Photorearrangement of o-methoxystilbenoids in acid media

Article abstract of DOI:10.1002/jccs.200500113

Photorearrangements of o-methoxystilbenoils (1a-1c) in acid me dia have been investigated. Irradiation of o-methoxystilbene (1c), for ex am pie, could lead to three majorre arrangement products: 2,3,4- trihydro-phenanthren-1- ones(2c), frans-1-arylbut-2-e

Full text of DOI:10.1002/jccs.200500113

Journal of the Chinese Chemical Society, 2005, 52, 805-810
805
Photorearrangement of o-Methoxystilbenoids in Acid Media
Jinn-Hsuan Ho (
Department of Chemistry, National Taiwan University, Taipei, Taiwan, R.O.C.
), Jui-Hsien Lin (
) and Tong-Ing Ho* (
)
Photorearrangements of o-methoxystilbenoils (1a-1c) in acid media have been investigated. Irradiation
of o-methoxystilbene (1c), for example, could lead to three major rearrangement products: 2,3,4-trihydro-
phenanthren-1-ones (2c), trans-1-arylbut-2-en-1-ones (3c), and 1-hydroxy-9,10-dihydrophenanthrenes (7).
Further irradiation of trans-1-arylbut-2-en-1-ones (3) could afford three more products (4, 5 and 6). The key
step for this photorearrangement is acid-catalyzed formal [1,9] hydrogen shift. The products of the elimina-
tive and oxidative photoreaction were also obtained; the formation of the oxidative product is due to the fact
that the unfavorable methoxy group in the intermediate DHP-3 retards the rate of acid-catalyzed formal [1,9]
hydrogen shift.
Keywords: Photorearrangement; Acid catalysis; Protic acid.
INTRODUCTION
Photochemistry of stilbenes is versatile and important.
Scheme I Acid-Catalyzed photorearrangement of
p-methoxystilbene
1
2
3
The influence of substituents and reaction media for the
photochemical reaction of stilbene-type compounds usually
results in different products. A new type of photochemical re-
arrangement of p-methoxystilbene that occurs by utilizing
acid-catalyzed hydrolysis of intermediates of stilbene have
OCH3
OCH3
4
p-Methoxy-
trans-Stilbene
DHP-1
i)
DHP-2
4
been reported previously (Scheme I). The photorearrange-
(
(ii)
ment results from the occurrence of acid-catalyzed formal
O
[
1,9] hydrogen shift via protonation on carbon-4 and depro-
O
tonation on carbon-4b of the dihydrophenanthrene intermedi-
ate DHP-1. The selectivity of reaction products is due to the
existence of two reaction pathways for the intermediate
DHP-2; one is a 6 electron conrotatory ring-opening reaction
and the other is hydrolysis of methyl vinyl ether. The latter is
very sensitive to the concentration of hydrochloric acid. The
photoreaction is also sensitive to the neutral solvents used,
(
(
i) ring-opening reaction;
ii) acid-catalyzed hydrolysis, then formal [1,3]H shift.
7
gave the 9,10-dihydrophenathrene derivatives as the major
products with a trace of the photorearrangement products.
For the o-methoxystilbene, the photochemical rearrangement
could obviously occur. In this report, the synthesis and photo-
chemical reactions of 2-(o-methoxystyryl)thiophene (1a),
2-(o-methoxystyryl)furan (1b) and o-methoxy-stilbene (1c)
(Scheme II) are presented.
5
such as dichloromethane and benzene. Furthermore, this
type of photorearrangement of 4¢-substitutedstyrylhetero-
6
cycles is also sensitive to its substituent so that only weak
electron-donating groups can enhance the electron density on
carbon-4 of intermediate DHP-1 which will bring about the
formal [1,9] hydrogen shift and also the reaction following
the hydrogen shift.
Now we would like to focus on the effects of the orien-
tation of methoxy group towards this photochemical rear-
rangement. In a preliminary investigation, irradiation of m-
methoxystilbene in hydrochloric acid/acetonitrile solution
RESULTS AND DISCUSSION
9
According to the literature, irradiation of o-methoxy-
th
Dedicated to Professor Ching-Erh Lin on the Occasion of his 66 Birthday and his Retirement from National Taiwan University

8
06 J. Chin. Chem. Soc., Vol. 52, No. 4, 2005
Ho et al.
Scheme II o-Methoxy-styrylarenes used as starting
formed for 1a and 1c, but not for 1b (Table 1). In compound
1a (the thiophene system), the sulfur atom is less electro-
negative than oxygen (for compound 1b); the [1,9] H shift is
slower; therefore, it needs more irradiation time (18 hours).
The prolonged reaction time allows the side product to be-
come dominant and leads to higher yields for compounds 4,
material
OCH3
OCH3
OCH3
S
O
1
a
1b
1c
5
, and 6. For the least reactive system (compound 1c) the
cyclized plus the addition products are the dominant prod-
ucts.
stilbene (1c) in the neutral deaerated solvent will lead to an
eliminative photocyclization, which then released a methanol
to form phenanthrene. However, when 0.005 M hydrochloric
acid (equal to the concentration of 1) was added into the sol-
vent, the photochemical reaction of these ortho methoxy sub-
stituted reactants would become different and complicated.
Irradiation of 2-(o-methoxystyryl)thiophene (1a) in the 0.005
M hydrochloric acid/acentonitrile solution at 350 nm for 18
hours gave the products 2a-6a and cyclized products which
were separated by chromatography on silica gel (Scheme III).
Both 2a and 3a were the products of acid-catalyzed photo-
chemical rearrangement. Cyclized products resulted the oxi-
To further confirm the source of products 4a, 5a, and
6
a, isolated compound 3a was irradiated in acentonitrile so-
lution containing 0.01 M hydrochloric acid. After a 17 hr-
irradiation at 350 nm, the reaction showed 67% conversion,
and the products are 4a (31%), 5a (20%), and 6a (16%), and
2
a (12%). The formation of 4a is from 3a through the g-hy-
12
drogen abstraction of Norrish type II photoreaction. Prod-
uct 5a is formed through addition of hydrogen chloride. And
1
3
the product 6a was formed via the dehalogenation of 4a.
Product 2a could also formed from 3a through 4a which is
undergoing acid catalyzed electrophilic aromatic substitu-
tion.
1
0
9
dative and eliminative photocyclization, respectively.
Products 4a, 5a and 6a should be secondary products which
are derived from the product 3a. Irradiation of 1a in 0.5 M hy-
drochloric acid/acetonitrile solution gave 7a as the major
product and minor products 2a-6a.
That the reaction results in 0.005 M hydrochloric acid
can be explained reasonably by the mechanism described in
Scheme IV. While irradiating at 350 nm, reactant 1c was
transformed to intermediates DHP-3 or DHP-4 via six elec-
tron conrotatory ring-closure and the side products, such as
oxidative and eliminative cyclized products, were derived
from them. For the intermediate DHP-3, there is another re-
action pathway, which is acid-catalyzed formal [1,9] hydro-
gen shift to form DHP-5. The electron density on the reactive
site (carbon-4) of DHP-3 is of great influence on the product
distribution. It is weaker for the methoxy group on carbon-1
than on carbon-3 (for the p-methoxystilbene system); there-
fore, the rate of this formal [1,9] hydrogen shift would be
slower. In DHP-5, there were two reaction pathways leading
to two different products. In one pathway, DHP-5 could un-
dergo formal [1,5] hydrogen shift to form DHP-6, and then
product 2 was produced by the hydrolysis of methyl vinyl
ether. The other pathway for DHP-5 is a six-electron ring-
opening reaction to intermediate 8, which follows the hydro-
lysis of dienyl methyl ether to product 3. Because 3 was un-
stable under this reaction condition, products 4, 5 and 6 were
formed by further irradiation. In the o-methoxystilbene sys-
tem, the selectivity of products is not as good as that in the p-
Scheme III
O
O
O
O
S
S
S
S
S
S
2
a
3a
4a
7a
O
Cl
OH
5
a
6a
Cl
OCH3
Ar'
Ar
S
S
Oxidative
Cyclized
Product
Eliminative
Cyclized
Product
HCl-Addition
Product
Photochemical rearrangements of 1b and 1c also oc-
4
curred in the acid media, but there are different product distri-
butions according to different reactants. In the excess hydro-
chloric acid (0.5 M), another rearrangement product 7 and
methoxystilbene system. It is because the competing steps in
DHP-5 are the ring-opening reaction and the formal [1,5] hy-
drogen shift that neither is very sensitive to the acid concen-
tration. To analyze the distribution of products, more than
1
1
photoaddition products with hydrochloride were also

Photorearrangement of o-Methoxystilbenoids in Acid Media
J. Chin. Chem. Soc., Vol. 52, No. 4, 2005 807
Table 1. The results for photoreactions of o-methoxystilbenes (1a-1c) in acid media
Yields (%)
a
React.
[HCl]
hv time conver.
2
3
(4+5+6)
7
cyclized
addition
1
1
1
1
1
a
a
b
b
c
0.005
0.5
0.005
0.5
18
18
05
05
50
100
037
100
062
100
08
16
05
25
13
27
08
14
05
09
24
05
25
06
05
00
23
00
00
13
34
33
44
32
32
0
3
0
0
180
0.5
a
1
For 1b and 1c, The amount of products 4-6 were decided by estimating by H NMR spectra.
Scheme IV Mechanism for 1c
8
9
7
H CO
3
6
1
2
cis-1c
OCH3
5
4
3
DHP-4
Eliminative
Cyclization
DHP-3
5
4
3
1
OCH3
OCH3
OCH3
2
Oxidative
Cyclization
DHP-5
DHP-6
O
OCH3
O
3
c
8c
2
c
5
0% of the intermediate DHP-3 should undergo formal [1,9]
Scheme V Reaction for DHP-3 at higher acid concen-
hydrogen shift, and this rearrangement was still the main re-
action pathway in the acid calatyzed photochemical reaction
of o-methoxystilbenes.
tration
H
O
OH
While in the presence of 0.5 M hydrochloric acid, ir-
radiation of 1a and 1c afford another new product, 10-hy-
droxy-6,7-dihydronaphatho[1,2-b]thiophene 7a and 1-hy-
droxy-9,10-dihydrophenathrene 7c, respectively. Because of
the effect of the excess acid, the acid-catalyzed hydrolysis of
the dienyl methyl ether to enol group may become a primary
process for DHP-3 (Scheme V). Another unstable intermedi-
ate DHP-7 was formed and then transformed to a stable
DHP-3
DHP-7
O
O
7
c
for the involvement of the hydrolysis of DHP-3 because the
rate of the [1,9] hydrogen shift in DHP-3b is very fast so that
the rate of hydrolysis can not compete with it even in 0.5 M
hydrochloric acid media. Furthermore, the existence of ex-
cess acid may retard the reaction conversion; this should be
because the rate of acid-catalyzed formal [1,9] hydrogen shift
9
,10-dihydophenathrene via a series of acid-catalyzed formal
[
1,x] hydrogen shift. The formation of 7 can not result from
two simple [1,3] hydrogen shifts because none of the 1-meth-
oxy-9,10-dihydrophenanthrene was discovered during the ir-
radiation. The lack of product 7b is another piece of evidence

8
08 J. Chin. Chem. Soc., Vol. 52, No. 4, 2005
Ho et al.
is sensitive to the concentration of acids.
tracted with ethyl acetate. The EtOAc was dried with anhy-
drous MgSO
4
and the solvent removed in vacuum. The resid-
ual mixture was then filtered quickly on silica gel with hex-
ane as the eluent. The spectral data of the reactants 1a-1c is
listed below.
CONCLUSION
In conclusion, irradiation of o-methoxystilbenoids in
the presence of 1 equivalent hydrochloric acid can afford re-
arrangement products 2,3,4-trihydrophenathren-1-ones 2,
and 1-arylbut-2-en-1-ones 3. But product 3 is unstable in the
reaction condition and will undergo further reactions to give
products 4, 5, and 6. With irradiation of o-methoxystilbenes
in 0.5 M acid media, another major product 7 is formed in-
stead. The reason for the distribution of products can be de-
scribed reasonably in Schemes IV and V. In analyzing the dis-
tribution of products, we found that more than 50% of the re-
actants undergo this photorearrangement reaction for o-meth-
oxystilbenes. There is no such photorearrangement reaction
for m-methoxystilbenes.
trans-2-(2¢-Methoxystyryl)thiophene (1a)
1
3
H NMR (300 MHz, CDCl ) d 7.48 (dd, J = 7.5, 1.4 Hz,
1H), 7.26 (s, 2H), 7.18 (tm, J = 7.7 Hz, 1H), 7.12 (d, J = 4.9
Hz, 1H), 7.02 (dd, J = 3.7, 1.1 Hz, 1H), 6.94 (dd, J = 4.9, 3.7
Hz, 1H), 6.91 (t, J = 7.5 Hz, 1H), 6.82 (d, J = 8.0 Hz, 1H), 3.81
1
3
3
(s, 3H). C NMR (75 MHz, CDCl ) d 156.74, 143.57,
128.50, 127.40, 126.39, 125.80, 125.63, 123.96, 123.23,
122.23, 120.61, 110.80, 55.29.
trans-2-(2¢-Methoxystyryl)furan (1b)
1
3
H NMR (300 MHz, CDCl ) d 7.50 (dd, J = 7.5, 1.4 Hz,
1H), 7.40 (d, J = 1.5 Hz, 1H), 7.35 (d, J = 16.4 Hz, 1H), 7.23
td, J = 7.4, 1.8 Hz, 1H), 6.97 (d, J = 16.4 Hz, 1H), 6.95 (t, J =
.7 Hz, 1H), 6.90 (d, J = 8.1 Hz, 1H), 6.41 (dd, J = 3.3, 1.5 Hz,
(
7
1
3
EXPERIMENTAL SECTION
General Methods
1H), 6.34 (d, J = 3.3 Hz, 1H), 3.89 (s, 3H). C NMR (100
MHz, CDCl ) d 156.81, 153.70, 141.75, 128.42, 126.49,
3
125.89, 122.13, 120.58, 117.13, 111.44, 110.86, 108.01,
55.52.
1
13
H and C NMR spectra were recorded using CDCl
3
solutions on Bruker AM-200 WB FT-NMR, Bruker AM-300
WB FT-NMR, and Bruker FT-NMR 400 MHz. Chemical
shifts are reported in parts per million (ppm) relative to TMS
as internal standards. Mass spectra were determined with a
Finnigan MAT TSCE-46C Spectrometer and high resolution
mass spectra with a JEOL JMS-HX110 spectrometer. A
Rayonet Photochemical Reactor (350 nm) was used as the ir-
radiation source. The acetonitrile used for irradiation is of
HPLC commercial grade without further purification. The
hydrochloride/acetonitrile solution was prepared by diluting
the concentrated HCl(aq) with acetonitrile.
o-Methoxy-trans-stilbene (1c)
1
3
H NMR (300 MHz, CDCl ) d 7.60 (dd, J = 7.9, 1.3 Hz,
1H), 7.54 (d, J = 7.6 Hz, 2H), 7.49 (d, J = 16.5 Hz, 1H), 7.35
(t, J = 7.6 Hz, 2H), 7.28-7.20 (m, 2H), 7.11 (d, J = 16.5 Hz,
1H), 6.97 (t, J = 7.4 Hz, 1H), 6.90 (d, J = 8.1 Hz, 1H), 3.89 (s,
1
3
3
3H). C NMR (75 MHz, CDCl ) d 156.83, 137.88, 128.99,
128.59, 128.50, 127.27, 126.49, 126.31, 126.31, 123.40,
120.66, 110.84, 55.39.
General Irradiation Procedure in the Presence of Hy-
drochloric Acid
Preparation of o-Methoxy-trans-stilbenoids (1a-1c)
A 70 mL acetonitrile solution containing o-methoxy-
trans-stilbenes (0.005 M) and ca. 0.5 M (or 0.005 M) hydro-
chloric acid in a Pyrex tube was deaerated by bubbling nitro-
gen for 20 min and was irradiated with a Rayonet Photochem-
ical Reactor at 350 nm. After irradiation, the solution was
neutralized with 1 M NaOH(aq) solution and diluted with wa-
ter. The aqueous layer was extracted with ethyl acetate sev-
eral times; then the EtOAc solution was collected and dried
All stilbene-type reactants were synthesized by Wittig
8
type reaction. The mixture of 2-methoxybenzyl chloride
4
.07 gm (26 mmol) and triethylphosphite 5.15 gm (31 mmol)
was refluxed under nitrogen atmosphere for 4 hours, and the
reaction was cooled down to room temperature. 20 mL dry
DMF was added as solvent, and then sodium methoxide 2.8
gm (52 mmol) was added quickly into the reaction at 0 °C.
After stirring for 10 min, the arylaldehyde 26 mmol was
added slowly. The reaction was kept stirring for several hours
at the room temperature. The reaction mixture was poured
into a lot of ice water, and then the aqueous layer was ex-
4
by anhydrous MgSO . The solvent was removed in vacuum
and the residual mixture was preliminarily separated by chro-
matography on silica gel with ethyl acetate and hexane as the
eluent. Each product was further purified by PTLC. The spec-

Photorearrangement of o-Methoxystilbenoids in Acid Media
J. Chin. Chem. Soc., Vol. 52, No. 4, 2005 809
+
tral data of these products are listed below.
111.46, 107.24, 18.58. MS (EI, 70 eV): 186 (M , 54), 171
(
10 2
28), 157 (7), 145 (100), 117 (29). HRMS (C12H O ) calc’d:
7
,8,9-Trihydronaphtho[2,1-b]thiophene-6-one (2a)
186.0681, found: 186.0684.
1
3
H NMR (400 MHz, CDCl ) d 8.04 (d, J = 8.5 Hz, 1H),
7
.80 (dd, J = 8.5, 0.6 Hz, 1H), 7.54 (d, J = 5.5 Hz, 1H), 7.50
1-(Naphthalen-2-yl)but-2-en-1-one (3c)
1
(
dd, J = 5.5, 0.7 Hz, 1H), 3.28 (t, J = 6.1 Hz, 2H), 2.72 (t, J =
3
H NMR (300 MHz, CDCl ): d 8.45 (s, 1H), 8.05-7.87
1
3
6
.6 Hz, 2H), 2.67 (fifth, J = 6.4 Hz, 2H). C NMR (100 MHz,
) d 198.26, 144.54, 140.20, 138.04, 128.94, 127.30,
22.52, 122.31, 120.64, 38.61, 27.06, 22.99. MS (EI, 70 eV):
(m, 4H), 7.63-7.53 (m, 2H), 7.22-7.10 (m, 1H), 7.08 (d, J =
1
3
CDCl
3
15.6 Hz, 1H), 2.05 (d, J = 5.4 Hz, 3H). C NMR (75 MHz,
CDCl ): d 190.55, 145.01, 135.39, 135.20, 132.51, 129.95,
1
2
3
+
02 (M , 100), 187 (24), 174 (88), 161 (18), 146 (81). HRMS
10OS) calc’d: 202.0452, found: 202.0457.
129.46, 128.44, 128.27, 127.78, 127.46, 126.70, 124.52,
(
C
12
H
18.68. (Literature Data: J. Org. Chem. 1990, 55, 4364-
4
370.)
7
,8,9-Trihydronaphtho[2,1-b]furan-6-one (2b)
1
H NMR (300 MHz, CDCl
3
): d 8.06 (d, J = 8.8 Hz, 1H),
1-(Benzo[b]thiophen-5-yl)but-3-en-1-one (4a)
1
7
2
2
1
1
8
.69 (d, J = 2.2 Hz, 1H), 7.43 (d, J = 8.8 Hz, 1H), 6.87 (d, J =
.2 Hz, 1H), 3.15 (t, J = 6.1 Hz, 2H), 2.72 (t, J = 6.5 Hz, 2H),
3
H NMR (300 MHz, CDCl ) d 8.45 (s, 1H), 7.95 (s, 2H),
7.54 (d, J = 5.5 Hz, 1H), 7.45 (d, J = 5.5 Hz, 1H), 6.18-6.07
(m, 1H), 5.28 (d, J = 1.4 Hz, 1H), 5.24-5.21 (m, 1H), 3.86 (dt,
1
3
3
.24 (fifth, J = 6.3 Hz, 2H). C NMR (75 MHz, CDCl ): d
1
3
97.83, 157.25, 145.84, 139.18, 127.96, 126.19, 124.13,
3
J = 6.6, 1.4 Hz, 3H). C NMR (75 MHz, CDCl ) d 197.86,
+
10.23, 105.62, 38.83, 26.74, 23.09. MS (70 eV, EI): 186 (M ,
144.37, 139.43, 133.19, 131.23, 127.89, 124.61, 124.31,
+
), 169 (8), 158 (12), 141 (12), 85 (60). HRMS (C12
H
10
O
2
):
123.51, 122.64, 118.70, 43.60. MS (EI, 70 eV): 202 (M , 12),
calc’d 186.0681, found 186.0685.
187 (5), 171 (3), 161 (100), 133 (47). HRMS (C12
calc’d: 202.0452, found: 202.0454.
H10OS)
2
,3,4-Trihydrophenanthren-1-one (2c)
1
H NMR (300 MHz, CDCl
3
): d 8.16-8.13 (m, 1H), 8.12
1-(Benzo[b]thiophen-5-yl)-3-chlorobutan-1-one (5a)
1
(
d, J = 8.9 Hz, 1H), 7.90-7.86 (m, 1H), 7.76 (d, J = 8.7 Hz,
3
H NMR (300 MHz, CDCl ) d 8.44 (s, 1H), 7.96 (s, 2H),
1
6
H), 7.65-7.56 (m, 2H), 3.40 (t, J = 6.1 Hz, 2H), 2.75 (t, J =
7.55 (d, J = 5.3 Hz, 1H), 7.46 (d, J = 5.3 Hz, 1H), 4.72 (sixth, J
= 6.6 Hz, 1H), 3.69 (dd, J = 16.9, 6.4 Hz, 1H), 3.34 (dd, J =
1
3
.6 Hz, 2H), 2.31 (fifth, J = 6.4 Hz, 2H). C-NMR (75 MHz,
): d 198.59, 142.96, 135.73, 131.42, 130.03, 128.79,
28.29, 126.94, 126.70, 124.83, 122.78, 38.39, 25.64, 22.78.
Literature Data: Magn. Reson. Chem. 1989, 27, 606-607.)
1
3
CDCl
3
16.9, 6.5 Hz, 1H), 1.67 (d, J = 6.6 Hz, 3H). C NMR (75
MHz, CDCl ) d 196.42, 144.66, 139.43, 133.23, 128.07,
124.60, 124.20, 123.23, 122.75, 52.90, 48.69, 25.37. MS (EI,
1
3
(
+
+
7
0 eV): 240 (M +2, 4), 238 (M , 8), 202 (27), 187 (16), 174
3
7
1
-(Benzo[b]thiophen-5-yl)but-2-en-1-one (3a)
(9), 161 (100), 133 (34). HRMS (C12
H
11O ClS) calc’d:
1
35
H NMR (300 MHz, CDCl
3
) d 8.41 (s, 1H), 7.94 (s, 2H),
240.0190, found: 240.0188; (C12
found: 238.0244.
H
11O ClS) calc’d: 238.0219,
7
1
.52 (d, J = 5.5 Hz, 1H), 7.43 (d, J = 5.5 Hz, 1H), 7.12 (dq, J =
5.9, 6.4 Hz, 1H), 7.01 (d, J = 15.9 Hz, 1H), 2.03 (d, J = 6.9
1
3
Hz, 3H). C NMR (75 MHz, CDCl
3
) d 190.44, 144.80,
1-(Benzo[b]thiophen-5-yl)butan-1-one (6a)
1
1
43.88, 139.35, 134.41, 127.70, 127.53, 124.54, 124.43,
We failed to separate this compound several times, so
+
23.89, 122.56, 18.60. MS (EI, 70 eV): 202 (M , 75), 187
10OS) calc’d:
we compared the characteristic peaks of the butanone group
1
(
28), 174 (14), 161 (100), 133 (46). HRMS (C12
H
with butyrophenanone: H NMR (300 MHz, CDCl
3
) d 3.04 (t,
2
02.0452, found: 202.0451.
J = 7.3 Hz, 2H), 1.82 (sixth, J = 7.3 Hz, 2H), 1.04 (t, J = 7.3
Hz, 3H). (ref: Aldrich)
1
-(Oxainden-5-yl)but-2-en-1-one (3b)
1
H NMR (200 MHz, CDCl
3
) d 8.24 (d, J = 1.7 Hz, 1H),
6-Hydroxy-4,5-dihydronaphtho[1,2-b]thiophene (7a)
1
7
.95 (dd, J = 8.7, 1.7 Hz, 1H), 7.70 (d, J = 2.2 Hz, 1H), 7.56
3
H NMR (300 MHz, CDCl ) d 7.32 (d, J = 5.2 Hz, 1H),
(
d, J = 8.7 Hz, 1H), 7.11 (dq, J = 15.7, 6.4 Hz, 1H), 6.99 (d, J =
5.7 Hz, 1H), 6.86 (dd, J = 2.2, 0.8 Hz, 1H), 2.02 (d, J = 6.4
7.15-7.08 (m, 3H), 6.66 (m, 1H), 4.79 (s, br, 1H), 3.00 (m,
1
3
1
3
4H). C NMR (100 MHz, CDCl ) d 152.68, 137.07, 135.37,
1
3
Hz, 3H). C NMR (75 MHz, CDCl
3
) d 190.24, 157.32,
133.87, 127.20, 123.53, 122.40, 120.01, 115.97, 113.76,
+
1
46.29, 144.53, 133.36, 127.66, 127.49, 125.29, 122.68,
22.91, 21.66. MS (EI, 70 eV): 202 (M , 100), 185 (20), 171

8
10 J. Chin. Chem. Soc., Vol. 52, No. 4, 2005
Ho et al.
(
18). HRMS (C12
H
10OS) calc’d: 202.0452, found: 202.0435.
Org. Chem. 1992, 5, 355-360. (c) Lewis, F. D.; Cohen, B. E.
J. Phys. Chem. 1994, 98, 10591-10597. (d) Nakayama, T.;
Hamana, T.; Miki, S.; Hamanoue, K. J. Chem. Soc., Faraday
Trans. 1996, 92, 1473-1479. (e) Saito, M.; Kamei, Y.;
Kuribara, K.; Yoshioka, M. J. Org. Chem. 1998, 63, 9013-
Received February 17, 2005.
9
018.
. (a) Ho, T.-I.; Ho, J.-H.; Wu, J.-Y. J. Am. Chem. Soc. 2000,
22, 8575-8576. (b) Ho, J.-H; Ho, T.-I.; Liu, R. S. H. Org.
Lett. 2001, 3, 409-411.
4
REFERENCES
1
1
. (a) Hugelshofer, P.; Kalvoda, J.; Schaffner, K. Helvetica
Chim. Acta 1960, 165, 1322-1332. (b) Hammond, G. S.;
Turro, N. J. Science 1962, 142, 1541-1553. (c) Hammond,
G. S.; Saltiel, J. J. Am. Chem. Soc. 1963, 84, 4983-4984. (d)
Stephenson, L. M.; Hammond, G. S. Angew. Chem., Int. Ed.
Engl. 1969, 8, 261-270. (e) Kaupp, G. Angew. Chem. 1980,
5. Wu, J.-Y.; Ho, J.-H.; Shih, S.-M.; Hsieh, T.-L.; Ho, T.-I. Org.
Lett. 1999, 1, 1039-1041.
6. Ho, T.-I.; Wu, J.-Y.; Wang, S.-L. Angew. Chem. Int. Ed.
1999, 38, 2558-2560.
7. Ho, J.-H.; PhD. Thesis, National Taiwan University, 2001.
8. Petrova, J.; Momchilova, S.; Vassilev, N. G. Phosphorus,
Sulfur Silicon Relat. Elem. 1992, 68, 45-52.
9. Horspool, W. M. J. Photochem. 1984, 27, 122.
10. Kaupp, G.; Ringer, E. Chem. Ber. 1986, 199, 1525.
11. Oppolzer, W. Acc. Chem. Res. 1982, 15, 135.
12. Yang, N. C.; Elliott, S. P. J. Am. Chem. Soc. 1969, 91, 7550.
13. Kropp, P. J. Acc. Chem. Res. 1984, 17, B1.
9
2, 245-277; Angew. Chem., Int. Ed. Engl. 1980, 19, 243-
75. (f) Mallory, F. B.; Mallory, C. W. Organic Reactions;
2
Wiley: New York, 1983; Vol. 30, pp 1-456. (g) Waldeck, D.
H. Chem. Rev. 1991, 91, 415-436.
. Gudton, H.; Klasinc, L. Tetrahedron Lett 1968, 33, 3097.
. (a) Schultz, A. G. Acc. Chem. Res. 1983, 16, 210-218. (b)
Inoue, H.; Sakurai, T.; Hoshi, T.; Ono, I.; Okubo, J. J. Phys.
2
3