An efficient synthesis of dinaphthothiophene derivatives

Article abstract of DOI:10.1016/j.tetlet.2008.05.045

A short and efficient synthesis of dinaphthothiophene and its derivatives was achieved by employing oxidative photocyclization of the corresponding dinaphthyl sulfides as a key step.

Full text of DOI:10.1016/j.tetlet.2008.05.045

Tetrahedron Letters 49 (2008) 4519–4521
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
An efficient synthesis of dinaphthothiophene derivatives
Karoon Sadorn a, Warapon Sinananwanich a, Jetsuda Areephong a, Chakkrapan Nerungsi a,
Chalayut Wongma a, Chaveng Pakawatchai b, Tienthong Thongpanchang a,
*
a Department of Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
b Department of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
a r t i c l e i n f o
a b s t r a c t
Article history:
A short and efficient synthesis of dinaphthothiophene and its derivatives was achieved by employing oxi-
dative photocyclization of the corresponding dinaphthyl sulfides as a key step.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 10 April 2008
Revised 7 May 2008
Accepted 8 May 2008
Available online 13 May 2008
1. Introduction
Li
S
Dinaphthothiophene 1 can be classified as a sulfur-containing
heteroaromatic system with a unique structure. Despite its helical
structure, the molecule does not exhibit optical activity due to ra-
pid racemization at ambient temperature.1,2 The molecule has re-
ceived much attention recently due to its potential as a precursor
for the synthesis of axially chiral binaphthyl derivatives, which
are effective chiral building blocks in asymmetric reactions.2,3
A number of dinaphthothiophene syntheses have been reported
in the literature as outlined in Scheme 1. For example, in chrono-
logical order, Tominaga and co-workers reported the synthesis of
dinaphthothiophene derivatives via the photocyclization of 2.4 La-
ter Murata et al. reported that the reaction between the lithiated
binaphthyl 3 and sulfur provided dinaphthothiophene 1 in 19%
yield.5 De Lucchi et al.6 and Smith et al.7 reported the application
of the Newman–Kwart thermal rearrangement of the dimethyl-
thiocarbamate of binaphthol 4 to provide the desired product 1.
This approach was later improved by Hayashi and co-workers
and the yield was increased to 68%.3 In 1999, Otsubo and co-work-
ers8 reported an approach via the flash vacuum pyrolysis of diethy-
nyl thiophene 5. Finally, Matzger and co-workers9 employed a
cascade Bergman cyclization of 6 to furnish dinaphthothiophene
1 in trace amount.
Li
O
O
NMe2
NMe2
3
1
S
S
Murata5
4
2
De Lucchi6
Smith7
Tominaga4
Matzger9
Hayashi3
S
Otsubo8
S
S
6
5
Scheme 1. Reported syntheses of dinaphthothiophene 1.
Our research focuses on the development of new methodology
towards helical conjugated structures.10 Interestingly, it was re-
ported, by Zeller and Petersen,11 that the oxidative photocycliza-
tion of diphenyl sulfide could lead to dibenzothiophene. It was
envisioned that such an approach could be applied for the direct
synthesis of dinaphthothiophene 1. Retrosynthetic disconnection
at the C1–C10 bond of dinaphthothiophene suggested that the pre-
cursor for photochemical reaction could be dinaphthyl sulfide 7
which could be derived straightforwardly from the acid-mediated
nucleophilic aromatic substitution between 2-naphthol 8 and 2-
naphthalenethiol 9 (Scheme 2).12
2. Result and discussion
The reaction of 2-naphthol 8 and 2-naphthalenethiol 9 was thus
carried outin thepresenceof p-TsOHin refluxingtoluene for 2 htopro-
vide the desired dinaphthyl sulfide 7 in 97% yield. The sulfide 7 was
then subjected to oxidative photocyclization in the presence of I2 and
propylene oxide (PO), Scheme 3.11,13 Conditions for the oxidative
photo-cyclization process and yields are summarized in Table 1.
* Corresponding author. Tel./fax: +66 2 201 5139.
E-mail address: tettp@mahidol.ac.th (T. Thongpanchang).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.05.045

4520
K. Sadorn et al. / Tetrahedron Letters 49 (2008) 4519–4521
I2
OH
SH
h
ν
H
H
1
1'
S
S
S
8
9
S
S
7
1
10
1
7
Scheme 4. Mechanism of the oxidative photocyclization.
Scheme 2. Retrosynthetic analysis of dinaphthothiophene 1.
The mechanism of the reaction is proposed to be similar to that
reported by Zeller and Petersen11 (Scheme 4). Electrocyclic ring
closure of dinaphthyl sulfide 7 provided the cyclic intermediate
10 which, upon reaction with I2, yielded the dinaphthothiophene
1. Propylene oxide served as a HI-quencher.13 The decreased extent
of aromatic energy in naphthalene is believed to facilitate the
photo-electrocyclic process and this provides a rationalization for
the better yield and higher conversion when compared to the reac-
tion of diphenyl sulfide.
This oxidative photocyclization was a very efficient and conve-
nient procedure for the construction of other dinaphthothiophene
derivatives. For example, compounds 11, 12 and 13 could be pre-
pared by photocyclization of their corresponding dinaphthyl sul-
fides in 84%, 83% and 80% yields, respectively.
OH
8
+
p-TsOH
ν
h
S
S
Toluene, reflux
SH
97%
79-86%
7
1
9
Scheme 3. Synthesis of dinaphthothiophene 1.
Table 1
Conditions and yields of the oxidative photocyclization reaction of dinaphthyl sulfide
7a
Entry
Time (min)
I2 (equiv)
PO (equiv to I2)
Yield % (conversion %)b
1
2
3
4
5
6
7
8
9
10
20
30
40
60
30
30
30
30
30
1.0
1.0
1.0
1.0
1.0
0.8
1.2
1.5
1.2
1.2
10.0
10.0
10.0
10.0
10.0
10.0
10.0
10.0
0.0
79 (48)
83 (78)
85 (87)
84 (89)
86 (88)
82 (86)
85 (91)
84 (92)
81 (80)
85 (90)
OCH3 H3CO
S
OCH3
S
OCH3
S
H3CO
11
12
13
10
5.0
84%
83%
80%
a
The reaction was conducted in a 1 L Hanovia 450 W medium pressure Hg lamp
photochemical reactor. All experiments were performed on 1 mmol scale at a
concentration of 1 mM.
b
The % conversion refers to the percentage of reacted starting material; the %
yield refers to the percentage of the product from the reacted starting material.
SH
S
S
OH
h
It was found that a stoichiometric amount of I2 was required for
the reaction. On 1 mmol scale, the appropriate reaction time was
30 min. A shorter reaction time led to a decreased percent conver-
sion whilst prolonged irradiation did not increase the yield and %
conversion, but did result in the formation of a brownish stain
on the surface of the quartz tube and reactor. Addition of propylene
oxide did not significantly improve the percent yield and conver-
sion, but it did influence the purity of the crude product.
I2
O
OH
p-TsOH,
Toluene, reflux
S
S
14
15
16
Scheme 5. Two-step synthesis of 16.
S1
S2
C2
C1
C28
C27
C30
C29
C3
C26
C25
C4
C10
C11
C19
C18
C20
C9
C5
C6
C12
C24
C17
C21
C8
C13
C14
C23
C22
C16
C7
C15
Figure 1. ORTEP diagram of compound 16.

K. Sadorn et al. / Tetrahedron Letters 49 (2008) 4519–4521
4521
Compounds with complicated skeletons, such as 16, could also
References and notes
be accessed via this oxidative photocyclization method. Indeed,
treatment of 2,3-naphthalenediol 14 with 2-naphthalenethiol 9
in refluxing toluene in the presence of p-TsOH yielded 15 (87%),
which upon oxidative photocyclization by the aforementioned pro-
cedure provided 16 in 83% yield (Scheme 5).
1. Fabbri, D.; Dore, A.; Gladiali, S.; De Lucchi, O.; Valle, G. Gazz. Chim. Ital. 1996,
126, 11.
2. Shimada, T.; Cho, Y.-H.; Hayashi, T. J. Am. Chem. Soc. 2002, 124, 13396.
3. Cho, Y.-H.; Kina, A.; Shimada, T.; Hayashi, T. J. Org. Chem. 2004, 69, 3811.
4. Tedjamulia, M. L.; Tominaga, Y.; Castle, R. N.; Lee, M. L. J. Heterocycl. Chem.
1983, 20, 1143.
5. Murata, S.; Suzuki, T.; Yanagisawa, A.; Suga, S. J. Heterocycl. Chem. 1991, 28, 433.
6. Fabbri, D.; Delogu, G.; De Lucchi, O. J. Org. Chem. 1993, 58, 1748.
7. Bandarage, U. K.; Simpson, J.; Smith, R. A. J.; Weavers, R. T. Tetrahedron 1994,
50, 3463.
8. Imamura, K.; Hirayama, D.; Yoshimura, H.; Takimiya, K.; Aso, Y.; Otsubo, T.
Tetrahedron Lett. 1999, 40, 2789.
X-ray analysis of compound 1614 (Fig. 1) revealed an interesting
structural feature where the product adopted a conformation that
possessed a plane of symmetry, rather than a C2-axis. A detailed
investigation of this molecule as a new type of organic material
is currently in progress.
9. Lewis, K. D.; Rowe, M. P.; Matzger, A. J. Tetrahedron 2004, 60, 7191.
10. Areephong, J.; Ruangsupapichart, N.; Thongpanchang, T. Tetrahedron Lett. 2004,
60, 3067.
11. Zeller, K.-P.; Petersen, H. Synthesis 1975, 532.
12. Charoonniyomporn, P.; Thongpanchang, T.; Witayakran, S.; Thebtaranonth, Y.;
Phillips, K. E. S.; Katz, T. J. Tetrahedron Lett. 2004, 45, 457.
In conclusion, an alternative synthesis of dinaphthothiophene
has been described. The method is highly efficient and can be ap-
plied to the synthesis of
derivatives.
a variety of dinaphthothiophene
13. Liu, L.; Yang, B.; Katz, T. J.; Poindexter, M. K. J. Org. Chem. 1991, 56, 3769.
14. Crystallographic data for compound 16 have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication no.
CCDC 680516. Copies of the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033; e-
mail: deposit@ccdc.cam.ac.uk or via www.ccdc.cam.ac.uk/data_request/cif).
15. Compound characterization: Dinaphthyl sulfide 7: 1H NMR (300 MHz, CDCl3, d/
ppm): 7.48–7.55 (m, 6H, Ar–H); 7.76–7.78 (m, 6H, Ar–H); 7.94 (br s, 2H, Ar–H).
13C NMR (75 MHz, CDCl3, d/ppm): 133.8, 133.1, 132.3, 129.8, 128.9, 128.7,
127.7, 127.4, 126.6, 126.2. MS (EI [70 eV], m/z (%)): 286 (100) [M+]; 252 (34)
[{MꢀH2S}+]. CHN: Required for C20H14S: C, 83.88; H, 4.93. Found: C, 83.72; H,
4.53. Melting point 157–160 °C.
3. General procedures15
3.1. Synthesis of dinaphthyl sulfide 7
A solution of 2-naphthol 8 (1.24 g, 8.60 mmol) and 2-napht-
halenethiol 9 (2.07 g, 12.90 mmol) in the presence of p-TsOH
(1.64 g, 8.60 mmol) was refluxed in toluene for 2 h. The reaction
was cooled down and then quenched with saturated NaHCO3 solu-
tion. The mixture was then extracted with CH2Cl2 (3 times), and
the combined organic extracts were washed with H2O, dried over
Na2SO4 and then evaporated to dryness. The crude product was
purified by column chromatography (SiO2, hexane as eluent) to
yield dinaphthyl sulfide 7 (2.39 g, 97% yield).
Dinaphthothiophene 1: 1H NMR (300 MHz, CDCl3, d/ppm): 7.60 (m, 4H, Ar–H);
7.95 (d, J = 8.6 Hz, 2H, Ar–H); 7.99 (d, J = 8.6 Hz, 2H, Ar–H); 8.06 (m, 2H, Ar–H);
8.90 (m, 2H, Ar–H). 13C NMR (75 MHz, CDCl3, d/ppm): 138.5, 132.1, 131.4,
129.9, 128.6, 127.4, 126.1, 125.2, 124.8, 120.8. MS (EI [70 eV], m/z (%)): 284
(72) [M+]. CHN: Required for C20H12S: C, 84.47; H, 4.25. Found: C, 84.92; H,
4.18. Melting point 213–216 °C.
6-Methoxy-dinaphthothiophene 11: 1H NMR (300 MHz, CDCl3, d/ppm): 4.20 (s,
3H, OCH3); 7.26 (s, 1H, Ar–H); 7.47 (m, 1H, Ar–H); 7.54–7.62 (m, 3H, Ar–H);
7.93–8.07 (m, 4H, Ar–H); 8.85–8.94 (m, 2H, Ar–H). 13C NMR (75 MHz, CDCl3, d/
ppm): 152.5, 139.0, 134.1, 133.4, 132.2, 131.7, 131.6, 130.0, 128.6, 127.6, 127.4,
126.2, 126.0, 125.9, 125.5, 125.2, 124.8, 122.5, 121.1, 103.5, 55.9. MS (EI
[70 eV], m/z (%)): 314 (100) [M+]; 282 (60) [{M–CH3OH}+]. CHN: Required
for C21H14OS: C, 80.22; H, 4.49. Found: C, 80.57; H, 4.41. Melting point 190–
192 °C.
3.2. Oxidative photocyclization of diaryl sulfide: synthesis of
dinaphthothiophene 1
A solution of dinaphthyl sulfide 7 (300 mg, 1.05 mmol) and I2
(320 mg, 1.26 mmol) in cyclohexane (1000 mL) was charged into
a 1 L Hanovia photochemical reactor equipped with a 450 W med-
ium pressure Hg lamp. The solution was purged with argon for
20 min. Then, propylene oxide (366 mg, 0.44 mL, 6.30 mmol) was
added and the solution was irradiated for 30 min. Upon comple-
tion, the solution was evaporated to dryness and the crude product
was subjected to column chromatography (SiO2, hexane as eluent)
3,6-Dimethoxy-dinaphthothiophene 12: 1H NMR (300 MHz, CDCl3, d/ppm): 4.02
(s, 3H, OCH3); 4.17 (s, 3H, OCH3); 7.12 (dd, J = 2.69, 9.21 Hz, 1H, Ar–H); 7.18 (s,
1H, Ar–H); 7.33 (d, J = 2.65, 1H, Ar–H); 7.56–7.62 (m, 2H, Ar–H); 7.93 (d,
J = 8.65 Hz, 1H, Ar–H); 7.98 (d, J = 8.64 Hz, 1H, Ar–H); 8.04 (m, 1H, Ar–H); 8.77
(d, J = 9.21 Hz, 1H, Ar–H); 8.89 (m, 1H, Ar–H). 13C NMR (75 MHz, CDCl3, d/
ppm): 157.4, 153.1, 139.0, 135.7, 133.5, 132.1, 131.5, 130.3, 129.2, 128.6, 127.5,
127.3, 126.0, 125.1, 124.8, 121.1, 120.9, 113.4, 107.2, 103.1, 55.9, 55.4. MS (EI
[70 eV], m/z (%)): 344 (100) [M+]; 312 (20) [{M–H3OH}+]. CHN: Required
for C22H16O2S: C,76.72; H,4.68. Found: C, 76.97; H, 4.65. Melting point 213–
216 °C.
to yield dinaphthothiophene
conversion).
1
(228 mg, 85% yield, 90%
2,6-Dimethoxy-dinaphthothiophene 13: 1H NMR (300 MHz, CDCl3, d/ppm): 3.89
(s, 3H, OCH3); 4.17 (s, 3H, OCH3); 7.23–7.26 (m, 2H, Ar–H); 7.58–7.62 (m, 2H,
Ar–H); 7.87 (d, J = 8.88 Hz, 1H, Ar–H); 7.94–8.08 (m, 3H, Ar–H); 8.18 (d,
J = 2.27 Hz, 1H, Ar–H); 8.92 (m, 1H, Ar–H). 13C NMR (75 MHz, CDCl3, d/ppm):
155.4, 151.0, 138.9, 132.5, 132.2, 132.0, 131.6, 129.7, 129.0, 128.7 (2C), 127.2,
126.7, 126.6, 125.2, 124.3, 121.1, 117.3, 106.6, 103.6, 55.9, 55.4. MS (EI [70 eV],
m/z (%)): 344 (100) [M+]. CHN: Required for C22H16O2S: C, 76.72; H, 4.68.
Found: C, 76.38; H, 4.57. Melting point 184–186 °C.
Acknowledgements
Financial support from the Thailand Research Fund (TRF-
RMU4980021) and National Synchrotron Research Center (Grant
2-2549/PS01) for T.T. is gratefully acknowledged. K.S., C.N. and
C.W. thank the Center for Innovation in Chemistry: Postgraduate
Education and Research Program in Chemistry (PERCH-CIC), the
Development and Promotion of Science and Technology Talents
(DPST) program and the Royal Golden Jubilee (RGJ) program for
their scholarships.
2,3-Dinaphthyl disulfide 15: 1H NMR (300 MHz, CDCl3, d/ppm): 7.43 (m, 2H, Ar–
H); 7.48–7.55 (m, 6H, Ar–H); 7.64 (m, 2H, Ar–H); 7.74–7.80 (m, 4H, Ar–H);
7.83–7.88 (m, 4H, Ar–H); 7.93 (br s, 2H, Ar–H). 13C NMR (75 MHz, CDCl3, d/
ppm): 135.3, 134.0, 132.8, 132.5, 132.2, 130.9, 130.6, 129.0, 128.9, 127.8, 127.5,
127.1, 126.5, 126.3. MS (EI [70 eV], m/z (%)): 444 (75) [M+]; 284 (100) [{M–
C
10H8S}+]. CHN: Required for C30H20S2: C, 81.04; H, 4.53. Found: C, 80.46; H,
4.52. Melting point 122–125 °C.
Compound 16: 1H NMR (300 MHz, CDCl3, d/ppm): 7.57 (m, 2H, Ar–H); 7.65 (m,
4H, Ar–H); 7.98 (d, J = 8.68 Hz, 2H, Ar–H); 8.03 (d, J = 8.63 Hz, 2H, Ar–H); 8.09
(m, 2H, Ar–H); 8.98 (m, 2H, Ar–H); 9.05 (m, 2H, Ar–H). 13C NMR (75 MHz,
CDCl3, d/ppm): 137.9, 133.3, 132.3, 131.7, 131.6, 129.7, 129.3, 128.8, 127.5,
126.4, 126.1, 125.5, 125.3, 124.7, 120.9. MS (EI [70 eV], m/z (%)): 440 (100)
[M+]. CHN: Required for C30H16S2: C, 81.78; H, 3.66. Found: C, 81.91; H, 3.55.
Melting point 316–318 °C.
Supplementary data
Supplementary data (1H and 13C NMR spectra of compounds 1,
7, 11, 12, 13, 15 and 16) associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2008.05.045.