One-pot synthesis of dihydropyrimidiones via environmentally friendly enzyme-catalyzed Biginelli reaction

Article abstract of DOI:10.3987/COM-11-12267

A novel enzyme-catalyzed Biginelli reaction of acetoacetate, aromatic aldehyde and urea (thiourea) was described. Great acceleration of the one-pot multicomponent reaction was observed by the aid of enzymes. Various dihydropyrimidiones were prepared in go

Full text of DOI:10.3987/COM-11-12267

HETEROCYCLES, Vol. 83, No. 9, 2011
2067
HETEROCYCLES, Vol. 83, No. 9, 2011, pp. 2067 - 2077. © The Japan Institute of Heterocyclic Chemistry
Received, 25th May, 2011, Accepted, 27th June, 2011, Published online, 6th July, 2011
DOI: 10.3987/COM-11-12267
ONE-POT
SYNTHESIS
OF
DIHYDROPYRIMIDIONES
VIA
ENVIRONMENTALLY FRIENDLY ENZYME-CATALYZED BIGINELLI
REACTION
Wanmei Li, Guobin Zhou, Pengfei Zhang,* Yifeng Lai, and Shifu Xu
College of Material, Chemistry and Chemical Engineering, Hangzhou Normal
University, Hangzhou 310036, China; Fax/Tel: +86-571-88484468; E-mail:
pfzhang@hznu.edu.cn
Abstract – A novel enzyme-catalyzed Biginelli reaction of acetoacetate, aromatic
aldehyde and urea (thiourea) was described. Great acceleration of the one-pot
multicomponent reaction was observed by the aid of enzymes. Various
dihydropyrimidiones were prepared in good yields under the conditions using
trypsin from porcine pancreas as the catalyst.
INTRODUCTION
Multicomponent reactions (MCRs) are of increasing importance in the fields of organic and medicinal
chemistry, for their high atom economy, extensive applications in combinatorial chemistry, and
diversity-oriented synthesis.1-6 As one of the most useful multicomponent reactions, the Biginelli reaction,
originally described by Biginelli in 1893, offers an efficient route to obtain multifunctionalized
3,4-dihydropyrimidin-2(1H)-ones (DHPMs) and related heterocyclic compounds.7 These heterocycles
exhibit a wide spectrum of biological effects such as antibacterial,8 antiviral,9 anticancer,10
anti-inflammatory,11 and antihypertensive effects.12 The first one-pot cyclocondensation reaction of
ethylacetoacetate, benzaldehyde and urea was carried out by simply heating the three components mixture
dissolved in ethanol with a catalytic amount of HCl at reflux temperature. However, the product yields
are quite low (20–50%). Biginelli reactions with higher yields up to 95% have been achieved by replacing
the HCl catalyst to ZnCl2,13 FeCl3,14 BF3,15 ZrCl4,16 InBr3,17 In(OTf)3,18 Ln(OTf)3,19 Cu(OTf)2,20
Sr(OTf)2,21 MgBr2,22 [bmim]BF4-immobilized Cu(II) acetylacetonate,23 [bmim] [FeCl4],24 etc. However,
all the above methods displayed some drawbacks, such as environmental pollution, strongly acidic
reaction conditions, unsatisfactory yields, toxic catalysts, and complicated operations.

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HETEROCYCLES, Vol. 83, No. 9, 2011
As the increase of environmental consciousness in chemical and medicine industry, efficient, economic,
and clean procedures have received increased attention in recent years. Although the development of the
application of microwave or ultrasound irradiation25 and green solvent26 in Biginelli reaction is
undergoing, it is also urgent to further develop an efficient, convenient and environmentally friendly
method to construct such significant scaffold. Enzymes are efficient and environmentally friendly
catalysts in organic and bioorganic synthesis. Besides the natural catalytic ability to catalyze a primary
reaction, many enzymes can also catalyze secondary reaction, which is termed ‘catalytic promiscuity’.27,28
For example, lipase can catalyze Michael addition,29 and arylmalonate decarboxylase can catalyze aldol
additions.30 Recently, we have report a lipase-catalysed tandem Knoevenagel and esterification reaction,
and lipase has higher activity for this “promiscuous” reaction.31
Herein, we report a high efficient one-pot synthesis of dihydropyrimidiones by an enzyme-catalyzed
Biginelli reaction using trypsin as catalyst. To the best of our knowledge, this is the first report of specific
enzyme-catalyzed Biginelli reaction (Scheme 1).32
O
R
X
O
O
enzyme
R'
R'
+
+
R CHO
H2N
NH2
O
NH
O
conditions
N
H
X
1
2
3
4
R' = Et, 2a
Me, 2b
X = O, 3a
3b
R = Ar
S,
Scheme 1. Enzyme-catalyzed Biginelli reaction
RESULTS AND DISCUSSION
Firstly, several common enzymes were screened in our experiments as shown in Table 1 using 2 mmol
benzaldehyde 1a, 2.1 mmol of ethyl acetoacetate 2a and 2.1 mmol of urea 3 in 5 mL of anhydrous ethanol.
In the absence of enzyme, the reaction led to none detectable adduct in 72 h. In contrast, in the presence
of some enzymes the reaction is distinctly accelerated (Table 1). For example, in the presence of porcine
pancreatic lipase (PPL), about 10% yield of adduct was detected after 96 h (Entry 2). Lipases AY30 and
CAL-B (lipase from Candida antarctica) also showed some catalytic activity in the Biginelli reaction
(Entries 3 and 4). Amano lipase M from Mucor javanicus displayed moderate activity for Biginelli
reaction in the reaction conditions, and 65% yield of 3,4-dihydropyrimidin-2(1H)-ones 4a could be
isolated (Entry 7). Different amylases exhibit huge difference in catalytic activities in this tested Biginelli
reaction. α-Amylase from Bacillus Subtilis or Aspergillus oryzae, and -amylase from soybean showed
no detectable catalytic activity (Entries 8, 9 and 10). However, the product 4a could be obtained with a

HETEROCYCLES, Vol. 83, No. 9, 2011
2069
high yield of 75% if -amylase from hog pancreas was used as catalyst (Entry 11). Excitingly, pepsin
from hog stomach and trypsin from porcine pancreas show significant catalytic activities, and the final
yields of the desired product 3,4-dihydropyrimidin-2(1H)-ones 4a were 85% and 88% respectively, after
72 h reaction in our tests (Entries 12 and 13). If trypsin from porcine pancreas was denatured or
deactivated, only trace amount of the desired product 4a was detected. Bovine serum albumin, as a
non-catalytic protein, either shew none catalysis in this reaction.
Table 1. Specific catalytic effect of enzymesa
O
Ph
O
O
O
catalyst, 37oC
EtO
NH
+
Ph CHO
+
H2N
NH2
5 mL of EtOH
OEt
N
O
H
1a
2a
3a
4a
Entry
Catalyst
Amount
(mg)
-
30
30
30
Time
(h)
72
96
96
Yield
(%)
0
10
< 5
< 5
0
1
2
3
4
5
none
PPL
lipase AY30
lipase CAL-B
lipase
96
96
A
from 30
Aspergillus niger
lipase AK from 30
Pseudomonas
6
96
0
fluorescens
7
lipase
Mucor javanicus
α-amylase
Bacillus subtilis
M
from 30
72
96
96
96
72
72
72
72
72
65
0
8
from 30
9
α-amylase
from 30
0
Aspergillus oryzae
aAmylase from
soybean
-amylase
hog pancreas
pepsin from hog 20
stomach
trypsin
10
11
12
13
14
15
30
30
0
75
85
88
trace
0
from
from 20
porcine pancreas
trypsin
from 20
porcine pancreasb
bovine
serum 30
albumin
a 2 mmol of 1a, 2.1 mmol of 2a and 2.1 mmol of 3a in 5 mL of anhydrous EtOH.
b Trypsin from porcine pancreas was denatured or deactivated at 100 oC.

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HETEROCYCLES, Vol. 83, No. 9, 2011
Solvent effect was also carefully investigated in the case of using trypsin from porcine pancreas as
catalyst due to its highest catalytic activity. It is found that the Biginelli multicomponent reaction could
proceed in most common polar solvents, such as MeOH, EtOH, DMSO, MeCN and DMF (Table 2,
Entries 1, 2, 3, 4, 9). Among them, the dihydropyrimidione 4a was obtained with much higher yield when
MeOH or EtOH is used as solvent (Table 2, Entries 2, 3). In other solvents including THF, CH2Cl2,
chloroform, and cyclohexane, only small amount of product was detected (Table 2, Entries 58). It is also
found that water could greatly influence the reaction rate. None of desired product was obtained if the
reaction was carried out using H2O as solvent (Table 2, Entry 11). When 1 mL of H2O was added into
EtOH solvent, the yield decreased from 88 to 10% (Table 2, Entries 3 and 10).
Table 2. Effects of different solvents on MCR of benzaldehyde 1a and ethyl acetoacetate 2a with urea 3aa
Entry
1
Solvent
DMSO
MeOH
Temperature (oC)
Yield (%)
37
37
37
37
37
37
37
37
37
37
37
37
25
80
85
88
86
21
33
35
trace
65
10
-
2
3
EtOH
4
MeCN
5
THF
6
CH2Cl2
CHCl3
7
8
cyclohexane
DMF
9
10
11
12
13
EtOH + H2O(1 mL)
H2O
EtOH
95b
8c
EtOH
a Condition: 2 mmol of 1a, 2.1 mmol of 2a and 2.1 mmol of 3, 20 mg of trypsin from porcine pancreas, 5
mL of solvent, 72 h.
b 3A molecular sieve was used. c The reaction was carried out at 25 oC for 72 h.
When 0.2 g of 3A molecular sieve was added into the reaction mixture to further remove the water
byproduct formed during the reaction, the yield of 4a product can be increased up to 95% in 72 h (Table 2,
Entry 12).
The influence of reaction temperature on the enzymatic Biginelli reaction was also considered. It is found
that the yield decreased with the decrease of temperature. The yield was only 8% at 25 oC (Table 2, Entry

HETEROCYCLES, Vol. 83, No. 9, 2011
2071
13). This is quite reasonable result because most of the enzymes give highest activities at about 35 - 40 oC,
which close to the body temperature of most mammals.
With the optimal conditions in hand, we applied this protocol to other substrates and the obtained results
o
are shown in Table 3. In the presence of 20 mg of trypsin from porcine pancreas at 37 C, most three
components condensation reactions reached the equilibrium after 72 h in anhydrous ethanol and could
provide expected products in good yields.
Table 3. Preparation of different dihydropyrimidiones via enzyme-catalyzed Biginelli reactiona
Entry
R’
X
Time
(h)
72
72
72
72
72
72
72
72
72
72
72
72
96
72
72
72
72
72
R
Yield
(%)
1
Et
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
Ph(4a)
95 (93, 92, 92, 89)b
2
Et
3,4-(OCH2O)-C6H3(4b)
4-MeO- C6H4 (4c)
4-Cl-C6H4 (4d)
4-Cl-C6H4 (4e)
4-NO2-C6H4 (4f)
4-HO-C6H4 (4g)
4-(NMe2)-C6H4 (4h)
3-Cl-C6H4 (4i)
94
96
95
93
89
90
93
93
92
89
92
82
87
85
91
90
93
3
Et
4
Et
5
Me
Me
Et
6
7
8
Et
9
Et
10
11
12
13
14
15
16
17
18
a
Me
Et
3-HO-C6H4 (4j)
3-Br-C6H4 (4k)
3-MeO-4-HO-C6H3 (4l)
2-Cl-C6H4 (4m)
2-furyl (4n)
Et
Et
Et
Et
2-pyridyl (4o)
Et
4-Me-C6H4 (4p)
4-CN-C6H4 (4q)
4-CN-Ph (4r)
Me
Et
S
S
2 mmol of 1, 2.1 mmol of 2 and 2.1 mmol of 3, 20 mg of trypsin from porcine pancreas, 5 mL of
anhydrous EtOH, 37 oC, 72 h, 0.4 g 3A molecular sieve.
b Enzyme was recovered and reused for four times.
The results on the reaction of the different aldehydes revealed that the substituent on the aromatic ring
plays a little role in governing the reactivity. A variety of para-substituted aromatic aldehydes, bearing

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HETEROCYCLES, Vol. 83, No. 9, 2011
either electron-donating or electron-withdrawing substituents, afforded high yields of the products. The
similar results were obtained when using meso-substituted aromatic aldehydes. Ortho-substituted
aldehydes such as 2-chlorobenzaldehyde, needed longer time and gave 82% yield (Entry 13).
Heterocyclic aldehydes such as 2-pyridylaldehyde and 2-furylaldehyde worked well and afforded the
desired product in 87 and 85% yield, respectively. However, the sterically hindered 2,
6-dimethoxylbenzaldehyde couldn’t afford any desired product even after 96 h under the same conditions.
In addition, thiourea 3b was also tested, satisfactorily, corresponding 3,4-dihydropyrimidin-2(1H)-thiones
were obtained with 9093% yields (Entries 1618). Furthermore, methyl acetoacetate also afforded the
desired products in high yields (Entries 5, 6, 10, and 17).
It should be pointed out that another advantage of this protocol is the easy recovering of the catalyst, and
enzyme could be obtained by straight filtration due to its poor solubility in organic solvent. The enzyme
was recovered and reused for four times, the recovered enzyme shows good catalytic activity under the
same reaction conditions with 93%, 92%, 92%, and 89% yield respectively (Table 3, Entry 1).
According to these satisfactory results, we so proposed a tentative mechanism for this new process
(Scheme 2). The proposed mechanism would start with the accommodation of the carbonyl in the active
site. The intermediate A was formed then the final product was obtained through cyclization and
dehydration.
H
O
H
O
H
O
H
O
H
O
H
H
O
Aldol
- H2O
OH
OR
O
OR
OH
+
Ph
H
OR
Ph
Ph
H2N
NH2
Michael
addition
H
O
H
H
H
O
OH
O
O
cyclization
- H2O
OR
Ph
HN
OR
HN
OR
Ph
H2N
O
N
H
O
N
H
Ph
O
N
H
A
Scheme 2. The proposed mechanism of enzyme-catalyzed Biginelli reaction
CONCLUSION
In conclusion, here we have reported a novel and environmentally friendly enzyme catalyzed
multicomponent Biginelli reaction. The advantages of this method included mild reaction conditions,
good yields, simple operation and environmentally friendly procedure.

HETEROCYCLES, Vol. 83, No. 9, 2011
2073
EXPERIMENTAL
Lipase A from Aspergillus niger, AY from Candida Antarctica, AK from Pseudomonas fluorescens, and
M from Mucor javanicus were obtained from Amano Pharmaceuticals Co., Ltd. All amylases and
trypsins were obtained from Sigma-Aldrich. Analytical grade solvents and commercially available
reagents were used without further purification. The Thin layer chromatography (TLC), which was used
to monitor the reaction, was carried out over silica gel (GF254), purchased from Qingdao Haiyang
Chemical Co., Ltd. Melting points were determined on a Büchi B-540 capillary melting point apparatus
1
13
and were uncorrected. H NMR and C NMR spectra were recorded at VARAIN–400 or BRUKER
AC400 using DMSO-d6 as the solvent with tetramethylsilane (TMS) as an internal standard at room
temperature. Chemical shifts are given in relative to TMS, the coupling constants J are given in Hz.
General procedure for the synthesis of dihydropyrimidiones via enzyme-catalyzed Biginelli reaction
(Using Trypsin from porcine pancreas, Table 3):
In 5 mL of anhydrous EtOH, 2 mmol of aromatic aldehyde, 2.1mmol of ethyl acetoacetate, 2.1 mmol of
urea or thiourea, 0.4g of 3A molecular sieve, 20 mg of trypsin from porcine pancreas was added
successfully, and the mixture was orbitally shaken at 37 °C for the given time (see Table 3) and
monitored by TLC. When the reaction completed, additional 10 mL of anhydrous EtOH was added to the
mixture and heated to 37 °C. The enzyme catalyst and 3A molecular sieve were isolated by hot filtration,
then the filtrate was condensed to half volume and cooled to -5 °C, finally the precipitate was collected to
obtain the desired dihydropyrimidiones 4a-4r. All products were known compounds, and were analyzed
by IR, 1H NMR and 13C NMR. The spectra data were identical with authentic samples.
CHARACTERISTIC DATA
4a, Straw yellow solid,33 Mp 201-203 °C. IR (KBr): 3440, 3210, 3102, 2936, 1710, 1655, 1579 cm-1. 1H
NMR (DMSO-d6): δ = 9.16 (s, 1 H), 7.75 (s, 1 H), 7.22–7.33 (m, 5 H), 5.13 (s, 1 H), 3.99 (q, J = 7.2 Hz,
2 H), 2.25 (s, 3 H), 1.06 (t, J = 7.2 Hz, 3 H). 13C NMR (DMSO-d6): δ= 165.3, 151.9, 148.3, 144.8, 128.3,
127.2, 126.2, 99.1, 59.1, 54.1, 17.9, 14.2.
1
4b, White solid,33 Mp 186-188 °C. IR (KBr): 3434, 3228, 3112, 2955, 1695, 1644, 1515 cm-1. H NMR
(DMSO-d6): δ = 9.13 (s, 1 H), 7.68 (s, 1 H), 6.84 (d, J = 8.0 Hz, 1 H), 6.75 (s, 1 H), 6.64 (d, J = 8.0 Hz, 1
H), 5.98 (s, 2 H), 5.07 (d, J = 3.2 Hz, 1 H), 3.96 (q, J = 7.2 Hz, 2 H), 2.22 (s, 3 H), 1.10 (t, J = 7.2 Hz, 3
H). 13C NMR (DMSO-d6): δ = 165.2, 152.1, 148.2, 147.1, 146.2, 138.9, 119.2, 107.9, 106.5, 100.8, 99.2,
59.2, 53.7, 17.7, 14.0.

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HETEROCYCLES, Vol. 83, No. 9, 2011
1
4c, White solid,33 Mp 203-204 °C. IR (KBr): 3428, 3238, 3104, 2964, 1712, 1654, 1518 cm-1. H NMR
(DMSO-d6): δ = 9.15 (s, 1 H), 7.67 (s, 1 H), 7.14 (d, J = 8.4 Hz, 2 H), 6.87 (d, J = 8.4 Hz, 2 H), 5.07 (d, J
= 2.8 Hz, 1 H), 3.96 (q, J = 7.2 Hz, 2 H), 3.73 (s, 3 H), 2.22 (s, 3 H), 1.08 (t, J = 7.2 Hz, 3 H). 13C NMR
(DMSO-d6): δ = 165.3, 158.3, 152.1, 148.1, 137.1, 127.5, 113.6, 99.6, 59.1, 55.0, 53.2, 17.6, 14.0.
1
4d, White solid,33 Mp 213-215 °C. IR (KBr): 3423, 3241, 3121, 2970, 1705, 1655, 1477 cm-1. H NMR
(DMSO-d6): δ = 9.21 (s, 1 H), 7.76 (s, 1 H), 7.37 (d, J = 8.8 Hz, 2 H), 7.23 (d, J = 8.8 Hz, 2 H), 5.13 (d, J
= 2.8 Hz, 1 H), 3.98 (q, J = 7.2 Hz, 2 H), 2.23 (s, 3 H), 1.07 (t, J = 7.2 Hz, 3 H). 13C NMR (DMSO-d6): δ
= 165.1, 151.9, 148.8, 143.7, 131.7, 128.3, 128.1, 98.8, 59.2, 53.4, 17.7, 14.2.
1
4e, White solid,33 Mp 203-204 °C. IR (KBr): 3366, 3222, 3113, 2953, 1718, 1641, 1504 cm-1. H NMR
(DMSO-d6): δ = 9.28 (s, 1 H), 7.81 (s, 1 H), 7.41 (d, J = 8.4 Hz, 2 H), 7.24 (d, J = 8.4 Hz, 2 H), 5.13 (d, J
= 2.8 Hz, 1 H), 3.54 (s, 3 H), 2.26 (s, 3 H). 13C NMR (DMSO-d6): δ = 165.5, 151.8, 148.8, 143.5, 131.7,
128.3, 128.1, 98.3, 53.1, 50.7, 17.8.
1
4f, White solid,33 Mp 235-237 °C. IR (KBr): 3361, 3225, 3111, 2959, 1719, 1638, 1510 cm-1. H NMR
(DMSO-d6): δ = 9.40 (s, 1 H), 8.21 (d, J = 8.4 Hz, 2 H), 7.94 (s, 1 H), 7.50 (d, J = 8.4 Hz, 2 H), 5.26 (d, J
= 2.8 Hz, 1 H), 3.53 (s, 3 H), 2.28 (s, 3 H). 13C NMR (DMSO-d6): δ = 165.5, 151.6, 149.4, 146.6, 127.4,
123.7, 109.1, 97.8, 53.3, 50.8, 17.9.
4g, Straw yellow solid,33 Mp 226-227 °C. IR (KBr): 3412, 3249, 3125, 2974, 1695, 1659, 1508 cm-1. 1H
NMR (DMSO-d6): δ = 9.33 (s, 1 H), 9.11 (s, 1 H), 7.62 (s, 1 H), 7.02 (d, J = 8.4 Hz, 2 H), 6.67 (d, J = 8.4
Hz, 2 H), 5.03 (d, J = 3.2 Hz, 1 H), 3.98 (q, J = 7.2 Hz, 2 H), 2.22 (s, 3 H), 1.07 (t, J = 7.2 Hz, 3 H). 13C
NMR (DMSO-d6): δ = 165.3, 156.5, 152.3, 147.8, 135.4, 127.4, 115.0, 99.7, 59.1, 53.5, 17.8, 14.1.
1
4h, Straw yellow solid,33 Mp 255-257 °C. IR (KBr): 3417, 3241, 3115, 2986, 1713, 1637, 1520cm-1. H
NMR (DMSO-d6): δ = 9.06 (s, 1 H), 7.56 (s, 1 H), 7.02 (d, J = 8.4 Hz, 2 H), 6.65 (d, J = 8.4 Hz, 2 H),
5.03 (d, J = 3.2 Hz, 1 H), 3.97 (q, J = 7.2 Hz, 2 H), 2.84 (s, 6 H), 2.22 (s, 3 H), 1.10 (t, J = 7.2 Hz, 3 H).
13C NMR (DMSO-d6): δ = 165.6, 152.3, 149.8, 147.6, 132.7, 126.9, 112.2, 100.0, 59.2, 53.4, 17.6, 14.2.
4i, Straw yellow solid,33 Mp 189-190 °C. IR (KBr): 3431, 3231, 3102, 2978, 2931, 1709, 1653, 1598 cm-1.
1H NMR (DMSO-d6): δ = 8.32 (s, 1 H), 7.25–7.36 (m, 4 H), 6.94 (s, 1 H), 5.37 (d, J = 3.2 Hz, 1 H), 4.06
13
(q, J = 7.2 Hz, 2 H), 2.38 (s, 3 H), 1.14 (t, J = 7.2 Hz, 3 H). C NMR (DMSO-d6): δ = 166.0, 152.5,
149.0, 148.2, 134.5, 131.0, 128.2, 127.4, 125.8, 100.8, 60.2, 55.5, 18.4, 14.4.

HETEROCYCLES, Vol. 83, No. 9, 2011
2075
o
1
4j, White solid,34 Mp 220-221 C. IR (KBr): 3323, 3180, 1678, 1579, 1474, 1283, 1190, 1112 cm-1. H
NMR (DMSO-d6) δ = 10.30 (s, 1H), 9.61 (br, 1H), 9.46 (s, 1H), 7.14 (t, J = 7.6 Hz, 1H), 6.64 (d, J = 8.8
13
Hz, 3H), 5.08 (d, J = 3.6 Hz, 1H), 3.57 (s, 3H), 2.28 (s, 3H). C NMR (DMSO-d6) δ = 174.6, 166.3,
158.1, 145.5, 145.2, 130.0, 117.3, 115.2, 113.6, 101.1, 54.3, 51.5, 17.7.
4k, Straw yellow solid,33 Mp 185-186 °C. IR (KBr): 3419, 3230, 3111, 2966, 2931, 1708, 1649, 1615,
1587cm-1. 1H NMR (DMSO-d6): δ = 9.27 (s, 1 H), 7.77 (s, 1 H), 7.22–7.45 (m, 4 H), 5.13 (d, J = 3.2 Hz,
1 H), 3.95 (q, J = 7.2 Hz, 2 H), 2.26 (s, 3 H), 1.10 (t, J = 7.2 Hz, 3 H). 13C NMR (DMSO-d6): δ = 165.1,
151.9, 148.8, 147.6, 130.8, 130.1, 129.2, 125.2, 121.5, 98.7, 59.3, 53.7, 17.9, 14.2.
4l, Straw yellow solid,33 Mp 232-234 °C. IR (KBr): 3530, 3233, 3109, 2978, 2930, 1705, 1651, 1519 cm-1.
1H NMR (DMSO-d6): δ = 9.16 (s, 1 H), 8.96 (s, 1 H), 7.66 (s, 1 H), 6.80 (s, 1 H), 6.76 (d, J = 8.4 Hz, 2
H), 6.61 (d, J = 8.4 Hz, 1 H), 5.03 (d, J = 2.8 Hz, 1 H), 3.96 (q, J = 7.2 Hz, 2 H), 3.75 (s, 3 H), 2.21 (s, 3
H), 1.12 (t, J = 7.2 Hz, 3 H). 13C NMR (DMSO-d6): δ = 165.3, 152.2, 147.7, 145.6, 135.8, 118.0, 115.2,
110.7, 99.4, 59.1, 55.4, 53.3, 17.6, 14.1.
1
4m, Straw yellow solid,33 Mp 211-213 °C. IR (KBr): 3368, 3255, 3107, 1698, 1657 cm-1. H NMR
(DMSO-d6): δ = 1.05 (t, J = 7.6 Hz, 3H), 2.46 (s, 3H), 3.99 (q, J = 7.6 Hz, 2H), 5.63 (s, 1H), 5.87 (d, J =
2.4 Hz, 1H), 7.20–7.25 (m, 3H), 7.37–7.39 (m, 1H), 7.86 (s, 1H). 13C NMR (DMSO-d6): δ = 165.9, 156.4,
152.4, 147.2, 140.1, 136.5, 129.4, 128.2, 127.2, 103.1, 58.0, 53.2, 17.9, 15.0.
1
4n, White solid,33 Mp 203-204 °C. IR (KBr): 3428, 3302, 3109, 2988, 1712, 1654, 1463 cm-1. H NMR
(DMSO-d6): δ = 9.23 (s, 1 H), 7.74 (s, 1 H), 7.54 (s, 1 H), 6.34 (d, J = 2.8 Hz, 1 H), 6.06 (d, J = 2.8 Hz, 1
H), 5.22 (d, J = 3.6 Hz, 1 H), 3.98 (q, J = 7.2 Hz, 2 H), 2.21 (s, 3 H), 1.11 (t, J = 7.2 Hz, 3 H). 13C NMR
(DMSO-d6): δ = 165.1, 156.0, 152.3, 149.2, 142.2, 110.3, 105.2, 96.7, 59.2, 47.6, 17.8, 14.0.
o
4o, White solid,35 Mp 196-198 C. IR (KBr): 3420, 3228, 2932, 2863, 1659, 1566, 1487, cm-1 1H NMR
(DMSO-d6) δ = 9.21 (s, 1H), 8.51 (s, 1H), 7.72-7.74 (m, 2H), 7.51 (d, J = 7.6 Hz, 1H), 7.22-7.24 (m, 1H),
13
5.33 (s, 1H), 4.20 (q, J = 7.2 Hz, 2H), 2.45 (s, 3H), 1.17 (t, J = 7.2 Hz, 3H). C NMR (DMSO-d6): δ =
167.8, 154.8, 150.4, 147.8, 147.2, 138.1, 125.1, 121.1, 106.8, 62.1, 50.1, 17.2, 14.1.
o
4p, Straw yellow solid,34 Mp 212-213 C. IR (KBr): 3323, 3190, 3116, 2983, 1676, 1613, 1572, 1513
cm-1. 1H NMR (DMSO-d6): δ = 10.18 (s, 1H), 9.60 (s, 1H), 7.14 (d, 2H, J = 8.0 Hz), 6.92 (d, 2H, J = 8.0
Hz), 5.11 (s, 1H), 3.99 (q, 2H, J = 6.8 Hz), 3.73 (s, 3H), 2.30 (s, 3H), 1.11 (t, 3H, J = 6.8 Hz). 13C NMR

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HETEROCYCLES, Vol. 83, No. 9, 2011
(DMSO-d6): δ = 174.1, 165.1, 158.6, 144.7, 135.6, 127.5, 113.9, 100.7, 59.3, 55.0, 53.5, 17.1, 14.2.
o
1
4q, White solid,34 Mp 157-168 C. IR (KBr): 3335, 3158, 2931, 2225, 1692, 1536, and 1174 cm-1. H
NMR (DMSO-d6) δ = 10.43 (s, 1H), 9.71 (d, J = 2.4 Hz, 1H), 7.81 (d, J = 8.4 Hz, 2H), 7.34 (d, J = 8.0 Hz,
13
2H), 5.21 (d, s = 3.2 Hz, 1H), 3.50 (s, 3H), 2.23 (s, 3H). C NMR (DMSO-d6) δ = 175.1, 165.2, 147.1,
143.5, 132.7, 127.6, 118.2, 112.3, 102.1, 55.5, 51.6, 18.3.
o
1
4r, White solid,34 Mp 240-242 C. IR (KBr): 3327, 3155, 2225, 1536, 1420, 1178, 776 cm-1. H NMR
(DMSO-d6) δ = 8.68 (s, 1H), 7.96 (s, 1H), 7.65 (d, J = 8.0 Hz, 2H), 7.41 (d, J = 8.4 Hz, 2H), 5.46 (d, J =
13
3.2 Hz, 1H), 4.13 (q, J = 7.2 Hz, 2H), 2.39 (s, 3H,), 1.20 (t, J = 7.2 Hz,3H). C NMR (DMSO-d6) δ =
174.6, 164.7, 146.9, 143.4, 132.9, 127.3, 118.1, 112.0, 101.9, 60.7, 55.4, 18.2, 14.0.
ACKNOWLEDGEMENTS
We are grateful to the natural science foundation of China (no. 21076052) and Key SCI-Tech Innovation
Team of Zhejiang Province (2010R50017) for financial help.
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