Electronic control of product formation in the rearrangement of 1,3-dithian-2-yl-arylmethanols

Article abstract of DOI:10.1016/j.tet.2003.09.100

1,3-Dithian-2-yl-phenylmethanols undergo efficient rearrangement to afford 2-phenyl-6,7-dihydro-5H-1,4-dithiepines. The reactions were found to show remarkable variation in products formation that is dictated by the substituents on the aryl ring.

Full text of DOI:10.1016/j.tet.2003.09.100

Tetrahedron 59 (2003) 9677–9682
Electronic control of product formation in the rearrangement
of 1,3-dithian-2-yl-arylmethanols
*
Chi Wi Ong and Chien Yen Yu
Department of Chemistry, National Sun Yat Sen University, Kaohsiung 804, Taiwan, ROC
Received 26 February 2003; revised 8 August 2003; accepted 9 September 2003
Abstract—1,3-Dithian-2-yl-phenylmethanols undergo efficient rearrangement to afford 2-phenyl-6,7-dihydro-5H-1,4-dithiepines. The
reactions were found to show remarkable variation in products formation that is dictated by the substituents on the aryl ring.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Ring expansion of a-hydroxydithiane derivatives 1 into
5,6-dihydro-7H-1,4-dithiepines 2 has been widely described
in the literature.1–5 In general, dithiane derivatives with a
good leaving group at the a-position such as an acetate,6 a
chloride,7 a mesylate,5 an amide,8 or an epoxide9 have all
been reported to undergo rearrangement to the 5,6-dihydro-
7H-1,4-dithiepines. Furthermore, it has been shown that the
presence of an a-hydrogen atom in the R2 substituent of 1
(R2¼CHR3R4) can lead to the formation of both the endo-
and exo-dithiepanes 2 and 3.3 Recently, it has also been
shown that the endo-double bond of dithiepines 2 can
undergo photo-induced 1,3-hydrogen migration to give the
exo-dithiepanes 3,10 a property which may be useful for the
design of a photo-switch. Additionally, dithianylidenes 411
are formed when the R2 group of 1 is a hydrogen atom.
Scheme 1 summarizes the products that have been obtained
from the reaction of a-hydroxydithiane derivatives 1.
The 1,3-dithian-2yl-arylmethanols 5a–d for this study were
prepared by the reaction of 2-lithio-1,3-dithiane with the
corresponding arylaldehyde in good yields according to
reported procedures.3,10,12 The reaction of 1,3-dithian-2-yl-
phenylmethanol 5a with a catalytic amount of concentrated
sulfuric acid in refluxing toluene led to the formation of the
2-phenyl-6,7-dihydro-5H-1,4-dithiepine (6a) in 25% yield
together with non-polar hydrocarbon derivative 2-phenyl-
naphthalene (7) in 10% yield. Compound (7) was identified
by its 1H NMR spectrum, mass and melting point.13,14 The
reaction was monitored by t.l.c until the complete
disappearance of starting material, approximately 24 h. A
substantial amount of polymeric material was also observed.
This reaction sequence was not confined to 5a. Interestingly,
1,3-dithian-2-yl-2-naphthylmethanol (5b), under similar
conditions, also gave the corresponding ring expansion
product, 2-(2-naphthalenyl)-6,7-dihydro-5H-1,4-dithiepine
(6b) in 20% yield together with 3-naphthalen-2-yl-phenan-
threne (8) in 10% yield. The 1H NMR spectrum of 8 showed
the presence of protons at d 9.03 (singlet) and d 8.84
(doublet) typical of the 4- and 5-positions in 3-substituted
phenanthrenes. This ruled out the formation of the other
In the present work, we report the first complete overview of
the electronic control of the aromatic ring on the product
formation for acid catalyzed reactions of a-hydroxydithiane
derivatives.
Scheme 1. Possible products from the reaction of a-hydroxydithiane 1 with acid.
Keywords: 1,3-dithian-2-yl-arylmethanol; rearrangement; dimerization; cyclodimerization; electronic factors.
*
Corresponding author. Tel.: þ886-7-5252000; fax: þ886-7-5253908; e-mail: cong@mail.nsysu.edu.tw
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.09.100

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Scheme 2. Products from the reaction of 5a–d under acid catalysis.
possible isomeric cyclization product, 2-naphthalen-2-yl-
anthracene, since all the protons in this compound would be
expected to resonate much higher up field, ca. d 8.50. Our
results are in good agreement with the fact that substitution
at the 1-position of naphthalene is preferred over the
2-position,15 thus favoring the formation of the phenan-
threne ring over the anthracene ring. Although the yields of
the cyclodimerization products 7 and 8 are low, their
formation is important, as this reaction has not been
described in the literature (Scheme 2).
we examined this issue. Acid treatment of 1,3-dithian-2-yl-
4-nitrophenylmethanol 5c gave the single product 6c in 55%
yield. Figure 1 shows the crystal structure of 6c. Interest-
ingly, this structure shows the aromatic ring twisting out of
conjugation with the double bond of the dithiepine moiety.
This observation may explain the reported ease by which
2-methyl-3-aryl-6,7-dihydro-5H-dithiepines undergo a
photo-induced 1,3-proton shift to form the exo-methylene
dithiepines.10
We next study the acid catalyzed reaction of a 1,3-dithian-2-
yl-arylmethanol derivative having an electron-donating
group on the aryl ring. Interestingly, the reaction of
1,3-dithian-2-yl-4-methoxy-phenylmethanol (5d) was
There has been no data published concerning the electronic
influence of substituents on the aryl ring in the reactions of
aryl substituted 1,3-dithian-2-yl-arylmethanols. Therefore,
Figure 1. X-Ray structures for compound 6c (brown prism crystal, triclinic) and 9 (yellow prism crystal, monoclinic).16

C. W. Ong, C. Y. Yu / Tetrahedron 59 (2003) 9677–9682
9679
Scheme 3. Proposed mechanism for the formation of 9.
found to afford 6d in 15% yield together with another new
product isolated in 20% yield by chromatographic separa-
tion over silica gel. A substantial amount of polymerized
material was also formed. The 1H NMR of the new
compound did not correlate to a naphthalene derivative.
We were able to obtain a crystal of this product suitable for
a X-ray crystallographic analysis of the new compound and
determined its structure to be 9 (Fig. 1).16
yield. The formation of 10 was in good agreement with
electron rich aryl ring. The structure of compound 10 was
assigned based on the similarity between the H NMR and
1
13C NMR spectra of this compound to those of 9.
Compound 10 showed the presence of two conjugated
vinylic protons in a trans-orientation (J¼15 Hz). Further-
more, the parent ion peak in the mass spectrum at
322 corresponds to the dimer of 6f less a molecule of
1,3-dimercaptopropane and two molecules of water. A
substantial amount of 2-(2-thienylmethylene)-1,3-dithiane
(11) formed also illustrate that it is less prone to
dimerization. The formation of dithianylidenes by acid
catalyzed dehydration has been reported (Scheme 1).11
The proposed mechanism for the formation of 9 is shown in
Scheme 3. The acid catalyzed dehydration of 5d would give
the dithianylidene intermediate. Self-condensation of this
would produce 10. Friedel–Crafts cycloaromatization of 10
would yield the naphthalene derivative, while deprotonation
of the dithiolium moiety followed by desulfuration of the
dithioacetal group would yield 9. Interestingly, the electron
density in the aryl ring also controls the balance between the
Friedel–Crafts and deprotonation–desulfuration reactions.
3. Conclusion
In summary, all 1,3-dithian-2-yl-arylmethanol derivatives
studied led to the familiar ring expansion products that have
been widely reported. However, this reaction was found to
proceed with a remarkable degree of product selectivity that
was dictated by the electron density of the aromatic ring.
This can be summarized as followed: (i) electron with-
drawing groups favor rearrangement to form 2-aryl-6,7-
dihydro-5H-[1,4]dithiepines, (ii) unsubstituted phenyl and
naphthyl rings favor cycloaromatization products and
(iii) electron donating groups lead to dimerization products.
The low yields obtained with 5a,b and d can be attributed to
competing polymerization reactions. Heterocyclic 5e and 5f
also afforded similar results.
The electronic control by the aromatic ring was further
examined by studying the rearrangement of 1,3-dithian-2yl-
pyridylmethanol (5e) and 1,3-dithian-2yl-thiophenyl-
methanol (5f) under the same reaction conditions (Scheme
4). Pyridine is an electron deficient aromatic heterocycle
and the reaction of 5e gave only rearrangement product 6e,
in low yield. Thus, 5e was found to mimic the reactivity
observed with 5c. Similarly, the electron rich thiophene ring
on 5f was chosen to mimic electron rich group on the aryl
ring of 5d. Therefore, 5f was found to afford the
rearrangement product 6f in 10% yield and 10 in 5%
yield, together with dithianylidene derivative 11 in 40%
Scheme 4. Products from the reaction heterocycle 5e and 5f under acid catalysis.

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C. W. Ong, C. Y. Yu / Tetrahedron 59 (2003) 9677–9682
4. Experimental
J¼78.7 Hz, ArCHO), 4.07 (1H, d, J¼8.7 Hz, SCHS), 3.82
(3H, s, OMe), 2.90 (1H, br, OH), 2.88–2.84 (2H, m, CH2S),
2.76–2.73 (2H, m, CH2S), 2.08–1.99 (2H, m, CH2); dC
(CDCl3) 159.7, 132.2, 128.0, 113.7, 74.4, 55.2, 52.7, 28.3,
27.6, 25.4; m/z (EI, 30 eV) 256 (2, Mþ), 137 (100), 119
(63%).
Proton and carbon-13 NMR spectra were recorded using a
300 MHz spectrometer in CDCl3 with tetramethylsilane as
the internal standard. Melting points were measured on a
Fisher–John apparatus and are uncorrected. Unless
otherwise noted, all reactions were performed under an
atmosphere of nitrogen.
4.1.5. 1,3-Dithian-2-yl-pyridylmethanol (5e). Isolated in
55% yield (SiO2, hexane/EA, 1:3) as light brown solid, mp
85–868C; [Found: C, 52.82; H, 5.77. C10H13ONS2 requires
C, 52.83; H, 5.76]; nmax (CHCl3) 3458 (br), 1580, 1470,
1206 cm21; dH (CDCl3) 8.66 (1H, s, ArH), 8.56 (1 H, d,
J¼4.5 Hz, ArH), 7.80 (1H, d, J¼4.5 Hz, ArH), 7.32 (1H, dd,
J¼7.8, 4.5 Hz, ArH), 4.98 (1H, d, J¼47.5 Hz, ArCHO),
3.96 (1H, d, J¼7.5 Hz, SCHS), 3.65 (1H, br, OH), 3.02–
2.94 (2H, m, CH2S), 2.76–2.70 (2H, m, CH2S), 2.08–2.03
(2H, m, CH2); dC (CDCl3) 149.2, 148.5, 136.0, 134.6, 123.3,
72.2, 52.1, 27,6, 27.0, 25.2; m/z (EI, 30 eV) 227 (2, Mþ),
259 (16), 119 (100), 108 (6%).
4.1. General procedure for the preparation of
1,3-dithian-2-yl-arylmethanols (5a–d)
These compounds were prepared from 2-lithio-1,3-dithiane
and the corresponding arylaldehydes in a good yield
according to reported procedures.3,10,12 To a solution of
1,3-dithiane (33 mmol) in 50 mL THF at 2408C was added
an equimolar amount of butyllithium (1.6 M in hexane) and
stirred for 1.5 h. The calculated amount of arylaldehyde
dissolved in THF was added slowly through a dropping
funnel, after which the reaction mixture stirred at 2208C
for a further 12–24 h. The THF was removed under vacuo
and the product extracted with chloroform.
4.1.6. 1,3-Dithian-2-yl-2-thienylmethanol (5f). Isolated in
95% yield (SiO2, hexane/Et2O, 1:1) as light brownish liquid;
[Found: C, 46.47; H, 5.14. C9H12OS3 requires C, 46.52; H,
5.20]; nmax (CHCl3) 3554 (br), 1417, 1381, 1225 cm21; dH
(CDCl3) 7.30 (1H, d, J¼5.5 Hz, ArH), 7.11 (1H, d, J¼
4.0 Hz, ArH), 6.98 (1H, dd, J¼5.5, 4.0 Hz, ArH), 5.18 (1H,
d, J¼7.8 Hz, ArCHO), 4.05 (1H, d, J¼7.8 Hz, SCHS), 3.24
(1H, br, OH), 3.00–2.92 (2H, m, CH2S), 2.77–2.68 (2H, m,
CH2S), 2.04–2.00 (2H, m, CH2); dC (CDCl3) 143.5, 126.4,
125.8, 125,2, 52.5, 27.8, 27.3, 25.2; m/z (EI, 30 eV) 232 (3,
Mþ), 119 (100%).
4.1.1. 1,3-Dithian-2-yl-phenylmethanol (5a).3 Isolated in
85% yield (SiO2, hexane/CH2Cl2, 1:2) as white solid, mp
72–738C; nmax (CHCl3) 3450 (br), 1495, 1420, 1280 cm21
dH (CDCl3) 7.39–7.28 (5H, m, ArH), 4.88 (1H, d, J¼7.4,
3.0 Hz, ArCHO), 4.05 (1H, d, J¼7.4 Hz, SCHS), 3.35 (1H,
br, OH), 2.88–2.81 (2H, m, CH2S), 2.70–2.61 (2H, m,
CH2S), 1.95 (2H, m, CH2); m/z (EI, 30 eV) 226 (15 Mþ),
119 (100), 77 (58%).
;
4.1.2. 1,3-Dithian-2-yl-napthylmethanol (5b). Isolated in
80% yield (SiO2, hexane/EA, 5:2) as light yellowish
brown solid, mp 126–1288C; [Found: C, 65.05; H, 5.85.
C15H16OS2 requires C, 65.18; H, 5.83%]; nmax(CHCl3) 3468
(br), 1411, 1354, 1240 cm21; dH (CDCl3) 7.89–7.82 (4H,
m, ArH), 7.56–7.46 (3H, m, ArH), 5.09 (1H, d, J¼7.5 Hz,
ArCHO), 4.20 (1H, d, J¼7.5 Hz, SCHS), 3.20 (1H, br, OH),
3.00–2.93 (2H, m, CH2S), 2.78–2.71 (2H, m, CH2S), 2.06–
2.01 (2H, m, CH2); dC (CDCl3) 137.5, 133.4, 133.1, 128.1,
127.8, 126.3, 126.2, 126.2, 124.3, 74.9, 52.8, 28.2, 27.6,
25.3; m/z (EI, 30 eV) 276 (8, Mþ), 259 (16), 184 (78), 127
(48), 119 (100%).
4.2. General procedure for the reaction of (5a–f) under
acid catalysis
Conc. H2SO4 (1–2 drops) was added to the 1,3-dithian-2-yl-
arylmethanol (500 mg) in toluene under nitrogen and the
solution heated under reflux for approx. 24 h. After cooling
to room temperature, the solution was filtered through a
celite cake to remove polymeric products and the cake was
further washed twice with toluene. The toluene solution
was washed with sodium bicarbonate, saturated brine, dried
over sodium sulfate, and evaporated. The residue was
purified by preparative thin layer chromatography (SiO2,
20£20 cm).
4.1.3. 1,3-Dithia-2-yl-4-nitrophenylmethanol (5c). Iso-
lated in 65% yield (SiO2, hexane/EtOAc, 1:1) as a light
brownish solid, mp 83–848C; [Found: C, 48.88; H, 4.87.
C11H13NO3S2 requires C, 48.69; H, 4.83%]; nmax (CHCl3)
3446 (br), 1522, 1349, 1176 cm21; dH (CDCl3) 8.23 (2H, d,
J¼7.0 Hz, ArH), 7.62 (2H, d, J¼7.0 Hz, ArH), 5.03 (1H, d,
J¼7.5 Hz ArCHO), 3.95 (1H, d, J¼7.5 Hz, SCHS), 3.05
(1H, br, OH), 3.00–2.95 (2H, m, CH2S), 2.76–2.72 (2H, m,
CH2S), 2.07–2.03 (2H, m, CH2); dC (CDCl3) 147.4, 127.8,
123.4, 73.5, 52.2, 27.8, 27.2, 25.1; m/z (EI, 30 eV) 271 (4,
Mþ), 259 (6), 121 (15), 119 (100%).
4.2.1. 2-Phenyl-6,7-dihydro-5H-1,4-dithiepine (6a) and
2-phenylnaphthalene (7). Reaction of 5a by the general
procedure gave a mixture of 6a as yellowish oil (25%) and 7
as pale yellowish solid (10%) (hexane/CH2Cl2, 5:1).
Compound 6a.3 dH (CDCl3) 7.54–7.50 (2H, m, ArH), 7.34–
7.30 (3H, m, ArH), 6.15 (1H, s, CvCH), 3.66–3.58 (4H, m,
SCH2£2), 2.27–2.21 (2H, m, CH2); m/z (EI, 30 eV) 208
(100 Mþ), 179 (45), 134 (72), 102 (42%).
Compound 7. Mp 100–1028C (lit.15,16 101–1038C); dH
(CDCl3) 8.04 (1H, s, ArH), 7.93–7.85 (3H, m, ArH), 7.77–
7.72 (3H, m, ArH), 7.53–7.46 (4H, m, ArH), 7.40–7.35
(1H, m, ArH); m/z (EI 30 eV) 204 (100, Mþ), 127 (8%).
4.1.4. 1,3-Dithian-2-yl-4-methoxyphenylmethanol (5d).
Isolated in 85% yield (SiO2, hexane/EtOAc, 3:1) as a
yellowish solid, mp 79–8088C; [Found: C, 56.20; H, 6.21.
C12H16O2S2 requires C, 56.22; H, 6.29]; nmax(CHCl3) 3434
(br), 1513, 1249, 1169, 1026 cm21; dH (CDCl3) 7.35 (2H, d,
J¼8.7 Hz, ArH), 6.90 (2H, d, J¼8.7 Hz, ArH), 4.86 (1H, d,
4.2.2. 2-(2-Naphthyl)-6,7-dihydro-5H-1,4-dithiepine (6b)
and 3-naphthalen-2-nyl-phenanthrene (8). Reaction of

C. W. Ong, C. Y. Yu / Tetrahedron 59 (2003) 9677–9682
9681
5b by the general procedure gave a mixture of 6b (20%)
and 8 as yellowish solids (10%) (hexane/CH2Cl2, 1:7).
nmax (CHCl3) 1565, 1533, 1421, 1294 cm21; dH (CDCl3)
8.67 (1H, s, ArH), 8.48 (1H, d, J¼4.6 Hz, ArH), 7.76 (1H, d,
J¼8.6 Hz, ArH), 7.22 (1H, dd, J¼8.6, 4.6 Hz, ArH) 6.13
(1H, s, CvCH), 3.64 (4H, m, SCH2£2), 2.24 (2H, m, CH2);
dC (CDCl3) 148.8, 148.2, 137.0, 134.6, 131.5, 122.9, 120.2,
32.7, 31.0, 30.3; m/z (EI, 30 eV) 209 (100, Mþ), 135 (26),
106 (50), 103 (38%); HRMS: found: 209.0335. C10H11NS2
requires 209.0333.
Compound 6b. Mp 67–688C; [Found: C, 69.77; H, 5.53.
C15H14S2 requires C, 69.72; H, 5.46]; nmax (CHCl3) 1597,
1533, 1408, 1294 cm21; dH (CDCl3) 7.98 (1H s, ArH),
7.80–7.74 (3H, m, ArH), 7.65–7.60 (1H, m, ArH), 7.49–
7.44 (2H, m, ArH), 6.27 (1H, s, CvCH), 3.76–3.68 (4H, m,
SCH2£2), 2.26–2.20 (2H, m, CH2); dC (CDCl3) 138.6,
135.4, 133.2, 133.1, 128.2, 127.7, 127.5, 126.3, 126.2,
126.1, 125.5, 118.9, 32.6, 31.0, 30.4; m/z (EI, 70 eV) 258
(96, Mþ), 152 (100), 184 (86), 106 (48%).
4.2.6. 2-(2-Thienyl)-6,7-dihydro-5H-1,4-dithiepine (6f),
(E)-3-(1,3-dithian-2yliden)-1,3-di(2-thienyl)-1-propene
(10) and 2-(2-thienylmethylene)-1,3-dithiane (11). Reac-
tion of 5f by the general procedure gave a mixture of 6f as
yellowish oil (10%), 10 (5%) as pale yellowish solid and 11
as brownish oil (40%), (hexane/CH2Cl2, 3:1).
Compound 8. Mp 123–1258C; [Found: C, 94.43; H, 5.34.
C24H16 requires C, 94.70; H, 5.30]; nmax(CHCl3) 1595,
1495, 1447 cm21; dH (CDCl3) 9.03 (1H, s, ArH), 8.84 (1H,
d, J¼8.0 Hz, ArH), 8.25, (1H, s, ArH, 8.90–8.05 (7H, bs,
ArH), 7.95–7.53 (6H, m, ArH); dC (CDCl3) 139.3, 138.8,
133.7, 132.7, 132.3, 131.2, 130.6, 130.4, 129.1, 128.7,
128.6, 128.2, 127.7, 127.1, 126.7, 126.5, 126.4, 126.3,
126.2, 126.0, 125.9, 122.7, 121.4; m/z (EI, 30 eV) 304 (12,
Mþ), 178 (15%).
Compound 6f. [Found: C, 50.04; H, 4.62. C9H10S3 requires
C, 50.42; H, 4.70]; nmax (CHCl3) 1653, 1411, 1299 cm21
;
dH (CDCl3) 7.18 (1H, d, J¼5.2 Hz, ArH), 7.14 (1H, d, J¼
3.6 Hz, ArH), 6.95 (1H, dd, J¼5.2, 3.6 Hz, ArH), 6.31 (1H,
s, CvCH), 3.58–3.52 (4H, m, SCH2£2), 2.25–2.17 (2H, m,
CH2); dC (CDCl3) 145.0, 128.4, 127.3, 124.9, 123.8, 116.8,
32.6, 30.9, 30.3; m/z (EI, 30 eV) 214 (70, Mþ), 108 (45), 105
(30%). HRMS: found: 213.9942. C10H11NS2 requires
213.9945.
4.2.3. 2-(4-Nitrophenyl)-6,7-dihydro-5H-1,4-dithiepine
(6c). Reaction of 5c by the general procedure gave only
6c as light brownish solid in 55% yield (hexane/Et2O, 1:1).
Mp 120–1218C; [Found: C, 52.01; H, 4.49. C11H11NO2S2
requires C, 52.15; H, 4.38]; nmax (CHCl3) 1578, 1510,
1341 cm21; dH (CDCl3) 8.15 (2H, d, J¼8 Hz, ArH), 7.63
(2H, d, J¼8 Hz, ArH), 6.28 (1H, s, CvCH), 3.71–3.62 (4H,
m, SCH2£2), 2.28–2.22 (2H, d, CH2); dC (CDCl3) 147.5,
147.0, 132.4, 127.7, 123.5, 122.8, 33.0, 30.8, 30.0; m/z (EI,
30 eV) 253 (55, Mþ), 106 (50%).
Compound 10. Mp 93–948C. [Found: C, 55.95; H,.4.46.
C15H14S4 requires C, 55.86; H, 4.37]; nmax (CHCl3) 1614,
1557, 1423, 1285 cm21; dH (CDCl3) 7.48–7.38 (2H, m,
ArH), 7.40 (1H, d, J¼15.5 Hz, CvCH), 7.13–7.07 (2H, m,
ArH), 6.93–6.85 (2H, m, ArH), 6.28 (1H, d, J¼15.5 Hz,
CvCH), 3.03 (2H, t, J¼6.8 Hz, SCH2), 2.90 (2H, t, J¼
6.8 Hz, SCH2), 2.21–2.08 (2H, m, CH2); dC (CDCl3) 143.4,
138.6, 136.7, 129.8, 128.5, 127.6, 127.25, 126.9, 126.4,
125.9, 124.2, 123.2, 29.5, 29.3, 24.0; m/z (EI, 30 eV) 322
(100, Mþ), 247 (45), 216 (30), 203 (96), 171 (60%).
4.2.4. 2-(4-Methoxyphenyl)-6,7-dihydro-5H-1,4-dithie-
pine (6d) and (E)-3-(1,3-dithian-2-yliden)-1,3-di(4-meth-
oxyphenyl)-1-propene (9). Reaction of 5d by the general
procedure gave a mixture of 6d as yellowish oil (15%) and 9
as a pale yellowish solid (20%) (hexane/EtOAc, 4:1).
Compound 11. [Found: C, 50.46; H, 4.72. C9H10S3 requires
C, 50.42; H, 4.70]; nmax (CHCl3) 1562, 1428, 1419,
1300 cm21; dH (CDCl3) 7.25 (1H, d, J¼4.2 Hz, ArH),
7.07 (1H, J¼5.6 Hz, ArH), 7.05 (1H, s, CvCH), 6.96 (1H,
dd, J¼5.6, 4.2 Hz, ArH), 3.03–2.95 (4H, m, SCH2£2),
2.24–2.12 (2H, m, CH2); dC (CDCl3) 139.3, 127.8, 127.5,
126.4, 125.6, 122.8, 30.0, 29.6, 24.2; m/z (EI, 30 eV) 214
(90, Mþ), 140 (100%).
Compound 6d. [Found: C, 60.34; H, 6.05. C12H14OS2
requires C, 60.46; H, 5.92]; nmax (CHCl3) 1600, 1510, 1285,
1172 cm21; dH (CDCl3) 7.40 (2H, d, J¼8.8 Hz, ArH), 6.80
(2H, d, J¼8.8 Hz, ArH), 6.00 (1H, s, CvCH), 3.78 (s, 3H),
3.78–3.49 (m, 4H), 2.52–2.26 (m, 2H); dC (CDCl3) 159.48,
135.35, 133.76, 128.54, 116.30, 113.48, 55.31, 32.41, 31.11,
30.56; m/z (EI, 30 eV) 238 (90, Mþ), 132 (98), 106 (85%).
Acknowledgements
Compound 9. Mp 130–1318C; [Found: C, 68.15; H, 6.02.
C21H22O2S2 requires C, 68.07; H, 5.98]; nmax (CHCl3) 1606,
1510, 1285, 1174 cm21; dH (CDCl3) 7.57 (1H, d, J¼15 Hz,
CvCH), 7.29 (2H, d, J¼8.7 Hz, ArH), 7.12 (2H, d, J¼
8.7 Hz, ArH), 6.96 (2H, d, J¼8.7 Hz, ArH), 6.80 (2H, d,
J¼8.7 Hz, ArH), 5.93 (1H, d, J¼15 Hz, CvCH), 3.85 (3H,
s, OMe), 3.79 (3H, s, OMe), 3.02 (2H, t, J¼6.5 Hz, SCH2),
2.87 (2H, t, J¼6.5 Hz, SCH2), 2.19–2.12 (2H, m, CH2); dC
(CDCl3) 158.9, 158.8, 139.5, 131.0, 130.6, 130.1, 129.7,
127.6, 125.8, 114.0, 113.9, 113.6, 55.3, 55.2, 29.8, 29.5,
24.4; m/z (EI, 30 eV) 370 (100, Mþ), 309 (20), 237 (35%).
The authors wish to acknowledge the National Science
Council of Taiwan for financial support. The authors also
thank Dr Michael Y. N. Chang for performing the X-ray
analyses.
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