Diastereoselective enzymatic synthesis of highly substituted 3,4-dihydropyridin-2-ones via domino Knoevenagel condensation-Michael addition-intramolecular cyclization

Article abstract of DOI:10.1016/j.tet.2011.09.086

A direct method to construct 3,4-dihydropyridin-2-ones by enzymatic condensation of aldehyde with cyanoacetamide and 1,3-dicarbonyl compounds was developed. One ring and four new bonds (two C-C, one C-N, one CC) were formed in one pot. And reaction condit

Full text of DOI:10.1016/j.tet.2011.09.086

Tetrahedron 67 (2011) 9736e9740
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Diastereoselective enzymatic synthesis of highly substituted 3,4-dihydropyridin-
2-ones via domino Knoevenagel condensationeMichael additioneintramolecular
cyclization
*
Zhi-Qiang Liu, Bo-Kai Liu, Qi Wu, Xian-Fu Lin
Department of Chemistry, Zhejiang University, Hangzhou 310027, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 July 2011
Received in revised form 13 September 2011
Accepted 20 September 2011
Available online 25 September 2011
A direct method to construct 3,4-dihydropyridin-2-ones by enzymatic condensation of aldehyde with
cyanoacetamide and 1,3-dicarbonyl compounds was developed. One ring and four new bonds (two CeC,
one CeN, one C]C) were formed in one pot. And reaction conditions involving hydrolases, solvents,
substrate molar ratios, and hydrolase loading were optimized. A series of new compounds based on the 3,4-
dihydropyridin-2-one core were synthesized by the unprecedented three-component domino reaction.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Acylase
3,4-Dihydropyridin-2-ones
Three-component
Cyanoacetamide
Diastereoselective
1. Introduction
et al.7generated the 1-azadiene intermediate in situ via a Hor-
nereWadswortheEmmons (HWE) reaction of phosphonates, ni-
The synthesis of the 3,4-dihydropyridin-2-ones moiety is an in-
teresting field because its derivatives have exhibited significant bi-
ological and pharmacological activities, such as antibacterial,1
antifungal,2 and antitumor,3 also served as HIV-1 specific reverse
transcriptase inhibitors.4 Compounds 1 and 2 (Fig. 1) have been
triles, and aldehydes in tetrahydrofuran, and at ꢀ78 ꢁC, then the 1-
azadiene was trapped by
a-aryl isocyanoacetates to form 3,4-
dihydropyridin-2-ones. Noguez et al.8exposed the mixture of Mel-
drum’s acid, methyl or ethyl acetoacetate, substituted benzaldehyde
and ammonium acetate to infrared irradiation for 3 h, a series of 3,4-
dihydropyridin-2-ones were gotten in moderated yields (50e75%).
Despite several reports have appeared for the synthesis, the im-
portance of this class of molecules means that new method must
always be exploited, in particular the mild, efficient, and environ-
mentally friendly entry to this heterocycle.
found to show hypolipidemic and 5a-reductase inhibitory activities,
respectively. Due to their important medicinal activities, the quick
and efficient preparation of this scaffold has drawn much more at-
tention of chemists. So far, some methods have been invented.
Pendleton et al.5 found that the 3,4-dihydropyridin-2-one could be
gotten as the byproduct through the reaction of hydrazone with
methyl 3-aminocrotonate in hot acetic acid, the yield was only 22%.
Yang et al.6 synthesized the oxirane-containing enamide from the
cross-coupling reaction of oxiranecarboxamide with (E)-(2-
bromovinyl)benzene followed by N-methylation, then in the pres-
ꢀ
ence of trifluoroacetic acid and molecular sieve (4 A), the oxirane-
containing enamide underwent 6-endo-enamideeepoxide cycliza-
tion reaction to produce 3,4-dihydropyridin-2-one derivatives. In
recent decades, multicomponent reactions (MCRs) have repre-
sented a fascinating tool in organic synthesis owing to the fact that
sophisticated products can be synthesized efficiently just by mixing
three or more reactants in a single vessel. For example, Paravidino
Fig. 1. Compounds with 3,4-dihydropyridin-2-one core.
The pioneered work by Klibanov in the early 1980s initiated
nonaqueous enzymology.9 During the following decades, it was
found that they can not only catalyze the ‘natural’ reactions but also
* Corresponding author. E-mail address: llc123@zju.edu.cn (X.-F. Lin).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.09.086

Z.-Q. Liu et al. / Tetrahedron 67 (2011) 9736e9740
9737
have one or more secondary activities,10 which defined the catalytic
Table 2
Optimization of reaction conditions using different solventsa
promiscuity of enzymes. Enzymatic promiscuity largely expands the
application of enzymes in organic synthesis. For example, Berglund
et al. reported the unprecedented carbonecarbon bond formation
by an engineered mutant of CAL-B.11 Seebeck and Hilvert reported
that a mutated PLP-dependent racemase could catalyze the aldol
Cl
O
CN
O
O
AA
solvent
O
H
O
NC
O
H2N
Cl
reaction.12 Also, our group reported that
D-aminoacylase from
N
H
3
1
2
Escherichia coli catalyzed the Michael addition of 1,3-dicarbonyl
compounds to methyl vinyl ketone in organic solvent.13 MCRs are
important for generating high levels of diversity and give rise to
complex structures by simultaneous formation of two or more
bonds. However, MCRs catalyzed by natural enzymes were very
rare, especially the construction of novel heterocycles.14 Here, we
surprisingly discovered a zinc-dependent acylase showed the pro-
miscuous property to form the 3,4-dihydropyridin-2-one ring by the
three-component reaction among aldehydes, the cyanoacetamide
and 1,3-dicarbonyl compounds in nonaqueous solvent.
Entry
Solvent
Yielde (%)
1
2
3
DMSO
DMF
EG
EG
EG
EG
Di-EG
Glycerol
8
Trace
33
40
55
81
26
3
4b
5c
6d
7
8
9
1,4-Butylene glycol
7
a
Reaction conditions: 1 (0.5 mmol), 2 (0.5 mmol), 3 (0.5 mmol), AA (30 mg) in
2. Results and discussion
organic solvent (1 mL), 50 ꢁC, 24 h.
b
Compound 1 (0.5 mmol), 2 (1.0 mmol), 3 (0.5 mmol), AA (30 mg) in organic
Initial endeavor was focused on the search of an efficient enzyme
for the one-pot three-component condensation of 4-
chlorobenzaldehyde, cyanoacetamide, and acetyl acetone at 50 ꢁC
for24 h in ethylene glycol(EG). The results are summarized inTable 1.
solvent (1 mL), 50 ꢁC, 24 h.
c
Compound 1 (0.5 mmol), 2 (1.0 mmol), 3 (0.75 mmol), AA (30 mg) in organic
solvent (1 mL), 50 ꢁC, 24 h.
d
Compound 1 (0.125 mmol), 2 (1.0 mmol), 3 (0.75 mmol), AA (30 mg) in organic
solvent (1 mL), 50 ꢁC, 24 h.
e
Determined by HPLC.
Table 1
Optimization of reaction conditions using different enzymesa
Meanwhile, week polar solvents, like n-hexane, isooctane, and
acetonitrile, etc. were also checked, however, no product was
detected because the cyanoacetamide failed to dissolve in them.
Thus, EG was selected as the reaction solvent to test the ratio of
substrates.
The molar ratio of cyanoacetamide and acetyl acetone had an
impact on the yield. When the amount of compound 2 increased to
1 mmol, the yield was 40% (Table 2, entries 4 vs 3), then 0.75 mmol
compound 3 was applied, the yield increased to 55% (Table 2, en-
tries 5 vs 4 and 3). The dramatic improvement in yield from 55% to
81% was observed when compound 1 was 0.125 mmol. So the best
molar ratio of substrates was compound 1 (0.125 mmol), compound
2 (1.0 mmol), and compound 3 (0.75 mmol), after 24 h the yield
reached to 81% (Table 2, entry 6).
A survey of catalyst loading was made and the result was shown
in Fig. 2. In general, the reaction yield was proportional to the
amount of enzyme. When 40 mg enzyme was added to the reaction
mixture, the yield was 93%. While the yield scarcely changed along
with further increase of enzyme (from 93% to 87%).
Consequently, considering the overall effects of catalyst, sol-
vents, substrate ratio, catalyst loading, and further studies on the
exploration of substrate scopes and limitations were carried out. As
Cl
O
CN
O
O
catalyst
EG
O
H
O
NC
O
H2N
Cl
N
H
3
1
2
Entry
Catalyst
Yieldb (%)
1
2
3
4
5
6
7
8
9
d
Trace
16
17
34
34
30
5
AAc
BSA
DA
AA
MJL
PGA
AKL
CRL
6
14
a
Reaction conditions: 1 (0.5 mmol), 2 (0.5 mmol), 3 (0.5 mmol), catalyst (30 mg)
in 1 mL EG, 50 ꢁC, 24 h.
b
Determined by HPLC.
Denatured by urea at 100 ꢁC for 12 h.
c
As shown in Table 1, the reaction almost could not proceed
without enzyme (Table 1, entry 1). Gratifyingly, the yield in the
presence of D-Aminoacylase (DA) or Acylase ‘Amano’ (AA) increased
to 34% (Table 1, entries 4 and 5). Amano Lipase M from Mucor jav-
anicus (MJL) also showed activity toward the reaction (Table 1, entry
6). While, immobilized penicillin G acylase from E. coli (PGA), Lipase
AK ‘Amano’ (AKL) and Lipase from Candida rugosa (CRL) had very
low catalytic activity (Table 1, entries 7e9). Considering the cost of
enzyme, we chose AA as the catalyst. Also, denatured AA or bovine
serum albumin (BSA) had a little catalytic effect (Table 1, entries 2
and 3). Finally, AA acted as the catalyst in the following exploration.
With optimal catalyst in hand, different organic solvents were
screened to investigate the effect on the reaction. As described in
Table 2, the efficiency of solvents was of overwhelming distinction.
EG and Di-EG were extremely superior to others (Table 2, entries 3
and 6). Only very poor yield was obtained when EG was substituted
by Dimethyl sulfoxide (DMSO), Dimethylformamide (DMF), Glyc-
erol or 1,4-butylene glycol (Table 2, entries 1, 2, 7, and 8).
Fig. 2. Influence of catalyst loading on the yield after 24 h.

9738
Z.-Q. Liu et al. / Tetrahedron 67 (2011) 9736e9740
shown in Table 3, the enzyme-catalyzed one-pot condensation of
various aldehydes, 1,3-dicarbonyl compounds and cyanoacetamide
proceeded efficiently to desired 3,4-dihydropyridin-2-ones in
moderate to excellent yields mostly. It appeared that the aromatic
ring could participate in the process irrespective of the electronic
nature and the substitution pattern, for example, aromatic systems
that possessed substitutions at the ortho, meta or para positions had
the yield without substantial loss from 82% to 99% (Table 3, entries
2e4), however, the yield of aromatic aldehydes bearing electron-
withdrawing group was higher than that of the aldehydes with
electron-donating group (Table 3, entries 3 and 9, 4 and 7, 8). Fur-
thermore, heteroaromatic aldehyde also fit in good yields (Table 3,
entries 10 and 19). Aliphatic aldehyde could join in the system
successfully with the fact that longer carbon chain got lower yield
(Table 3, entries 11 and 12). It was noteworthy that not only acetyl
acetone but methyl acetoacetate and acetoacetanilide could also
play the role of 1,3-dicarbonyl compounds successfully. Because the
product 4 has two adjacent chiral centers, we got the mixture of
diastereoisomers whose ratio could be detected in 1H NMR.
attack to the carbonyl group of acetyl acetone, intermediate 3 lost
one molecular water to get the final product 4.
3. Conclusion
In summary, we have developed a novel one-pot enzymatic
method to construct highly substituted 3,4-dihydropyridin-2-ones
derivatives via a three-component condensation of aldehyde, cya-
noacetamide, and 1,3-dicarnonyl compound. The simple, conve-
nient and efficient strategy described here is a useful synthetic
protocol for the synthesis of potentially bioactive and pharmaco-
logical compounds. Further application of this strategy is ongoing
in our laboratory.
4. Experimental section
4.1. Materials
D
-Aminoacylase from E. coli (10,000 U/mg, 1 U is defined as en-
zyme quantity, which produces 1 mmol of -Amino acid per 30 min)
and Acylase ‘Amano’ (AA) from Aspergillus oryzae (ꢂ30,000 U/g, 1 U
is defined as enzyme quantity, which produces 1 mmol of -Amino
D
Table 3
Substrate scope studiesa
L
R1
O
acid per 30 min) were purchased from Amano Enzyme Inc (Japan).
Amano Lipase M from M. javanicus (ꢂ10,000 U/g enzyme activity, pH
7.0, 40 ꢁC). Lipase AK ‘Amano’ (ꢂ20,000 U/g enzyme activity, pH 7.0,
55 ꢁC). Immobilized penicillin G acylase from E. coli (EC 3.5.1.11,
immobilized on acrylic beads) was purchased from Hunan Flag
Biotech Co. All solvents were analytical grade and were dried by
CN
O
O
NC
O
O
AA
EG
R2
O
R1
H
N
H
H2N
R2
3
4
1
2
ꢀ
Product Yieldb (%) Ratio of diastereoisomersc
storing over activated 3 A molecular sieves for 24 h prior to use. All
Entry R1
R2
other reagents were used as received.
1
2
3
4
5
6
7
8
Ph
Me
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
44
99
84
82
59
93
51
42
65
70
82
50
87
64
28
35
29
28
81
64:36
86:14
86:14
91:9
88:12
68:22
86:14
90:10
94:6
2-NO2C6H4 Me
3-NO2C6H4 Me
4-NO2C6H4 Me
2-ClC6H4
4-ClC6H4
4-MeC6H4 Me
4-OMeC6H4 Me
3-OHC6H4 Me
2-Furyl
CH3CH2
CH3CH2CH2 Me
3-NO2C6H4 OMe
4-ClC6H4
4-MeC6H4 OMe
CH3CH2
4.2. Analytical methods
Me
Me
The 1H and 13C NMR spectra were recorded with TMS as internal
standard using a Bruker AMX-400 MHz spectrometer. Chemical
shifts were expressed in parts per million and coupling constants (J)
in hertz. Analytical HPLC was performed using an Agilent 1100 series
with a reversed-phase Shim-Pack VP-ODS column (150ꢃ4.6 mm)
and a UV detector (290 nm). IR spectra were measured with
a Nicolet Nexus FTIR 670 spectrophotometer. Melting points were
determined using XT-4 apparatus and were not corrected. All the
known products were characterized by comparing the 1H NMR data
with those reported in the literature. The structures of new com-
pounds were confirmed by 1H NMR, 13C NMR, and HRMS.
9
10
11
12
13
14
15
16
17
18
19
Me
Me
95:5
64:36
78:22
94:6
90:10
83:17
81:19
65:35
74:26
78:14
OMe
OMe
4-NHC6H5 4q
4-ClC6H4
4-MeC6H4 4-NHC6H5 4r
2-Furyl 4-NHC6H5 4s
a
4.3. General procedure for the three-component condensation
of aldehyde, cyanoacetamide, and 1,3-dicarbonyl compound
Reaction conditions: 1 (0.125 mmol), 2 (1 mmol), 3 (0.75 mmol), AA (40 mg) in
EG (1 mL), 50 ꢁC, 24 h.
b
Detected by HPLC.
c
Detected by 1H NMR.
A mixture of aldehyde (0.125 mmol), cyanoacetamide (1.0 mmol),
1,3-dicarbonyl compound (0.75 mmol), and AA (40 mg) was added to
EG (1 mL), and it was stirred at 50 ꢁC for 24 h. After the completion of
the reaction, the mixture was separated by silica gel column chro-
matography using petroleum ether/ethyl acetate mixture (1/1 v/v) as
eluent to afford the desired product of 3,4-dihydropyridin-2-ones.
To gain an insight into the reaction process, we, respectively,
prepared two possible intermediates, the Knoevenagel condensa-
tion products of p-chlorobenzaldehyde with cyanoacetamide and
p-chlorobenzaldehyde with acetyl acetone, in order to probe the
mechanistic pathway in detail. We found that two condensation
products could react with the third component to form the target
molecular. We took the mechanism initiated by the condensation of
p-chlorobenzaldehyde with acetyl acetone, for example (Scheme
1). The zinc ion would coordinate with one carbonyl group of
acetyl acetone to increase the nucleophilicity. Then Asp366 de-
prived one C3eH of acetyl acetone, at the same time, the nucleo-
phile would attack the carbonyl group of aldehyde to form the
Knoevenagel condensation product. Next, the interaction of zinc
ion with the carbonyl group of cyanoacetamide would enhance the
nucleophilic ability of Michael donor, so intermediate 2 was
formed. Then, the electron-rich NeH underwent the nucleophilic
4.3.1. 5-Acetyl-6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyridine-
3-carbonitrile (4a). Light yellow solid. IR (neat) (nmax/cmꢀ1): 3224,
3139, 2257, 1713, 1668. 1H NMR (400 MHz, CDCl3): dH 2.08, 2.12 (s,
3H, eCH3C]O), 2.37, 2.40 (s, 3H, eCH3C]C), 3.72e3.73, 4.16e4.18
(d, 1H, J¼6.4 Hz, eCHC]C), 4.32e4.34, 4.47e4.48 (d, 1H, J¼6.4 Hz,
eCHCN), 7.17e7.40 (m, 4H, AreH), 8.51e8.59 (s, 1H, eNH).
4.3.2. 5-Acetyl-6-methyl-4-(2-nitrophenyl)-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4b). Light yellow solid. Mp
106e107 ꢁC. IR (neat) (nmax/cmꢀ1): 3237, 3139, 2254, 1712, 1686. 1H
NMR (400 MHz, DMSO-d6): dH 1.63, 1.66 (s, 3H, eCH3C]O), 1.85,

Z.-Q. Liu et al. / Tetrahedron 67 (2011) 9736e9740
9739
Scheme 1. Proposed mechanism of lipase-catalyzed reaction of aldehyde with cyanoacetamide and 1,3-dicarbonyl compounds.
1.89 (s, 3H, eCH3C]C), 3.77e3.78, 4.47e4.49 (d, 1H, J¼7.6 Hz,
eCHC]C), 4.54e4.55, 4.86e4.88(d, 1H, J¼7.2 Hz, eCHCN),
6.82e7.61 (m, 4H, AreH), 10.11, 10.28 (s, 1H, eNH). 13C NMR
(100 MHz, DMSO-d6): dC 19.4, 30.8, 35.4, 115.1, 115.6, 125.8, 128.9,
130.0, 133.0, 134.8, 148.2, 149.1, 162.8, 196.6. HRMS (EI) calcd for
C15H13N3O4 [Mþ]: 299.0906, found: 299.0910.
(100 MHz, DMSO-d6): dC 19.0, 30.1, 40.7, 41.4, 114.7, 116.0, 129.2,
130.2, 133.3, 136.2, 147.3, 162.9, 197.1. HRMS (EI) calcd for
C15H13N2O2Cl [Mþ]: 288.0661, found: 288.0660.
4.3.7. 5-Acetyl-6-methyl-2-oxo-4-p-tolyl-1,2,3,4-tetrahydropyridine-
3-carbonitrile (4g). Light yellow solid. IR (neat) (nmax/cmꢀ1): 3234,
3139, 2260, 1702, 1678. 1H NMR (400 MHz, DMSO-d6): dH 2.00 (s,
3H, Ar-CH3), 2.22, 2.23 (s, 3H, eCH3C]O), 2.27 (s, 3H, eCH3C]C),
4.0.3e4.04, 4.37e4.38 (d, 1H, J¼4.0 Hz, eCHC]C), 4.52e4.53,
4.71e4.73(d, 1H, J¼4.0 Hz, eCHCN), 7.07e7.15 (m, 4H, AreH), 10.39,
10.51 (s, 1H, eNH).
4.3.3. 5-Acetyl-6-methyl-4-(3-nitrophenyl)-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4c). Light yellow solid. IR (neat)
(
nmax/cmꢀ1): 3261, 3167, 2257, 1717, 1679. 1H NMR (400 MHz,
DMSO-d6): dH 2.03, 2.04 (s, 3H, eCH3C]O), 2.28, 2.29 (s, 3H,
eCH3C]C), 4.21e4.22, 4.63e4.65 (d, 1H, J¼6.4 Hz, eCHC]C),
4.75e4.76, 4.83e4.85(d, 1H, J¼6.8 Hz, eCHCN), 7.60e8.15 (m, 4H,
AreH), 10.56, 10.64 (s, 1H, eNH).
4.3.8. 5-Acetyl-4-(4-methoxyphenyl)-6-methyl-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4h). Light yellow solid. IR (neat)
(
nmax/cmꢀ1): 3257, 3172, 2210, 1713, 1608. 1H NMR (400 MHz,
4.3.4. 5-Acetyl-6-methyl-4-(4-nitrophenyl)-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4d). Light yellow solid. Mp
105e106 ꢁC. IR (neat) (nmax/cmꢀ1): 3266, 3165, 2257, 1719, 1677. 1H
NMR (400 MHz, DMSO-d6): dH 1.99, 2.01 (s, 3H, eCH3C]O), 2.24,
2.25 (s, 3H, eCH3C]C), 4.55e4.57 (d, 1H, J¼6.4 Hz, eCHC]C),
4.68e4.69, 4.80e4.82 (d, 1H, J¼6.8 Hz, eCHCN), 7.42e8.13 (m, 4H,
AreH), 10.47, 10.58 (s, 1H, eNH). 13C NMR (100 MHz, DMSO-d6): dC
19.1, 30.3, 40.0, 41.0, 114.4, 115.7, 124.3, 124.4, 129.3, 129.9, 145.1,
147.7, 148.0, 162.8, 196.8. HRMS (EI) calcd for C15H13N3O4 [Mþ]:
299.0906, found: 299.0909.
DMSO-d6): dH 2.00 (s, 3H, eCH3C]O), 2.26, 2.27 (s, 3H, eCH3C]C),
3.68, 3.69 (s, 3H, eOCH3), 4.36e4.37 (d, 1H, J¼6.4 Hz, eCHC]C),
4.50e4.51, 4.69e4.70 (d, 1H, J¼6.8 Hz, eCHCN), 6.87e7.14 (m,
AreH, 4H), 10.38, 10.51 (s, eNH, 1H).
4.3.9. 5-Acetyl-4-(3-hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile
(4i). Yellow
solid.
Mp
249e250 ꢁC. IR (neat) (nmax/cmꢀ1): 3355, 3262, 2255, 1712, 1664.
1H NMR (400 MHz, DMSO-d6): dH 1.99 (s, 3H, eCH3C]O), 2.23,
2.24 (s, 3H, eCH3C]C), 4.29e4.30 (d, 1H, J¼6.4 Hz, eCHC]C),
4.45e4.46, 4.69e4.70 (d, 1H, J¼6.8 Hz, eCHCN), 6.57e7.13 (m, 4H,
AreH), 9.67, 9.70 (s, 1H, eOH), 10.35, 10.48 (s, 1H, eNH). 13C NMR
(100 MHz, DMSO-d6): dC 18.9, 30.1, 41.5, 115.0, 115.1, 115.5, 116.2,
119.1, 130.4, 138.8, 146.9, 157.8, 163.2, 197.4. HRMS (EI) calcd for
C15H14N2O3 [Mþ]: 270.1011, found: 270.1004.
4.3.5. 5-Acetyl-4-(2-chlorophenyl)-6-methyl-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4e). White solid. Mp 220e221 ꢁC.
IR (neat) (nmax/cmꢀ1): 3221, 3134, 2251, 1716, 1675. 1H NMR
(400 MHz, DMSO-d6): dH 2.02, 2.03 (s, 3H, eCH3C]O), 2.28, 2.31 (s,
3H, eCH3C]C), 4.82e4.84 (d,1H, J¼6.8 Hz, eCHC]C), 4.98e5.00 (d,
1H, J¼6.8 Hz, eCHCN), 7.11e7.52 (m, 4H, AreH), 10.50, 10.65 (s, 1H,
eNH). 13C NMR (100 MHz, DMSO-d6): dC 19.1, 30.0, 37.4, 40.3, 114.8,
115.5,128.5,128.6,130.4,130.4,133.8,135.5,147.8,162.7,196.9. HRMS
(EI) calcd for C15H13N2O2Cl [Mþ]: 288.0666, found: 288.0664.
4.3.10. 5-Acetyl-4-(furan-2-yl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyr-
idine-3-carbonitrile (4j). Yellow solid. IR (neat) (nmax/cmꢀ1): 3286,
3179, 2260, 1707, 1663. 1H NMR (400 MHz, DMSO-d6): dH 1.71, 1.73 (s,
3H, eCH3C]O),1.76,1.79 (s, 3H, eCH3C]C), 3.73e3.75, 4.14e4.15 (d,
1H, J¼6.0 Hz, eCHC]C), 4.22e4.23 (d, 1H, J¼6.4 Hz, eCHCN),
5.89e5.90, 5.90e5.91 (d,1H, J¼1.2 Hz, -C]CH),5.92e5.93, 5.93e5.94
(d, 1H, J¼2.0 Hz, OeC]HC]CH), 7.07 (d, 1H, J¼1.2 Hz, OeCH]),
9.95, 10.13 (s, 1H, eNH).
4.3.6. 5-Acetyl-4-(4-chlorophenyl)-6-methyl-2-oxo-1,2,3,4-
tetrahydropyridine-3-carbonitrile (4f). Light yellow solid. Mp
173e174 ꢁC. IR (neat) (nmax/cmꢀ1): 3255, 3167, 2257, 1712, 1675. 1H
NMR (400 MHz, DMSO-d6): dH 2.11, 2.14 (s, 3H, eCH3C]O), 2.37,
2.40 (s, 3H, eCH3C]C), 3.69e3.70, 4.17e4.18 (d, 1H, J¼6.8 Hz,
eCHC]C), 4.34e4.35, 4.48e4.49 (d, 1H, J¼6.8 Hz, eCHCN),
7.12e7.36 (m, 4H, AreH), 8.75, 8.77 (s, 1H, eNH). 13C NMR
4.3.11. 5-Acetyl-4-ethyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyridine-
3-carbonitrile (4k). Yellow liquid. IR (neat) (nmax/cmꢀ1): 3258, 3152,
2253, 1717, 1617. 1H NMR (400 MHz, DMSO-d6): dH 0.94e0.98 (t, 3H,

9740
Z.-Q. Liu et al. / Tetrahedron 67 (2011) 9736e9740
J¼7.6 Hz, eCH2CH3), 1.39e1.87 (m, 2H, eCH2CH3), 2.32, 2.33 (s, 3H,
eCH3C]O), 2.38, 2.39 (s, 3H, eCH3C]C), 3.18e3.21, 3.32e3.37 (m,
1H, eCHC]C), 3.54e3.55, 3.90e3.92 (d, 1H, J¼5.6 Hz, eCHCN),
8.66, 8.72 (s, 1H, eNH). 13C NMR (100 MHz, DMSO-d6): dC 11.0, 11.1,
19.5, 19.6, 23.5, 24.6, 30.4, 30.5, 35.9, 36.7, 39.5, 39.6, 114.8, 115.4,
116.5, 117.0, 143.0, 143.7, 162.3, 163.9, 196.7, 196.8. HRMS (EI) calcd
for C11H14N2O2 [Mþ]: 206.1055, found: 206.1053.
116.2, 120.2, 124.4, 128.9, 129.1, 129.2, 130.2, 130.3, 133.3, 136.2,
136.9, 138.5, 138.5, 138.8, 162.5, 165.8. HRMS (EI) calcd for
C
20H16N3O2Cl [Mþ]: 365.0935, found: 365.0931.
4.3.18. 5-Cyano-2-methyl-6-oxo-N-phenyl-4-p-tolyl-1,4,5,6-
tetrahydropyridine-3-carboxamide (4r). White solid. Mp
108e109 ꢁC. IR (neat) (nmax/cmꢀ1): 3278, 3140, 2257, 1709, 1654. 1H
NMR (400 MHz, DMSO-d6): dH 2.06, 2.07,2.12 (s, 3H, eCH3Ph), 2.22,
2.27 (s, 3H, eCH3C]C), 4.36e4.38,4.84e4.86(d,1H, J¼7.2 Hz, eCHC]
C), 4.31e4.33 (d,1H, J¼7.2 Hz, eCHCN), 6.97e7.58 (m, 9H, AreH), 9.68,
9.71 (s, 1H, eNH), 10.20, 10.21 (s, 1H, eNHPh). 13C NMR (100 MHz,
DMSO-d6): dC 17.8,21.0, 41.1, 41.4,112.2,116.5,120.0,120.0,123.9,128.2,
128.9, 129.0, 129.5, 129.7, 134.4, 137.7, 138.4, 139.3, 162.7, 165.5. HRMS
(EI) calcd for C21H19N3O2 [Mþ]: 345.1477, found: 345.1476.
4.3.12. 5-Acetyl-6-methyl-2-oxo-4-propyl-1,2,3,4-tetrahydropyridine-
3-carbonitrile (4l). Yellow solid. Mp 138e139 ꢁC IR (neat) (nmax
/
cmꢀ1): 3221, 3134, 2251, 1716, 1675. 1H NMR (400 MHz, CDCl3): dH
0.91e0.94 (t, 3H, J¼6.8 Hz, eCH2CH3), 1.26e1.77 (m, 4H,
eCH2CH2e), 2.29e2.33 (s, 3H, eCH3C]O), 2.36e2.39 (s, 3H,
eCH3C]C), 3.26e3.29, 3.37e3.41 (m, 1H, eCHC]C), 3.52,
3.88e3.89 (d, 1H, J¼5.2 Hz, eCHCN), 8.66, 8.72 (s, 1H, eNH). 13C
NMR (100 MHz, CDCl3): dC 13.7, 14.2, 19.5, 19.6, 19.8, 20.0, 30.4, 30.6,
32.7, 33.6, 35.5, 36.2, 37.7, 39.8, 114.8, 115.3, 116.8, 117.7, 142.8, 143.3,
162.4, 163.9, 196.6, 196.7. HRMS (EI) calcd for C12H16N2O2 [Mþ]:
220.1212, found: 220.1213.
4.3.19. 5-Cyano-4-(furan-2-yl)-2-methyl-6-oxo-N-phenyl-1,4,5,6-
tetrahydropyridine-3-carboxamide (4s). Yellow solid. Mp 98e99 ꢁC.
IR (neat) (nmax/cmꢀ1): 3284, 3134, 2259, 1712, 1654. 1H NMR
(400 MHz, DMSO-d6): dH 2.07 (s, 3H, eCH3C]C), 4.42e4.44,
4.82e4.84 (d, 1H, J¼6.4 Hz, eCHC]C), 4.61e4.63 (d, 1H, J¼6.8 Hz,
eCHCN), 6.29e6.30 (d, 1H, J¼2.8 Hz, eCH]C), 6.40 (s, eOCH, 1H),
7.03e7.07 (t, 1H, J¼7.2 Hz, OeCH]CH), 7.27e7.62 (m, 5H, AreH),
9.75, 9.80 (s, 1H, eNH), 10.21, 10.29 (s, 1H, eNHPh). 13C NMR
(100 MHz, DMSO-d6): dC 17.9, 30.0, 36.1, 108.1, 109.5, 110.9, 116.3,
120.1,123.9,129.0,129.0,129.2,139.4,139.6,143.7,151.2,162.7,165.1.
HRMS (EI) calcd for C18H15N3O3 [Mþ]: 321.1113, found: 321.1112.
4.3.13. Methyl 5-cyano-2-methyl-4-(3-nitrophenyl)-6-oxo-1,4,5,6-
tetrahydropyridine-3-carboxylate (4m). White solid. IR (neat)
(
nmax/cmꢀ1): 3272, 3182, 2268, 1709, 1639. 1H NMR (400 MHz,
DMSO-d6): dH 2.33, 2.36 (s, 3H, eCH3C]C), 3.50, 3.51 (s, 3H,
eOCH3), 4.21e4.22, 4.56e4.58 (d, 1H, J¼6.8 Hz, eCHC]C),
4.67e4.68, 4.90e4.92 (d, 1H, J¼7.6 Hz, eCHCN), 7.60e8.16 (m, 4H,
AreH), 10.64, 10.75 (s, 1H, eNH).
Acknowledgements
4.3.14. Methyl 4-(4-chlorophenyl)-5-cyano-2-methyl-6-oxo-1,4,5,6-
tetrahydropyridine-3-carboxylate (4n). White solid. IR (neat) (nmax
/
The financial support from the National Natural Science Foun-
dation of China (No. 21072172) and the Zhejiang Provincial Natural
Science Foundation (Project No. 2010-Z4090225) is gratefully
acknowledged.
cmꢀ1): 3275, 3170, 2254, 1711, 1637. 1H NMR (400 MHz, DMSO-d6):
dH 2.30, 2.35 (s, 3H, eCH3C]C), 3.51 (s, 3H, eOCH3), 4.35e4.36 (d,
1H, J¼6.8 Hz, eCHC]C), 4.48e4.49, 4.81e4.82 (d, 1H, J¼7.2 Hz,
eCHCN), 7.17e7.37 (m, 4H, AreH), 10.49, 10.66 (s, 1H, eNH).
References and notes
4.3.15. Methyl 5-cyano-2-methyl-6-oxo-4-p-tolyl-1,4,5,6-
tetrahydropyridine-3-carboxylate (4o). White solid. IR (neat) (nmax
/
1. Li, Q.; Mitscher, L. A.; Shen, L. L. Med. Res. Rev. 2000, 20, 231e293.
2. Cox, R. J.; Ohagan, D. J. Chem. Soc., Perkin Trans. 1 1991, 2537e2540.
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cmꢀ1): 3283, 3181, 2265, 1713, 1639. 1H NMR (400 MHz, DMSO-d6):
dH 2.25, 2.27 (s, 3H, eCH3Ph), 2.32, 2.38 (s, 3H, eCH3C]C), 3.54,
3.55 (s, 3H, eOCH3), 4.07e4.08, 4.30e4.31 (d, 1H, J¼6.8 Hz, eCHC]
C), 4.44e4.45, 4.87e4.89 (d, 1H, J¼6.8 Hz, eCHCN), 7.05e7.15 (m,
4H, AreH), 10.50, 10.62 (s, 1H, eNH).
4.3.16. Methyl 5-cyano-4-ethyl-2-methyl-6-oxo-1,4,5,6-tetrahy-
dropyridine-3-carboxylate (4p). White solid. Mp 133e134 ꢁC. IR
(neat) (nmax/cmꢀ1): 3229, 3137, 2248, 1701, 1648. 1H NMR (400 MHz,
DMSO-d6): dH 0.79e0.83 (t, 3H, J¼8.0 Hz, eCH2CH3), 1.29e1.68 (m,
2H, eCH2CH3), 2.20, 2.25 (s, 3H, eCH3C]C), 3.06e3.09, 3.15e3.19 (m,
1H, eCHC]C), 3.65, 3.68 (s, 3H, eOCH3), 3.89e3.90, 4.58e4.59 (d,
1H, J¼6.0 Hz, eCHCN), 10.30, 10.50 (s, 1H, eNH). 13C NMR (100 MHz,
DMSO-d6): dC 10.6, 18.4, 23.7, 35.7, 36.0, 51.6, 105.3, 116.7, 147.4, 164.2,
166.8. HRMS (EI) calcd for C11H14N2O3 [Mþ]: 222.1004, found:
222.1001.
5. Pendleton, M. D.; Beddoes, R. L.; Andrew, N. J.; Butters, M.; Joule, J. A. J. Chem.
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8. Noguez, M. O.; Marcelino, V.; Rodríguez, H.; Martí, O.; Martínez, J. O.; Perez, F. J.;
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4.3.17. 4-(4-Chlorophenyl)-5-cyano-2-methyl-6-oxo-N-phenyl-
1,4,5,6-tetrahydropyridine-3-carboxamide (4q). Yellow solid. Mp
157e158 ꢁC. IR (neat) (nmax/cmꢀ1): 3281, 3161, 2257, 1712, 1652. 1H
NMR (400 MHz, DMSO-d6): dH 1.98, 2.06, 2.07 (s, 3H, eCH3C]C),
4.33e4.35 (d, 1H, J¼7.2 Hz, eCHC]C), 4.77e4.79 (d, 1H, J¼6.8 Hz,
eCHCN), 6.99e7.49 (m, 9H, AreH), 9.85, 9.93 (s, 1H, eNH), 10.15 (s,
1H, eNHPh). 13C NMR (100 MHz, DMSO-d6): dC 17.7, 41.1, 41.3, 111.6,