A facile synthesis of trisubstituted alkenes from β-diketones and aldehydes with AlCl3 as catalyst

Article abstract of DOI:10.1007/s11164-011-0322-y

Preparation of trisubstituted alkenes from low-activity β-diketones and aldehydes with aluminum chloride as catalyst has been studied. The frequently used catalyst AlCl₃ is used for the first time to promote this condensation. The procedure is a convenient, low toxicity, and highly efficient method for industrial synthesis of trisubstituted alkenes in high yield. Springer Science+Business Media B.V. 2011.

Full text of DOI:10.1007/s11164-011-0322-y

Res Chem Intermed (2012) 38:25–35
DOI 10.1007/s11164-011-0322-y
A facile synthesis of trisubstituted alkenes
from b-diketones and aldehydes with AlCl3 as catalyst
•
Zheng-Nan Li Xiao-Liang Chen Yu-Jie Fu
•
•
•
Wei Wang Meng Luo
Received: 25 January 2011 / Accepted: 4 May 2011 / Published online: 17 May 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Preparation of trisubstituted alkenes from low-activity b-diketones and
aldehydes with aluminum chloride as catalyst has been studied. The frequently used
catalyst AlCl3 is used for the first time to promote this condensation. The procedure
is a convenient, low toxicity, and highly efficient method for industrial synthesis of
trisubstituted alkenes in high yield.
Keywords AlCl3 Á Knoevenagel condensation Á b-Diketones Á Aldehydes Á
Facile reaction conditions
Introduction
Trisubstituted alkenes, for example a,b-unsaturated carbonyl compounds and
a,b-unsaturated esters, are good Michael-addition acceptors and can be used directly
in the Diels–Alder reaction for further transformations. These important derivatives
are used widely in perfume, polymer, and pharmaceutical applications [1, 2],
especially as elegant intermediates in the production of anti-hypertensive drugs and
calcium antagonists. The Knoevenagel reaction is well-known to produce these
Zheng-Nan Li and Xiao-Liang Chen contributed equally to this work.
Electronic supplementary material The online version of this article (doi:
10.1007/s11164-011-0322-y) contains supplementary material, which is available to authorized users.
Z.-N. Li Á X.-L. Chen Á Y.-J. Fu (&) Á W. Wang Á M. Luo
Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University,
Harbin 150040, People’s Republic of China
e-mail: yujie_fu2002@yahoo.com
Z.-N. Li Á X.-L. Chen Á Y.-J. Fu Á W. Wang Á M. Luo
Engineering Research Center of Forest Bio-preparation, Ministry of Education, Northeast Forestry
University, Harbin 150040, People’s Republic of China
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Z.-N. Li et al.
O
O
Scheme 1 Knoevenagel
condensation of b-diketones and
aldehydes
R2
O
O
AlCl3
R1
CHO
+
R1
CH2Cl2,rt,1-3h
R1=H, OEt
R2=H, 4-OH, 4-OMe, 4-NO2, etc
R2
products [3]. Most Knoevenagel condensations are from active methylene
compounds carrying two electron-withdrawing groups, for example malononitrile
and malonate. Few examples of the use of b-diketones as starting materials have
been reported, probably because such compounds are less reactive than the
methylene compounds mentioned above, as a result of their tendency to form a
stable cyclic enol [2].
The importance of trisubstituted alkenes has led to exploration of several new
reagents to promote Knoevenagel condensation. Novel types of catalysts and
technologies have been used for Knoevenagel condensations, for example
procedures involving amino acids [3–5], azacyclo compounds [6, 7], metallohalides
[8–11], inorganic salts [2, 12, 13], solid support catalysts [10, 14–19], hydroxy-
apatite [6, 19, 20], metals [21], ionic liquids [18, 22–26], supercritical CO2
technology [27], and high-pressure conditions [28], etc. However, these procedures
either require harsh conditions or are expensive as a result of the cost of the energy
required, the catalyst used, or environmental protection. Also, some, for example
perchlorates, may cause explosions. Although the classic base-promoted conden-
sation is well-known, Lewis acids have attracted our attention. Basic compounds act
as catalysts in this condensation because they can abstract a proton from an active
methylene group, leading to an increase in the nucleophilicity of the active
methylene. Lewis acids with oxophilicity also have this property—they tend to form
oxides by hydrolysis or abstraction of oxygen, and so have a similar function to
basic compounds in this condensation reaction. AlCl3, a typical Lewis acid
containing an oxophilic metal, and a classic catalyst in the Friedel–Crafts reaction,
attracted our attention because of its use under facile conditions, with short reaction
times, high conversion ratios, low toxicity, and wide commercial availability.
Also, compared with the catalysts listed above, AlCl3 is very inexpensive, and
the by-product, Al(OH)3, can be used as an inorganic flame retardant additive.
Herein, we report a mild procedure for Knoevenagel condensation with AlCl3
as Lewis acid catalyst (Scheme 1); such reactions have high catalyst efficiency, are
of low cost, and are environmentally friendly.
Results and discussion
Optimization of the Lewis acid used for the Knoevenagel condensation
We investigated some common Lewis acids as possible catalysts for the
Knoevenagel reaction. To test the reactivity of Lewis acids we chose the reaction
of ethyl acetoacetate with benzaldehyde in the presence of different catalytic
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A facile synthesis of trisubstituted alkenes
27
Table 1 Optimization of the Lewis acid for the Knoevenagel condensation
Entry
Catalyst
Amount of
catalyst/mol%
Time/h
Yielda/%
1
2
3
4
5
6
ZnCl2
CaCl2
AlCl3
AlCl3
AlCl3
No
10
10
10
20
5
12
12
3
0
0
88
90
30
0
2
2
–
12
Conditions: benzaldehyde (1.0 mmol), ethyl acetoacetate (1.0 mmol); TLC detection
a
Isolated yield
systems at room temperature. ZnCl2 (10 mol%) was first used as the catalyst in the
reaction of ethyl acetoacetate (1 mmol) and benzaldehyde (1 mmol) stirred at room
temperature, with product detection by MS. Unfortunately, no target product was
formed. Use of CaCl2 was also unsuccessful (Table 1, entry 1–2). Then another
Lewis acid, AlCl3, was investigated. Fortunately, it was found that the reaction
proceeded well within 3 h, and the system was clean (Table 1, entry 3). The product
was isolated and characterized as a trisubstituted alkene. To find the optimum
amount of AlCl3, 20 mol% AlCl3 was added under the same conditions; although
the yield increased slightly, the duration of the reaction was reduced to 2 h (Table 1,
entry 4). When the amount of AlCl3 was reduced to 5 mol% the yield decreased
noticeably (Table 1, entry 5). When no catalyst was used no product was obtained
(Table 1, entry 6). It is apparent from Table 1 that the best reaction conditions are at
least 20 mol% AlCl3 to obtain 90% target product yield without any traces of
byproducts. Compared with traditional or novel catalysts reported recently, the
amount of AlCl3 required is almost the same, or even less, but the yield is higher.
Optimization of the solvent for the Knoevenagel condensation
The condensation reaction between ethyl acetoacetate and benzaldehyde in the
presence of 20 mol% AlCl3 was used to investigate the effect of the solvent used.
It was found that strongly polar solvents had a deleterious effect on the reaction.
As shown in Table 2, with CH2Cl2 as solvent the yield was slightly higher than with
THF, and with EtOH, acetonitrile, or DMF as solvent no target product was
obtained. Therefore, CH2Cl2 was chosen as solvent because of its low cost and ease
of use.
Knoevenagel reaction of ethyl acetoacetate with aromatic aldehyde
To test the universality of AlCl3 as catalyst, the procedure was applied in classical
Knoevenagel condensation reactions of b-diketones with different aromatic
aldehydes. We focused on the reaction of ethyl acetoacetate. Various benzaldehyde
123

28
Z.-N. Li et al.
Yielda/%
Table 2 Optimization of the
solvent for the Knoevenagel
reaction
Entry
Solvent
1
2
3
4
5
EtOH
AN
0
0
Conditions: benzaldehyde
(1.0 mmol), ethyl acetoacetate
(1.0 mmol), catalyst
THF
85
0
DMF
CH2Cl2
(0.2 mmol); TLC detection
a
Isolated yield
90
O
O
Scheme 2 Reaction of ethyl
acetoacetate with aromatic
aldehydes
CHO
O
O
AlCl3
OEt
+
OEt
CH2Cl2,
1.5~3h,rt
R2
R2
R2=H, 4-OH, 4-OMe, 4-NO2, etc
1-11a
derivatives carrying electron-withdrawing or electron-donating groups were used
for the condensation reactions under the established procedure (Scheme 2). As
shown in Table 3, because electron-withdrawing groups increased the electrophi-
licity of the carbonyl group, benzaldehyde derivatives carrying electron-withdraw-
ing groups afforded slightly higher yields than benzaldehyde derivatives carrying
electron-donating groups (Table 3, entries 6–9). In addition, it was found that
aromatic aldehyde with large functional groups hindered the reaction more than
those with small functional groups, irrespective of whether the groups were
electron-donating or electron-withdrawing (Table 3, entries 2–5, 7–11).
Knoevenagel reaction of acetylacetone with aromatic aldehydes
After these encouraging results, the procedure was applied to the reaction of
acetylacetone with aromatic aldehydes (Scheme 3). The results are reported in
Table 4. Fortunately, we obtained similar results. Higher yields were achieved
not only because of the symmetrical structure of acetylacetone, but also less
stereospecific hindrance of the reagents (Table 4).
Knoevenagel reaction of b-diketones with nonaromatic aldehydes
We tried to extend the procedure to nonaromatic aldehydes (Scheme 4) but,
unfortunately, unsatisfactory results were obtained. In fact, in the reaction of
b-diketones with furfural, cinnamaldehyde, and aliphatic aldehydes, the most
desired products were not obtained, only a mixture of starting materials and
unidentified by-products, except for furfural (Table 5). We suggest this is because
active methylene groups are electronegative, and the aliphatic hydrocarbon groups
of aliphatic aldehydes usually increase the electronegativity of the carbonyl carbon
because of their electron-donating properties, and this becomes a barrier to the
reaction. Correspondingly, neither the traditional or novel catalysts reported worked
efficiently with aliphatic aldehydes. Further research on the reactions of these
substrates might be worthwhile.
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A facile synthesis of trisubstituted alkenes
29
Table 3 Reaction of ethyl acetoacetate with aromatic aldehydes
Entry
R2
Time/h
Yielda/%
Entry
R2
Time/h
Yielda/%
1
2
3
4
5
6
H
2
2
2
3
2
2
88
78
80
80
70
90
7
8
4-NO2
3
85
82
78
65
68
4-OH
4-Me
4-N(Me)2
4-OMe
4-F
3-NO2
3
9
2-NO2
3
10
11
3,4-OMe
3-OMe, 4-OH
3
1.5
Conditions: aromatic aldehyde (1.0 mmol), ethyl acetoacetate (1.0 mmol), catalyst (0.2 mmol); TLC
detection
a
Isolated yield
O
O
Scheme 3 Reaction of
acetylacetone with aromatic
aldehydes
CHO
O
O
AlCl3
+
CH2Cl2,
1.5~2h,rt
R2
R2
R2=H, 4-OH, 4-OMe, 4-NO2, etc
1-11b
Table 4 Reaction of acetylacetone with aromatic aldehydes
Entry
R2
Time/h
Yielda/%
Entry
R2
Time/h
Yielda/%
1
2
3
4
5
6
H
2
90
85
80
84
78
90
7
8
4-NO2
2
85
85
80
70
70
4-OH
4-Me
4-N(Me)2
4-OMe
4-F
1.5
2
3-NO2
2
9
2-NO2
2
2
10
11
3,4-OMe
3-OMe,4-OH
2
1.5
2
1.5
Conditions: aromatic aldehyde (1.0 mmol), acetylacetone (1.0 mmol), catalyst (0.2 mmol); TLC
detection
a
Isolated yield
O
O
O
O
Scheme 4 Reaction of active
b-diketones with nonaromatic
aldehydes
AlCl3
R3
CHO
+
R1
R1
CH2Cl2,
2~3h,rt
R1=H, OEt
R3= Pr-, Bu-, etc
R3
1-8c
Conclusions
In summary, we have demonstrated an interesting application of AlCl3 as a Lewis
acid catalyst in promoting the synthesis of trisubstituted functionalized alkenes via a
Knoevenagel condensation between b-diketones and aromatic aldehydes. The
reaction conditions are very mild, and the condensation occurs at room temperature
123

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Z.-N. Li et al.
Table 5 Reaction of active
b-diketones with nonaromatic
aldehydes
Entry
1
R1
R3
Time/h
2
Yielda/%
70
H
O
2
H
3
0
3
4
5
H
nBu-
nPr-
O
3
3
2
0
H
0
OEt
60
6
OEt
3
0
Conditions: nonaromatic
aldehyde (1.0 mmol),
nBu-
nPr-
3
3
0
0
b-diketones (1.0 mmol), catalyst
(0.2 mmol); TLC detection
7
8
OEt
OEt
a
Isolated yield
with CH2Cl2 as solvent. Results demonstrated that the simple and highly efficient
catalyst AlCl3 can accelerate Knoevenagel condensation of aldehydes with
b-diketones, with excellent yields. We found that AlCl3 is efficient in reactions
of aromatic aldehydes, and the corresponding trisubstituted alkenes could be
synthesized in high yields. The reaction time is reduced to 2–3 h by using AlCl3 as
catalyst. Our results suggest that this method may displace most Knoevenagel
condensation methods with other catalysts.
Experimental
General procedure for Knoevenagel reactions
Unless otherwise indicated, reagents and solvents were obtained from commercial
suppliers. Thin-layer chromatography was performed on E. Merck TLC plates
precoated with silica gel 60 F254. Visualization was accomplished by use of a UV
lamp then vanillin staining. Flash column chromatography was accomplished with
silica gel 60 (300–400 mesh). NMR spectra were obtained at 500 MHz for proton
and 125 MHz for carbon in deuterated solvents, using tetramethylsilane as internal
standard.
Experimental procedures
AlCl3 (0.2 mmol) was added to a solution of the b-diketone (1.0 mmol) in
dichloromethane (2 mL), stirring at room temperature for 5 min, and then the
aldehyde (1.0 mmol) was added. The reaction was stirred at room temperature until
the reaction was complete (TLC detection), then quenched with saturated NaHCO3
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A facile synthesis of trisubstituted alkenes
31
solution. The dichloromethane solution was then washed with the same solution
(3 9 10 mL), then dried over Na2SO4. The solvent was removed under reduced
pressure, and the crude mixture was purified by silica gel column chromatography.
Compound 1a
Compound 1a was prepared according to the general procedure using benzaldehyde
and ethyl acetoacetate as starting materials. Yield: 88%; yellow oil; 1H NMR
(CDCl3, 500 MHz): d 1.336 (t, 3H), 2.357 (s, 3H), 4.283–4.326 (m, 2H), 7.386
(t, 5H), 7.678 (s, 1H); 13C NMR (CDCl3, 125 MHz): d 203.44, 164.45, 140.52,
134.11, 132.92, 130.43, 129.68, 128.93, 61.57, 31.23, 14.18; ESI–MS m/z calculated
for C13H14O3 ? H? 219.25, found 219.3.
Compound 2a
Compound 2a was prepared according to the general procedure using 4-OH-
benzaldehyde and ethyl acetoacetate as starting materials. Yield: 88%; yellow solid;
1H NMR (CDCl3, 500 MHz): d 1.301, 1.316 and 1.330 (t, 3H); 2.405 (s, 3H);
4.339–4.382 (m, 2H); 5.314 (m, 1H); 6.827, 6.844 (m, 2H); 7.372, 7.389 (m, 2H),
7.498 (s, 1H); 13C NMR (CDCl3, 125 MHz): d 194.78, 158.04, 141.07, 132.41,
131.97, 125.57, 115.97, 61.75, 26.47, 13.95; ESI–MS m/z calculated for
C13H14O4 ? H? 235.25, found 235.2.
Compound 3a
Compound 3a was prepared according to the general procedure using 4-Me-
benzaldehyde and ethyl acetoacetate as starting materials. Yield: 80%; white solid; 1H
NMR (CDCl3, 500 MHz): d 1.300–1.358 (m, 3H); 2.374, 2.410 (m, 3H); 3.028, 3.036
(m, 6H); 4.245–4.400 (m, 2H), 6,616–6,648 (m, 2H); 7.266–7.377 (m, 2H); 7.466 and
7.571 (d, 1H); 13C NMR (CDCl3, 125 MHz): d 204.81, 194.69, 169.16, 165.29,
152.07, 142.19, 141.42, 132.23, 129.15, 119.94, 111.62, 61.43, 40.00, 26.30, 14.05.
Compound 4a
Compound 4a was prepared according to the general procedure using 4-N(Me)2-
benzaldehyde and ethyl acetoacetate as starting materials. Yield: 80%; white solid;
1H NMR (CDCl3, 500 MHz): d 1.300–1.358 (m, 3H); 2.374, 2.410 (m, 3H); 3.028,
3.036 (m, 6H); 4.245–4.400 (m, 2H), 6.616–6.648 (m, 2H); 7.266–7.377 (m, 2H);
7.466 and 7.571 (d, 1H); 13C NMR (CDCl3, 125 MHz): d 204.81, 194.69, 169.16,
165.29, 152.07, 142.19, 141.42, 132.23, 129.15, 119.94, 111.62, 61.43, 40.00,
26.30, 14.05; ESI–MS m/z calculated for C15H19NO3 ? H? 261.32, found 261.1.
Compound 5a
Compound 5a was prepared according to the general procedure using 4-MeO-
benzaldehyde and ethyl acetoacetate as starting materials. Yield: 70%; white solid;
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Z.-N. Li et al.
1H NMR (CDCl3, 500 MHz): d 1.298 (t, 3H); 2.376 (s, 3H); 2.415 (s, 3H);
4.326–4.369 (m, 2H); 7.189 and 7.205 (d, 2H); 7.352,7.368 (d, 2H); 7.536 (s, 1H);
13C NMR (CDCl3, 125 MHz): d 194.77, 168.08, 141.49, 141.37, 133.67, 129.65,
61.70, 31.24, 26.48, 21.53, 13.92; ESI–MS m/z calculated for C14H16O4 ? H?
249.27, found 249.1.
Compound 7a
Compound 7a was prepared according to the general procedure using 4-NO2-
benzaldehyde and ethyl acetoacetate as starting materials. Yield: 85%; white solid;
1H NMR (CDCl3, 500 MHz): d 1.345–1.371 (m, 3H); 2.367, 2.370 (s, 3H);
4.322–4.361 (m, 2H); 7.553, 7.568 (m, 2H); 7.687 (m, 1H); 8.226 and 8.240 (m,
2H).
Compound 9a
Compound 9a was prepared according to the general procedure using benzaldehyde
1
and ethyl acetoacetate as starting materials. Yield: 78%; yellow solid; H NMR
(CDCl3, 500 MHz): d 1.352, 1.366 and 1.381 (t, 3H); 2.213 (s, 3H); 4.326–4.369
(m, 2H); 7.360 and 7.375 (t, 1H); 7.555–7.586 (m, 1H); 7.627–7.657 (m, 1H); 8.197
and 8.214 (m, 1H); 13C NMR (CDCl3, 125 MHz): d 200.60, 163.87, 147.21, 139.17,
136.20, 133.88, 131.10, 130.22, 130.12, 125.07.
Compound 10a
Compound 10a was prepared according to the general procedure using benzalde-
hyde and ethyl acetoacetate as starting materials. Yield: 65%; white solid; 1H NMR
(CDCl3, 500 MHz): d 1.312–1.340 (t, 3H); 2.413 (s, 3H); 3.830–3.926 (m, 9H);
4.340–4.383 (m, 2H); 6.872 and 6.889 (m, 1H); 7.032 (d, 1H); 7.098 and 7.115 (m,
1H); 7.501 (d, 1H); 13C NMR (CDCl3, 125 MHz): d 194.65, 168.41, 151.52, 149.02,
141.25, 132.52, 125.58, 124.53, 111.75, 111.03, 61.70, 55.99, 55.84, 26.45, 14.03.
Compound 11a
Compound 11a was prepared according to the general procedure using
3-OMe,4-OH-benzaldehyde and ethyl acetoacetate as starting materials. Yield:
1
68%; white solid; H NMR (CDCl3, 500 MHz): d 1.310–1.338 (t, 3H); 2.407 (s,
3H); 3.886 (s, 3H); 4.335–4.378 (m, 2H); 6.075 (d, 1H); 6.916 and 6.933 (m, 1H);
7.022–7.060 (m, 2H); 7.485 (s, 1H); 13C NMR (CDCl3, 125 MHz): d 194.74,
168.47, 148.52, 146.66, 141.46, 132.24, 125.26, 114.87, 111.40, 61.72, 55.94,
26.42, 14.02; ESI–MS m/z calculated for C14H16O5 ? H? 265.27, found 265.3.
Compound 1b
Compound 1b was prepared according to the general procedure using benzaldehyde
1
and acetylacetone as starting materials. Yield: 90%; white solid; H NMR (CDCl3,
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A facile synthesis of trisubstituted alkenes
33
500 MHz): d 2.289 (s, 3H), 2.430 (s, 3H), 7.401 (s, 4.96H), 7.501 (s, 1H); 13C NMR
(CDCl3, 125 MHz): d 205.59, 196.47, 142.82, 139.80, 132.91, 130.67, 129.71,
129.05, 31.66, 26.54; ESI–MS m/z calculated for C12H12O2 ? H? 189.22, found
189.5.
Compound 2b
Compound 2b was prepared according to the general procedure using 4-OH-
1
benzaldehyde and acetylacetone as starting materials. Yield: 85%; white solid; H
NMR (CDCl3, 500 MHz): d 2.361 and 2.423 (d, 6H), 6.278 (s,1H), 6.827 and 6.844
(d,2H), 7.265 and 7.279 and 7.297 (t, 2H), 7.424 (s, 1H); 13C NMR (CDCl3,
125 MHz): d 26.33, 31.77, 116.25, 125.09, 132.10, 140.35, 158.48, 196.94, 207.18;
ESI–MS m/z calculated for C12H12O3 ? H? 205.22, found 205.2.
Compound 3b
Compound 3b was prepared according to the general procedure using 4-Me-
1
benzaldehyde and acetylacetone as starting materials. Yield: 80%; white solid; H
NMR (CDCl3, 500 MHz): d 2.303 (s, 3H), 2.382 (s, 3H), 2.420 (s, 3H), 7.194, 7.210
(d, 2H), 7.289, 7.306 (d, 2H), 7.460 (s, 1H).
Compound 4b
Compound 4b was prepared according to the general procedure using 4-N(Me)2-
benzaldehyde and acetylacetone as starting materials. Yield: 84%; white solid;
1H NMR (CDCl3, 500 MHz): d 2.365, 2.385 (d, 6H); 3.042 (s, 6H); 6,635, 6.653
(d, 2H); 7.292, 7.309 (d, 2H), 7.388 (s, 1H).
Compound 5b
Compound 5b was prepared according to the general procedure using 4-OMe-
1
benzaldehyde and acetylacetone as starting materials. Yield: 78%; white solid; H
NMR (CDCl3, 500 MHz): d 2.306, 2.320 (d, 3H); 2.338, 2.402 (d, 3H); 3.819, 3.835
(m, 3H); 6.893–6.910 (m, 2H), 7.342–7.369 (m, 2H); 7.415–7.426 (m, 1H).
Compound 6b
Compound 6b was prepared according to the general procedure using 4-F-
1
benzaldehyde and acetylacetone as starting materials. Yield: 90%; white solid; H
NMR (CDCl3, 500 MHz): d 2.371 (s, 3H), 2.428 (s, 3H), 6.831 and 6.848 (d, 2H),
7.015 (s, 1H), 7.270 and 7.284 (d, 1H), 7.434 (s, 1H); 13C NMR (CDCl3, 125 MHz):
d 205.52, 196.42, 164.91, 162.90, 142.58, 138.47, 131.87, 131.80, 129.08, 116.37,
116.20, 77.35, 77.10, 76.84; ESI–MS m/z calculated for C12H11FO2 ? H? 207.11,
found 207.0.
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Z.-N. Li et al.
Compound 7b
Compound 7b was prepared according to the general procedure using 4-NO2-
benzaldehyde and acetylacetone as starting materials. Yield: 85%; yellow solid;
1H NMR (CDCl3, 500 MHz): d 2.295, 2.337 (m, 3H); 2.469 (m, 2H); 3.166 (s, 1H);
7.503–7.579 (m, 3H); 8.214–8.262 (m, 2H); 13C NMR (CDCl3, 125 MHz): d
204.42, 200.64, 195.96, 148.50, 145.63, 139.26, 136.47, 130.24, 128.54, 124.14,
81.16, 75.83, 57.03, 31.75, 29.16, 24.04.
Compound 8b
Compound 8b was prepared according to the general procedure using 3-NO2-
benzaldehyde and acetylacetone as starting materials. Yield: 85%; Yellow solid; 1H
NMR (CDCl3, 500 MHz): d 2.326 (s, 3H); 2.478 (s, 3H); 7.503 (s, 1H); 7.589–7.622
(m, 1H); 7.722 and 7.737 (m, 1H); 8.260 and 8.273 (d, 2H); 13C NMR (CDCl3,
125 MHz): d 204.27, 200.37, 195.96, 148.50, 145.95, 139.26, 136.47, 130.24,
128.54, 127.33, 126.66, 124.14, 123.59, 81.16, 75.83, 57.03, 31.75, 29.16, 26.70.
Compound 10b
Compound 10b was prepared according to the general procedure using 3,4-OMe-
1
benzaldehyde and acetylacetone as starting materials. Yield: 70%; white solid; H
NMR (CDCl3, 500 MHz): d 2.331 (m, 3H); 2.418 (s, 3H); 3,872 (m, 3H); 3.926
(m, 3H); 6.869–6.930 (m, 2H); 7.026–7.045 (m, 1H); 7.422 (s, 1H); 13C NMR
(CDCl3, 125 MHz): d 196.40, 151.37, 149.11, 139.89, 124.27, 112.00, 111.15,
55.99, 55.89, 31.75, 26.40; ESI–MS m/z calculated for C14H16O4 ? H? 249.27,
found 249.4.
Compound 1c
Compound 1c was prepared according to the general procedure using furfural and
1
acetylacetone as starting materials. Yield: 70%; yellow solid; H NMR (CDCl3,
500 MHz): d 1.367–1.395 (m, 3H); 2.379 (s, 3H); 6.523–6.529 (m, 1H); 6.822 and
6.829 (t, 1H); 7.308 (s, 1H); 7.544 (m, 1H); 13C NMR (CDCl3, 125 MHz): d 193.94,
167.58, 148.98, 146.39, 129.98, 126.43, 118.79, 112.92, 61.69, 26.54, 14.14;
ESI–MS m/z calculated for C10H10O3 ? H? 179.18, found 179.3.
Compound 5c
Compound 5c was prepared according to the general procedure using benzaldehyde
and acetylacetone as starting materials. Yield: 60%; yellow solid; 1H NMR (CDCl3,
500 MHz): d 2.378 (m, 3H); 2.449 (m, 3H); 6.521–6.527 (m, 1H); 6.784 and 6.791
(m, 1H); 7.169 (s, 1H); 7.559 (t, 1H); 13C NMR (CDCl3, 125 MHz): d 204.47,
195.90, 148.82, 146.58, 138.31, 124.98, 118.37, 112.99, 50.81, 31.50, 26.13;
ESI–MS m/z calculated for C11H12O4 ? H? 208.21, found 209.3.
123

A facile synthesis of trisubstituted alkenes
35
Acknowledgments We gratefully acknowledge financial support by the Key Program for Science and
Technology Development of Harbin (2009AA3BS083), Heilongjiang Province Science Foundation for
Excellent Youths (JC200704), the Agricultural Science and Technology Achievements Transformation
Fund Program (2009GB23600514), the Project for Distinguished Teacher Abroad, Chinese Ministry of
Education (MS2010DBLY031), Fundamental Research Funds for the Central Universities (DL09EA04),
and the Special Fund of Forestry Industrial Research for Public Welfare of China (201004040).
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