utilized as useful intermediates for the preparation of polycyclic compounds.9 The
reaction of o-xylene dihalides with disodium sulfide has been used to prepare 1,3-
dihydrobenzo[c]thiophenes,10 though an efficient method based on the Ga-promoted cycloaddition of
alkynyl enynes have recently been reported11 and we recently have reported a synthesis of
1-aryl-1,3-dihydrobenzo[c]thiophenes by acid mediated cyclization of 1-[aryl(methoxy)methyl-2-
[(tert-butylsulfanyl)methyl]benzenes.12 However, few general methods for the preparation of
1,1-disubstituted 1,3-dihydrobenzo[c]thiophenes have been reported; Nishio reported the formation of
1,1-dimethyl-1,3-dihydrobenzo[c]thiophene by
a
Lawesson’s reagent-mediated cyclization of
1-[(2-hydroxymethyl)phenyl]-1-methylethanol.13
RESULTS AND DISCUSSION
The synthesis of the precursor sulfides (5) was accomplished according to the sequence illustrated in
Scheme 1. Thus, -substituted 2-bromostyrenes 1, which were easily prepared from 2-
bromobenzaldehydes as described previously,3b,4-7 were treated with butyllithium in THF at –78 ˚C and
the resulting -substituted 2-lithiostyrenes were allowed to react with N-formylpiperidine at –78 to 0 ˚C
to afford -substituted 2-vinylbenzaldehydes (2) in generally good yields as compiled in Table 1. Initially,
the bromine/lithium exchange between 1 and butyllithium was carried out in diethyl ether at 0 ˚C as
described previously.4-8 However, after reactions with N-formylpiperidine only low-to-moderate yields of
2 were obtained. The reduction of 2 with sodium borohydride in methanol at 0 ˚C provided -substituted
o-vinylbenzyl alcohols (3) in good to excellent yields. Treatment of these alcohols with thionyl chloride
in dichloromethane at 0 ˚C to rt in the presence of pyridine produced the corresponding -substituted

HETEROCYCLES, Vol. 94, No. 11, 2017
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o-vinylbenzyl chlorides (4), which were used in the next step without purification after aqueous workup.
The resultant crude chlorides were allowed to react with tert-butyl mercaptide, generated from tert-butyl
mercaptan
and
sodium
hydride,
in
DMF
at
0
˚C
to
give
-substituted
o-[(tert-butylsulfanyl)methyl]styrenes (5) in good overall yields from 3.
Table 1. Preparation of the precursor sulfides (5)
Entry
1
R1
H
R2
H
R3
2
Yield/%a
83
3
Yield/%a
82
5
Yield/%a,b
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
1g
1h
1i
Ph
2a
2b
2c
2d
3a
3b
3c
3d
3e
3f
3g
3h
3i
5a
5b
5c
5d
5e
5f
5g
5h
5i
64
69
64
53
89
77
92
93
75
H
H
H
H
H
Cl
MeO
MeO
H
H
H
H
H
H
H
MeO
4-MeC6H4
4-ClC6H4
4-MeOC6H4
80
85
87
87
94
89
79
93
90
88
98
93
88
88
96
95
naphthalen-1-yl 2e
Me
Ph
Ph
Ph
2f
2g
2h
2i
a Yields of isolated products. b Overall yields from 3.
We hoped that these tert-butyl sulfides (5) would produce 4-substituted isothiochromenes (8) on
treatment with iodine. In practice, it was found that compounds (5) reacted with three equivalents of
iodine in acetonitrile at 0 ˚C in the presence of three equivalents of sodium hydrogencarbonate to result in
the isolation of the corresponding desired products (8) as the sole products, as depicted in Scheme 2. The
1
synthetic material (8a) gave IR and H NMR data, which were identical to those reported for
4-phenylisothiochromene.2 As shown in Table 2, the yields of the products (8) are generally moderate to
good, though the yield of 4-methylisothiochromene (8f) was only low. Yields of the products (8)
decreased somewhat if two equivalent each of iodine and sodium hydrogencarbonate were used. In
Scheme 2, the pathway to these products from 5 is also shown. Thus, the iodonium ion intermediate (6) is

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HETEROCYCLES, Vol. 94, No. 11, 2017
formed on treatment with iodine. The 6-endo cyclization by the attack of one of the lone pairs of the
sulfur atom on the -position of the styryl moiety of 6 occurs exclusively to produce the benzopyranium
ion intermediate (7). The subsequent eliminations of hydrogen iodide and tert-butyl iodide give rise to 8.
1-(Iodomethyl)-1,3-dihydrobenzo[c]thiophenes (10), which might be produced via the
dihydrobenzo[c]thiophenium ion intermediate (9), generated by the attack of the sulfur atom lone pair on
the benzylic carbon of the iodonium ion intermediate (6) were not detected at all. Unfavorableness of this
pathway may be ascribed to the steric crowd at the reaction center.
Table 2. Preparation of isothiochromenes (8) and 1,3-dihydrobenzo[c]thiophenes (13)
Entry
5
R1
H
H
H
H
H
H
Cl
R2
H
R3
8
Yield/%a
67
13
Temp Yield/%a
1
2
3
4
5
6
7
8
9
5a
5b
5c
5d
5e
5f
Ph
4-MeC6H4
4-ClC6H4
4-MeOC6H4
naphthalen-1-yl
Me
8a
8b
8c
8d
8e
8f
8g
8h
8i
13a
13b
13c
13d
13e
13f
13g
13h
13i
rt
rt
78
83
52
67
83
86
63
76
88
H
H
H
H
H
H
H
MeO
81
63
82
35
17
50
63
53
rt
0 ˚C
rt
rt
rt
rt
5g
Ph
Ph
Ph
5h MeO
5i MeO
0 ˚C
a Yields of isolated products.
We also found that when tert-butyl sulfides (5) were treated with concentrated hydrobromic acid in
acetonitrile at 0 ˚C or rt, 1,1-disubstituted 1,3-dihydrobenzo[c]thiophenes (13) were obtained, as
illustrated in Scheme 3. As compiled in Table 2 as well, the yields of the products were generally good,
while those of the products carrying an electron-withdrawing chloro substituent on each of the benzene
rings were only moderate (Entries 3 and 7). The precursors (5) carrying a methoxy group at 4-position on
each of the benzene rings (5d) and (5i) found to be more reactive than the others; therefore, the reaction
of these precursors with hydrobromic acid can be conducted at 0 ˚C. Scheme 3 also shows the pathway to
the products (13). The Markovnikov addition of a proton to the vinyl moiety of 5 generates the benzyl
cation intermediate (11), which intramolecularly cyclizes by the attack of the sulfur lone pair on the
cation center to produce the dihydrobenzo[c]thiophenium ion intermediate (12). A loss of tert-butyl
bromide from this intermediate affords 13. The use of catalytic amounts of the acid resulted in recovery
of considerable amounts of the starting materials.

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In summary, the results reported above demonstrate that 4-substituted isothiochromene and
1,1-disubstituted 1,3-dihydrobenzo[c]thiophene derivatives, which are hard to prepare by previous
methods, can be tunably prepared from readily available starting materials. Work on further applications
utilizing o-functionalized (tert-butylsulfanyl)alkylbenzenes for the preparation of related heterocycles is
now in progress in our laboratory. Results of those efforts will be described in due course.
EXPERIMENTAL
All melting points were obtained on a Laboratory Devices MEL-TEMP II melting apparatus and are
1
uncorrected. IR spectra were recorded with a Perkin–Elmer Spectrum 65 FTIR spectrophotometer. H
13
NMR and C NMR spectra were recorded in CDCl3 using TMS as an internal reference with a JEOL
ECP500 FT NMR spectrometer operating at 500 and 125 MHz, respectively. High-resolution MS spectra
were measured by a JEOL JMS-T100GCV (EI or FI, TOF; 70 eV or 2100 V, respectively) or a Thermo
Scientific Exactive (ESI, positive) spectrometer. Elemental analyses were performed with an Elementar
Vario EL II instrument. TLC was carried out on Merck Kieselgel 60 PF254. Column chromatography was
performed using WAKO GEL C-200E. All of the organic solvents used in this study were dried over
appropriate drying agents and distilled prior to use.
Starting Materials. (2-Bromo-5-chlorophenyl)(phenyl)methanone,14 (2-bromophenyl)(naphthalen-1-
yl)methanone,15 2-(1-arylethenyl)-1-bromobenzenes 1a,4 1b,5 1c,3b 1d,6 1f,4 1h,5 and 1i7 were prepared
according to the previously reported method. Butyllithium was supplied by Asia Lithium Corporation. All
other chemicals used in this study were commercially available.
1-[1-(2-Bromophenyl)ethenyl]naphthalene (1e). This compound was prepared in 94% yield from
(2-bromophenyl)(naphthalen-1-yl)methanone as described for the preparation of 1a.4 A pale-yellow oil; Rf
0.64 (CH2Cl2/hexane 1:10); IR (neat) 1612 cm–1; 1H NMR  5.73 (d, J = 1.1 Hz, 1H), 5.82 (d, J = 1.1 Hz,
1H), 7.13 (td, J = 6.9, 1.7 Hz, 1H), 7.24–7.34 (m, 3H), 7.36–7.50 (m, 3H), 7.58 (d, J = 8.0 Hz, 1H), 7.78
13
(d, J = 8.0 Hz, 1H), 7.84 (dd, J = 9.2, 2.9 Hz, 1H), 8.23 (dd, J = 9.2, 2.3 Hz, 1H), C NMR  122.09,
122.53, 125.06, 125.61, 125.96, 126.18, 126.70, 127.21, 127.97, 128.34, 128.75, 131.29, 131.41, 133.51,
134.00, 139.38, 143.43, 147.12. HR-MS (EI). Calcd for C18H13Br (M): 308.0201. Found: m/z 308.0190.
1-Bromo-4-chloro-2-(1-phenylethenyl)benzene (1g). This compound was prepared in 68% yield from
(2-bromo-5-chlorophenyl)(phenyl)methanone as described for the preparation of 1a.4 A colorless oil; Rf

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HETEROCYCLES, Vol. 94, No. 11, 2017
0.64 (CH2Cl2/hexane 1:10); IR (neat) 1616 cm–1; 1H NMR  5.27 (s, 1H), 5.85 (s, 1H), 7.19 (dd, J = 7.4,
13
1.1 Hz, 1H), 7.25–7.33 (m, 6H), 7.51 (d, J = 8.6 Hz, 1H); C NMR  116.67, 121.26, 126.48, 127.98,
128.43, 129.04, 131.34, 133.27, 134.02, 138.86, 144.19, 147.91. Anal. Calcd for C14H10BrCl: C, 57.28; H,
3.43. Found: C, 57.39; H, 3.68.
Typical Procedure for the Preparation of 2-(1-Arylethenyl)benzaldehydes (2). 2-(1-
Phenylethenyl)benzaldehyde (2a). To a stirred solution of 1a (1.2 g, 4.6 mmol) in THF (10 mL) at –78
˚C was added n-BuLi (1.6 M in hexane; 4.6 mmol) dropwise. After 15 min, 1-formylpiperidine (0.57 g,
5.1 mmol) was added and the temperature was gradually raised to 0 ˚C. Saturated aqueous NH4Cl (20
mL) was added and the mixture was extracted with AcOEt (3  15 mL). The combined extracts were
washed with brine (20 mL), dried (Na2SO4), and concentrated by evaporation. The residue was purified
by column chromatography on SiO2 (Et2O/hexane 1:10) to give 2a (0.79 g, 83%); a pale-yellow oil; Rf
0.45. The spectral data (IR and 1H NMR) were identical to those reported previously.16
2-[1-(4-Methylphenyl)ethenyl]benzaldehyde (2b): a pale-yellow oil; Rf 0.41 (AcOEt/hexane 1:25); IR
(neat) 2848, 2752, 1696 cm–1; 1H NMR  2.34 (s, 3H), 5.22 (s, 1H), 5.94 (s, 1H), 7.12 (d, J = 8.6 Hz, 2H),
7.17 (d, J = 8.6 Hz, 2H), 7.35 (d, J = 7.4 Hz, 1H), 7.47 (td, J = 7.4, 1.1 Hz, 1H), 7.58 (td, J = 7.4, 1.1 Hz,
13
1H), 7.98 (dd, J = 7.4, 1.1 Hz, 1H); 10.04 (s, 1H); C NMR  21.10, 117.03, 126.77, 127.35, 128.00,
129.31, 130.85, 133.62, 134.45, 138.00, 138.23, 145.57, 145.80, 192.10. HR-MS (EI). Calcd for C16H14O
(M): 222.1045. Found: m/z 222.1040.
2-[1-(4-Chlorophenyl)ethenyl]benzaldehyde (2c): a colorless oil; Rf 0.47 (AcOEt/hexane 1:25); IR
(neat) 2846, 2753, 1697 cm–1; 1H NMR  5.30 (s, 1H), 5.96 (s, 1H), 7.21 (d, J = 8.6 Hz, 2H), 7.29 (d, J =
8.6 Hz, 2H), 7.32 (d, J = 7.4 Hz, 1H), 7.50 (t, J = 7.4 Hz, 1H), 7.61 (t, J = 7.4 Hz, 1H), 7.99 (d, J = 7.4 Hz,
13
1H), 10.02 (s, 1H); C NMR  118.27, 127.85, 128.13, 128.34, 129.79, 130.84, 133.81, 134.23, 134.33,
139.18, 144.78, 144.85, 191.70. HR-MS (EI). Calcd for C15H11ClO (M): 242.0498. Found: m/z 242.0504.
2-[1-(4-Methoxyphenyl)ethenyl]benzaldehyde (2d): a colorless oil; Rf 0.26 (AcOEt/hexane 1:25). The
spectral data (IR and 1H NMR) were identical to those reported previously.17
2-[1-(Naphthalen-1-yl)ethenyl]benzaldehyde (2e): a pale-yellow solid; mp 55–58 ˚C (hexane/CH2Cl2);
1
IR (neat) 2843, 2751, 1690, 1657 cm–1; H NMR  5.60 (s, 1H), 5.89 (s, 1H), 7.23 (d, J = 6.9 Hz, 1H),
7.31 (d, J = 6.9 Hz, 1H), 7.38–7.46 (m, 5H), 7.81 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 7.97–8.00
(m, 2H), 10.40 (s, 1H); 13C NMR  124.46, 125.23, 125.46, 125.89, 126.47, 127.62, 127.90, 128.04,
128.59, 128.61, 130.07, 131.09, 133.42, 134.09, 134.27, 139.45, 144.51, 146.52, 191.98. HR-MS (EI).
Calcd for C19H14O (M): 258.1045. Found: m/z 258.1042.
2-(1-Methylethenyl)benzaldehyde (2f):18 a colorless liquid; Rf 0.44 (CH2Cl2/hexane 1:2). The 1H NMR
data for this compound was identical to those reported previously.19

HETEROCYCLES, Vol. 94, No. 11, 2017
2071
4-Chloro-2-(1-phenylethenyl)benzaldehyde (2g): a pale-yellow oil; Rf 0.29 (AcOEt/hexane 1:25); IR
(neat) 2848, 2754, 1693, 1614 cm–1; 1H NMR  5.31 (s, 1H), 6.00 (s, 1H), 7.26 (dd, J = 8.6, 1.7 Hz, 2H),
13
7.32–7.35 (m, 4H), 7.46 (d, J = 8.0 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H), 9.97 (s, 1H); C NMR  118.56,
126.79, 128.55, 128.76, 129.00, 130.76 (2 overlapped Cs), 132.77 (2 overlapped Cs), 140.05, 144.65,
146.96, 190.70. Anal. Calcd for C15H11ClO: C, 74.23; H, 4.57. Found: C, 74.17; H, 4.75.
4-Methoxy-2-(1-phenylethenyl)benzaldehyde (2h): a colorless liquid; Rf 0.26 (AcOEt/hexane 1:15); IR
(neat) 2841, 2759, 1684 cm–1; 1H NMR  3.87 (s, 3H), 5.30 (s, 1H), 5.96 (s, 1H), 6.81 (d, J = 2.9 Hz, 1H),
13
6.99 (dd, J = 8.6, 2.9 Hz, 1H), 7.27–7.33 (m, 5H), 7.98 (d, J = 8.6 Hz, 1H), 9.90 (s, 1H); C NMR 
55.58, 114.05, 115.46, 117.42, 126.70, 127.91, 128.24, 128.60, 129.87, 140.44, 145.75, 147.99, 163.81,
190.67. HR-MS (EI). Calcd for C16H14O2 (M): 238.0994. Found: m/z 238.0990.
4,5-Dimethoxy-2-(1-phenylethenyl)benzaldehyde (2i): a pale-yellow oil; Rf 0.23 (AcOEt/hexane 1:8);
IR (neat) 2851, 1769, 1679 cm–1; 1H NMR  3.91 (s, 3H), 3.97 (s, 3H), 5.27 (s, 1H), 5.98 (s, 1H), 6.74 (s,
13
1H), 7.31 (s, 5H), 7.51 (s, 1H), 9.92 (s, 1H); C NMR  56.05, 56.18, 108.46, 112.50, 117.89, 126.85,
127.86, 128.26, 128.59, 140.73, 140.88, 145.10, 148.90, 153.55, 190.78. HR-MS (EI). Calcd for C17H16O3
(M): 268.1099. Found: m/z 268.1099.
Typical Procedure for the Preparation of 2-(1-Arylethenyl)benzyl Alcohols (3). [2-(1-
Phenylethenyl)phenyl]methanol (3a). To a stirring solution of 2a (0.66 g, 3.2 mmol) in MeOH (6 mL)
at 0 ˚C was added NaBH4 (0.12 g, 3.2 mmol) in several portions. After 5 min, 1% aqueous HCl (v/v) (20
mL) was added and the organic solvent was removed by evaporation. The mixture was extracted with
AcOEt (3  15 mL), and the combined extracts were washed with brine (20 mL), dried (Na2SO4) and
concentrated by evaporation. The residue was purified by column chromatography on SiO2 (Et2O/hexane
1
1:1) to give 3a (0.55 g, 82%); a pale-yellow oil; Rf 0.35. The spectral data (IR and H NMR) were
identical to those reported previously.20
{2-[1-(4-Methylphenyl)ethenyl]phenyl}methanol (3b): a colorless oil; Rf 0.28 (AcOEt/hexane 1:5); IR
(neat) 3351, 1610 cm–1; 1H NMR  1.59 (br s, 1H), 2.33 (s, 3H), 4.43 (s, 2H), 5.19 (s, 1H), 5.75 (s, 1H),
7.10 (d, J = 8.0 Hz, 2H), 7.16 (d, J = 8.0 Hz, 2H), 7.25 (d, J = 7.4 Hz, 1H), 7.32 (t, J = 7.4 Hz, 1H), 7.37
13
(t, J = 7.4 Hz, 1H), 7.48 (d, J = 7.4 Hz, 1H); C NMR  21.11, 63.23, 114.68, 126.42, 127.55, 127.94,
128.11, 129.21, 130.16, 137.80, 137.90, 138.65, 140.71, 148.13. HR-MS (EI). Calcd for C16H16O (M):
224.1201. Found: m/z 224.1195.
{2-[1-(4-Chlorophenyl)ethenyl]phenyl}methanol (3c): a colorless oil; Rf 0.24 (AcOEt/hexane 1:5); IR
(neat) 3334, 1615 cm–1; 1H NMR  1.54 (br s, 1H), 4.43 (s, 2H), 5.26 (s, 1H), 5.78 (s, 1H), 7.19–7.23 (m,
3H), 7.26 (d, J = 8.6 Hz, 2H), 7.33 (t, J = 7.4 Hz, 1H), 7.39 (t, J = 7.4 Hz, 1H), 7.50 (d, J = 7.4 Hz, 1H);

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13C NMR  63.05, 116.03, 127.66, 127.81, 127.98, 128.20, 128.63, 130.13, 133.82, 138.56, 138.97,
139.86, 147.12. HR-MS (EI). Calcd for C15H13ClO (M): 244.0655. Found: m/z 244.0662.
{2-[1-(4-Methoxyphenyl)ethenyl]phenyl}methanol (3d): a colorless oil; Rf 0.24 (AcOEt/hexane 1:5);
IR (neat) 3887, 1606 cm–1; 1H NMR  1.56 (br, 1H), 3.79 (s, 3H), 4.44 (s, 2H), 5.14 (s, 1H), 5.70 (s, 1H),
6.82 (d, J = 8.6 Hz, 2H), 7.20 (d, J = 8.6 Hz, 2H), 7.24 (d, J = 7.4 Hz, 1H), 7.32 (d, J = 7.4 Hz, 1H), 7.37
13
(t, J = 7.4 Hz, 1H), 7.48 (d, J = 7.4 Hz, 1H); C NMR  55.25, 63.21, 113.67, 113.82, 127.55, 127.72,
127.93, 128.05, 130.10, 133.14, 138.61, 140.74, 147.60, 159.43. HR-MS (EI). Calcd for C16H16O2 (M):
240.1150. Found: m/z 240.1158.
{2-[1-(Naphthalen-1-yl)ethenyl]phenyl}methanol (3e): a colorless oil; Rf 0.51 (AcOEt/hexane 1:7); IR
1
(neat) 3363 cm–1; H NMR  1.37 (br s, 1H), 4.46 (s, 2H), 5.67 (d, J = 1.7 Hz, 1H), 5.74 (d, J = 1.7 Hz,
1H), 7.28–7.46 (m, 8H), 7.79 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 8.14 (d, J = 8.6 Hz, 1H); 13C
NMR  63.26, 121.10, 125.19, 125.61, 125.78, 126.22, 126.82, 127.72, 127.95, 128.16, 128.52, 128.55,
130.07, 131.02, 134.05, 138.19, 140.01, 141.89, 147.33. HR-MS (EI). Calcd for C19H16O (M): 260.1201.
Found: m/z 260.1189.
1
[2-(1-Methylethenyl)phenyl]methanol (3f):21 a colorless liquid; Rf 0.57 (AcOEt/hexane 1:2). The H
NMR data for this compound was identical to those reported previously.22
[4-Chloro-2-(1-phenylethenyl)phenyl]methanol (3g): a colorless oil; Rf 0.32 (AcOEt/hexane 1:5); IR
(neat) 3335, 1615 cm–1; 1H NMR 1.52 (br s, 1H), 4.38 (d, J = 5.7 Hz, 2H), 5.26 (d, J = 1.1 Hz, 1H), 5.80
(d, J = 1.1 Hz, 1H), 7.24–7.33 (m, 6H), 7.35 (dd, J = 8.6, 2.3 Hz, 1H), 7.44 (d, J = 8.6 Hz, 1H); 13C NMR
 62.43, 116.22, 126.46, 128.02, 128.23, 128.62, 129.35, 129.91, 133.15, 137.21, 139.87, 141.97, 147.14.
HR-MS (EI). Calcd for C15H13ClO (M): 244.0655. Found: m/z 244.0659.
[4-Methoxy-2-(1-phenylethenyl)phenyl]methanol (3h): a colorless oil; Rf 0.62 (AcOEt/hexane 2:3); IR
1
(neat) 3378, 1606 cm–1; H NMR  1.37 (br s, 1H), 3.82 (s, 3H), 4.36 (s, 2H), 5.27 (d, J = 1.1 Hz, 1H),
5.79 (d, J = 1.1 Hz, 1H), 6.81 (d, J = 2.9 Hz, 1H), 6.91 (dd, J = 8.6, 2.9 Hz, 1H), 7.26–7.29 (m, 5H), 7.38
13
(d, J = 8.6 Hz, 1H); C NMR  55.30, 62.82, 113.23, 115.52, 115.74, 126.52, 128.02, 128.52, 129.99,
131.05, 140.47, 142.09, 148.24, 158.96. HR-MS (EI). Calcd for C16H16O2 (M): 240.1150. Found: m/z
240.1147.
[4,5-Dimethoxy-2-(1-phenylethenyl)phenyl]methanol (3i):
a
white solid; mp 64–66 ˚C
(hexane/CH2Cl2); IR (neat) 3491, 1606 cm–1; 1H NMR  1.41 (br s, 1H), 3.86 (s, 3H), 3.93 (s, 3H), 4.38 (s,
13
2H), 5.24 (s, 1H), 5.78 (s, 1H), 6.75 (s, 1H), 7.03 (s, 1H), 7.28–7.30 (m, 5H); C NMR  55.93, 56.02,
62.99, 111.53, 113.29, 115.48, 126.56, 127.97, 128.50, 131.13, 133.04, 140.92, 148.02, 148.11, 148.62.
HR-MS (EI). Calcd for C17H18O3 (M): 270.1256. Found: m/z 270.1261.

HETEROCYCLES, Vol. 94, No. 11, 2017
2073
Typical
Procedure
for
the
Preparation
of
tert-Butyl
Sulfides
(5).
1-{[(1,1-
Dimethylethyl)sulfanyl]methyl}-2-(1-phenylethenyl)benzene (5a). To a stirred solution of 3a (0.55 g,
2.6 mmol) in CH2Cl2 (8 mL) containing pyridine (0.21 g, 2.6 mmol) at 0 ˚C was added SOCl2 (0.31 g, 2.6
mmol) dropwise and temperature was raised to rt. After 4 h, the mixture was diluted by adding CH2Cl2
(20 mL) and treated with H2O (20 mL). The layers were separated and the aqueous layer was extracted
with CH2Cl2 (2  15 mL). The combined organic layers were washed with brine (15 mL), dried (Na2SO4)
and concentrated by evaporation. The crude product 4a (0.46 g) was used in the next reaction without
purification. Thus, to a stirred suspension of NaH (60% in mineral oil; 88 mg, 2.2 mmol) in DMF (3 mL)
at 0 ˚C was added t-BuSH (0.20 g, 2.2 mmol) dropwise. After evolution of H2 gas had ceased, a DMF (2
mL) solution of the above 4a was added. After 5 min, saturated aqueous NH4Cl (20 mL) was added and
the mixture was extracted with AcOEt (3  15 mL). The combined extracts were washed with brine (20
mL), dried (Na2SO4), and concentrated by evaporation. The residue was purified by column
chromatography on SiO2 (CH2Cl2/hexane 1:3) to give 5a (0.47 g, 64%); a white solid; mp 80–81 ˚C
(hexane); IR (KBr) 1615 cm–1; 1H NMR
 1.21 (s, 9H), 3.55 (s, 2H), 5.33 (s, 1H), 5.82 (d, J = 1.4 Hz, 1H),
7.18 (d, J = 7.8 Hz, 1H), 7.22 (dd, J = 7.8, 7.3 Hz, 1H), 7.25–7.31 (m, 6H), 7.47 (d, J = 7.8 Hz, 1H); 13C
NMR  30.64, 30.68, 42.75, 115.78, 126.61, 126.71, 127.69, 127.74, 128.32, 130.07, 130.36, 136.14,
140.74, 141.32, 148.04. HR-MS (EI). Calcd for C19H22S (M): 282.1442. Found: m/z 282.1453.
1-{[(1,1-Dimethylethyl)sulfanyl]methyl}-2-[1-(4-methylphenyl)ethenyl]benzene (5b): a yellow oil; Rf
0.21 (AcOEt/hexane 1:100); IR (neat) 1610 cm–1; 1H NMR  1.21 (s, 9H), 2.33 (s, 3H), 3.56 (s, 2H), 5.26
(s, 1H), 5.78 (s, 1H), 7.09 (d, J = 8.0 Hz, 1H), 7.14–7.19 (m, 4H), 7.22 (t, J = 7.4 Hz, 1H), 7.28 (t, J = 7.4
13
Hz, 1H), 7.46 (d, J = 8.0 Hz, 1H); C NMR  21.11, 30.69 (2 overlapped Cs), 42.75, 114.84, 126.51,
126.66, 127.64, 129.01, 130.03, 130.31, 136.22, 137.50, 137.98, 141.55, 147.85. HR-MS (FI). Calcd for
C20H24S (M): 296.1599. Found: m/z 296.1603.
1-[1-(4-Chlorophenyl)ethenyl]-2-{[(1,1-dimethylethyl)sulfanyl]methyl}benzene (5c): a colorless oil;
1
Rf 0.20 (AcOEt/hexane 1:100); IR (neat) 1615 cm–1; H NMR  1.22 (s, 9H), 3.53 (s, 2H), 5.33 (s, 1H),
5.80 (s, 1H), 7.15 (d, J = 7.4 Hz, 1H), 7.21–7.32 (m, 6H), 7.46 (d, J = 7.4 Hz, 1H); 13C NMR  33.63,
33.67, 116.19, 126.86, 127.94, 127.96, 128.46, 130.26, 130.31, 133.54, 135.54, 136.08, 139.23, 140.84,
146.98. HR-MS (FI). Calcd for C19H21ClS (M): 316.1052. Found: m/z 316.1068.
1-{[(1,1-Dimethylethyl)sulfanyl]methyl}-2-[1-(4-methoxyphenyl)ethenyl]benzene (5d): a pale-yellow
oil; Rf 0.30 (CH2Cl2/hexane 1:4); IR (neat) 1607 cm–1; 1H NMR  1.14 (s, 9H), 3.49 (s, 2H), 3.72 (s, 3H),
5.13 (s, 1H), 5.65 (s, 1H), 6.74 (d, J = 8.6 Hz, 2H), 7.09 (d, J = 7.4 Hz, 1H), 7.14–7.20 (m, 3H), 7.21 (t, J
13
= 7.4 Hz, 1H), 7.39 (d, J = 7.4 Hz, 1H); C NMR  30.62, 30.68, 42.75, 55.27, 113.66, 113.86, 126.67,

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HETEROCYCLES, Vol. 94, No. 11, 2017
127.65, 127.81, 130.03, 130.27, 133.44, 136.19, 141.58, 147.39, 159.28. HR-MS (FI). Calcd for
C20H24OS (M): 312.1548. Found: m/z 312.1548.
1-[(2-{[(1,1-Dimethylethyl)sulfanyl]methyl}phenyl)ethenyl]naphthalene (5e): a pale-yellow oil; Rf
0.46 (CH2Cl2/hexane 1:3); IR (neat) 1607 cm–1; 1H NMR
 1.17 (s, 9H), 3.67 (s, 2H), 5.69 (s, 1H), 5.87 (d,
J = 1.1 Hz, 1H), 7.17 (t, J = 7.4 Hz, 1H), 7.25 (t, J = 7.4 Hz, 1H), 7.35 (d, J = 6.9 Hz, 1H), 7.38–7.46 (m,
5H), 7.77 (d, J = 8.0 Hz, 1H), 7.84 (d, J = 8.0 Hz, 1H), 8.22 (d, J = 8.6 Hz, 1H); 13C NMR  30.63, 30.91,
42.78, 121.06, 125.21, 125.60, 125.97, 126.00, 126.81, 126.95, 127.64, 127.87, 128.38, 130.12, 130.79,
131.21, 134.08, 135.34, 140.25, 142.72, 147.16. HR-MS (FI). Calcd for C23H24S (M): 332.1599. Found:
m/z 333.1593.
1-{[(1,1-Dimethylethyl)sulfanyl]methyl}-2-(1-methylethenyl)benzene (5f): a colorless liquid; Rf 0.44
(CH2Cl2/hexane 1:5); IR (neat) 1639 cm–1; 1H NMR  1.35 (s, 9H), 2.11 (s, 3H), 3.79 (s, 2H), 4.98 (d, J =
1.1 Hz, 1H), 5.23 (q, J = 1.7 Hz, 1H), 7.11 (dd, J = 7.4, 1.1 Hz, 1H), 7.17–7.20 (m, 2H), 7.39 (dd, J = 7.4,
1.1 Hz, 1H); 13C NMR  25.24, 30.49, 30.73, 42.89, 115.09, 126.60, 126.97, 128.05, 130.26, 134.46,
143.75, 144.75. HR-MS (ESI). Calcd for C14H20S (M+H): 221.1364. Found: m/z 221.1360.
1-Chloro-4-{[(1,1-dimethylethyl)sulfanyl]methyl}-3-(1-phenylethenyl)benzene (5g): a pale-yellow oil;
Rf 0.53 (CH2Cl2/hexane 1:4); IR (neat) 1615 cm–1; 1H NMR  1.19 (s, 9H), 3.49 (s, 2H), 5.33 (s, 1H), 5.83
13
(s, 1H), 7.19 (d, J = 1.7 Hz, 1H), 7.26–7.30 (m, 6H), 7.41 (d, J = 8.6 Hz, 1H); C NMR  30.12, 30.63,
42.92, 116.40, 126.55, 127.82, 127.97, 128.46, 130.07, 131.45, 132.30, 134.94, 140.03, 142.93, 147.02.
HR-MS (FI). Calcd for C19H21ClS (M): 316.1052. Found: m/z 316.1061.
1-{[(1,1-Dimethylethyl)sulfanyl]methyl}-4-methoxy-2-(1-phenylethenyl)benzene (5h): a pale-yellow
oil; Rf 0.54 (AcOEt/hexane 1:10); IR (neat) 1604 cm–1; 1H NMR  1.20 (s, 9H), 3.49 (s, 2H), 3.78 (s, 3H),
5.33 (s, 1H), 5.81 (s, 1H), 6.73 (d, J = 2.3 Hz, 1H), 6.85 (dd, J = 8.6, 2.3 Hz, 1H), 7.25–7.31 (m, 5H),
7.37 (d, J = 8.6 Hz, 1H); 13C NMR  30.07, 30.67, 42.61, 55.27, 113.39, 115.59, 115.67, 126.60, 127.72,
128.14, 128.32, 131.18, 140.50, 142.49, 148.00, 158.20. HR-MS (FI). Calcd for C20H24OS (M): 312.1548.
Found: m/z 312.1545.
1-{[(1,1-Dimethylethyl)sulfanyl]methyl}-4,5-dimethoxy-2-(1-phenylethenyl)benzene (5i): a colorless
oil; Rf 0.59 (AcOEt/hexane 1:4); IR (neat) 1604 cm–1; 1H NMR  1.21 (s, 9H), 3.53 (s, 2H), 3.82 (s, 3H),
3.92 (s, 3H), 5.33 (s, 1H), 5.80 (s, 1H), 6.67 (s, 1H), 6.99 (s, 1H), 7.26–7.31 (m, 5H); 13C NMR  30.60,
30.69, 42.70, 55.91, 55.94, 112.76, 113.30, 115.61, 126.67, 127.70, 128.25, 128.31, 133.59, 140.87,
147.52, 147.86, 148.38. HR-MS (FI). Calcd for C21H26O2S (M): 342.1654. Found: m/z 342.1667.
Typical Procedure for the Preparation of 1H-2-Benzothiopyrans (8). 4-Phenyl-1H-2-
benzothiopyran (8a).2 To a stirred solution of 5a (0.24 g, 0.85 mmol) in MeCN (5 mL) containing
NaHCO3 (0.21 g, 2.6 mmol) at 0 ˚C was added I2 (0.65 g, 2.6 mmol) in portions. The temperature was

HETEROCYCLES, Vol. 94, No. 11, 2017
2075
raised to rt, and the mixture was stirred for 15 min before 10% aqueous Na2S2O3 (15 mL) was added.
After evaporation of MeCN, the organic materials were extracted with AcOEt (3  15 mL), and the
combined extracts were washed with saturated aqueous NaHCO3 and brine (20 mL each), and dried over
anhydrous K2CO3. Evaporation of the solvent gave a residue, which was purified by column
chromatography on SiO2 to afford 8a (0.12 g, 67%); a pale-yellow oil; Rf 0.45 (CH2Cl2/hexane 1:4). The
spectral data (IR and 1H NMR) were identical to those reported previously.2
4-(4-Methylphenyl)-1H-2-benzothiopyran (8b): a white solid; mp 94–96 ˚C (hexane/CH2Cl2); IR (KBr)
1
1595, 1509, 1485 cm–1; H NMR  2.38 (s, 3H), 3.85 (s, 2H), 6.51 (s, 1H), 7.01 (d, J = 7.4 Hz, 1H),
7.14–7.25 (m, 7H); 13C NMR  21.16, 31.19, 120.69, 126.29, 126.70, 127.27, 128.19, 128.52, 129.15,
129.60, 134.41, 137.06, 137.50, 138.79. HR-MS (EI). Calcd for C16H14S (M): 238.0816. Found: m/z
238.0814. Anal. Calcd for C16H14S: C, 80.63; H, 5.92; S, 13.45. Found: C, 80.41; H, 5.91; S, 13.16.
4-(4-Chlorophenyl)-1H-2-benzothiopyran (8c): a white solid; mp 166–168 ˚C (hexane/CH2Cl2); IR
(KBr) 1535, 1487 cm–1; 1H NMR  3.86 (s, 2H), 6.54 (s, 1H), 6.96 (d, J = 8.0 Hz, 1H), 7.16–7.20 (m, 2H),
13
7.25–7.29 (m, 3H), 7.35 (d, J = 8.6 Hz, 2H); C NMR  31.12, 121.92, 126.03, 126.87, 127.43, 128.49,
128.68, 129.47, 129.94, 133.17, 133.93, 137.66, 138.81. HR-MS (EI). Calcd for C15H11ClS (M): 258.0270.
Found: m/z 258.0259.
4-(4-Methoxyphenyl)-1H-2-benzothiopyran (8d): a white solid; mp 80–83 ˚C (hexane/CH2Cl2); IR
(KBr) 1608, 1543, 1505 cm–1; 1H NMR  3.84 (s, 3H), 3.85 (s, 2H), 6.49 (s, 1H), 6.92 (d, J = 8.6 Hz, 2H),
7.02 (d, J = 7.4 Hz, 1H), 7.16 (t, J = 7.4 Hz, 1H), 7.19 (d, J = 7.4 Hz, 1H), 7.25 (t, J = 7.4 Hz, 1H), 7.28
13
(d, J = 8.6 Hz, 2H); C NMR  31.16, 55.29, 113.81, 120.22, 126.27, 126.70, 127.27, 128.20, 129.63,
129.73, 132.86, 134.43, 138.46, 158.92. HR-MS (EI). Calcd for C16H14OS (M): 254.0765. Found: m/z
254.0758. Anal. Calcd for C16H14OS: C, 75.56; H, 5.55; S, 12.60. Found: C, 75.34; H, 5.53; S, 12.46.
4-(Naphthalen-1-yl)-1H-2-benzothiopyran (8e): reaction time: 15 h; a white solid; mp 128–129 ˚C
(hexane/CH2Cl2); IR (KBr) 1505, 1483 cm–1; 1H NMR  3.84 (d, J = 13.7 Hz, 1H), 4.09 (d, J = 13.7 Hz,
1H), 6.50 (s, 1H), 6.51 (d, J = 6.9 Hz, 1H), 6.91–6.95 (m, 1H), 7.15–7.17 (m, 2H), 7.28 (dd, J = 8.0, 7.4
Hz, 1H), 7.38 (t, J = 6.9 Hz, 2H), 7.44 (dd, J = 8.0, 6.9 Hz, 1H), 7.68 (d, J = 8.0 Hz, 1H), 7.79 (d, J = 8.0
13
Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H); C NMR  31.08, 123.21, 125.69, 125.84, 125.94, 126.00, 126.07,
126.76, 127.44, 127.58, 127.88, 128.07, 128.20, 128.24, 131.97, 133.62, 134.95, 136.68, 138.19. HR-MS
(EI). Calcd for C19H14S (M): 274.0816. Found: m/z 274.0806. Anal. Calcd for C19H14S: C, 83.17; H, 5.14.
Found: C, 83.00; H, 5.24.
4-Methyl-1H-2-benzothiopyran (8f):23 a pale- yellow oil; Rf 0.41 (CH2Cl2/hexane 1:4); IR (neat) 1600,
1487 cm–1; 1H NMR  2.11 (s, 3H), 3.68 (s, 2H), 6.16 (s, 1H), 7.05 (d, J = 7.4 Hz, 1H), 7.15 (td, J = 7.4,

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HETEROCYCLES, Vol. 94, No. 11, 2017
1.7 Hz, 1H), 7.17–7.23 (m, 2H); 13C NMR
 20.43, 30.84, 118.57, 123.27, 126.70, 127.44, 127.93, 129.29,
131.16, 134.58.
6-Chloro-4-phenyl-1H-2-benzothiopyran (8g): colorless needles; mp 114–115 ˚C (hexane/CH2Cl2); IR
(KBr) 1586, 1475 cm–1; 1H NMR  3.82 (s, 2H), 6.61 (s, 1H), 6.98 (d, J = 1.7 Hz, 1H), 7.13 (d, J = 8.0 Hz,
1H), 7.23 (dd, J = 8.0, 1.7 Hz, 1H), 7.33–7.42 (m, 5H); 13C NMR  30.60, 122.96, 126.04, 127.65, 127.96,
128.05, 128.51, 128.69 (2 overlapped Cs), 133.16, 135.91, 138.02, 139.62. HR-MS (EI). Calcd for
C15H11ClS (M): 258.0270. Found: m/z 258.0272. Anal. Calcd for C15H11ClS: C, 69.63; H, 4.29. Found: C,
69.56; H, 4.28.
6-Methoxy-4-phenyl-1H-2-benzothiopyran (8h):24 a white solid; mp 74–77 ˚C (hexane); IR (KBr) 1604,
1489 cm–1; 1H NMR  3.67 (s, 3H), 3.83 (s, 2H), 6.57 (br s, 2H), 6.81 (dd, J = 8.0, 2.3 Hz, 1H), 7.12 (d, J
= 8.0 Hz, 1H), 7.31–7.39 (m, 5H); 13C NMR  30.55, 55.26, 112.49, 112.99, 121.96, 122.02, 127.34,
127.57, 128.48, 128.58, 135.34, 138.66, 140.25, 158.78.
6,7-Dimethoxy-4-phenyl-1H-2-benzothiopyran (8i): a white solid; mp 101 ˚C (hexane); IR (KBr) 1602,
1
1514 cm–1; H NMR  3.65 (s, 3H), 3.82 (s, 2H), 3.92 (s, 3H), 6.46 (s, 1H), 6.56 (s, 1H), 6.73 (s, 1H),
7.33–7.38 (m, 5H); 13C NMR  30.81, 55.92, 56.00, 110.01, 110.22, 118.86, 122.38, 127.12, 127.36,
128.45 (2 overlapped Cs), 138.69, 140.32, 147.76, 148.71. Anal. Calcd for C17H16O2S: C, 71.80; H, 5.67.
Found: C, 71.56; H, 5.69.
General Procedure for the Preparation of 1,3-Dihydrobenzo[c]thiophenes (13). To a stirred solution
of 5 (1.0 mmol) in MeCN (5 mL) at 0 ˚C was added concentrated HBr (0.18 g, 1.0 mmol). Stirring was
continued at the temperature indicated in Table 2 until disappearance of the starting materials had been
confirmed by TLC analyses on silica gel. Saturated aqueous NaHCO3 (20 mL) was added, and MeCN
was removed by evaporation. The mixture was extracted with AcOEt (3  15 mL), and the combined
extracts were washed with water and brine (20 mL each), and dried over anhydrous Na2SO4. Evaporation
of the solvent gave a residue, which was purified by preparative TLC on silica gel to afford 13.
1-Methyl-1-phenyl-1,3-dihydrobenzo[c]thiophene (13a): a pale-yellow oil; Rf 0.29 (CH2Cl2/hexane
1:5); IR (neat) 1485, 1445 cm–1; 1H NMR  2.11 (s, 3H), 4.30 (d, J = 15.4 Hz, 1H), 4.32 (d, J = 15.4 Hz,
1H), 6.99 (dd, J = 7.8, 1.4 Hz, 1H), 7.19 (t, J = 7.3 Hz, 1H), 7.22–7.30 (m, 5H), 7.33 (dd, J = 7.8, 1.4 Hz,
13
2H); C NMR  30.80, 36.74, 63.63, 124.45, 124.72, 126.63, 126.73, 126.97, 127.11, 128.08, 140.40,
147.53, 148.94. HR-MS (EI). Calcd for C15H14S (M): 226.0816. Found: m/z 226.0817.
1-Methyl-1-(4-methylphenyl)-1,3-dihydrobenzo[c]thiophene (13b): a pale-yellow oil; Rf 0.25
(CH2Cl2/hexane 1:10); IR (neat) 1510, 1483, 1452 cm–1; 1H NMR  2.09 (s, 3H), 2.30 (s, 3H), 4.29 (d, J =
14.3 Hz, 1H), 4.30 (d, J = 14.3 Hz, 1H), 6.98 (d, J = 6.9 Hz, 1H), 7.07 (d, J = 8.0 Hz, 1H), 7.19–7.25 (m,
13
5H), 7.28 (d, J = 6.9 Hz, 1H); C NMR  20.91, 30.87, 36.49, 63.24, 124.38, 124.66, 126.64, 126.83,

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127.03, 128.75, 136.21, 140.43, 144.78, 149.25. HR-MS (EI). Calcd for C16H16S (M): 240.0973. Found:
m/z 240.0981.
1-(4-Chlorophenyl)-1-methyl-1,3-dihydrobenzo[c]thiophene (13c): a pale-yellow oil; Rf 0.27
(CH2Cl2/hexane 1:10); IR (neat) 1592, 1481 cm–1; 1H NMR  2.08 (s, 3H), 4.30 (s, 2H), 6.95 (d, J = 6.9
13
Hz, 1H), 7.20–7.30 (m, 7H); C NMR  30.78, 36.55, 62.91, 124.28, 124.80, 127.12, 127.21, 128.13,
128.28, 132.40, 140.38, 146.37, 148.71. HR-MS (EI). Calcd for C15H13ClS (M): 260.0427. Found: m/z
260.0415.
1-(4-Methoxyphenyl)-1-methyl-1,3-dihydrobenzo[c]thiophene (13d): a pale-yellow oil; Rf 0.34
1
(CH2Cl2/hexane 3:10); IR (neat) 1608, 1581, 1508 cm–1; H NMR  2.08 (s, 3H), 3.77 (s, 3H), 4.30 (s,
2H), 6.80 (d, J = 8.6 Hz, 2H), 6.96 (dd, J = 8.6, 1.1 Hz, 1H), 7.20–7.23 (m, 2H), 7.25–7.29 (m, 3H); 13C
NMR  31.05, 36.43, 55.21, 63.12, 113.30, 124.31, 124.68, 126.82, 127.04, 128.02, 139.80, 140.31,
149.47, 158.10. HR-MS (EI). Calcd for C16H16OS (M): 256.0922. Found: m/z 256.0932.
1-Methyl-1-(naphthalen-1-yl)-1,3-dihydrobenzo[c]thiophene (13e): a pale-yellow solid; mp 119–120
˚C (hexane/ CH2Cl2); IR (neat) 1598, 1510, 1482, 1455 cm–1; 1H NMR
 2.27 (s, 3H), 4.38 (d, J = 14.3 Hz,
1H), 4.47 (d, J = 14.3 Hz, 1H), 6.88 (d, J = 7.4 Hz, 1H), 7.15 (t, J = 7.4 Hz, 1H), 7.24–7.48 (m, 6H), 7.76
13
(d, J = 8.0 Hz, 1H), 7.81 (d, J = 8.0 Hz, 1H), 8.01 (d, J = 8.6 Hz, 1H); C NMR  33.93, 36.81, 63.22,
124.33, 124.49, 124.67, 125.03 (2 overlapped Cs), 125.27, 126.95, 127.10, 127.26, 129.02, 129.09,
130.85, 135.16, 139.52, 140.54, 150.10. HR-MS (EI). Calcd for C19H16S (M): 276.0973. Found: m/z
276.0966. Anal. Calcd for C19H16S: C, 82.57; H, 5.84. Found: C, 82.33; H, 5.81.
1
1-Methyl-1-phenyl-1,3-dihydrobenzo[c]thiophene (13f): a colorless liquid; Rf 0.32 (hexane). The H
and 13C NMR data for this compound were identical to those reported previously.14
6-Chloro-1-methyl-1-phenyl-1,3-dihydrobenzo[c]thiophene (13g): a pale-yellow oil; Rf 0.59
1
(Et2O/hexane 1:20); IR (neat) 1592, 1481 cm–1; H NMR  2.09 (s, 3H), 4.26 (s, 2H), 6.94 (s, 1H),
13
7.21–7.23 (m, 3H), 7.29–7.34 (m, 4H); C NMR  30.64, 35.98, 63.12, 124.57, 125.68, 126.73, 126.89,
127.15, 128.21, 133.00, 139.01, 146.80, 151.26. HR-MS (EI). Calcd for C15H13ClS (M): 260.0427. Found:
m/z 260.0435. Anal. Calcd for C15H13ClS: C, 69.09; H, 5.02. Found: C, 68.90; H, 5.24.
5-Methoxy-1-methyl-1-phenyl-1,3-dihydrobenzo[c]thiophene (13h): a pale-yellow oil; Rf 0.48
(AcOEt/hexane 1:10); IR (neat) 1607, 1580, 1494, 1443 cm–1; 1H NMR  2.10 (s, 3H), 3.73 (s, 3H), 4.21
(d, J = 13.2 Hz, 1H), 4.25 (d, J = 13.2 Hz, 1H), 6.49 (d, J = 2.3 Hz, 1H), 6.80 (dd, J = 8.6, 2.3 Hz, 1H),
7.18 (d, J = 8.6 Hz, 1H), 7.19 (t, J = 7.4 Hz, 1H), 7.27 (dd, J = 8.0, 7.4 Hz, 2H), 7.34 (d, J = 8.0 Hz, 2H);
13C NMR  30.63, 35.84, 55.44, 63.26, 109.61, 112.93, 125.13, 126.59, 126.68, 128.08, 132.53, 147.56,
150.64, 159.09. HR-MS (EI). Calcd for C16H16OS (M): 256.0922. Found: m/z 256.0921. Anal. Calcd for
C16H16OS: C, 74.96; H, 6.29. Found: C, 74.80; H, 6.24.

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HETEROCYCLES, Vol. 94, No. 11, 2017
5,6-Dimethoxy-1-methyl-1-phenyl-1,3-dihydrobenzo[c]thiophene (13i): a white solid; mp 69–70 ˚C
(hexane/ CH2Cl2); IR (KBr) 1603,1505 cm–1; 1H NMR  2.11 (s, 3H), 3.76 (s, 3H), 3.89 (s, 3H), 4.24 (d, J
= 15.5 Hz, 1H), 4.26 (d, J = 15.5 Hz, 1H), 6.44 (s, 1H), 6.77 (s, 1H), 7.20 (td, J = 7.4, 1.1 Hz, 1H), 7.27 (t,
13
J = 7.4 Hz, 2H), 7.32 (dd, J = 7.4, 1.1 Hz, 2H); C NMR  30.82, 36.55, 55.98, 56.03, 63.46, 106.92,
107.02, 126.50, 126.52, 128.11, 132.10, 140.76, 148.04, 148.42, 148.56. HR-MS (FI). Calcd for
C17H18O2S (M): 286.1028. Found: m/z 286.1034. Anal. Calcd for C17H18O2S: C, 71.30; H, 6.34. Found: C,
70.95; H, 6.22.
ACKNOWLEDGEMENTS
We wish to thank Mrs. Miyuki Tanmatsu of this university for recording mass spectra and performing
combustion analyses.
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