Synthesis of some acylated 2-pyrazoline and chalcone derivatives

Article abstract of DOI:10.1007/s11164-013-1032-4

α-Haloesters containing the chalcone structure and α-haloamides containing the pyrazoline ring have been synthesized by reaction of substituted hydroxy chalcones and pyrazoline derivatives (prepared as reported elsewhere; J Chem 8(4):1574-1581, 2011) with

Full text of DOI:10.1007/s11164-013-1032-4

Res Chem Intermed
DOI 10.1007/s11164-013-1032-4
Synthesis of some acylated 2-pyrazoline and chalcone
derivatives
•
Demet Cos¸kun Misir Ahmedzade
Received: 23 October 2012 / Accepted: 8 January 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract a-Haloesters containing the chalcone structure and a-haloamides con-
taining the pyrazoline ring have been synthesized by reaction of substituted hydroxy
chalcones and pyrazoline derivatives (prepared as reported elsewhere; J Chem
8(4):1574–1581, 2011) with chloroacetyl chloride in dry THF in the presence of
Et3N. The structures of the synthesized compounds were confirmed by IR,
1H NMR, and (for some compounds) 13C NMR spectroscopy.
Keywords Aromatic aldehydes Á Chalcones Á Pyrazolines Á Benzofurans Á
a-Haloamides Á a-Haloesters
Introduction
The pyrazoline function is stable, which has encouraged chemists to utilize the
structure for synthesis of new bioactive pyroline derivatives with such biological
properties as antibacterial [1–3], antifungal [4], antitumor [5], analgesic [6], and
cytotoxic [7] activity.
Benzofuran derivatives are an interesting class of heterocyclic compounds. Many
benzofuran derivatives have been used as antioxidants, brightening agents,
fluorescent sensors [8], and in other fields of chemistry [9]. Many natural products
are benzofuran derivatives, including bergapten, nodakenetin xanthotoxin, and
khellin (Fig. 1).
Compounds in which the benzofuran and pyrazoline rings are combined are more
effective against multidrug-resistant bacteria [10, 11]. This encouraged us to study
benzofuran-substituted pyrazoline and chalcone derivatives.
D. Cos¸kun (&) Á M. Ahmedzade
Department of Chemistry, Faculty of Science, Firat University, 23119 Elazig, Turkey
e-mail: dcoskun@firat.edu.tr
123

D. Cos¸kun, M. Ahmedzade
OMe
OCH
3
O
O
Me
O
H C
3
H C
3
HO
O
O
O
O
O
O
O
O
O
OCH
3
Khellin
Xanthotoxin
Nodakenetin
Bergapten
Fig. 1 Benzofuran-containing biological molecules
In this work, benzofuran-substituted a-haloesters and a-haloamides containing,
respectively, chalcone and pyrazoline structures were synthesized by reaction of
chalcone and pyrazoline derivatives [12] with chloroacetyl chloride in the presence
of Et3N.
Experimental
In a general method for the synthesis of [(1E)-3-(1-benzofuran-2-yl)-3-oxoprop-1-
en-1-yl]-substituted aryl acetates (2a, b) and [3-(1-benzofuran-2-yl)-1-(chloroace-
tyl)-4,5-dihydro-1H-pyrazol-5-yl] aryl and heteroaryl derivatives (4a, c, f, g, h),
3-(substituted aryl)-1-benzofuranyl-2-propanones (1a–c) (Scheme 1) or 3-(2-
benzofuranyl)-5-aryl and heteroaryl-2-pyrazolines (3a, d, g, h, i) (Scheme 2)
(2.65 mmol) were dissolved in 15 mL dry THF then triethylamine (0.39 mL,
2.8 mmol) was added. The mixture was cooled to 0 °C and chloroacetyl chloride
(3 mmol, 0.24 mL) was added dropwise. After stirring overnight at room
temperature the mixture was poured into 50 mL water and the precipitate obtained
was crystallized from ethanol.
In a general method for synthesis of [3-(1-benzofuran-2-yl)-1-(chloroacetyl)-4,5-
dihydro-1H-pyrazol-5-yl] aryl acetates (4b, d, e), 3-(2-benzofuranyl)-aryl-2-pyraz-
olines (4b, d, e) (2.65 mmol) were dissolved in 15 mL dry THF then triethylamine
(0.78 mL, 5.6 mmol) was added. The mixture was cooled to 0 °C and chloroacetyl
chloride (6 mmol, 0.48 m) was added dropwise. After stirring overnight at room
temperature the mixture was poured into water (50 mL) and the precipitate obtained
was crystallized from ethanol.
8
6
9
16
4
17
3
25 C0
chloroacetyl chloride Et3N
7
15
14
R3
R2
R3
20
absolute THF
12
2
5
O
18 R2
19
21
O
1
10
13
R1
R1
22
O
O
11
2 a - c
1 a - c
a. R1 = H , R2 = OCOCH2Cl , R3 = H
b. R1 = H , R2 = H , R3 =OCOCH2Cl
c. R1 = H , R2 = OCH3 , R3 = OCOCH2Cl
a. R1 = H , R2 = OH , R3 = H
b. R1 = H , R2 = H , R3 = OH
c. R1 = H , R2 = OCH3 , R3 = OH
Scheme 1 Acylation of 1a–c
123

Synthesis of acylated 2-pyrazolines and chalcones
9
6
3
4
5
R1
R2
8
7
R1
27
25 C0
chloroacetyl chloride Et3N
R2
26
10
14
absolute THF
21
22
2
20
O
N
R3
O
1
N
R3
25
17
13
11
N
H
N
12
18
19
4 a - f
C
O
15
16
3 a - f
CH2
23
a. R = R = R = H
1
2
3
3 g
3 h
4 g
a. R = R = R = H
1
2
3
S
Cl
24
b. R = H R = OCH
R = OCOCH Cl
3 2
S
1
2
3
b. R = H R = OCH
R = OH
3
1
2
3
c. R = R = H R =
3
c. R = R = H R =
3
1
2
4 h
1
2
O
O
N
N
O
O
N
N
H
d. R = R = H R = OCOCH Cl
1
3
2
2
C
O
CH2
Cl
d. R = R = H R = OH
1
3
2
e. R = OCOCH Cl R = R = H
1
3
2
3
e. R = OH R = R = H
1
2
3
f. R = R = H R = NO
f. R = R = H R = NO
2
1
3
2
2
1
3
2
Scheme 2 Acylation of 3a–h
Data
3-[(1E)-3-(1-benzofuran-2-yl)-3-oxoprop-1-en-1-yl]phenyl chloroacetate (2a)
Yield: 60 %; m.p. 159–160 °C. FTIR (KBr, cm-1): 3125 (Aromatic C–H), 1609
(Aromatic C=C); 1H NMR (400 MHz, DMSO-d6), ppm: 8.35 (s, 1H, 3-H), 7.94 (d,
J = 15.82 Hz, 1H, 13-H), 7.89–7.74 (m, 4H, 6-H, 7-H, 9-H, 19-H), 7.62–7.53 (m, 2H,
16-H, 18-H), 7.41 (t, J = 7.5 Hz, 1H, 8-H), 7.32 (dd, 1H, 17-H), 4,75 (s, 2H, 21-H).
4-[(1E)-3-(1-benzofuran-2-yl)-3-oxoprop-1-en-1-yl]phenyl chloroacetate (2b)
Yield: 58 %; m.p. 152–154 °C. FTIR (KBr, cm-1): 3115 (Aromatic C–H), 1663
(C=O); 1H NMR (400 MHz, DMSO-d6), ppm: 8.33 (s, 1H, 3-H), 8.00 (d,
J = 8.61 Hz, 2H, 15-H, 19-H), 7.94–7.70 (m, 4H, 6-H, 9-H, 12-H, 13-H), 7.58
(t, J = 7.50 Hz, 1H, 7-H), 7.41 (t, J = 7.80 Hz, 1H, 8-H), 7.33 (d, J = 8.56 Hz,
2H, 16-H, 18-H), 4,74 (s, 2H, 20-H), 13C NMR, ppm: 178.88 (20-C), 166.71 (10-C),
155.82 (5-C), 153.66 (3-C), 152.37 (17-C), 142.80 (13-C), 133.03 (4-C), 129.19
(15-C, 19-C), 127.43 (7-C), 124.62 (12-C), 124.28 (8-C), 122.67 (9-C), 122.64 (16-
C, 18-C), 115.78 (3-C), 112.76 (6-C).
4-[(1E)-3-(1-benzofuran-2-yl)-3-oxoprop-1-en-1-yl]-2-methoxyphenyl
chloroacetate (2c)
Yield: 63 %; m.p. 177–178 °C. FTIR (KBr, cm-1): 3120 (Aromatic C–H), 1657
(C=O); 1H NMR (400 MHz, DMSO-d6), ppm: 8.34 (s, 1H, 3-H), 7.92 (d,
J = 15.68 Hz, 1H, 13-H), 7.91 (d, J = 7.80 Hz, 1H, 9-H), 7.84 (d,
J = 15.72 Hz, 1H, 12-H), 7.77 (d, J = 8.00 Hz, 1H, 6-H), 7.73 (d, J = 1.60 Hz,
1H, 19-H), 7.59 (dt, J = 7.20 and 1.00 Hz, 1H, 7-H), 7.55 (dd, J = 8.63 and
1.63 Hz, 1H, 15-H), 7.42 (t, J = 7.60 Hz, 1H, 8-H), 4.76 (s, 2H, 20-H), 3.92 (s, 3H,
21-H), 13C NMR, ppm: 178.88 (20-C), 166.13 (10-C), 155.84 (5-C), 153.66 (18-C),
151.46 (17-C), 143.25 (2-C), 141.23 (13-C), 134.34 (4-C), 129.19 (14-C), 127.40
(7-C), 124.63 (12-C), 124.24 (8-C), 123.53 (9-C), 122.80 (15-C), 122.77 (3-C),
115.83 (19-C), 113.20 (16-C), 112.77 (6-C), 56.68 (21-C), 41.40 (20-C).
123

D. Cos¸kun, M. Ahmedzade
1-[3-(1-Benzofuran-2-yl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl]-2-
chloroethanone (4a)
Yield: 57 %; m.p. 160–162 °C. FTIR (KBr, cm-1): 3090 (Aromatic C–H), 1668
(C=O), 1608 (C=N); H NMR (400 MHz, DMSO-d6), ppm: 7.73 (d, J = 7.80 Hz,
1
1H, 6-H), 7.71 (d, J = 8.10 Hz, 1H, 9-H), 7.48 (s, 1H, 3-H), 7.46–7.23 (m, 7H, 7-8-18-
19-20-21-22-H), 5.63 (dd, J = 11.79 and 4.55 Hz, 1H, 13-H), 4.80 (d, J = 13.97 Hz,
1H, 23-H), 4.68 (d, J = 13.95, 1H, 23-H), 3.94 (dd, J = 17.89 and 11.80 Hz, 1H,
14-H), 3.20 (dd, J = 17.92 and 4.61 Hz, 1H, 14-H), 13C NMR, ppm: 163.85 (15-C),
155.42 (5-C), 147.98 (2-C), 147.48 (4-C), 141.70 (10-C), 129.26 (22-C), 128.05 (18-
C), 127.94 (21-C), 127.30 (19-C), 126.00 (7,20-C), 124.25 (8-C), 122.62 (9-C), 112.04
(6-C), 111.84 (3-C), 60.34 (13-C), 42.95 (23-C), 42.29 (14-C).
4-[3-(1-Benzofuran-2-yl)-1-(chloroacetyl)-4,5-dihydro-1H-pyrazol-5-yl]-2-
methoxyphenyl chloroacetate (4b)
Yield: 50 %; m.p. 200–201 °C. FTIR (KBr, cm-1): 3050 (Aromatic C–H), 1777
(C=O), 1668 (C=N); 1H NMR (400 MHz, DMSO-d6), ppm: 7.75–7.70 (m, 2H, 6-9-
H), 7.48 (s, 1H, 3-H), 7.45 (t, J = 8.41 Hz, 1H, 7-H), 7.33 (t, J = 7.38 Hz, 1H,
8-H), 7.12 (d, J = 8.17 Hz, 1H, 21-H), 7.07 (d, J = 1.59 Hz, 1H, 22-H), 6.84 (dd,
J = 8.23 and 1.70 Hz, 1H, 18-H), 5.65 (dd, J = 11.83 and 4.73 Hz, 1H, 13-H), 4,72
(s, 2H, 25-H), 4.84 (d, J = 13.86 Hz, 1H, 23-H), 4.68 (d, J = 13.96, 23-H), 3.93
(dd, J = 17.89 and 11.84 Hz, 1H, 14-H), 3,79 (s, 3H, 26-H), 3.26 (dd, J = 17.88
and 4.78 Hz, 1H, 14-H), 13C NMR, ppm: 166.27 (25-C), 164.03 (15-C), 155.41 (5-
C), 151.20 (19-C), 147.98 (2-C), 147.54 (4-C), 141.11 (20-C), 138.56 (10-C),
127.96 (21-C), 127.31 (7-C), 124.26 (17-C), 123.28 (8-C), 122.62 (9-C), 117.80
(22-C), 112.05 (18-C), 111.88 (6-C), 110.89 (3-C), 60.08 (13-C), 56.38 (26-C),
42.95 (25-C), 42.26 (23-C), 41.39 (14-C).
1,4-Bis[3-(benzofuran-2-yl)-1-(2-chloroethyl)-2-pyrazoline-5-yl]benzene (4c)
Yield: 50 %; m.p. 161–162 °C. FTIR (KBr, cm-1): 3125 (Aromatic C–H), 1693
(C=O), 1610 (C=N); 1H NMR (400 MHz, DMSO-d6), ppm: 7.72 (d, 2H, 9-H), 7.71
(d, 2H, 6-H), 7.47 (s, 2H, 3-H), 7.45 (t, J = 8.10 Hz, 2H, 7-H), 7.32 (t,
J = 7.50 Hz, 2H, 8-H), 7.24 (s, 4H, 18-19-21-22-H), 5.62 (dd, J = 11.80 and
4.42 Hz, 2H, 13-H), 4.79 (d, J = 13.64 Hz, 2H, 23-25-H), 4.70 (d, J = 13.64, 2H,
23-25-H), 3.92 (dd, J = 17.77 and 11.82 Hz, 2H, 14-H), 3.20 (dd, J = 17.87 and
4.46 Hz, 2H, 14-H), 13C NMR, ppm: 164.02 (15-C), 155.48 (5-C), 147.85 (4,2-C),
140.69 (10-C), 130.40 (22-C), 128.45 (18-C), 126.83 (7,17-C), 124.52 (8-C), 122.90
(9-C), 112.04 (3,6-C), 60.06 (13-C), 41.42 (23-C), 40.55 (14-C).
3-{3-(1-Benzofuran-2-yl)-1-[(chloroacetyl)oxy]-4,5-dihydro-1H-pyrazol-5-
yl}phenyl chloroacetate (4d)
Yield: 50 %; m.p. 137–138 °C. FTIR (KBr, cm-1): 3130 (Aromatic C–H), 1770
(C=O), 1586 (C=N); H NMR (400 MHz, DMSO-d6), ppm: 7.73 (d, J = 7.09 Hz,
1
123

Synthesis of acylated 2-pyrazolines and chalcones
1H, 6-H), 7.72 (d, J = 7.80 Hz, 1H, 9-H), 7.50 (s, 1H, 3-H), 7.48–7.41 (m, 2H, 7-8-
H), 7.33 (t, J = 7.50 Hz, 1H, 19-H), 7.21 (d, J = 7.80, 1H, 20-H), 7.15–7.09 (m,
2H, 18-22-H), 5.66 (dd, J = 11.83 and 4.70 Hz, 1H, 13-H), 4.80 (d, J = 14.10 Hz,
1H, 23-H), 4.71 (d, 1H, 23-H), 4.68 (s, 2H, 26-H), 3.95 (dd, J = 17.94 and
11.88 Hz, 1H, 14-H), 3.23 (dd, J = 17.97 and 4.76 Hz, 1H, 14-H).
2-[3-(1-Benzofuran-2-yl)-1-(chloroacetyl)-4,5-dihydro-1H-pyrazol-5-yl]phenyl
chloroacetate (4e)
Yield: 43 %; m.p. 199–200 °C. FTIR (KBr, cm-1): 3130 (Aromatic C–H), 1782
(C=O), 1610 (C=N); 1H NMR (400 MHz, DMSO-d6), ppm: 7.75–7.70 (m, 2H, 6-9-
H), 7.50 (s, 1H, 3-H), 7.49–7.24 (m, 6H, 7-8-18-19-20-21-H), 5.71 (dd, J = 12.20
and 5.27 Hz, 1H, 13-H), 4.76-4.66 (m, 4H, 23-27-H), 3.93 (dd, J = 17.97 Hz, 1H,
14-H), 3.08 (dd, J = 17.98 and 5.28 Hz, 1H, 14-H), 13C NMR, ppm: 166.61 (27-C),
163.82 (15-C), 155.45 (5-C), 147.81 (22-C), 147.70 (2-C), 147.60 (2-C), 133.14 (4-
C), 129.51 (17-C), 128.00 (18-C), 127.92 (7-C), 127.39 (20-C), 127.27 (19-C),
124.28 (8-C), 123.46 (9-C), 122.70 (21-C), 112.00 (6-C), 111.81 (3-C), 56.52 (13-
C), 42.78 (27-C), 41.57 (23-C), 41.15 (14-C).
1-[3-(1-Benzofuran-2-yl)-5-(3-nitrophenyl)-4,5-dihydro-1H-pyrazol-1-yl]-2-
chloroethanone (4f)
Yield: 51 %; m.p. 209–210 °C. FTIR (KBr, cm-1): 3100 (Aromatic C–H), 1679
(C=O); 1H NMR (400 MHz, DMSO-d6), ppm: 8.20–8.14 (m, 2H, 20-22-H),
7.76–7.64 (m, 4H, 6-9-18-19-H), 7.49 (s, 1H, 3-H), 7.46 (t, J = 7.80 Hz, 1H, 7-H),
7.33 (t, J = 7.20 Hz, 1H, 8-H), 5.82 (dd, J = 11.92 and 5.12 Hz, 1H, 13-H), 4.84
(d, J = 14.00, 1H, 23-H), 4.69 (d, J = 14.00, 1H, 23-H), 3.99 (dd, J = 18.05 and
11.96 Hz, 1H, 14-H), 3.32 (dd, J = 18.15 and 5.15 Hz, 1H, 14-H), 13C NMR, ppm:
164.23 (15-C), 155.43 (5-C), 148.46 (21-C), 147.80 (2-C), 147.60 (10-C), 143.66
(17-C), 132.94 (18-C), 130.94 (19-C), 127.91 (4-C), 127.36 (7-C), 124.27 (22-C),
123.09 (8-C), 122.65 (9-C), 121.35 (20-C), 112.05 (3-C), 111.99 (6-C), 56.73 (13-
C), 42.90 (23-C), 41.94 (14-C).
1-[(5R)-3-(1-benzofuran-2-yl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-1-yl]-
2-chloroethanone (4g)
Yield: 60 %; m.p. 174–175 °C. FTIR (KBr, cm-1): 3115 (Aromatic C–H), 1685
(C=O); H NMR (400 MHz, DMSO-d6), ppm: 7.77–7.70 (m, 2H, 6-9-H), 7.56 (s,
1
1H, 3-H), 7.49–7.43 (m, 2H, p4-7-H), 7.34 (dt, J = 7.35 and 0.90 Hz, 1H, 8-H),
7.10 (d, J = 3.00 Hz, 1H, p2-H), 6.98 (dd, J = 5.55 and 3.60 Hz, 1H, p3-H), 5.95
(dd, J = 11.40 and 3.91 Hz, 1H, 13-H), 4.75 (d, J = 14.05 Hz, 1H, 23-H), 4.65 (d,
J = 14.07, 1H, 23-H), 3.92 (dd, J = 17.89 and 11.40 Hz, 1H, 14-H), 3.41 (dd,
J = 17.92 and 3.99 Hz, 1H, 14-H), 13C NMR, ppm: 163.84 (15-C), 155.45 (5-C),
147.84 (10-C), 147.61 (2-C), 143.83 (p5-C), 127.93 (4-C), 127.36 (p3-C), 126.00
(p4-C), 125.60 (p2-C), 124.28 (8-C), 122.65 (9-C), 112.06 (6-C), 112.04 (3-C),
55.95 (13-C), 42.89 (23-C), 41.86 (14-C).
123

D. Cos¸kun, M. Ahmedzade
1-[3-(1-Benzofuran-2-yl)-5-(furan-2-yl)-4,5-dihydro-1H-pyrazol-1-yl]-2-
chloroethanone (4h)
Yield: 51 %; m.p. 171–172 °C. FTIR (KBr, cm-1): 3143 (C–H furan), 3118
(Aromatic C–H), 1608 (C=N); 1H NMR (400 MHz, DMSO-d6), ppm: 7.75 (d,
J = 9.70 Hz, 1H, 9-H), 7.72 (d, J = 8.70 Hz, 1H, 6-H), 7.61 (m, 1H, f19-H), 7.55 (s,
1H, 3-H), 7.46 (dt, J = 7.65 and 1.50 Hz, 1H, 7-H), 7.34 (dt, J = 7.65 and 1.10 Hz,
1H, 8-H), 6.44–6.41 (m, 2H, f20-21-H), 5.73 (dd, J = 11.99 and 4.74 Hz, 1H, 13-H),
4.73 (d, J = 14.15, 1H, 23-H), 4.66 (d, J = 14.16 Hz, 1H, 23-H), 3.81 (dd, J = 17.77
and 11.80 Hz, 1H, 14-H), 3.44 (dd, J = 17.77 and 4.67 Hz, 1H, 14-H), 13C NMR,
ppm: 164.02 (15-C), 155.24 (18-C), 152.47 (17-C), 148.31 (2,4-C), 143.23 (10-C),
128.72 (20-C), 127.98 (7-C), 124.28 (18-C), 122.90 (9-C), 112.06 (3.6-C), 111.12 (3-
C), 108.58 (19-C), 54.04 (13-C), 42.96 (23-C), 38.49 (14-C).
Results and discussion
This work is the third part of our studies on 3-(substituted aryl)-1-benzofuranyl-2-
propenones and describes the synthesis and characterization of a-haloesters
containing the chalcone structure and a-haloamides containing the pyrazoline
structure. a-Haloesters containing the chalcone structure were synthesized by
reaction of substituted hydroxyl chalcones with chloroacetyl chloride in the
presence of Et3N. a-Haloamides containing the pyrazoline structure were synthe-
sized by reaction of pyrazoline derivatives with chloroacetyl chloride in the
presence of Et3N. a-Haloesters were obtained in 30–60 % yields. a-Haloamides
were obtained in 45–60 % yields.
1
All new compounds were characterized by H NMR, Fourier transform infrared
(FTIR), and (for some compounds) 400-MHz 13C NMR spectroscopy.
The disappearance of the OH stretching vibration between 3,200 and 3,250 cm-1
in FTIR spectra and the appearance of a new band between 1,760 and 1,780 cm-1
(C=O stretching in ClCH2COO) confirms the formation of a-haloester derivatives
of the chalcones. In addition, aliphatic C–H stretching vibrations are observed at
2,850–3,000 cm-1. The stretching vibration at 1,640–1,670 cm-1 attributed to the
C=C–C=O group was shifted to higher energy because of the presence of an
electron-withdrawing group. Absorption bands at 1,770–1,780 cm-1 were attributed
to O–C=O bond stretching.
1
The most characteristic signal in the H NMR spectra of the a-haloesters with a
chalcone side group was observed as a singlet between 4.49 and 4.76 (methylene
protons in OCOCH2Cl). The appearance of NH absorption at 3,350 and 3,500 cm-1
in the FTIR spectra of a-haloamide derivatives containing the pyrazoline structure
was evidence of the formation of the expected structures (a-haloamide derivatives
containing a pyrazoline ring). In addition, the new absorption band between 1,650
and 1,690 cm-1 was attributed to the (NC=O) stretch vibration which also
confirmed formation of desired a-haloamide derivatives containing a pyrazoline
ring. The disappearance of the OH absorption at approximately 3,200 cm-1 and the
appearance of a new absorption band at 1,760–1,770 cm-1, attributed to the OC=O
123

Synthesis of acylated 2-pyrazolines and chalcones
stretching vibration, are the most important findings in the FTIR spectra of
OC=OCH2Cl-substituted a-haloamide derivatives containing the pyrazoline
structure.
Acknowledgments The authors are grateful to the Firat University Research Fund for financial support
of this work (Project no. 1305).
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