Synthesis and anti-TMV activity of novel N-(3-alkyl-1H-pyrazol-4-yl)-3- alkyl-4-substituted-1H-pyrazole-5-carboxamides

Article abstract of DOI:10.1016/j.cclet.2012.04.010

In order to investigate the biological activity of novel bis-pyrazole compounds, a series of N-(3-alkyl-5-(N-methylcarbamyl)-1H-pyrazol-4-yl)-3-alkyl- 4-substituted-1H-pyrazole-5-carboxamides were designed and synthesized with ethyl 3-alkyl-1H-pyrazole-5-

Full text of DOI:10.1016/j.cclet.2012.04.010

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 669–672
www.elsevier.com/locate/cclet
Synthesis and anti-TMV activity of novel N-(3-alkyl-1H-pyrazol-4-
yl)-3-alkyl-4-substituted-1H-pyrazole-5-carboxamides
Da Qiang Zhang a, Gao Fei Xu a, Zhi Jin Fan b, Dao Quan Wang a,
Xin Ling Yang a, De Kai Yuan a,
*
a Department of Applied Chemistry, Science College, China Agricultural University, Beijing 100193, China
b The State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
Received 15 February 2012
Available online 11 May 2012
Abstract
In order to investigate the biological activity of novel bis-pyrazole compounds, a series of N-(3-alkyl-5-(N-methylcarbamyl)-
1H-pyrazol-4-yl)-3-alkyl-4-substituted-1H-pyrazole-5-carboxamides were designed and synthesized with ethyl 3-alkyl-1H-pyr-
azole-5-carboxylate 1 as starting materials. N-Methyl-3-alkyl-4-amino-1H-pyrazole-5-carboxamides 6 were obtained from 1 via 5
steps. 3-Alkyl-4-substitued-1H-pyrazole-5-carboxyl chlorides 4a, 4b, 11a, 11b, 11c or 12 were also obtained from 1 via several
steps. Target compounds 7a–7g were obtained after the reaction of 6 with the above 1H-pyrazole-5-carboxyl chlorides. Preliminary
bioassay showed some compounds possessing good inactivation effect against TMV (tobacco mosaic virus). Compound 7a showed
higher activity superior to ningnanmycin at a concentration of 5.0 ꢀ 10ꢁ4 g/mL and equal activity at 1.0 ꢀ 10ꢁ4 g/mL; 7b and 7c
showed equal activity to virazole both at concentrations of 5.0 ꢀ 10ꢁ4 g/mL and 1.0 ꢀ 10ꢁ4 g/mL.
# 2012 De Kai Yuan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Bis-pyrazole compounds; 3-Alkyl-4-amino-1H-pyrazole-5-carboxamides; 3-Alkyl-1H-pyrazole-5-carboxyl chlorides; Inactivation
effect; TMV
Pyrazole compounds play important roles in pesticide science and some of them have been used as herbicides,
insecticides and fungicides world widely, such as fipronil and chlorantraniliprole, azimsulfuron and pyrazoxyfen,
furametpyr and penthiolpyrad, whichare therepresentatives of green pesticides fortheir low toxicity, high selectivity and
environmental kindness [1–6]. Great efforts are still focused on the design and synthesis of pyrazole compounds in order
to find novel leading structures for pesticides innovation [7–14]. There are many novel pyrazole structures which have
been reported recently nearly in every aspect of pesticide research, and that some di- or bis-pyrazole derivatives were
found possessing herbicidal, fungicidal or viralcidal activities [15–18]. Using ethyl 3-alkyl-1H-pyrazole-5-carboxylates
1 asstarting material, wedesignedand synthesizeda series ofbis-pyrazolecompounds, inwhichtwosubstituted pyrazole
subunits were attached to each other with an amide bond. All the seven target compounds were reported for the first time.
The synthetic route of the compounds was outlined in Scheme 1. Starting materials 1 were obtained by literal
methods [19]. Intermediates 6 were obtained in high yields from 1 via hydrolysis, nitration, chlorination, ammoniation
* Corresponding author.
E-mail address: yuandekai@yahoo.com.cn (D.K. Yuan).
1001-8417/$ – see front matter # 2012 De Kai Yuan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.04.010

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D.Q. Zhang et al. / Chinese Chemical Letters 23 (2012) 669–672
X
R
H CHN
3
3
NO
NO
NO
2
O
NH
2
2
R
2
1
R
1
O
O
R
R
R
1
O
R
1
1
1
a
O
NHCH
O
O
d
e
O
c
f
b
N
HN
N
N
Y
OEt
N
N
H
OH
Cl
N
NHCH
3
3
N
H
N
H
N
N
N
N
N
N
N
N
H
H
H
H
R
2
R
1
2a: R =Me,Y=OH;
2b: R =Et,Y=OH;
5a: R = Me;
6a: R = Me;
1a: R = Me;
4a: R = Me;
1
1
1
1
1
3a: R = Me;
1
1
5b: R =Et;
6b: R =Et;
7a ~7g
1b: R = Et;
4b: R = Et;
1
1
1
3b: R = Et;
1
1
c
12: R =Et, Y=Cl;
1
R
g or h
X
O
3
R
3
X
R
X
3
O
a
O
i
N
N
N
N
OEt
N
Y
OEt
N
H
CH
3
CH
3
9a: R = Me, X=Br;
8a: R = Me, X=Br;
3
3
3
3
3
3
10a~10c: Y=OH;
9b: R = Et, X=Cl;
8b: R = Et, X=Cl;
c
9c: R = Et, X=Br;
8c: R = Et, X=Br;
11a~11c: Y=Cl;
Scheme 1. Reagents and conditions: (a) (i) aqueous NaOH (4 equiv.), methanol, reflux, 4 h; (ii) H+, pH = 2; (b) HNO3 (98%)/H2SO4ꢂxSO3 (1:1.2, v/
v), ꢁ5 8C for 1 h, 60 8C for 18 h; (c) SOCl2, reflux, 4 h; (d) aqueous CH3NH2 (35%) (25 equiv.), Et2O, 0 8C for 3 h, r.t. for 5 h; (e) H2 (8 atm), Pd/C
(0.5% equiv.), methanol, r.t., 24 h; (f) 4a, 4b, 11a, 11b, 11c or 12 (1.2 equiv.), Et3N (1.5 equiv.), CH2Cl2 or THF, 0 8C for 3 h, r.t. for 5 h; (g) SO2Cl2
(1.3 equiv.), CHCl3, 0 8C, reflux for 4 h; (h) NBS (1.2 equiv.), CHCl3, r.t., 12 h; (i) CH3I (1.5 equiv.), K2CO3 (1.0 equiv.), and acetone, 50 8C, 10 h.
and reduction successively and used for the next step directly [20–22]. During the preparation of 6, intermediates 2, 3,
5 were purified by recrystallization in methanol, and 4 could be used directly without further purification. 3-Alkyl-1,4-
disubstituted-1H-pyrazole-5-carboxyl chlorides 4a, 4b, 11a–11c, and 12 were prepared from 1a or 1b via two to four
steps [23–25]. Intermediates 11 were also obtained from 1 via halogenation, methylation, hydrolysis and chlorination
successively and used directly to react with 6. During the preparation, compounds 8 and 9 were purified by column
chromatography. And 12 could be easily obtained from 2b. Target compounds 7a–7g were obtained as white solids in
moderate to high yields after the two sub-structures reacted in dichloromethane, which could be further purified by
recrystallization in methanol. Structural and some physical data of 7a–7g were listed in Table 1 and 1H NMR data of
them were illustrated in Table 2.
Inactivation effect of compounds 7a–7g against TMV in vivo was evaluated on N. tabacum L. leaves [26]. The
healthy fresh leaves growing at 6 leaves age were selected for the test. The TMV virus with a concentration of
5.88 ꢀ 10ꢁ6 g/mL was inhibited by mixing with the target compound solution at the same volume for 30 min. Then
the mixture was inoculated on the upper three leaves using the conventional juice robbing method, and the solvent was
smeared on the lower three leaves as a control. The local lesion numbers were recorded 2–3 days after inoculation. For
each compound, three repetitions were conducted. All compounds for testing were conducted at concentrations of
5.0 ꢀ 10ꢁ4 g/mL and 1.0 ꢀ 10ꢁ4 g/mL respectively. Virazole and ningnanmycin were used as positive control at the
same time. The activity data of inactivation effect against TMV was calculated by the following equation:
CK ꢁ T
Inhibitionð%Þ ¼
ꢀ 100%
CK
Table 1
Structures and some physical data of compounds 7a–7f.
Compd.
X
R1
R2
R3
mp (8C)
Yields (%)y
MS (m/z, ESI)
Calcd.
Found
7a
7b
7c
7d
7e
7f
NO2
NO2
NO2
H
Et
Et
Me
Et
Et
Et
Et
H
Et
154–155
212–214
270–272
213–214
184–186
171–172
221–222
78
69
88
53
78
56
73
335.13
321.12
307.27
290.15
338.13
382.08
368.06
358.12 (M+Na+)
344.11 (M+Na+)
330.09 (M+Na+)
313.14 (M+Na+)
361.12 (M+Na+)
405.07 (M+Na+)
391.05(M+Na+)
H
Me
Me
Et
H
H
Cl
Me
Me
Me
Et
Br
Et
7g
Br
Me
y
Yields of the last step.

D.Q. Zhang et al. / Chinese Chemical Letters 23 (2012) 669–672
671
Table 2
1H NMR data of compounds 7a–7f.
Compd.
Solvent
1H NMR (300 MHz, TMS): d
7a
DMSO-d6
13.94 (s, 1H), 13.00 (s, 1H), 9.88 (s, 1H), 8.06 (d, 1H), 2.95 (q, 2H, J = 7.5 Hz), 2.72 (s, 3H), 2.71
(q, 2H, J = 7.6 Hz), 1.27 (t, 3H, J = 7.5 Hz), 1.18 (t, 3H, J = 7.6 Hz)
13.95 (s, 1H), 13.01 (s, 1H), 9.89 (s, 1H), 8.07 (d, 1H), 2.72 (s, 3H), 2.71 (q, 2H, J = 7.6 Hz), 2.53
(s, 3H), 1.18 (t, 3H, J = 7.6 Hz)
7b
DMSO-d6
7c
7d
DMSO-d6
DMSO-d6
13.96 (s, 1H), 13.02 (s, 1H), 9.93 (s, 1H), 7.78 (s, 1H), 2.72 (d, 3H, J = 4.5Hz), 2.54 (s, 3H), 2.27 (s, 3H)
13.04 (s, 1H), 12.91 (s, 1H), 9.90 (s, 1H), 8.12 (d, 1H), 6.48 (s, 1H), 2.77 (q, 2H, J = 7.5 Hz), 2.66
(q, 2H, J = 7.6 Hz), 1.21 (t, 3H, J = 7.6 Hz), 1.14 (t, 3H, J = 7.5 Hz)
7e
7f
CDCl3
10.43 (s, 1H), 9.57 (s, 1H), 6.91 (d, 1H), 4.11 (s, 3H), 2.95 (d, 3H), 2.89 (q, 2H, J = 7.5Hz), 2.66
(q, 2H, J = 7.5 Hz), 1.26 (t, 3H, J = 7.5 Hz), 1.25 (t, 3H, J = 7.5 Hz)
CDCl3
9.57 (s, 1H), 6.97 (d, 1H), 5.20(s, 3H), 4.11 (s, 3H), 2.97 (d, 3H), 2.89 (q, 2H, J = 6.9 Hz), 2.62
(q, 2H, J = 6.9 Hz)
7g
DMSO-d6
13.05 (s, 1H), 9.79 (s, 1H), 8.10 (d, 1H), 3.96 (s, 1H), 2.71 (s, 3H), 2.67 (q, 2H, J = 7.5 Hz), 2.17
(s, 3H), 1.17 (t, 3H, J = 7.5 Hz)
Table 3
Anti-TMV activity of compounds 7a–7f.
Compd.
7a
7b
7c
7d
7e
7f
7g
Virazole
Ningnanmycin
Inhibit. (%)
5.0 ꢀ 10ꢁ4 g/mL
1.0 ꢀ 10ꢁ4 g/mL
62.02
37.21
37.21
27.13
32.56
27.13
32.56
4.65
10.08
8.53
13.18
10.85
12.40
3.88
34.11
23.26
46.51
39.53
where CK was the average number of viral inflammations on the control leaves in vivo, T was the average number of
viral inflammations on the target compound treated leaves in vivo. The inhibition rates of the title compounds were
listed in Table 3.
From the data, we could find that compounds 7a, 7b, 7c and 7d possessing good anti-TMV activity at a
concentration of 5.0 ꢀ 10ꢁ4 g/mL. After the concentration was reduced to 2.0 ꢀ 10ꢁ4 g/mL, the activity of 7a, 7b and
7c was still higher than that of virazole, but the activity of 7d decreased sharply. Compounds 7e, 7f and 7g showed very
poor activity at both concentration. After a structural comparison, it was very clear that X group at C4 of the pyrazole-
5-carboyl part was very important to the antivirus activity of compounds 7a–7g. When X group was NO2, title
compounds, such as 7a–7c, showed high anti-TMV activity both at high or low concentration, but the activity
disappeared when X was changed to a Cl or Br atom and N1 position was attached with a methyl group. This work
provides us with useful information in further research for novel anti-viral leading compounds.
Acknowledgments
We are grateful to the National Natural Science Fund of China (No. 20902107) and the Fundamental Research Fund
for the Central Universities (No. 2011JS033).
References
[1] M. Casado, P. Le Roy, V. Pevere, EP 668269, 1995-02-17.
[2] T. Mita, Y. Kudo, T. Mizukoshi, et al., JP 2005272452, 2005-02-23.
[3] G. Levitt, US 004,746,353, 1988-05-2.
[4] T. Konotsune, K. Kawakubo, T. Honma, JP 55033454, 1980-03-08.
[5] T. Mori, T. Ohsumi, S. Nakamura, et al., EP 315502, 1989-05-10.
[6] Y. Yoshikawa, K. Tomiya, H. Katsuta, et al., EP 737682, 1996-10-16.
[7] H.L. Elbe, H. Rieck, R. Dunkel, et al., WO 2003010149, 2003-02-06.
[8] S. Schnatterer, M. Maier, F. Petry, et al., US 20080132487, 2008-06-05.
[9] S. Tarh, WO 9417060, 1994-08-04.
[10] G. Bartels, A. Becker, J. Benting, et al., WO 2010130767, 2010-11-18.
[11] M. Gewehr, J. Dietz, T. Grote, et al., WO 2007017450, 2007-02-15.
[12] G.P. Ouyang, X.J. Cai, Z. Chen, et al. J. Agric. Food Chem. 56 (2008) 10160.

672
D.Q. Zhang et al. / Chinese Chemical Letters 23 (2012) 669–672
[13] H. Dai, Y.Q. Li, D. Du, et al. J. Agric. Food Chem. 56 (2008) 10805.
[14] R.J. Pasteris, M.A. Hanagan, R. Shapiro, WO 2008013925, 2008-01-31.
[15] H. Uwe, D. Gabriele, F. Helga, et al., EP 0542388, 1993-05-19.
[16] M.R. Sayed, A.F. Thoraya, A.A. Magda, et al. Eur. J. Med. Chem. 45 (2010) 1042.
[17] Y.H. Cheng, X.M. Zou, Y. Gao, et al. Chem. J. Chin. Univ. 25 (2004) 2024.
[18] W.J. Ji, T.M. Xu, Y.C. Wei, et al. Chin. J. Pest. Sci. 13 (2) (2011) 121.
[19] W.Z. Fan, B.Q. Gu, W.Q. Zhu, et al. Mod. Agrochem. 4 (2) (2005) 9.
[20] L.J. Harris, P.C. Levett, EP 1176142, 2002-01-30.
[21] D.K. Yuan, D.Q. Zhang, R.X. Li, et al. Chin. Chem. Lett. 22 (2011) 18.
[22] K. Watanabe, K. Kamata, JP 04001180, 1992-01-06.
[23] K. Yoshida, I. Okada, S. Okui, et al.. JP 02053776, 1990-02-22.
[24] M. Sekiya, K. Umezawa, A. Sato, et al. Chem. Commun. 21 (2009) 3047.
[25] X.L. Ren, C. Wu, F.Z. Hu, et al. Chin. J. Chem. 22 (2004) 194.
[26] X. Zuo, N. Mi, Z.J. Fan, et al. J. Agric. Food Chem. 58 (2010) 2755.