A novel reaction of 4-(arylmethylene)-2-phenyloxazol-5(4H)-ones with pyridin-2-amine: Formation of 3-(arylmethyl)-3-(benzoylamino)imidazo-[1,2-a] pyridin-2(3H)-ones

Article abstract of DOI:10.1055/s-2007-965898

A new series of imidazo[1,2-a]pyridin-2-one derivatives were synthesized by a novel reaction of 4-(arylmethylene)-2-phenyloxazol-5(4H)-one with pyridin-2-amine under microwave irradiation in ethylene glycol. The starting materials were easily obtained and

Full text of DOI:10.1055/s-2007-965898

558
PAPER
A Novel Reaction of 4-(Arylmethylene)-2-phenyloxazol-5(4H)-ones with
Pyridin-2-amine: Formation of 3-(Arylmethyl)-3-(benzoylamino)imidazo-
[1,2-a]pyridin-2(3H)-ones
Formationof
3
h
-(Arylmethy
u
l)-3-(benzoy
j
lamino
i
)imida
a
zo[1,2-
a
]py
n
ridin-2(3
H
)-
o
g
nes Tu,* Junyong Zhang, Runhong Jia, Yan Zhang, Bo Jiang, Feng Shi
Department of Chemistry, Xuzhou Normal University, Key Laboratory of Biotechnology for Medicinal Plant, Xuzhou, Jiangsu, 221116,
P. R. of China
Fax +86(516)83403164; E-mail: laotu@xznu.edu.cn
Received 28 September 2006; revised 29 November 2006
a]pyridin-2-ones with both a benzyl and a benzamido
Abstract: A new series of imidazo[1,2-a]pyridin-2-one derivatives
group at the 3-position has seldom been reported. In the
context of our interest in the design and development of
were synthesized by a novel reaction of 4-(arylmethylene)-2-phenyl-
oxazol-5(4H)-one with pyridin-2-amine under microwave irradia-
useful tactics and strategies for the synthesis of nitrogen
heterocycles,15 in this paper, we wish to report a new route
for the synthesis of a new imidazo[1,2-a]pyridin-2-one
derivatives by a novel cascade reaction. The starting ma-
terial 4-(arylmethylene)-2-phenyloxazol-5(4H)-ones 1
were easily prepared according to our reported proce-
dure.16 Our novel approach, treatment of 1 and with an
equimolar amount of pyridin-2-amine 2 under microwave
irradiation (MW) in ethylene glycol, to our great satisfac-
tion proceeded smoothly to afford a series of 3-(arylmeth-
yl)-3-(benzoylamino)imidazo[1,2-a]pyridin-2(3H)-ones
3 (not 4) (Scheme 1).
tion in ethylene glycol. The starting materials were easily obtained
and the operation was convenient.
Key words: heterocycles, microwave irradiation, 4-(arylmethyl-
ene)-2-phenyloxazol-5(4H)-ones, 3-(arylmethyl)-3-(benzoylami-
no)imidazo[1,2-a]pyridin-2(3H)-ones, cascade reaction
Imidazo[1,2-a]pyridine moieties represent important
building blocks in both natural and synthetic bioactive
compounds, which show anticytomegalo-zoster and anti-
varicella-zoster virus,1 antibacterial,2 antiinflammatory,
analgesic, antipyretic,3 hypnoselective, and anxioselec-
tive activities.4 They are b-amyloid formation inhibitors5
and constitute a novel class of orally active nonpeptide
bradykinin B2 receptor antagonists.6 Recently, bicyclic
imidazole derivatives (imidazo[1,2-a]pyridine, imida-
zo[2,1-b]thiazole) were screened as new anti-HIV-1 com-
pounds (Figure 1) as non-nucleoside reverse transcriptase
inhibitors (NNRTIs).7 Several imidazo[1,2-a]pyridines
already on the market include zolimidine (an antiulcer
drug),3c zolpidem (a hypnotic drug), and alpidem (a
nonsedative anxiolytic).8
O
Ar
HN
Ph
N
O
NH2
N
O
N
O
N
3
Ph
+
Ar
H
N
1
Ph
2
N
Ar
O
N
O
4
NMe2
Scheme 1
X
O
O
In order to find the optimum reaction condition, different
organic solvents, such as ethanol, N,N-dimethylform-
amide, glacial acetic acid, and ethylene glycol, were test-
ed in the synthesis of 3a at 100 °C and 300 W. As shown
in Table 1, we could see the reaction in ethylene glycol
gave the best results (Table 1, entry 4).
N
N
Me
Me
N
N
Me
zolpidem
HIV-1 RT inhibitors
X = S, O
Figure 1
Table 1 Solvent Optimization for the Synthesis of 3a under Micro-
wave Irradiation
Due to their diverse biological activities, researchers have
been interested in the synthesis of derivatives of this struc-
tural type. Several groups have described the synthesis of
imidazo[1,2-a]pyridines derivatives.1a,b,9–14 However, to
the best of our knowledge, the syntheses of imidazo[1,2-
Entry Solvent
Temp (°C) Time (min) Yield (%)
1
2
3
4
EtOH
100
100
100
100
10
7
trace
31
DMF
AcOH
8
35
SYNTHESIS 2007, No. 4, pp 0558–0564
x
x
.
x
x
.2
0
0
7
Advanced online publication: 22.01.2007
DOI: 10.1055/s-2007-965898; Art ID: F16606SS
ethylene glycol
7
42
© Georg Thieme Verlag Stuttgart · New York

PAPER
Formation of 3-(Arylmethyl)-3-(benzoylamino)imidazo[1,2-a]pyridin-2(3H)-ones
559
Table 4 Synthesis of Compounds 3 under Microwave Irradiation
Moreover, to further optimize the reaction temperature,
reaction of 4-(4-fluorobenzylidene)-2-phenyloxazol-
5(4H)-one (1a) and 2 was carried out at the temperatures
ranging from 100 °C to 140 °C in increments of 10 °C
each time in ethylene glycol at 300 W. As can be seen
from Table 2, when the temperature was increased from
100 °C to 120 °C, the yield of product 3a improved from
42% to 70%. However, no significant increase in the yield
of product 3a was observed as the reaction temperature
was raised from 120 °C to 140 °C. Therefore, the temper-
ature of 120 °C was chosen for all further microwave-
assisted reactions.
Entry Product Ar
Time
(min)
Yield
(%)
Mp
(°C)
1
2
3a
3b
3c
3d
3e
3f
4-FC6H4
4
4
4
5
4
5
5
6
6
7
6
6
7
74
76
75
78
73
77
61
63
67
68
58
75
62
>300
4-ClC6H4
>300
3
4-BrC6H4
>300
4
2,4-Cl2C6H3
4-O2NC6H4
3-O2NC6H4
2-ClC6H4
281–282
295–296
291–292
280–282
>300
5
6
Table 2 Temperature Optimization for the Synthesis of 3a under
Microwave Irradiation
7
3g
3h
3i
8
4-Me2NC6H4
4-MeOC6H4
3,4-(OCH2O)C6H3
3,4-(MeO)2C6H3
4-MeC6H4
Ph
Entry
Temp (°C)
100
Time (min)
Yield (%)
9
>300
1
2
3
4
5
7
7
4
4
4
42
51
70
65
63
10
11
12
13
3j
>300
110
3k
3l
290–292
>300
120
130
3m
296–298
140
For comparison, we performed the synthesis of 3a under
both microwave irradiation and classical heating condi-
tions at 120 °C. The reactions were efficiently promoted
by microwave irradiation; under classical conditions the
reaction time was five hours and the yield of 3a was 35%,
however, strikingly, using microwave irradiation the reac-
tion time was to four minutes and the yield of 3a increased
to 74%. Therefore, microwave irradiation exhibited sev-
eral advantages over conventional heating by significant-
ly reducing the reaction time and dramatically improving
the yield of the reaction by a specific nonthermal micro-
wave effect.
The power of microwave irradiation was optimized by
carrying out the same reaction synthesizing 3a at powers
of 60–300 W (at 30-watt increments), using ethylene gly-
col as solvent at 120 °C (Table 3).
Table 3 Power Optimization for the Synthesis of 3a under Micro-
wave Irradiation
Entry
Power (W)
60
Temp (°C)
120
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
12
10
10
9
trace
26
90
120
The electronic effect of the aryl group was investigated.
Under our reaction conditions, both electron-withdrawing
(such as nitro) and electron-donating (such as alkoxy)
groups readily provided imidazo[1,2-a]pyridin-2-ones 3
in good yields.
120
120
31
150
120
48
180
120
7
53
210
120
6
61
The assigned molecular structures of new compounds 3
are based on rigorous spectroscopic analysis including IR,
NMR (1H, 13C, COSY, DEPT 135) and elemental analy-
sis.
240
120
4
74
270
120
4
71
300
120
4
70
Regarding the structure of 3, the assignment of NMR data
1
for 3e is described: H NMR shows two methylene pro-
tons at d = 3.69 (d, J = 13.2 Hz, 1 H, CH2) and 3.46 (d,
J = 13.2 Hz, 1H, CH2), respectively. The 13C NMR spec-
trum contained peaks at d = 41.49 and 77.51 that are con-
sistent with the existence of one secondary carbon and one
quaternary carbon; the DEPT of the secondary carbon was
at d = 41.49. Furthermore, the C–H correlated spectra also
suggested the presence of a methylene group.
As shown in Table 3, we could see that microwave irradi-
ation at 240 W gave the highest yield (Table 3, entry 7).
Therefore, microwave power of 240 W was chosen as the
optimum power.
Under these optimized reaction conditions, a series of
3-(arylmethyl)-3-(benzoylamino)imidazo[1,2-a]pyridin-
2(3H)-ones 3 were synthesized with this simple reaction
procedure; the results are collected in Table 4.
In order to broaden the scope of this novel reaction, we re-
acted 1 with aromatic amine 5, instead of 2, under the
aforementioned conditions. This reaction also proceeded
Synthesis 2007, No. 4, 558–564 © Thieme Stuttgart · New York

560
S. Tu et al.
PAPER
smoothly; however, the desired products 6 were not de- Although we have not established the mechanism of this
tected. Instead, a series of uncyclized products 7 were ob- reaction in an experimental manner, to explain the forma-
tained in high yields (Scheme 2). The results are tion of products 3 from the corresponding materials, we
summarized in Table 5.
propose the mechanism in Scheme 4.
Ar
Ar
Ar
Ph
N
O
N
N
+
N
O
Ph
O
NH HN
..
4–7 min
O
OH
..
NH2
N
O
H
7
NH2
Ph
O
O
O
O
Ar
O
H
Ar
H
N
O
Ph
+
N
Ph
Ph
Ar
N
N
N
HN
Ph
O
..
N
H
Ar
1
5
N
O
N
H
Scheme 4
6
Scheme 2
Table 5 Reaction of 1 with 5 under Microwave Irradiation
In summary, we have provided a route for the synthesis of
a series of imidazo[1,2-a]pyridin-2-one derivatives by a
novel cascade reaction. The starting materials were easily
obtained and the operation is convenient. Most important-
ly, the series of imidazo[1,2-a]pyridin-2-one derivatives
may provide new classes of biological active compounds
for biomedical screening. An extension of this work is
currently under investigation.
Entry Product Ar
Yield Mp
(%) (°C)
1
2
3
4
5
7a
7b
7c
7d
7e
3,4,5-(MeO)3C6H2 82
241–243
4-FC6H4
2,4-Cl2C6H3
Ph
88
84
86
85
264–266
257–258
All reactions were performed in a monomodal Emrys Creator from
Personal Chemistry, Uppsala, Sweden. Melting points were deter-
mined in open capillaries and are uncorrected. IR spectra were re-
247–249 (Lit.17 235 °C)
269–270 (Lit.18 255 °C)
4-MeC6H4
1
corded on a FT-IR-tensor 27 spectrophotometer. H NMR spectra
were measured on a DPX 400 MHz spectrometer using TMS as an
internal standard and DMSO-d6 as solvent. Elemental analysis was
determined by using a Perkin-Elmer 240c elemental analysis instru-
ment.
Similarly, when naphthalen-1- or naphthalen-2-amines 8
were tested under the same conditions, uncyclized prod-
ucts 9 were obtained in good yields (Scheme 3). The re-
sults are summarized in Table 6.
Reaction of 4-(Arylmethylene)-2-phenyloxazol-5(4H)-one with
Pyridin-2-amine or Aromatic Amines; General Procedure
All reactions were performed in a monomodal Emrys Creator from
Personal Chemistry, Uppsala, Sweden. Typically, an 4-(arylmethyl-
ene)-2-phenyloxazol-5(4H)-one 1 (1 mmol) and 2, 5, or 8 (1 mmol)
in ethylene glycol (2 mL) was added to the 10-mL reaction vessel
of the monomodal Emrys Creator microwave synthesizer and al-
lowed to react under microwave irradiation at 240 W power and 120
°C for 4–7 min. The mixture was cooled to r.t. then poured into H2O
(50 mL) and filtered to give crude product, which was further puri-
fied by recrystallization (EtOH) to give pure 3 (Table 4), 7
(Table 5), or 9 (Table 6).
Table 6 Reaction of 1 with 8 under Microwave Irradiation
Entry Product Amine
Ar
Yield Mp
(%) (°C)
1
2
3
4
5
6
7
9a
9b
9c
9d
9e
9f
naphthalen-1-amine 4-ClC6H4
89
244–245
naphthalen-1-amine 2,4-Cl2C6H3 90
220–221
234–235
242–244
247–248
252–254
250–252
naphthalen-1-amine 3-O2NC6H4
naphthalen-1-amine 4-MeC6H4
naphthalen-2-amine 4-FC6H4
naphthalen-2-amine 4-BrC6H4
88
84
91
90
3-(Benzoylamino)-3-(4-fluorobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3a)
IR (KBr): 3261, 3036, 2976, 1694, 1668, 1580, 1544, 860, 828, 784,
740, 576 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 9.59 (s, 1 H, NH), 8.25 (d,
J = 6.4 Hz, 1 H, ArH), 7.92 (d, J = 7.2, 2 H, ArH), 7.65–7.51 (m, 4
H, ArH), 7.01–6.73 (m, 6 H, ArH), 3.53 (d, J = 13.6 Hz, 1 H, CH2),
3.33 (d, J = 13.6 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.53, 166.68, 165.86, 143.01, 135.01,
134.07, 132.64, 132.45, 129.66, 129.15, 128.59, 128.10, 127.08,
114.26, 114.44, 77.53, 37.91; DEPT (135): 143.02, 132.64, 132.45,
129.15, 128.10, 128.05, 127.08, 114.26, 111.44, 37.91.
9g
naphthalen-2-amine 4-MeOC6H4 87
Ar
O
H2N
O
O
O
4–7 min
NH HN
Ph
+
Ph
N
1
8
9
Ar
Anal. Calcd for C21H16FN3O2: C, 69.80; H, 4.46; N, 11.63. Found:
C, 69.92; H, 4.35; N, 11.57.
Scheme 3
Synthesis 2007, No. 4, 558–564 © Thieme Stuttgart · New York

PAPER
Formation of 3-(Arylmethyl)-3-(benzoylamino)imidazo[1,2-a]pyridin-2(3H)-ones
561
3-(Benzoylamino)-3-(4-chlorobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3b)
3-(Benzoylamino)-3-(3-nitrobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3f)
IR (KBr): 3284, 3057, 2959, 1684, 1668, 1551, 1486, 840, 804, 755,
IR (KBr): 3268, 3026, 2988, 1701, 1669, 1579, 1528, 823, 808, 755,
711, 584 cm–1.
731, 584 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 9.59 (s, 1 H, NH), 8.25 (d,
J = 6.4 Hz, 1 H, ArH), 7.91 (d, J = 7.2 Hz, 2 H, ArH), 7.66–7.51 (m,
4 H, ArH), 7.22 (d, J = 8.4 Hz, 2 H, ArH), 6.89 (d, J = 8.4 Hz, 2 H,
ArH), 6.80–6.74 (m, 2 H, ArH), 3.52 (d, J = 13.6 Hz, 1 H, CH2),
3.30 (d, J = 13.6 Hz, 1 H, CH2).
1H NMR (400 MHz, DMSO-d6): d = 9.72 (s, 1 H, NH), 8.31 (d,
J = 6.4 Hz, 1 H, ArH), 8.08 (d, J = 8.4 Hz, 1 H, ArH), 7.92 (d,
J = 7.6 Hz, 2 H, ArH), 7.71–7.47 (m, 6 H, ArH), 7.35 (d, J = 7.6 Hz,
1 H, ArH), 6.85–6.71 (m, 2 H, ArH), 3.71 (d, J = 13.2 Hz, 1 H,
CH2), 3.47 (d, J = 13.2 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.31, 166.56, 165.87, 142.79, 134.21,
132.70, 132.37, 131.84, 130.94, 130.24, 128.58, 128.15, 128.04,
114.57, 111.90, 77.56, 41.27; DEPT (135): 142.79, 134.21, 132.37,
131.84, 128.58, 128.15, 128.04, 114.57, 111.90, 41.27.
13C NMR (DMSO-d6): d = 183.12, 167.31, 166.13, 148.03, 142.54,
138.55, 134.14, 132.46, 132.28, 131.33, 128.37, 128.04, 124.25,
120.13 116.35 114.59, 112.19, 76.81, 42.12; DEPT (135): 142.54,
134.14, 132.46, 131.33, 128.37, 128.04, 124.25, 120.13, 116.35
114.59, 112.19, 42.12.
Anal. Calcd for C21H16ClN3O2: C, 66.76; H, 4.27; N, 11.12. Found:
C, 66.81; H, 4.19; N, 11.27.
Anal. Calcd for C21H16N4O4: C, 64.94; H, 4.15; N, 14.43. Found: C,
64.89; H, 4.10; N, 14.36.
3-(Benzoylamino)-3-(4-bromobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3c)
3-(Benzoylamino)-3-(2-chlorobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3g)
IR (KBr): 3285, 3056, 2930, 1695, 1668, 1580, 1551, 846, 803, 779,
711, 581 cm–1.
IR (KBr): 3259, 3016, 2998, 1716, 1669, 1587, 1535, 865, 823, 754,
721, 568 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 9.64 (s, 1 H, NH), 8.29 (d,
J = 6.0 Hz, 1 H, ArH), 7.91 (d, J = 7.2 Hz, 2 H, ArH), 7.68–7.51 (m,
4 H, ArH), 7.36 (d, J = 8.4 Hz, 2 H, ArH), 6.83–6.78 (m, 4 H, ArH),
3.52 (d, J = 13.2 Hz, 1 H, CH2), 3.30 (d, J = 13.2 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.30, 166.55, 165.87, 142.83, 134.23,
132.20, 131.84, 131.37, 131.09, 128.71, 128.60, 128.06, 121.00,
114.59, 111.94, 77.52, 41.34; DEPT (135): 142.83, 132.20, 131.84,
131.37, 128.71, 128.60, 121.00, 114.59, 111.94, 41.34.
1H NMR (400 MHz, DMSO-d6): d = 9.65 (s, 1 H, NH), 8.29 (d,
J = 7.2 Hz, 1 H, ArH), 8.10 (d, J = 7.6 Hz, 2 H, ArH), 7.92–7.38 (m,
4 H, ArH), 7.04–6.92 (m, 4 H, ArH), 6.75 (d, J = 7.2 Hz, 2 H, ArH),
3.82 (d, J = 13.6 Hz, 1 H, CH2), 3.51 (d, J = 13.6 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.52, 166.67, 165.86, 143.00, 134.99,
134.07,132.64, 132.62, 132.43, 130.32, 129.65, 129.15, 128.58,
128.09, 127.07, 114.25, 111.44, 77.52, 37.90; DEPT (135): 143.00,
134.99, 132.64, 132.43, 129.65, 129.15, 128.58, 128.09, 127.07,
114.25, 111.44, 37.90
Anal. Calcd for C21H16BrN3O2: C, 59.73; H, 3.82; N, 9.95. Found:
C, 59.65; H, 3.72; N, 9.89.
Anal. Calcd for C21H16ClN3O2: C, 66.76; H, 4.27; N, 11.12. Found:
C, 66.81; H, 4.18; N, 11.02.
3-(Benzoylamino)-3-(2,4-dichlorobenzyl)imidazo[1,2-a]pyri-
din-2(3H)-one (3d)
IR (KBr): 3279, 3008, 2920, 1690, 1667, 1582, 1542, 852, 824, 775,
3-(Benzoylamino)-3-[4-(dimethylamino)benzyl]imidazo[1,2-
a]pyridin-2(3H)-one (3h)
710, 584 cm–1.
IR (KBr): 3276, 3052, 2994, 1692, 1667, 1581, 1545, 813, 783, 715,
1H NMR (400 MHz, DMSO-d6): d = 9.66 (s, 1 H, NH), 8.12 (d,
J = 6.4 Hz, 1 H, ArH), 7.92 (d, J = 7.2 Hz, 2 H, ArH), 7.68–7.33 (m,
7 H, ArH), 6.81–6.71 (m, 2 H, ArH), 3.86 (d, J = 14.0 Hz, 1 H,
CH2), 3.39 (d, J = 14.0 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.33, 166.61, 165.86, 146.64, 143.20,
134.99, 133.91, 133.33, 132.58, 132.47, 128.90, 128.60, 128.55,
128.09 127.33, 114.32, 111.68, 77.40, 37.41; DEPT (135): 143.20,
134.99, 133.33, 132.47, 128.90, 128.55, 128.09 127.33, 114.32,
111.68, 37.41.
694, 577 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 9.45 (s, 1 H, NH), 8.19 (d,
J = 6.4 Hz, 1 H, ArH), 7.90 (d, J = 7.2 Hz, 2 H, ArH), 7.63–7.50 (m,
4 H, ArH), 6.76–6.65 (m, 4 H, ArH), 6.45 (d, J = 8.8 Hz, 2 H, ArH),
3.36 (d, J = 13.6 Hz, 1 H, CH2), 3.21 (d, J = 13.6 Hz, 1 H, CH2),
2.80 (s, 6 H, 2 CH3).
13C NMR (DMSO-d6): d = 183.08, 170.33, 166.51, 147.77, 140.90,
136.31, 134.10, 131.49, 129.70, 128.61, 128.32, 128.07, 127.54,
124.10, 121.60, 77.59, 53.46, 37.13; DEPT (135): 140.90, 136.31,
131.49, 129.70, 128.32, 128.07, 127.54, 124.10, 121.60, 53.46,
37.13.
Anal. Calcd for C21H15Cl2N3O2: C, 61.18; H, 3.67; N, 10.19. Found:
C, 61.23; H, 3.58; N, 10.10.
3-(Benzoylamino)-3-(4-nitrobenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3e)
Anal. Calcd for C23H22N4O2: C, 71.48; H, 5.74; N, 14.50. Found: C,
71.59; H, 5.83; N, 14.54.
IR (KBr): 3241, 3014, 2987, 1679, 1664, 1567, 1532, 868, 809, 786,
724, 591 cm–1.
3-(Benzoylamino)-3-(4-methoxybenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3i)
1H NMR (DMSO-d6): d = 9.69 (s, 1 H, NH), 8.30 (d, J = 6.4 Hz, 1
H, ArH), 8.04 (d, J = 8.4 Hz, 2 H, ArH), 7.92 (d, J = 7.6 Hz, 2 H,
ArH), 7.65–7.52 (m, 4 H, ArH), 7.15 (d, J = 8.4 Hz, 2 H, ArH),
6.82–6.74 (m, 2 H, ArH), 3.69 (d, J = 13.2 Hz, 1 H, CH2), 3.46 (d,
J = 13.2 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.05, 166.46, 165.93, 147.03, 143.03,
140.01, 134.22, 132.62, 132.46, 131.52, 128.61, 128.06, 123.15,
114.59, 112.19, 77.51, 41.49; DEPT (135): 143.03, 134.22, 132.46,
131.52, 128.61, 128.06, 123.15, 114.59, 112.19, 41.49.
IR (KBr): 3286, 3062, 2994, 1694, 1666, 1581, 1548, 824, 783, 712,
692, 579 cm–1.
1H NMR (DMSO-d6): d = 9.51 (s, 1 H, NH), 8.22 (d, J = 6.4 Hz, 1
H, ArH), 7.91 (d, J = 8.0 Hz, 2 H, ArH), 7.63–7.50 (m, 4 H, ArH),
6.79–6.68 (m, 6 H, ArH), 3.66 (s, 3 H, OCH3), 3.43 (d, J = 13.6 Hz,
1 H, CH2), 3.26 (d, J = 13.6 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.58, 166.67, 165.85, 158.60, 142.50,
134.17, 132.85, 132.30, 131.08, 128.54, 128.02, 123.64, 114.56,
113.55, 111.62, 77.68, 55.09, 41.37; DEPT (135): 142.50, 134.17,
132.30, 131.08, 128.54, 128.02, 114.56, 113.55, 111.62, 55.09,
41.37.
Anal. Calcd for C21H16N4O4: C, 64.94; H, 4.15; N, 14.43. Found: C,
65.12; H, 4.20; N, 14.28.
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Anal. Calcd for C22H19N3O3: C, 70.76; H, 5.13; N, 11.25. Found: C,
70.91; H, 5.09; N, 11.42.
13C NMR (DMSO-d6): d = 183.14, 167.32, 165.45, 144.53, 142.46,
134.25, 133.51, 132.36, 128.51, 128.40, 128.13, 126.67, 126.01,
122.35, 110.71, 79.54, 41.35; DEPT (135): 142.46, 133.51, 132.36,
128.51, 128.40, 128.13, 126.67, 126.01, 122.35, 110.71, 41.35.
3-(Benzoylamino)-3-[3,4-(methylenedioxy)benzyl]imidazo[1,2-
a]pyridin-2(3H)-one (3j)
Anal. Calcd for C21H17N3O2: C, 73.45; H, 4.99; N, 12.24. Found: C,
73.31; H, 4.87; N, 12.13.
IR (KBr): 3255, 3021, 2988, 1694, 1666, 1578, 1548, 884, 813, 776,
715, 544 cm–1.
1H NMR (DMSO-d6): d = 9.51 (s, 1 H, NH), 8.19 (d, J = 6.4 Hz, 1
H, ArH), 7.90 (d, J = 7.6 Hz, 2 H, ArH), 7.66–7.50 (m, 4 H, ArH),
6.79–6.75 (m, 2 H, ArH), 6.67 (d, J = 8.0 Hz, 1 H, ArH), 6.41 (s, 1
H, ArH), 6.31 (d, J = 8.0 Hz, 1 H, ArH), 5.94 (s, 2 H, OCH2O), 3.43
(d, J = 13.6 Hz, 1 H, CH2), 3.24 (d, J = 13.6 Hz, 1 H, CH2).
13C NMR (DMSO-d6): d = 183.58, 166.65, 165.83, 146.89, 146.56,
142.65, 134.25, 132.76, 132.35, 128.56, 128.03, 125.35, 123.38,
114.58, 111.73, 110.09, 107.97, 101.04, 77.65, 41.70; DEPT (135):
142.65, 134.25, 132.35, 128.56, 128.03, 125.35, 114.58, 111.73,
110.09, 107.97, 101.04, 41.70.
2-(Benzoylamino)-N-phenyl-3-(3,4,5-trimethoxyphenyl)prop-
2-enamide (7a)
IR (KBr): 3242, 3135, 3019, 2981, 1671, 1646, 1532, 1521, 864,
822, 634, 617 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.31 (s, 1 H, NH), 10.20 (s, 1
H, NH), 7.61 (d, J = 7.6 Hz, 2 H, ArH), 7.24 (d, J = 8.0 Hz, 2 H,
ArH), 7.21–7.10 (m, 6 H, ArH), 6.88 (s, 2 H, ArH), 6.94 (s, 1 H,
CH), 3.76 (s, 6 H, 2 OCH3), 3.62 (s, 3 H, OCH3).
Anal. Calcd for C25H24N2O5: C, 69.43; H, 5.59; N, 6.48. Found: C,
69.28; H, 5.48; N, 6.62.
Anal Calcd. for C22H17N3O4: C, 68.21; H, 4.42; N, 10.85. Found: C,
68.36; H, 4.30; N, 10.71.
2-(Benzoylamino)-3-(4-fluorophenyl)-N-phenylprop-2-en-
amide (7b)
3-(Benzoylamino)-3-(3,4-dimethoxybenzyl)imidazo[1,2-a]pyri-
din-2(3H)-one (3k)
IR (KBr): 3235, 3121, 3028, 2986, 1661, 1643, 1568, 1538, 852,
818, 646, 618 cm–1.
IR (KBr): 3252, 3024, 2934, 1692, 1669, 1579, 1545, 804, 780, 765,
1H NMR (400 MHz, DMSO-d6): d = 10.24 (s, 1 H, NH), 10.14 (s, 1
H, NH), 8.01 (d, J = 7.6 Hz, 2 H, ArH), 7.72 (d, J = 8.0 Hz, 2 H,
ArH), 7.66–7.46 (m, 8 H, ArH), 7.33 (t, J = 8.0 Hz, 2 H, ArH), 7.10
(s, 1 H, CH).
649, 567 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 9.52 (s, 1 H, NH), 8.21 (d,
J = 6.4 Hz, 1 H, ArH), 7.91 (d, J = 7.2 Hz, 2 H, ArH), 7.65 (m, 4 H,
ArH), 6.79–6.46 (m, 3 H, ArH), 6.45 (d, J = 8.0 Hz, 1 H, ArH), 6.34
(s, 1 H, ArH), 3.66 (s, 3 H, OCH3), 3.53 (s, 3 H, OCH3), 3.42 (d,
J = 13.6 Hz, 1 H, CH2), 3.25 (d, J = 13.6 Hz, 1 H, CH2).
Anal. Calcd for C22H17FN2O2: C, 73.32; H, 4.75; N, 7.77. Found: C,
73.47; H, 4.56; N, 7.58.
13C NMR (DMSO-d6): d = 183.63, 166.65, 165.85, 148.11, 148.02,
142.51, 134.30, 132.80, 132.34, 128.56, 128.05, 123.93, 122.50,
114.63, 113.30, 111.56, 111.34, 77.71, 55.42, 55.34, 41.70; DEPT
(135): 142.51, 134.30, 132.34, 128.56, 128.05, 122.50, 114.63,
113.30, 111.56, 111.34, 55.42, 55.34, 41.70.
2-(Benzoylamino)-3-(2,4-dichlorophenyl)-N-phenylprop-2-en-
amide (7c)
IR (KBr): 3236, 3168, 3008, 2976, 1671, 1648, 1567, 1521, 842,
812, 678, 624 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.29 (s, 1 H, NH), 10.13 (s, 1
H, NH), 8.01 (d, J = 7.6 Hz, 2 H, ArH), 7.72 (d, J = 8.0 Hz, 3 H,
ArH), 7.63–7.49 (m, 4 H, ArH), 7.45 (s, 1 H ArH,), 7.34 (t, J = 7.6
Hz, 2 H, ArH), 7.34 (t, J = 8.0 Hz, 1 H, ArH), 7.07 (s, 1 H CH).
Anal. Calcd for C23H21N3O4: C, 68.47; H, 5.25; N, 10.42. Found: C,
68.61; H, 5.46; N, 10.59.
3-(Benzoylamino)-3-(4-methylbenzyl)imidazo[1,2-a]pyridin-
2(3H)-one (3l)
Anal. Calcd for C22H16Cl2N2O2: C, 64.25; H, 3.92; N, 6.81. Found:
C, 64.38; H, 4.01; N, 6.75.
IR (KBr): 3282, 3058, 2993, 1695, 1665, 1580, 1549, 805, 799, 713,
694, 579 cm–1.
2-(Benzoylamino)-N,3-diphenylprop-2-enamide (7d)
IR (KBr): 3277, 3154, 3056, 2983, 1677, 1648, 1574, 1548, 842,
828, 686, 658 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.20 (s, 1 H, NH), 10.14 (s, 1
H, NH), 8.03 (d, J = 7.6 Hz, 2 H, ArH), 7.73 (d, J = 8.0 Hz, 2 H,
ArH), 7.66–7.54 (m, 6 H, ArH), 7.42–7.31 (m, 4 H, ArH), 7.14 (s,
1 H, CH), 7.08 (t, J = 7.2 Hz, 1 H, ArH).
1H NMR (400 MHz, DMSO-d6): d = 9.52 (s, 1 H, NH), 8.23 (d,
J = 6.8 Hz, 1 H, ArH), 7.91 (d, J = 7.6 Hz, 2 H, ArH), 7.62–7.50 (m,
4 H, ArH), 6.93 (d, J = 7.6 Hz, 2 H, ArH), 6.77–6.71 (m, 4 H, ArH),
3.45 (d, J = 13.2 Hz, 1 H, CH2), 3.28 (d, J = 13.2 Hz, 1 H, CH2),
2.19 (s, 3 H, CH3).
13C NMR (DMSO-d6): d = 184.37, 167.36, 166.73, 143.75, 140.15,
135.34, 132.56, 132.13, 131.26, 129.29, 128.26, 128.15, 128.01,
111.50, 109.80, 76.50, 41.23, 31.32; DEPT (135): 140.15, 135.34,
132.56, 132.13, 128.26, 128.15, 128.01, 111.50, 109.80, 41.23,
31.32.
Anal. Calcd for C22H18N2O2: C, 77.17; H, 5.30; N, 8.18. Found: C,
77.11; H, 5.18; N, 8.06.
2-(Benzoylamino)-3-(4-methylphenyl)-N-phenylprop-2-en-
amide (7e)
Anal. Calcd for C22H19N3O2: C, 73.93; H, 5.36; N, 11.76. Found: C,
74.05; H, 5.23; N, 11.61.
IR (KBr): 3264, 3153, 3037, 2976, 1671, 1643, 1578, 1532, 858,
815, 675, 629 cm–1.
3-Benzyl-3-(benzoylamino)imidazo[1,2-a]pyridin-2(3H)-one
(3m)
1H NMR (400 MHz, DMSO-d6): d = 10.16 (s, 1 H, NH), 10.08 (s, 1
H, NH), 8.03 (d, J = 7.6 Hz, 2 H, ArH), 7.73 (d, J = 8.0 Hz, 2 H,
ArH), 7.63–7.52 (m, 5 H, ArH), 7.33 (t, J = 8.0 Hz, 2 H, ArH), 7.21
(d, J = 8.0 Hz, 2 H, ArH), 7.13 (s, 1 H, CH), 7.07 (t, J = 7.2 Hz, 1
H, ArH), 2.31 (s, 3 H, CH3).
IR (KBr): 3267, 3061, 2958, 1702, 1665, 1578, 1539, 815, 789, 733,
684, 565 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.11 (s, 1 H, NH), 7.98 (d,
J = 7.6 Hz, 2 H, ArH), 7.68 (d, J = 7.2 Hz, 2 H, ArH), 7.62–7.52 (m,
4 H, ArH), 7.48–7.38 (m, 6 H, ArH), 4.18 (d, J = 13.2 Hz, 1 H,
CH2), 3.63 (d, J = 13.2 Hz, 1 H, CH2).
Anal. Calcd for C23H20N2O2: C, 77.51; H, 5.66; N, 7.86. Found: C,
77.29; H, 5.47; N, 7.64.
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Formation of 3-(Arylmethyl)-3-(benzoylamino)imidazo[1,2-a]pyridin-2(3H)-ones
563
2-(Benzoylamino)-3-(4-chlorophenyl)-N-naphthalen-1-ylprop-
2-enamide (9a)
1H NMR (400 MHz, DMSO-d6): d = 10.32 (s, 1 H, NH), 10.10 (s, 1
H, NH), 8.39 (s, 1 H, ArH), 8.07 (d, J = 7.6 Hz, 2 H, ArH), 7.89–
7.78 (m, 4 H, ArH), 7.65–7.40 (m, 7 H, ArH), 7.23 (s, 1 H, CH),
6.98 (d, J = 8.8 Hz, 2 H, ArH), 3.78 (s, 3 H, OCH3).
IR (KBr): 3213, 3026, 1640, 1540, 819, 785, 770, 693, 655 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.24 (s, 1 H, NH), 10.22 (s, 1
H, NH), 8.13–8.07 (m, 3 H, ArH), 7.95 (t, J = 4.8 Hz, 1 H, ArH),
7.84 (t, J = 4.8 Hz, 1 H, ArH), 7.69 (d, J = 8.4 Hz, 2 H, ArH), 7.63–
7.48 (m, 9 H, ArH), 7.37 (s, 1 H, CH).
Anal. Calcd for C27H22N2O3: C, 76.76; H, 5.25; N, 6.63. Found: C,
76.92; H, 5.34; N, 6.77.
Anal. Calcd for C26H19ClN2O2: C, 73.15; H, 4.49; N, 6.56. Found:
C, 72.98; H, 4.41; N, 6.44.
Acknowledgment
We thank the National Science Foundation of China (No. 20372057
and 20672090) and Natural Science Foundation of the Jiangsu
Province (No. BK 2006033) for financial support and the Key Item
of Natural Science Foundation of Xuzhou Normal University (No.
05XLA06) for financial support.
2-(Benzoylamino)-3-(2,4-dichlorophenyl)-N-naphthalen-1-yl-
prop-2-enamide (9b)
IR (KBr): 3223, 3057, 1645, 1529, 896, 790, 770, 690, 670 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.37 (s, 1 H, NH), 10.28 (s, 1
H, NH), 8.10 (t, J = 4.4 Hz, 1 H, ArH), 8.01–7.96 (m, 3 H, ArH),
7.86 (t, J = 4.4 Hz, 1 H, ArH), 7.68 (d, J = 6.4 Hz, 1 H, ArH), 7.62–
7.52 (m, 8 H, ArH), 7.45 (dd, J1 = 8.4 Hz, J2 = 2.4 Hz, 1 H, ArH),
7.36 (s, 1 H, CH).
References
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Anal. Calcd for C26H18Cl2N2O2: C, 67.69; H, 3.93; N, 6.07. Found:
C, 67.56; H, 4.01; N, 5.94.
2-(Benzoylamino)-N-naphthalen-1-yl-3-(3-nitrophenyl)prop-2-
enamide (9c)
IR (KBr): 3211, 3028, 1641, 1532, 829, 786, 770, 693, 670 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.40 (s, 1 H, NH), 10.37 (s, 1
H, NH), 8.60 (s, 1 H, ArH), 8.21–8.06 (m, 5 H, ArH), 7.97 (t, J = 4.8
Hz, 1 H, ArH), 7.85 (t, J = 4.8 Hz, 1 H, ArH), 7.73 (t, J = 8.0 Hz, 1
H, ArH), 7.64–7.53 (m, 7 H, ArH), 7.48 (s, 1 H, CH).
Anal. Calcd for C26H19N3O4: C, 71.39; H, 4.38; N, 9.61. Found: C,
71.61; H, 4.29; N, 9.50.
2-(Benzoylamino)-3-(4-methylphenyl)-N-naphthalen-1-ylprop-
2-enamide (9d)
IR (KBr): 3218, 3025, 1646, 1538, 908, 791, 773, 691, 658 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.18 (s, 2 H, NH), 8.09 (d,
J = 7.2 Hz, 3 H, ArH), 7.95 (t, J = 4.8 Hz, 1 H, ArH), 7.84 (dd,
J1 = 6.8 Hz, J2 = 2.0 Hz, 1 H, ArH), 7.63–7.52 (m, 9 H, ArH), 7.39
(s, 1 H, CH), 7.22 (d, J = 8.4 Hz, 2 H, ArH), 2.31 (s, 3 H, CH3).
Anal. Calcd for C27H22N2O2: C, 79.78; H, 5.46; N, 6.89. Found: C,
79.65; H, 5.36; N, 6.76.
2-(Benzoylamino)-3-(4-fluorophenyl)-N-naphthalen-2-ylprop-
2-enamide (9e)
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IR (KBr): 3227, 3033, 1643, 1548, 831, 743, 726, 692, 656 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.42 (s, 1 H, NH), 10.18 (s, 1
H, NH), 8.40 (s, 1 H, ArH), 8.05 (d, J = 7.6 Hz, 2 H, ArH), 7.90–
7.78 (m, 4 H, ArH), 7.72 (q, J = 4.4 Hz, 2 H, ArH), 7.64–7.40 (m, 5
H, ArH), 7.27 (t, J = 8.8 Hz, 2 H, ArH), 7.21 (s, 1 H, CH).
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Antiviral Res. 1994, 24, 275.
Anal. Calcd for C26H19FN2O2: C, 76.08; H, 4.67; N, 6.83. Found: C,
75.96; H, 4.58; N, 6.75.
(8) Langer, S. Z.; Arbilla, S.; Benavides, J.; Scatton, B. Adv.
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2-(Benzoylamino)-3-(4-bromophenyl)-N-naphthalen-1-ylprop-
2-enamide (9f)
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IR (KBr): 3228, 3057, 1646, 1558, 818, 750, 736, 696, 675 cm–1.
1H NMR (400 MHz, DMSO-d6): d = 10.48 (s, 1 H, NH), 10.21 (s, 1
H, NH), 8.40 (s, 1 H, ArH), 8.03 (d, J = 7.6 Hz, 2 H, ArH), 7.90–
7.77 (m, 4 H, ArH), 7.64–7.40 (m, 9 H, ArH), 7.15 (s, 1 H, CH).
Anal. Calcd for C26H19BrN2O2: C, 66.25; H, 4.06; N, 5.94. Found:
C, 66.41; H, 3.96; N, 6.05.
2-(Benzoylamino)-3-(4-methoxyphenyl)-N-naphthalen-1-yl-
prop-2-enamide (9g)
IR (KBr): 3225, 3056, 1646, 1554, 821, 748, 701, 674, 619 cm–1.
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Synthesis 2007, No. 4, 558–564 © Thieme Stuttgart · New York