A mild isomerization reaction for β,γ-unsaturated ketone to α,β-unsaturated ketone

Article abstract of DOI:10.1002/jccs.200400058

A series of β,γ-unsaturated ketones were isomerized to their corresponding α,β-unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo-cyclic double bond (β,γ-position) on ketone was rearranged to exo-cyclic double bond (α,β-position) under the reaction conditions.

Full text of DOI:10.1002/jccs.200400058

Journal of the Chinese Chemical Society, 2004, 51, 371-376
371
A Mild Isomerization Reaction for b,g-Unsaturated Ketone to
a,b-Unsaturated Ketone
Adam Shih-Yuan Lee* (
Shu-Huei Wang (
Department of Chemistry, Tamkang University, Tamsui, Taiwan 251, R.O.C.
), Mei-Chun Lin (
) and Li-Shin Lin (
),
)
A series of b,g-unsaturated ketones were isomerized to their corresponding a,b-unsaturated ketones by
the introduction of DABCO in iPrOH at room temperature. The endo-cyclic double bond (b,g-position) on
ketone was rearranged to exo-cyclic double bond (a,b-position) under the reaction conditions.
Keywords: Isomerization; b,g-unsaturated ketone; a,b-unsaturated ketone; DBU.
Rearrangement of carbon-carbon double bond is an im-
portant and useful method in organic synthesis.1-4 a,b-Unsat-
urated carbonyl compounds play an important role and are
ideal precursors for 1,4-addition reactions5-7 and Diels-Alder
reactions.8-11 Isomerization reaction for b,g-unsaturated
ketone to a,b-unsaturated ketone is a prerequisite for the
preparation of these synthetic intermediates in synthetic
chemistry. The rearrangement reaction of b,g-unsaturated
ketone to a,b-unsaturated ketone is typically performed with
acidic reagents such as HCl,12 H2SO413 and p-TsOH14 or with
basic reagents such as Et3N,15 DBU,16 NaOH17 and tBuOK.18
The yield of expected isomerized product usually is low and
accompanied by side products when the a-protons exist on
the b,g-unsaturated ketone. Herewith, we wish to report a
mild and an efficient double bond isomerization reaction for
b,g-unsaturated ketone by using DABCO (1,4-Diazabicyclo-
[2.2.2]octane) as base, and the b,g-double bond is rearranged
to a,b-position at room temperature.
gated the double bond rearrangement reaction of 5-phenyl-
pent-1-en-4-one under acidic reaction conditions. The very
low yield of expected a,b-unsaturated ketone and some un-
identified compounds as major products were obtained under
these acidic reaction conditions. Therefore, we then investi-
gated the isomerization reaction under basic reaction condi-
tions and using methanol as solvent and as proton source
(Scheme II). The b-methoxy ketone A was produced as the
major product when amines such as Et2NH, iPr2NH and DBU
(1,5-diazabicyclo[5.4.0]undec-5-ene) were introduced. The
experimental results showed that DABCO was the best
choice for the rearrangement reaction, and 80% yield of
a,b-unsaturated ketone I was produced and without the for-
mation of A. It should be noted that one equivalent of
DABCO is necessary for the rearrangement reaction. The
choice of solvent exhibits a tremendous impact for this rear-
rangement reaction; the yield of isomerized ketone increased
to 89%, and fewer unidentified side products were observed
when iPrOH was used instead of MeOH.
Scheme I
Scheme II
Our previous studies showed that b,g-unsaturated ke-
tones were synthesized by a Lewis acid promoted Barbier-
type reaction.19 It should be noted that the isomerized a,b-un-
saturated ketone was not detected and obtained after acidic
quenching. We think that a simple method for the synthesis of
a,b-unsaturated ketones may be achieved by the isomeriza-
tions of b,g-unsaturated ketones. Thus, we firstly investi-

372 J. Chin. Chem. Soc., Vol. 51, No. 2, 2004
Lee et al.
A series of b,g-unsaturated ketones was investigated
and transformed to a,b-unsaturated ketones under the reac-
tion conditions, and the results are shown in Table 1. All the
b,g-unsaturated ketones were converted to a,b-unsaturated
ketones with moderate to high yields under the reaction con-
ditions. The b,g-unsaturated ketones which exist a-protons
on substituents also undergo isomerization reactions and con-
vert to their corresponding a,b-unsaturated ketones with
high yields (Table 1, Entries 1-3, 6-8).
or under a higher temperature (refluxing reaction condition
for 2 hours). The rearrangement reaction for oct-1,6-dien-4-
one (Table 1, Entry 3) was also investigated and a higher
yield (78%) and more isomerization completion (3a/3b =
1/5) was achieved under refluxing reaction conditions.
The reaction mechanism for this mild isomerization is
not clear. We think that DABCO (base) and alcohol (acid) as
solvent and proton source may provide an acid-base complex
to generate the isomerization process. Therefore, we believe
that these mild isomerization reaction conditions can be fur-
ther applied to some compounds which contain sensitive
functionality such as a hydroxy group. The existing hydroxy
group behaves as a proton source and then the isomerization
reaction may proceed in aprotic solvent instead of protic sol-
The isomerization reaction for endo-cyclic double
bond on b,g-unsaturated ketone (Table 1, Entry 2) was further
investigated under the optimum reaction conditions. The
2a/2b ratio remained even when the reaction was proceeded
at room temperature for a prolonged reaction time (72 hours)
Table 1. Isomerizations for b,g-Unsaturated Ketones to a,b-Unsaturated Ketones
Entry
Substrate
Product
Time (h)
Yielda
89%
O
O
1
2
CH3
O
O
4
1
76% (1/2)b
79% (1/2)c
O
2
3
4
CH3
CH3
2a
2b
O
O
47% (2/1)d
78% (1/5)e
O
2
1
CH3
CH3
3a
3b
O
O
1
74%
CH3
O
O
CH3
5
6
2
2
88%
89%
MeO
MeO
O
O
CH3
O
O
O
CH3
7
8
2
2
92%
86%
O
S
S
CH3
a The yields were determined after chromatographic purification.
b The 2a/2b ratio was obtained under the optimum reaction conditions.
c The 2a/2b ratio was obtained under refluxing reaction conditions.
d The 3a/3b ratio was obtained under the optimum reaction conditions.
e The 3a/3b ratio was obtained under refluxing reaction conditions.

A Mild Isomerization from b,g- to a,b-Unsaturated Ketone
J. Chin. Chem. Soc., Vol. 51, No. 2, 2004 373
vent. Thus, we synthesized b-hydroxy allyl ketone and inves-
tigated the isomerization reaction for its b,g-position double
bond under aprotic solvent (Scheme III). These compounds
were transformed to their corresponding a,b-unsaturated ke-
tones in good yields in THF instead of iPrOH and without the
protection of a hydroxy group.
ters (cm-1).
All experiments were carried out under a nitrogen at-
mosphere which was dried primarily by passing through a
column of potassium hydroxide (KOH) layered with calcium
sulfate (CaSO4). Methanol and i-propanol were distilled from
sodium and recirculated prior to use. Hexane and ethyl ace-
tate were distilled from calcium hydride. Thin-layer chroma-
tography (TLC) analysis was performed on a plastic plate (or
aluminum sheet) precoated with silica gel (Merck, 5554 Sil-
ica gel 60F254). Visualization was accomplished by UV light
or developed by spraying with a 10% phosphomolybdic acid
ethanol solution. Column chromatography was performed
using silica gel (Merck 230-400 mesh) and ethyl acetate/hex-
ane mixture as the eluent. All reagents (Table 1 and 2) were
purchased from Aldrich, Merck and Riedel-deHaen and all
were used directly without further purification. b,g-Unsatu-
rated ketones shown in Table 1 were prepared by the reported
method.19
Scheme III
HO
O
HO
O
1.0 eq. DABCO,
THF, rt.
R
R
R =
5h
5h
96%
O
80%
77%
S
O
4h
O
In conclusion, we demonstrated a mild and an efficient
rearrangement reaction for the b,g-unsaturated ketone to
a,b-unsaturated ketone under DABCO/iPrOH reaction con-
ditions. The b,g-endo-cycilc double bond of ketone can be re-
arranged to a,b-exo-cyclic double bond under the reaction
conditions. The b-hydroxy allyl ketone also was isomerized
to its a,b-unsaturated ketone under DABCO/THF reaction
conditions at room temperature and without the protection of
a hydroxy group.
Typical procedure for isomerization reaction of b,g-un-
saturated ketone to a,b-unsaturated ketone
A reaction mixture of b,g-unsaturated ketone (1.0
mmol) and DABCO (1.0 mmol) in anhydrous iPrOH (5.0
mL) was stirred at room temperature. After the reaction was
complete (monitored by TLC), the organic solvent was re-
moved directly under reduced pressure. Further purification
was achieved on a flash chromatograph with silica gel and
ethyl acetate/hexane as eluant. Isomerizations were investi-
gated under the typical procedure, and the yields are the iso-
lated yields after chromatography. All these b,g-unsaturated
ketones and a,b-unsaturated ketones were characterized by
spectral analysis and by comparsion with the authentic com-
pounds.
EXPERIMENTAL SECTION
1
The H-NMR (proton nuclear magnetic resonance)
spectra were recorded at 300 MHz (Bruker-AC300P) with
deuteriochloroform (CDCl3, Aldrich 99.8 atom% D) as the
solvent and the internal standard. The 13C-NMR (carbon nu-
clear magnetic resonance) spectra were recorded at 75.5 MHz
(Bruker-AC300P) with CDCl3 as the solvent and the internal
standard. Chemical shifts are reported in parts per million
and resonance patterns are reported with the notations of ei-
ther s (singlet), d (doublet), t (triplet), q (quartet), or m (multi-
plet). Coupling constants (J) are reported in hertz (Hz). Mass
spectra (MS) were recorded on JOEL SX-102A and VG
70-250S spectrophotometers and are reported in m/e units for
the most abundant peaks. Infrared spectra (IR) were recorded
on a BIO-RAD FTS-40 infrared spectrophotometer as a liq-
uid film (neat) or a Nujol mull. Polystyrene was used as a
standard, and the spectra are reported in reciprocal centime-
4-Methoxy-1-phenyl-pentan-2-one (Scheme II, A)
1H-NMR: d 1.13 (3H, d, J = 6.1 Hz), 2.43 (1H, dd, J =
15.9, 5.5 Hz), 2.74 (1H, dd, J = 15.9, 7.1 Hz), 3.28 (3H, s),
3.71 (2H, s), 3.78 (1H, ddq, J = 7.1, 5.5, 6.1 Hz), 7.18-7.35
(5H, m). 13C-NMR: d 19.0, 48.6, 50.9, 56.1, 73.1, 126.8,
128.5, 129.4, 133.9, 206.5. IR (neat): 3088 (sp2-CH, w), 3064
(sp2-CH, w), 3030 (sp2-CH, w), 2974 (sp3-CH, m), 2932
(sp3-CH, m), 2824 (sp3-CH, m), 1717 (C=O, s), 1603 (w),
1373 (w), 1193 (w), 1134 (C-O, s), 1088 (C-O, s), 902 (w),
751 (w), 701 (s) cm-1. HRMS: 192.1142 (calcd. for C12H16O2,
192.1150). MS: m/z 193 (3, M+1), 192 (17, M), 118 (10), 105

374 J. Chin. Chem. Soc., Vol. 51, No. 2, 2004
Lee et al.
(12), 101 (17), 91 (28), 77 (6), 69 (12), 65 (6), 59 (base).
1.5 Hz), 3.21 (2H, dd, J = 4.5, 1.8 Hz), 5.53-5.57 (2H, m),
6.13 (1H, dq, J = 15.6, 1.5 Hz), 6.86 (1H, dq, J = 15.6, 6.8
Hz). 13C-NMR: d 17.9, 18.1, 44.0, 123.3, 129.3, 131.2, 142.9,
198.4. HRMS: 124.0873 (calcd. for C8H12O, 124.0888). MS:
m/z 124 (1, M), 99 (15), 97(17), 88 (11), 86 (68), 84 (base), 69
(60), 51 (45).
Oct-1-en-4-one (Table 1, Entry 1)
1H-NMR: d 0.90 (3H, t, J = 7.3), 1.31 (2H, m), 1.56
(2H, m), 2.43 (2H, t, J = 7.3 Hz), 3.16 (2H, d, J = 7.0 Hz), 5.10
(1H, dd, J = 16.9, 1.4 Hz), 5.17 (1H, dd, J = 9.5, 1.0 Hz), 5.92
(1H, m). 13C-NMR: d 13.8, 22.3, 25.8, 42.1, 47.7, 118.6,
130.7, 208.9. HRMS: 126.1045 (calcd. for C8H14O, 126.1044).
MS: m/z 119 (34), 117 (31), 111 (21), 97 (21), 91 (33), 85
(44), 83 (24), 71 (42), 69 (69), 58 (50), 57 (base), 55 (42), 43
(93), 41 (79), 39 (29), 29 (52), 27 (25), 18 (86), 15 (26).
Octa-2,5-dien-4-one (Table 1, Entry 3, 3b)
1H-NMR: d 1.08 (3H, t, J = 7.4 Hz), 1.91 (3H, dd, J =
6.8, 1.3 Hz), 2.20-2.31 (2H, m), 6.30 (1H, dt, J = 15.0, 1.7
Hz), 6.35 (1H, dq, J = 15.6, 1.3 Hz), 6.85-6.98 (2H, m).
13C-NMR: d 12.2, 18.2, 25.6, 127.7, 130.2, 142.7, 149.0,
189.4. HRMS: 124.0878 (calcd. for C8H12O, 124.0888). MS:
m/z 125 (6, M+1), 124 (8, M), 123 (9), 109(22), 97 (11), 95
(12), 83 (68), 69 (base), 57 (16), 55 (32), 53(10).
Oct-2-en-4-one (Table 1, Entry 1)
1H-NMR: d 0.90 (3H, t, J = 7.3), 1.26-1.39 (2H, m),
1.53-1.63 (2H, m), 1.88 (3H, dd, J = 6.9, 1.7 Hz), 2.51 (2H, t,
J = 7.5 Hz), 6.11 (1H, dq, J = 15.8, 1.7 Hz), 6.83 (1H, dq, J =
15.8, 6.9 Hz). 13C-NMR: d 13.8, 18.1, 22.4, 26.4, 39.8, 132.0,
142.2, 200.7. HRMS: 126.1019 (calcd. for C8H14O, 126.1045).
MS: m/z 127 (11, M+1), 126 (12, M), 125 (15), 111(25), 97
(35), 85 (57), 83 (35), 81 (30), 71 (55), 69 (49), 67 (23), 57
(base), 55 (52).
4-Phenylbut-1-en-4-one (Table 1, Entry 4)
1H-NMR: d 3.76 (2H, d, J = 6.6 Hz), 5.21 (1H, dd, J =
18.2, 1.5 Hz), 5.24 (1H, dd, J = 9.6, 1.5 Hz), 6.10 (1H, m),
7.47-7.75 (3H, m), 7.97 (1H, m). 13C-NMR: d 43.4, 118.7,
128.3, 128.6, 131.0, 133.1, 136.6, 198.0. HRMS: 146.0732
(calcd. for C10H10O, 146.0731). MS: m/z 146 (base), 145 (29),
131 (34), 105 (23). IR: (neat) 3071 (sp2-CH, m), 2983 (sp3-
CH, w), 1684 (C=O, s), 1644 (C=C, m), 1598 (m), 1451 (m),
1232 (m), 911 (s), 750 (s), 697 (s) cm-1.
5-Cyclophentenylpent-1-en-4-one (Table 1, Entry 2)
1H-NMR: d 1.89 (2H, m), 2.24-2.38 (4H, m), 3.20-3.22
(4H, m), 5.13 (1H, dd, J = 15.0, 0.9 Hz), 5.18 (1H, dd, J =
11.6, 0.7 Hz), 5.52 (1H, t, J = 1.4 Hz), 5.90 (1H, m). 13C-
NMR: d 23.5, 32.6, 35.3, 45.1, 118.8, 128.9, 130.6, 136.9,
206.6. HRMS: 150.1048 (calcd. for C10H14O, 150.1044). MS:
m/z 135 (28), 109 (27), 107 (33), 81 (36), 79 (37), 77 (21), 69
(base), 67 (21), 53 (23), 43 (26), 41 (82), 39 (56). IR: (neat)
3098 (sp2-CH, w), 3053 (sp2-CH, w), 2974 (sp3-CH, s), 2855
(sp3-CH, s), 1717 (C=O, s), 1641 (C=C, m), 1410 (m), 1321
(m), 1053 (m), 860 (s) cm-1.
1-Phenylbut-2-en-1-one (Table 1, Entry 4)
1H-NMR: d 2.00 (3H, dd, J = 6.6, 1.6 Hz), 6.90 (1H, dq,
J = 15.5, 1.6 Hz), 7.07 (1H, dq, J = 15.5, 6.6 Hz), 7.42-7.48
(2H, m), 7.52-7.58 (1H, m), 7.90-7.94 (2H, m). 13C-NMR: d
18.5, 127.6, 128.5, 132.5, 137.9, 145.0, 190.8. HRMS:
146.0736 (calcd. for C10H10O, 146.0732). MS: m/z 147 (7,
M+1), 146 (53, M), 145(17), 131 (50), 117 (16), 115 (11), 105
(base), 77 (89), 69 (49), 51 (40).
1,6-Octdien-4-one (Table 1, Entry 3)
1H-NMR: d 1.70 (3H, dd, J = 4.6, 1.0 Hz), 3.12 (2H, dd,
J = 5.0, 1.0 Hz), 3.19 (2H, dt, J = 7.0, 1.0 Hz), 5.13 (1H, dd, J
= 17.5, 1.5 Hz), 5.18 (1H, dd, J = 11.0, 1.2 Hz), 5.90 (1H, m).
13C-NMR: d 18.0, 46.2, 47.0, 118.8, 122.7, 129.9, 130.5,
207.2. HRMS: 124.0847 (calcd. for C8H12O, 124.0888). MS:
m/z 97 (27), 69 (60), 55 (22), 43 (base), 41 (40), 39 (42). IR:
(neat) 3071 (sp2-CH, m), 3035 (sp2-CH, m), 2965 (sp3-CH,
m), 2919 (sp3-CH, m), 1714 (C=O, s), 1641 (C=C, s), 975
(m), 914 (m), 744 (m) cm-1.
1-(4-Methoxy-phenyl)-but-2-en-1-one (Table 1, Entry 5)
1H-NMR: d 1.97 (3H, dd, J = 6.6, 1.4 Hz), 3.85 (3H, s),
6.87-6.95 (1H, m), 6.93 (2H, d, J = 8.7 Hz), 7.04 (1H, dq, J =
15.0, 6.6 Hz), 7.93 (2H, d, J = 8.7 Hz). 13C-NMR: d 18.5,
55.4, 113.7, 127.2, 130.8, 143.8, 163.3, 189.0. HRMS:
176.0836 (calcd. for C11H12O2, 176.0837). MS: m/z 177 (60,
M+1), 176 (59, M), 175(39), 161 (80), 145 (28), 136 (84),
135 (59), 107 (73), 92 (96), 77 (base), 69 (65), 64 (56), 63
(35).
Octa-2,6-dien-4-one (Table 1, Entry 3, 3a)
5-Phenylpent-1-en-4-one (Table 1, Entry 6)
1H-NMR: d 1.68-1.70 (3H, m), 1.89 (3H, dd, J = 6.8,
1H-NMR: d 3.21 (2H, dt, J = 7.0, 1.3 Hz), 3.72 (2H, s),

A Mild Isomerization from b,g- to a,b-Unsaturated Ketone
J. Chin. Chem. Soc., Vol. 51, No. 2, 2004 375
5.11 (1H, dd, J = 16.9, 1.5 Hz), 5.18 (1H, dd, J = 9.5, 1.4 Hz),
5.89 (1H, m), 7.19-7.37 (5H, m). 13C-NMR: d 46.8, 49.5,
119.0, 127.1, 128.7, 129.5, 130.4, 134.0, 206.0. HRMS:
160.0884 (calcd. for C11H12O, 160.0888). MS: m/z 160
(base), 151 (17), 150 (10), 136 (12), 122 (17). IR: (neat) 3089
(sp2-CH, m), 3035 (sp2-CH, w), 2983 (sp3-CH, w), 2902
(sp3-CH, w), 1714 (C=O, s), 1641 (C=C, s), 1494 (m), 1451
(m), 1339 (m), 911 (s), 750 (s), 697 (s) cm-1.
3089 (sp2-CH, w), 2956 (sp3-CH, w), 2884 (sp3-CH, w), 1713
(C=O, s), 1641 (C=C, s), 1392 (m), 1330 (m), 1053 (m), 1005
(m), 920 (s), 776 (s), 742 (s) cm-1.
1-Thiophen-3-yl-pent-3-en-2-one (Table 1, Entry 8)
1H-NMR: d 1.89 (3H, dd, J = 6.9, 1.7 Hz), 3.83 (2H, s),
6.17 (1H, dq, J = 15.7, 1.7 Hz), 6.93 (1H, dq, J = 15.7, 6.9
Hz), 6.96 (1H, dd, J = 4.9, 1.2 Hz), 7.08 (1H, dd, J = 3.2, 1.2
Hz), 7.28 (1H, dd, J = 4.9, 3.2 Hz). 13C-NMR: d 18.2, 41.9,
122.7, 125.8, 128.6, 130.8, 134.2, 13.6, 196.7; HRMS:
166.0443 (calcd. for C9H10O, 166.0452). MS: m/z 167 (8,
M+1), 166 (55, M), 138 (27), 124 (16), 113 (15), 111 (38), 98
(24), 97 (base), 69 (61), 53 (20).
1-Phenylpent-3-en-2-one (Table 1, Entry 6)
1H-NMR: d 1.88 (3H, dd, J = 6.8, 1.5 Hz), 3.81 (2H, s),
6.17 (1H, dq, J = 15.6, 1.5 Hz), 6.93 (1H, dq, J = 15.6, 6.8
Hz), 7.20-7.35 (5H, m). 13C-NMR: d 18.2, 47.4, 126.8, 128.6,
129.4, 131.0, 134.7, 143.6, 197.1. HRMS: 160.0888 (calcd.
for C11H12O, 160.0888). MS: m/z 161 (13, M+1), 160 (18, M),
119 (35), 118 (61), 107 (44), 106 (22), 105 (93), 92 (47), 91
(75), 77 (88), 69 (base), 65 (30).
ACKNOWLEDGEMENT
We thank the National Science Council of Taiwan
(NSC 91-2113-M-032-004) and Tamkang University for fi-
nancial support.
5-Naphthalenylpent-1-en-4-one (Table 1, Entry 7)
1H-NMR: d 3.19 (2H, d, J = 6.9 Hz), 4.15 (2H, s), 5.07
(1H, dd, J = 15.9, 1.7 Hz), 5.16 (1H, dd, J = 9.6, 1.3 Hz), 5.90
(1H, m), 7.38-7.55 (4H, m), 7.80-7.90 (3H, m). 13C-NMR: d
46.3, 47.8, 118.9, 123.8, 125.5, 125.9, 126.5, 128.1, 128.3,
128.8, 130.4, 130.7, 132.2, 133.9, 206.4. HRMS: 210.1044
(calcd. for C15H14O, 210.1044). MS: m/z 210 (base), 202 (5),
182 (5), 178 (6), 165 (9). IR: (neat) 3053 (sp2-CH, w), 3035
(sp2-CH, w) 2974 (sp3-CH, w), 1714 (C=O, s), 1641 (C=C,
m), 1598 (m), 1396 (m), 776 (s) cm-1.
Received June 20, 2003.
REFERENCES
1. Larock, R. C. Comprehensive Organic Transformations-A
Guide to Functional Group Preparations; 2nd ed., John
Wiley & Sons, Inc.: New York, 1999.
1-Naphthalen-1-yl-pent-3-en-2-one (Table 1, Entry 7)
1H-NMR: d 1.84 (3H, dd, J = 6.8, 1.5 Hz), 4.23 (2H, s),
6.23 (1H, dq, J = 15.5, 1.5 Hz), 6.98 (1H, dq, J = 15.5, 6.8
Hz), 7.36-7.54 (4H, m), 7.78-7.91 (3H, m). 13C-NMR: d 18.2,
46.1, 124.0, 125.5, 125.8, 126.4, 127.9, 128.1, 128.7, 130.2,
131.2, 132.4, 133.9, 143.5, 197.2. HRMS: 210.1058 (calcd.
for C15H14O, 210.1045). MS: m/z 211 (48, M+1), 210 (base,
M), 182 (19), 157 (18), 155 (82), 142 (84), 141 (80), 139 (85),
127 (43), 115 (35), 69 (29).
2. Noyori, R. Asymmetric Catalysis in Organic Synthesis; John
Wiley & Sons, Inc.: New York, 1994, Chap. 3, pp 95-121.
3. Overman, L. E. Angew. Chem. Int. Ed. Engl. 1984, 23, 579.
4. Fleming, I. Pericyclic Reactions; Oxford University Press,
1999.
5. Rossiter, B. E.; Swingle, N. M. Chem. Rev. 1992, 92, 771.
6. Yoshikoshi, A.; Miyashita, M. Acc. Chem. Res. 1985, 18,
284.
7. Oare, D. A.; Heathcock, C. H. Top. Stereochem. 1989, 19,
227-407; 1991, 20, 87-170.
5-Thiopheneylpent-1-en-4-one (Table 1, Entry 8)
8. Oppolzer, W. in Comprehensive Organic Synthesis; Trost, B.
M.; Fleming, I., Eds; Pergamon: Oxford, 1991, Vol. 5, Chap.
4.1, pp 315-399.
1H-NMR: d 3.22 (2H, d, J = 7.1 Hz), 3.76 (2H, s), 5.12
(1H, dd, J = 16.9, 1.5 Hz), 5.19 (1H, dd, J = 10.5, 1.4 Hz),
5.91 (1H, m), 6.96 (1H, d, J = 5.1 Hz), 7.09 (1H, d, J = 3.1
Hz), 7.30 (1H, dd, J = 5.1, 3.1). 13C-NMR: d 43.7, 46.7, 119.0,
123.0, 126.0, 128.5, 130.0, 133.6, 205.5. HRMS: 166.0449
(calcd. for C9H10OS, 166.0452). MS: m/z 166 (47), 165 (31),
162 (25), 124 (26), 113 (40), 112 (22), 111 (base). IR: (neat)
9. Fringuelli, F.; Taticchi, A. Dienes in the Diels-Alder Reac-
tion; John Wiley & Sons, Inc.: New York, 1990.
10. Carruthers, W. Cycloaddition Reactions in Organic Synthe-
sis; Pergamon: Oxford, 1990, Chap. 1, pp 1-90 and Chap. 2,
pp 91-139.

376 J. Chin. Chem. Soc., Vol. 51, No. 2, 2004
Lee et al.
11. Posner, G. H. Chem. Rev. 1986, 56, 831.
Chem. 1998, 63, 8170.
12. Webster, F. X.; Siverstein, R. M. Synthesis, 1987, 10, 922.
13. Wenkert, E.; Bakuzis, P.; Baumgarten, R. J.; Doddrell, D.;
Jeffs, P. W.; Leicht, C. L.; Mueller, R. A.; Yoshikoshi, A. J.
Am. Chem. Soc. 1970, 92, 1617.
16. Alcaide, B.; Almendros, P.; Salgado, N. R. J. Org. Chem.
2000, 65, 3310.
17. Saha, M.; Bagby, B.; Nicholas, K. M. Tetrahedron Lett.
1986, 27, 915.
14. Paquette, L. A.; Crouse, G. D.; Sharma, A. K. J. Am. Chem.
Soc. 1982, 104, 4411.
18. Seebach, D.; Pohmakotr, M. Tetrahedron 1981, 37, 4047.
19. Lee, A. S.-Y.; Lin, L.-S. Tetrahedron Lett. 2000, 41, 8803.
15. Folmer, J. J.; Acero, C.; Thai, D. L.; Rapoport, H. J. Org.