A highly active ionic liquid catalyst for Morita-Baylis-Hillman reaction

Article abstract of DOI:10.1016/j.tet.2005.10.048

The Morita-Baylis-Hillman reaction is an efficient carbon-carbon bond forming reaction for the preparation of α-methylene-β-hydroxycarbonyl compounds. A new and highly active di-naphthalene imidazolium salt has been synthesized. We have found that 1,3-bis

Full text of DOI:10.1016/j.tet.2005.10.048

Tetrahedron 62 (2006) 872–877
A highly active ionic liquid catalyst for
Morita–Baylis–Hillman reaction
*
Yu-Sheng Lin, Chiao-Yang Lin, Chih-Wei Liu and Thomas Y. R. Tsai
Department of Chemistry, National Dong Hwa University, Shou-Feng, Hualien 974, Taiwan, ROC
Received 17 February 2005; revised 19 October 2005; accepted 19 October 2005
Available online 8 November 2005
Abstract—The Morita–Baylis–Hillman reaction is an efficient carbon–carbon bond forming reaction for the preparation of a-methylene-
b-hydroxycarbonyl compounds. A new and highly active di-naphthalene imidazolium salt has been synthesized. We have found that
1,3-bis[2-(naphthalene-2-yloxy)propyl]imidazolium bromid promoted the Morita–Baylis–Hillman reaction of various aryl aldehyde
compounds in the absence of solvents. Our studies show that the Morita–Baylis–Hillman reaction by the influence of ionic liquid to give a
high yield and short reaction time.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
solvents.15 Their properties, negligible vapor pressure, high
polarity, non-flammable, and easy handling, and the fact that
ionic liquids can often act as catalysts as well as reaction
media, enable them to be used as solvents for a variety of
transition metal catalyzed reactions (e.g., esterification,16
alkylation,17 oxidation,13a and hydrogenation18). There are
many reports concerning the applications of RTILs in
organic reactions, such as the Diels–Alders reaction,19
Friedel-Crafts reaction,20 Suzuki cross-coupling,21 Mannich
reaction,22 Heck reaction,23 and Baeyer–Villiger reaction24
that often afford greater yields, product selectivity25 and
accelerated reaction rates. A recent report described the
acceleration of the DABCO-catalysed MBH reaction in ionic
liquids26 and led us to investigate the effects of ionic liquids.
Beside, RTILs were usually based on the 1-n-alkyl-
3-methylimidazolium cation, which can be synthesized
easily from the commercially available starting material,
1-methylimidazole. Scheme 1 has shows general RTILs
applied in organic synthesis in literatures and reported that
ionic liquids such as [bmim][PF6] or [bdmim][PF6] acce-
lerate the rates and improve the yields of MBH reaction.27
The Morita–Baylis–Hillman (MBH) reaction is a particu-
larly powerful transformation because it permits the coupling
of various activated aldehydes and a,b-unsaturated ketones,
a process that has a great synthetic advantage.1 This reaction
involves three components: an activated alkene, an
electrophile, and a tertiary amine. Lewis bases, such as
1,4-diazabicyclo[2.2.2]octane (DABCO),2 DMAP,3 DBU,4
2,20-bis(diphenylphosphino)-1,10-binaphthyl (BINAP),5 and
imidazole,6 are frequently used in these reactions as
catalysts. In addition, Lewis acid-accelerated reactions
were also reported, such as TiCl4,7 Et2AlI,8 and BF3.9 In a
general process, the MBH reaction suffers from poor reaction
rates and long reaction time. For this reason, modifications
such as the use of high pressure,10 microwave irradiation11
and ultrasound12 have given some promising results. In
recent years, room temperature ionic liquids (RTILs) have
been gaining exposure for their potential in organic
synthesis. From both an environmental and an economical
point of view, the concept of recoverable and recyclable
catalysis has become increasingly important.13 RTILs have
received considerable attention for applications as green
solvents14 and replacements for traditional organic
A common MBH reaction carried out with [bmim][X] to
give lower yield (13–78%)26b and a longer reaction time.
Scheme 1. Ionic liquids.
Keywords: Morita–Baylis–Hillman reaction; Ionic liquids; DABCO.
*
Corresponding author. Tel.: C886 3 8633575; fax: C886 3 8633570; e-mail: yrtsai@mail.ndhu.edu.tw
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.10.048

Y.-S. Lin et al. / Tetrahedron 62 (2006) 872–877
873
Table 1. Reaction of various aldehydes with methyl vinyl ketone in the presence of [bmim][Br] or [bmim][BF4]
Aldehyde
[bmim][Br]
Time (h)
[bmim][BF4]
Time (h)
Yield (%)
Yield (%)
2-Pyridinecarboxaldehyde
4-Chlorobenzaldehyde
4-Biphenylcarboxaldehyde
2-Naphthaldehyde
Methyl 4-formylbenzoate
4-Methoxybenzaldehyde
32
46
36
78
57
112
46
72
58.5
26
18
9
29
35
34
69
71
89
57
68
66
33
13
11
We prepared [bmim][Br]28a and [bmim][BF4]28b and then
carried out the reactions of these RTILs with aldehydes and
a,b-unsaturated ketones in the presence of DABCO
(Table 1). Since we were not satisfied with the results, we
synthesized a new imidazolium salt for the MBH reaction
(Scheme 2). The reaction of methyl lactate with 2-naphthol
in the presence of DEAD29 is followed by sodium
borohydride reduction yields the primary alcohol 1.30
Scheme 2. Synthesis of di-naphthalene imidazolium salt.
Table 2. Reaction of various aldehydes with methyl vinyl ketone in the presence of 1,3-bis[2-(naphthalene-2-yloxy)propyl]imidazolium bromide
Entry
Aldehyde
Product
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
p-Nitrobenzaldehyde
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0.1
0.5
2.8
0.7
28
18
29
20
18
27
15
7
99
96
99
79
82
87
79
81
58
89
87
85
81
94
97
Methyl 4-formylbenzoate
4-(Trifluoromethyl)benzaldehyde
2-Naphthaldehyde
3-Phenylpropionaldehyde
4-Biphenylcarboxaldehyde
4-Methylbenzaldehyde
4-Chlorobenzaldehyde
9
4-Methoxybenzaldehyde
3,4,5-Trimethoxybenzaldehyde
4-(Methylthio)benzaldehyde
2-Pyridinecarboxaldehyde
3-Pyridinecarboxaldehyde
4-Bromo-2-thiophenecarbozaldehyde
5-(3-Chlorophenyl)furfural
10
11
12
13
14
15
12
0.5
18

874
Y.-S. Lin et al. / Tetrahedron 62 (2006) 872–877
Table 3. Reaction of various aldehydes with methyl acrylate in the presence of 1,3-bis[2-(naphthalene-2-yloxy)propyl]imidazolium bromide
Entry
Aldehyde
Product
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
p-Nitrobenzaldehyde
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
0.5
2.5
1.1
20
30
12
18
27
22
71
22
10
16
3
98
92
91
81
71
86
59
58
47
93
83
87
79
92
89
Methyl 4-formylbenzoate
4-(Trifluoromethyl)benzaldehyde
2-Naphthaldehyde
3-Phenylpropionaldehyde
4-Biphenylcarboxaldehyde
4-Methylbenzaldehyde
4-Chlorobenzaldehyde
9
4-Methoxybenzaldehyde
3,4,5-Trimethoxybenzaldehyde
4-(Methylthio)benzaldehyde
2-Pyridinecarboxaldehyde
3-Pyridinecarboxaldehyde
4-Bromo-2-thiophenecarbozaldehyde
5-(3-Chlorophenyl)furfural
10
11
12
13
14
15
22.4
The tosylation of the primary alcohol followed by a
treatment with 1.3 equiv of lithium bromide in acetone
produced bromide 2. The reaction of imidazole with
compound 2 afforded the imidazole derivative, isolated as
compound 3. Finally, the treatment of 3 with bromide 2 at
60 8C gave 1,3-bis[2-(naphthal-2-yl-oxy)propyl]imidazo-
lium bromide 4 in 96% yield after purification.
2.1. Typical procedure for the ionic liquid promoted
Morita–Baylis–Hillman reaction
In a dried flask, aldehyde (1 mmol), DABCO (224 mg,
2 mmol), and 1,3-bis[2-(naphthal-2-yl-oxy)propyl]imida-
zolium bromide (129.3 mg, 0.25 mmol) were measured
together. Methyl vinyl ketone (105 mg, 1.5 mmol) was
added, and the reaction mixture was stirred for 7–20 h at
ambient temperature in all cases. The mixture was washed
with ether (3!10 mL), and the solid was separated by
vacuum filtration. Then the solid was extracted with 130 mL
dichloromethane and followed by a general procedure to
recover the catalyst. The ethereal phase was concentrated,
and the solvent was removed under reduced pressure. The
residue was purified by silica gel column chromatography
(Hexane/ethyl acetate, 7:3, v/v).
The treatment of various aryl aldehydes with methyl vinyl
ketone (MVK) or methyl acrylate in the presence of
hydrophilic ionic liquid 4 not only produced the desired
product in moderate to high yield but also reduced the side
products. For example, in the reaction of methyl 4-formyl-
benzoate (1.0 equiv) with MVK (2.0 equiv), entry 2
(Table 2) can be obtained in 96% yield in the presence of
compound 4 (0.2 equiv) for 0.5 h at room temperature. We
also prepared MBH reaction with methyl acrylate (Table 3),
our condition goes very smoothly, producing high yields
and also accelerating the reaction rate. The recovered ionic
liquid was reused for subsequent runs.16b
2.1.1. Synthesis of 1. Methyl lactate (10.40 g, 0.1 mol) was
added to a solution of 2-naphthol (14.40 g, 0.11 mmol) and
triphenyl phosphine (31.44 g, 0.12 mol) in dichloromethane
(100 mL). The reaction mixture was stirred at 0 8C and
diethyl azodicarboxylate (17.04 g, 0.12 mol) was added.
After the mixture was stirred for 2 h at room temperature
and the white solid (Ph3P]O) was separated by vacuum
filtration. The organic layer was evaporated under vacuum,
the crude dissolved in a co-solvent (200 mL tetrahydrofuran
and 20 mL methol), sodium tetrahydridoborate (3.8 g,
0.1 mol) was added, and stirred at ambient temperature for
3.5 h. The organic phase was washed with 100 mL of water
and dried over anhydrous MgSO4. The organic solvent was
evaporated under reduced pressure to give 2-(1-methoxy-
propan-2-yloxy)naphthalene (17.56 g, 81%) as yellow oil.
In conclusion, the present procedure catalyzed by a
hydrophilic RTIL, 1,3-bis[2-(naphthal-2-yl-oxy)propyl]-
imidazolium bromide provides an efficient and general
methodology for the MBH reaction of aryl aldehydes and
MVK or methyl acrylate to yield a-methylene-b-hydro-
xycarbonyl compounds. The results presented in this paper,
demonstrate that the MBH reaction works well in the
presence of ionic liquid.
2. Experimental
IR (KBr) nmax: 3420 (OH), 3056, 1215, 2975, 2931, 1627,
1598, 1509, 1467, 1256, 1215, 1180, 1050, 970, 839, 748;
1H NMR (300 MHz, CDCl3) d: 1.39–1.37 (d, JZ7.0 Hz,
3H), 3.85–3.82 (d, JZ7.8 Hz, 2H), 4.70–4.63 (m, 1H),
7.22–7.15 (m, 2H), 7.45–7.35 (m, 2H), 7.79–7.71 (m, 2H);
13C NMR (CDCl3) d: 155.59, 134.60, 129.71, 127.74,
126.88, 126.53, 123.93, 119.62, 109.03, 74.83, 66.20, 15.81;
MS (EI, 70 eV, m/z, %): 202 (MC, 65), 171 (28), 143 (100),
All reagents were purchased from Acros, Aldrich Chimie,
Fluka and used without further purification. IR spectra were
taken as KBr plates. 1H and 13C NMR spectra were recorded
in CDCl3 solution at 300 and 75 MHz spectrometer. TLC
analysis was performed used glass plate with silica gel 60
F254. Flash column chromatography was carried out using
200–300 mesh silica gel.

Y.-S. Lin et al. / Tetrahedron 62 (2006) 872–877
875
127 (55), 115 (77), 101 (11); HRMS calcd for C13H14O2:
202.0994. Found: 202.0998.
144, 109. Anal. Calcd for C29H29BrN2O2: C, 67.31; H, 5.65.
Found: C, 67.35; H, 5.68; mp: 178 8C.
Compounds 5,31 7,31 9,32 11,33 12–13,34 16–17,35 20,36 22,2f
23,37 24,38 26,12a 27,39 28–29,40 and 31–32,41 were identical
to authentic samples by comparison of their spectral date.
2.1.2. Synthesis of 2. A mixture of 2-(1-methoxypropan-
2-yloxy)naphthalene (10.80 g, 0.05 mol), tosyl chloride
(11.44 g, 0.06 mol), and pyridine (5.3 mL, 0.06 mol) was
stirred in 100 mL of dichloromethane at room temperature
for 18 h. The organic phase was washed with 150 mL water,
dried over anhydrous MgSO4 and concentrated. Then the
tosylate crude mixture wit lithium bromide (5.66 g,
0.065 mol) was diluted in 50 mL of acetone, and lithium
carbonate (0.37 g, 0.05 mol) added. The mixture was stirred
at ambient temperature for 24 h. When the reaction was
completed by a TLC analysis, the solvent was evaporated
and a dark yellow oil was purified via flash chromatography
(Hexane/ethyl acetate, 9:1, v/v), producing a light yellow
oil, 2-(1-bromopropan-2-yloxy)naphthalene (12.28 g, 93%).
2.1.4. Methyl 4-[(1-hydroxy)(2-methylene)butyl-3-one]-
benzoate (6). IR (KBr) nmax: 3460 (OH), 1719 (C]O),
1
1677 (C]O), 1434, 1283, 1115, 960, 766, 707; H NMR
(300 MHz, CDCl3) d: 8.01 (d, JZ6.6 Hz, 2H), 7.44 (d,
JZ8.3 Hz, 1H), 6.22 (s, 1H), 5.97 (s, JZ5.97 Hz, 1H), 5.65
(s, 1H), 3.91 (s, 1H), 2.34 (s, 1H); 13C NMR (75.4 MHz,
CDCl3) d: 200.29 (C]O), 168.89, 149.46, 146.63, 129.72,
129.48, 127.32, 126.44, 72.64, 52.13, 26.44; MS (FAB,
m/z): 217 (MCC1KH2O); HRMS calcd for C13H14O4:
234.0892. Found: 234.0897.
2.1.5. 3-(Hydroxy(naphthalene-2-yl)methyl)but-3-en-2-
one (8). IR (KBr) nmax: 3436 (OH), 3055, 1672 (C]O),
1363, 1125, 1041, 952, 824, 747; 1H NMR (300 MHz,
CDCl3) d: 7.85–7.80 (m, 4H), 7.49–7.23 (m, 4H), 6.23 (s,
1H), 6.01 (s, JZ1.1 Hz, 1H), 5.80 (s, 1H), 2.35 (s, 3H); 13C
NMR (75.4 MHz, CDCl3) d: 200.46 (C]O), 149.92,
138.84, 133.26, 132.92, 128.17, 128.12, 127.67, 127.00,
126.18, 126.03, 125.47, 124.56, 72.91, 26.54; MS (EI,
70 eV, m/z, %): 226 (MC, 84), 225 (100), 211 (14), 166
(15), 165 (34), 155 (23), 128 (54), 127 (43), 84 (50); HRMS
calcd for C17H16O2: 226.0994. Found: 226.0996.
IR (KBr) nmax: 1627, 1598, 1509, 1466, 1255, 1214, 1177,
838, 747; 1H NMR (300 MHz, CDCl3) d: 1.54 (d,
JZ6.2 Hz, 3H), 3.53–3.48 (m, 1H), 3.67–3.61 (m, 1H),
4.76–4.70 (m, 1H), 7.19–7.15 (m, 2H), 7.39–7.36 (m, 1H),
7.46–7.43 (m, 1H), 7.79–7.72 (m, 3H); 13C NMR (CDCl3)
d: 155.12, 134.43, 129.77, 129.13, 127.67, 126.82, 126.49,
124.02, 119.54, 109.15, 73.53, 35.31, 18.79; MS (FAB, m/
z): 266 (MC), 264, 145, 144, 127; HRMS calcd for
C13H13BrO: 264.0150. Found: 264.0151.
2.1.3. Synthesis of 3 and 4. Bromide 2 (5.30 g, 0.02 mol)
was injected into a flask containing tetrahydrofuran (55 mL)
followed by potassium carbonate (0.55 g, 8 mmol) and
stirred at room temperature for 24 h. After completion of the
reaction, as indicated by TLC, the product was quenched
with 50 mL water and extracted with dichloromethane (3!
50 mL). The organic layer was dried over anhydrous
MgSO4, concentrated under reduced pressure and purified
by chromatography on silica gel to afford imidazole 3
(4.59 g, 91%). The combined bromide 2 (2.52 g, 0.01 mol)
and imidazole 3 (2.65 g, 0.01 mol) was stirred at 60 8C for
2 h. The mixture was washed with diethyl ether (3!
100 mL) and evaporated under vacuum. A brown solid, 1,3-
bis[2-(naphthalene-2-yloxy)propyl]imidazolium bromide,
was obtained (9.93 g, 96%).
2.1.6. 3-[Hydroxy(4-phenylphenyl)methyl]but-3-en-2-
one (10). IR (KBr) nmax: 3436 (OH), 3029, 1672 (C]O),
1485, 1363, 1038, 763, 700; 1H NMR (300 MHz, CDCl3) d:
7.60–7.56 (m, 4H), 7.45–7.43 (m, 4H), 7.42 (d, 1H), 6.23 (s,
1H), 6.05 (d, JZ1.1 Hz, 1H), 2.37 (s, 3H); 13C NMR
(75.4 MHz, CDCl3) d: 200.39 (C]O), 149.90, 140.80,
140.65, 140.59, 128.78, 127.33, 127.12, 127.11, 126.97,
126.80, 72.73, 26.55; MS (EI, 70 eV, m/z, %): 252 (MC,
87), 251 (100), 191 (22), 175 (75), 152 (35), 77 (26); HRMS
calcd for C17H16O2: 252.1150. Found: 252.1150.
2.1.7. 2-[Hydroxy(3,4,5-trimethoxyphenyl)methyl]-
cyclohex-2-enone (14). IR (KBr) nmax: 3480 (OH), 2937,
2838, 1672 (C]O), 1591, 1506, 1459, 1418, 1325, 1231,
1
1125, 1008, 843; H NMR (300 MHz, CDCl3), d 6.58 (s,
2H), 6.17 (s, 1H), 5.96 (s, 1H), 3.85, (s, 6H), 3.83 (s, 3H),
2.36 (s, 3H); 13C NMR (75.4 MHz, CDCl3) d: 200.53
(C]O), 153.24, 149.90, 137.36, 137.10, 126.88, 103.54,
72.75, 60.83, 56.12, 26.56; MS (70 eV, m/z, %): 266 (MC,
54), 235 (74), 196 (100), 181 (49), 169 (28), 138 (18), 125
(31), 110 (19), 84 (70); HRMS calcd for C14H18O5:
266.1154. Found: 266.1147.
Compound 3. IR (KBr) nmax: 2924, 1735, 1508, 1255, 1214,
748; 1H NMR (CDCl3) d: 1.37 (d, JZ6.0 Hz, 3H),
4.22–4.19 (m, 2H), 4.70–4.80 (m, 1H), 7.09–7.03 (m, 4H),
7.44–7.35 (m, 2H), 7.58 (s, 1H), 7.78–7.68 (m, 3H); 13C
NMR (CDCl3) d: 156.52, 137.89, 134.00, 129.89, 128.62,
129.60, 127.69, 126.75, 126.58, 124.11, 120.00, 119.31,
108.95, 73.21, 51.66, 17.15; MS (EI, 70 eV, m/z, %): 252
(MC, 83), 171 (46), 144 (93), 127 (56), 109 (100); HRMS
calcd for C16H16N2O: 252.1263. Found: 252.1259.
2.1.8. 3-[Hydroxy(4-methylthiophenyl)methyl]but-3-en-
2-one (15). IR (KBr) nmax: 3437 (OH), 2920, 1673 (C]O),
1
1596, 1493, 1403, 1364, 1092, 1038, 972, 820; H NMR
Compound 4. IR (KBr) nmax: 3056, 2195, 1626, 1598, 1509,
1467, 1255, 1180, 1119, 1078, 972, 732; 1H NMR (CDCl3)
d: 1.44 (d, JZ6.2 Hz, 6H), 4.47–4.39 (m, 2H), 4.96–4.89
(m, 4H), 7.01–6.98 (m, 2H), 7.13–7.12 (m, 2H), 7.44–7.34
(m, 8H), 7.71–7.62 (m, 8H); 13C NMR (CDCl3) d: 154.15,
132.24, 129.92, 128.80, 127.60, 126.88, 126.68, 124.27,
122.56, 118.80, 109.13, 72.41, 67.99, 54.21, 25.62, 16.63;
MS (FAB, m/z): 517 (M)C, 437 (MKBr)C, 293, 253, 185,
(300 MHz, CDCl3) d: 7.29–7.20 (dd, 4H), 6.19 (s, 1H), 5.99
(s, 1H), 5.58 (s, 1H), 2.49 (s, 3H), 2.34 (s, 3H); 13C NMR
(75.4 MHz, CDCl3) d: 200.33 (C]O), 149.88, 138.46,
137.87, 127.08, 126.63, 126.57, 72.46, 26.52, 15.84; MS
(EI, 70 eV, m/z, %): 222 (MC, 39), 221 (42), 207 (8), 175
(100), 153 (37), 151 (37), 124 (21), 109 (30), 77 (18);
HRMS calcd for C12H14O2S: 222.0715. Found: 222.0718.

876
Y.-S. Lin et al. / Tetrahedron 62 (2006) 872–877
2.1.9. 3-[(4-Bromothiophen-2-yl)(hydroxy)methyl]but-3-
en-2-one (18). IR (KBr) nmax: 3421 (OH), 3106, 2919, 1672
(C]O), 1367, 1033, 971, 821; 1H NMR (300 MHz, CDCl3)
d: 7.16 (s, JZ1.4 Hz, 1H), 6.85 (s, JZ1.2 Hz, 1H), 6.38 (s,
1H), 5.96 (s, 1H), 5.68 (s, 1H), 3.77 (s, 3H); 13C NMR
(75.4 MHz, CDCl3) d: 166.37 (C]O), 147.28, 140.35,
127.14, 127.03, 122.59, 109.35, 69.83, 52.27; MS (FAB,
m/z): 243 (MCC1KH2O); HRMS calcd for C9H9BrO2S:
259.9507. Found: 259.9512.
(300 MHz, CDCl3) d: 7.13 (s, JZ1.3 Hz, 1H), 6.83 (s, JZ
0.9 Hz, 1H), 6.24 (s, 1H), 6.12 (s, 1H), 5.72 (s, 1H), 2.37 (s,
3H); 13C NMR (75.4 MHz, CDCl3) d: 200.17 (C]O),
148.30, 147.49, 127.40, 127.04, 122.36, 109.30, 69.53,
26.50; MS (EI, 70 eV, m/z, %): 278 (MC2, 100), 276 (MC,
97), 261 (71), 246 (52), 218 (42), 191 (57), 166 (30), 121
(26), 109 (25), 97 (10), 84 (48); HRMS calcd for
C9H9BrO3S: 275.9456. Found: 275.9453.
2.1.15. Methyl 2-[(5-(3-chlorophenyl)furan-2-yl)-
(hydroxy)methyl]acrylate (34). IR (KBr) nmax: 3449
(OH), 2947, 1715 (C]O), 1628, 1438, 1286, 1202, 783;
1H NMR (300 MHz, CDCl3) d: 7.6 (d, JZ1.7 Hz, 1H), 7.48
(t, 1H), 7.31–7.19 (m, 2H), 6.61 (d, JZ3.3 Hz, 1H), 6.34 (d,
JZ3.3 Hz, 1H), 6.29 (s, 1H), 6.17 (s, 1H), 5.67 (s, 1H), 2.41
(s, 3H); 13C NMR (75.4 MHz, CDCl3) d: 200.02 (C]O),
154.48, 152.17, 147.05, 134.69, 132.28, 129.96, 127.70,
123.70, 127.33, 121.80, 109.44, 106.94, 67.51, 26.42; MS
(70 eV, m/z, %): 294 (MC2, 21), 292 (MC, 70), 260 (25),
232 (27), 207 (89), 205 (70), 178 (74), 153 (40), 149 (40),
141 (77), 139 (100), 115 (78), 113 (30), 111 (31), 75 (22);
HRMS calcd for C15H13ClO3: 292.0502. Found: 292.0509.
2.1.10. 3-{[5-(3-Chlorophenyl)furan-2-yl](hydroxy)-
methyl}but-3-en-2-one (19). IR (KBr) nmax: 3429 (OH),
2919, 2365, 1672 (C]O), 1605, 1430, 1367, 1019, 781; 1H
NMR (300 MHz, CDCl3) d: 7.6 (d, JZ1.3 Hz, 1H), 7.48 (t,
1H), 7.31–7.19 (m, 2H), 6.61 (d, JZ3.3 Hz, 1H), 6.34 (d,
JZ3.3 Hz, 1H), 6.29 (s, 1H), 6.17 (s, 1H), 5.67 (s, 1H), 2.41
(s, 3H); 13C NMR (75.4 MHz, CDCl3) d: 200.02 (C]O),
154.48, 152.17, 147.05, 134.69, 132.28, 129.96, 127.70,
123.70, 127.33, 121.80, 109.44, 106.94, 67.51, 26.42; MS
(70 eV, m/z, %): 278 (MC2, 33), 276 (MC, 100), 247 (6),
233 (19), 215 (18), 207 (72), 191 (12), 178 (74), 165 (8), 152
(21), 149 (32), 139 (89), 137 (40), 115 (69), 111 (29), 98
(81), 70 (38); HRMS calcd for C15H13ClO3: 276.0553.
Found: 276.0556.
Acknowledgements
2.1.11. Methyl 4-[2-(methoxycarbonyl)hydroxyallyl]-
benzoate (21). IR (KBr) nmax: 3491 (OH), 2955, 1723
(C]O), 1436, 1283, 1110, 1019, 818; 1H NMR (300 MHz,
CDCl3) d: 8.03 (s, 1H), 8.00 (s, 1H), 7.47 (s, 1H), 7.45 (s,
1H), 6.36 (s, 1H), 5.83 (s, 1H), 5.60 (s, 1H), 3.91 (s, 1H),
3.71 (s, 1H); 13C NMR (75 MHz, CDCl3) d: 166.9 (C]O),
166.6 (C]O), 146.3, 141.4, 129.8, 129.6, 126.9, 126.5,
73.13, 52.2, 52.1; MS (EI, 70 eV, m/z, %): 250 (MC, 35),
235 (18), 219 (25), 191 (31), 190 (35), 165 (18), 163 (100),
131 (13), 105 (31), 77 (30), 59 (21); HRMS calcd for
C13H14O5: 250.0841. Found: 250.0849.
We gratefully acknowledge Nancy J. Y. Tsai for her helpful
discussions.
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