Synthesis and bioactivity of N-tert-butyl-N′-acyl-5-methyl-1,2,3- thiadiazole-4-carbohydrazides

Article abstract of DOI:10.1016/j.cclet.2012.09.024

A series of novel N-tert-butyl-N′-acyl-5-methyl-1,2,3-thiadiazole-4- carbohydrazides were designed and synthesized. Their structures were characterized by melting points, ¹H NMR, IR, ESI-MS, and elemental analysis. The bioassay tests indicated that compound 7o exhibited excellent direct anti-TMV activity and induction activity in vivo at 50 μg/mL, which was better than that of Ninamycin and tiadinial. Our studies indicated that 1,2,3-thiadiazole was an active substructure for novel pesticide development.

Full text of DOI:10.1016/j.cclet.2012.09.024

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 1233–1236
www.elsevier.com/locate/cclet
Synthesis and bioactivity of N-tert-butyl-N0-acyl-5-methy
l-1,2,3-thiadiazole-4-carbohydrazides
b
b
Wu Tao Mao a, Hui Zhao b, Zhi Jin Fan b, , Xiao Tian Ji , Xue Wen Hua ,
*
Tatiana Kalinina c, Yu. Morzherin Yury c, A. Bakulev Vasiliy c
a Department of Chemistry, Tianjin University, Tianjin 300072, China
b State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
c The Ural Federal University Named after the First President of Russia B.N. Yeltsin, Yeltsin UrFU 620002, Ekaterinburg, Russia
Received 2 August 2012
Available online 24 October 2012
Abstract
A series of novel N-tert-butyl-N0-acyl-5-methyl-1,2,3-thiadiazole-4-carbohydrazides were designed and synthesized. Their
structures were characterized by melting points, 1H NMR, IR, ESI-MS, and elemental analysis. The bioassay tests indicated that
compound 7o exhibited excellent direct anti-TMVactivity and induction activity in vivo at 50 mg/mL, which was better than that of
Ninamycin and tiadinial. Our studies indicated that 1,2,3-thiadiazole was an active substructure for novel pesticide development.
# 2012 Zhi Jin Fan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Antivirus activity; Systemic acquired resistance; Synthesis; 1,2,3-Thiadiazole; Diacylhydrazine
Elicitors, which can induce the immunological system of the plant to produce a broad spectrum acquired resistance
by altering the physical and physiological status of the host plants [1], is a novel technique for plant protection.
Acibenzolar-S-methyl (BTH) [2] is the first successful elicitor, which is followed by tiadinial (TDL) [3]. Both of them
are derivatives of 1,2,3-thiadizole. 1,2,3-Thiadizoles are a versatile class of agrochemicals, which present a wide range
of biological activities, such as systemic acquired resistance [4], antivirus activity [5], herbicidal activity [6],
fungicidal activity [7] and insecticidal activity [8]. Diacylhydizine molecules also exhibit extensive biological
activities. For example, they can be used as insecticide [9] and anti-TMV reagent [10]. In addition, 1,2,3-thiadizole
ring can easily break down into low molecular weight compounds under light radiation [11]. These properties endow
1,2,3-thiadizoles as environmentally friendly pesticide candidates with low toxicity. Recently, agrochemicals used as
anti-TMV reagent have been received extensively attentions [12]. In search for new potential plant elicitors or anti-
TMV reagent, diacylhydizine group was introduced into 1,2,3-thiadizole, and a series of N-tert-butyl-N0-acyl-5-
methyl-1,2,3-thiadiazole-4-carbohydrazides were designed and synthesized. All the 16 target compounds were
reported for the first time.
The synthesis route of the target compounds was outlined in Scheme 1. The starting material compound 4 was
prepared by literal method [13]. Intermediates 3aꢀ3p were obtained from 1a to 1p via chlorination and hydrazinolysis
* Corresponding author.
E-mail address: fanzj@nankai.edu.cn (Z.J. Fan).
1001-8417/$ – see front matter # 2012 Zhi Jin Fan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.09.024

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W.T. Mao et al. / Chinese Chemical Letters 23 (2012) 1233–1236
Scheme 1. R = o-methylphenyl (7a); m-methylphenyl (7b); p-methylphenyl (7c); o-methoxyphenyl (7d); m-methoxyphenyl (7e); p-methoxyphenyl
(7f); p-chlorophenyl (7g); m-trifluoromethylphenyl (7h); 3,5-dichlorophenyl (7i); 2-methyl-3-methoxyphenyl (7j); 3,5-dinitrophenyl (7k); p-
chlorobenzyl (7l); 6-chloropyridine-3-yl (7m); furan-2-yl (7n); thiophene-2-yl (7o); naphthyl (7p). Reagents and conditions: (a) S(O)Cl2, reflux, 4 h;
(b) t-BuNHNH2HCl, aqueous NaOH (50%) (2.0 equiv.), CH2Cl2, r.t. for 6 h. (c) (i) aqueous NaOH (2.0 equiv.), methanol, r.t. for 8 h, (ii) H+, pH = 2;
(d) Et3N, CH2Cl2, 0 8C for 1 h, r.t. for 6 h.
successively in high yields and used directly for next step. 5-Methyl-1,2,3-thiadiazole-4-carbonyl chloride
intermediate 6 was prepared from 4 via hydrolysis and chlorination. The target compounds 7a–7p was obtained by the
coupling of 3a–3p with 6 in dichloromethane using triethylamine as the base in moderate yields, which were white or
pale yellow solid after column chromatography purification.
The structures of the target compounds synthesized herein were fully confirmed by melting points, 1H NMR, IR,
1
ESI-MS, and elemental analysis [14]. In the H NMR spectra of compound 7a–7p, the signals of CH3 of 1,2,3-
thiadizole were observed at d 2.69–2.85, and the signals of tert-butyl group were observed at d 1.52–1.71. Moreover,
the active proton signals of NHCO in most cases were observed at d 8.17–9.26. Whereas in the situation of compound
7k, the active proton signal was observed at d 10.17 because of the two electron withdrawing nitro-group. In ESI-Mass
spectra of compound 7a–7p, fifteen of the compounds showed [M+Clꢀ] peaks except compound 7k, which showed
[MꢀH]ꢀ peak.
First, direct antivirus activities against tobacco mosaic virus (TMV) of all the target compounds were detected
before their systemic acquired resistance determination. Healthy fresh tobacco leaves growing at six-leaf age were
selected to test the direct anti-TMVactivities of compounds 7a–7p, using the conventional juice-robbing method [4a].
Ninamycin was chosen as positive control, and the inhibition rates of the title compounds were listed in Table 1. Then,
systemic acquired resistance of the target compounds were detected using tobacco against TMV system as described in
Ref. [4a]. The induction activity was evaluated using the antivirus inhibition ratio, which was calculated by the average
number of viral inflammations on the inoculated leaves with corresponding control accordingly. Tiadinil (TDL) and
ribavirin were chosen as positive control and negative control, respectively, and all compounds tested were conducted
at 50 mg/mL. The results were shown in Table 1.
As can be seen from the data, compound 7a and 7o had very good anti-TMV activity with inhibition activity of
51.00% and 58.70% at 50 mg/mL, respectively; these were approximately equal to or higher than that of the positive
control. Some of the target compounds present good induction activity too, for example 7e, 7h, 7i, 7j and 7o with
49.14%, 51.71%, 52.56%, 54.27% and 61.03% of induction activity. It is clear that Ninamycin possesses good direct
anti-TMV activity; however it has very poor induction activity. In contrast, tiadinil exhibits very good induction
Table 1
Direct antivirus activity and induction activity in vivo against TMV of title compounds at 50 mg/mL.
Compd.
Anti-TMV (%)
Induction (%)
Compd.
Anti-TMV (%)
Induction (%)
Compd.
Anti-TMV (%)
Induction (%)
7a
7b
7c
7d
7e
7f
51.00
20.88
35.74
22.89
38.89
27.31
20.09
15.98
8.68
7g
7h
7i
32.48
32.05
25.21
22.22
17.09
18.80
39.74
51.71
52.56
54.27
42.73
32.91
7m
7n
35.04
35.74
58.72
35.90
54.93
7.94
29.91
34.70
61.03
38.04
18.58
59.25
7o
7p
37.90
49.14
19.63
7j
7k
7l
Ninamycin
Tiadinil

W.T. Mao et al. / Chinese Chemical Letters 23 (2012) 1233–1236
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activity, but it nearly has no direct anti-TMV activity. Fortunately, we found that compound 7o exhibited very good
direct anti-TMVactivity, which still has very good induction activity, that is to say compound 7o can be used as plant
elicitor and anti-TMV reagent at the same time. Compared to other compounds, compound 7o contains a thiophene
ring, which may play an important role here. Our studies indicated that 1,2,3-thiadiazole was an active substructure for
novel pesticide development. This provides us with useful information in further research for antivirus leading-
compounds with induction activity.
Acknowledgments
This study was funded in part by the NNSFC (No. 20872071), the NSF of Tianjin (No. 10JCZDJC17500), the
National Key Project for Basic Research (No. 2010CB126105) and National Key Technology Research and
Development Program (Nos. 2011BAE06B02 and 2011BAE06B05) and the Foundation of Achievements
Transformation and Application of Tianjin Agricultural Science and Technology (No. 201002250), Tianjin Key
Technology Research and Development Program (No. 11ZCGYNC00100).
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[13] A. Shafiee, J. Heterocyclic Chem. 13 (1976) 301.
[14] Selected characteristic data for the target compounds. 7a: Yield, 64%; White solid; mp 153ꢀ155 8C; 1H NMR (CDCl3, 400 MHz): d 1.67 (s,
9H, t-Bu), 2.10 (s, 3H, Ph-CH3), 2.82 (s, 3H, thiadiazol-CH3), 6.87 (d, 1H, J = 7.6 Hz, Ph-H), 7.11ꢀ7.17 (m, 3H, Ph-H), 8.17 (s, 1H, NH). IR
(KBr) n: 3261, 2982, 1680, 1578, 1483, 1385, 1221, 1181 cmꢀ1. ESI-MS m/z: 367.0 (M+Clꢀ). Anal. Clacd. for C16H20N4O2S: C 57.81, H 6.06,
N 16.85; found C 57.93, H 6.01, N 16.80. 7b: Yield, 51%; White crystal; mp 220ꢀ222 8C; 1H NMR (CDCl3, 400 MHz): d 1.64 (s, 9H, t-Bu),
2.33 (s, 3H, Ph-CH3), 2.77 (s, 3H, thiadiazol-CH3), 7.23ꢀ7.25 (m, 2H, Ph-H), 7.26ꢀ7.29 (m, 2H, Ph-H), 8.38 (s, 1H, NH). ESI-MS m/z: 367.0
(M+Clꢀ). 7c: Yield, 45%; Pink crystal; mp 194ꢀ195 8C; 1H NMR (CDCl3, 400 MHz): d 1.65 (s, 9H, t-Bu), 2.37 (s, 3H,), 2.78 (s, 3H,
thiadiazol-CH3), 7.15 (d, 2H, J = 8.0 Hz, Ph-H), 7.40 (d, 2H, J = 8.0 Hz, Ph-H), 8.60 (s, 1H, NH). ESI-MS m/z: 367.0 (M + Clꢀ). 7d: Yield,
48%; Light yellow crystal; mp 129ꢀ131 8C; 1H NMR (CDCl3, 400 MHz): d 1.63 (s, 9H, t-Bu), 2.76 (s, 3H, thiadiazol-CH3), 3.97 (s, 3H, Ph-
OCH3), 6.90ꢀ6.99 (m, 2H, Ph-H), 7.42 (s, 1H, Ph-H), 7.82 (d, 1H, J = 7.5 Hz, Ph-H), 9.67 (s, 1H, NH). ESI-MS m/z: 383.0 (M+Clꢀ). 7e: Yield,
49%; White crystal; mp 156ꢀ158 8C; 1H NMR (CDCl3, 400 MHz): d 1.66 (s, 9H, t-Bu), 2.79 (s, 3H, thiadiazol-CH3), 3.81 (s, 3H, Ph-OCH3),
7.03 (t, 3H, J = 4.0 Hz, Ph-H), 7.26ꢀ7.30 (m, 1H, Ph-H), 8.52 (s, 1H, NH). ESI-MS m/z: 383.0 (M+Clꢀ). 7f: Yield, 33%; Pale crystal; mp
183ꢀ184 8C; 1H NMR (CDCl3, 400 MHz): d 1.65 (s, 9H, t-Bu), 2.79 (s, 3H, thiadiazol-CH3), 3.83 (s, 3H, Ph-OCH3), 6.85 (d, 2H, J = 8.8 Hz,
Ph-H), 7.48 (d, 2H, J = 8.8 Hz, Ph-H), 8.46 (s, 1H, NH). ESI-MS m/z: 383.0 (M+Clꢀ) (7g) Yield, 51%; White crystal; mp 192ꢀ194 8C; 1H
NMR (CDCl3, 400 MHz): d 1.65 (s, 9H, t-Bu), 2.79 (s, 3H, thiadiazol-CH3), 7.35 (d, 2H, J = 8.8 Hz, Ph-H), 7.45 (d, 2H, J = 8.4 Hz, Ph-H), 8.57
(s, 1H, NH). ESI-MS m/z: 387.0 (M+Clꢀ). 7h: Yield, 31%; Light yellow crystal; mp 227ꢀ229 8C; 1H NMR (CDCl3, 400 MHz): d 1.65 (s, 9H, t-
Bu), 2.81 (s, 3H, thiadiazol-CH3), 7.50 (t, 1H, J = 8.4 Hz, Ph-H), 7.68 (d, 1H, J = 7.6 Hz, Ph-H), 7.75 (d, 1H, J = 8.0 Hz, Ph-H), 7.84 (s, 1H, Ph-
H), 9.02 (s, 1H, NH). ESI-MS m/z: 421.0 (M+Clꢀ). 7i: Yield, 48%; White crystal; mp 191ꢀ193 8C; 1H NMR (CDCl3, 400 MHz): d 1.62 (s, 9H,
t-Bu), 2.81 (s, 3H, thiadiazol-CH3), 7.41 (d, 2H, J = 1.6 Hz, Ph-H), 7.45 (t,1H, J = 2.0 Hz, Ph-H), 8.99 (s, 1H, NH). ESI-MS m/z: 423.3
(M+Clꢀ). 7j: Yield, 28%; Pale crystal; mp 203ꢀ205 8C; 1H NMR (CDCl3, 400 MHz): d 1.67 (s, 9H, t-Bu), 1.93(s, 3H, Ph-CH3),. 2.83 (s, 3H,
thiadiazol-CH3), 3.81 (s, 3H, Ph-OCH3), 6.40 (d, 1H, J = 7.6 Hz, Ph-H), 6.87 (d, 1H, J = 7.6 Hz, Ph-H), 7.09 (t, 1H, J = 8.0 Hz, Ph-H), 8.06 (s,
1H, NH). ESI-MS m/z: 397.0 (M+Clꢀ). 7k: Yield, 54%; Light yellow crystal; mp 189ꢀ191 8C; 1H NMR (CDCl3, 400 MHz): d 1.60 (s, 9H, t-
Bu), 2.85 (s, 3H, thiadiazol-CH3), 8.86 (d, 2H, J = 2.0 Hz, Ph-H), 9.11 (t, 1H, J = 2.0 Hz, Ph-H), 10.17 (s, 1H, NH). ESI-MS m/z:
407.0 ([MꢀH]ꢀ). 7l: Yield, 51%; Light yellow crystal; mp 135ꢀ137 8C; 1H NMR (CDCl3, 400 MHz): d 1.52 (s, 9H, t-Bu), 2.69 (s, 3H,

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W.T. Mao et al. / Chinese Chemical Letters 23 (2012) 1233–1236
thiadiazol-CH3), 3.27 (s, 2H, CH2), 6.93 (d, 2H, J = 8.4 Hz, Ph-H), 7.23 (d, 2H, J = 8.0 Hz, Ph-H), 8.45 (s, 1H, NH). ESI-MS m/z: 401.0
(M+Clꢀ). 7m: Yield, 55%; White crystal; mp 173ꢀ175 8C; 1H NMR (CDCl3, 400 MHz): d 1.63 (s, 9H, t-Bu), 2.80 (s, 3H, thiadiazol-CH3),
7.34 (d, 1H, J = 8.8 Hz, pyridine-H), 7.81 (q, 1H, J = 8.4 Hz, pyridine-H), 8.60 (d, 1H, J = 2.4 Hz, pyridine-H), 9.27 (s, 1H, NH). 7n: Yield,
48%; White crystal; mp 204ꢀ206 8C; 1H NMR (CDCl3, 400 MHz): d 1.64 (s, 9H, t-Bu), 2.79 (s, 3H, thiadiazol-CH3), 6.45 (q, 1H, J = 3.6 Hz,
furan-H), 7.00 (d, 1H, J = 3.6 Hz, furan-H), 7.45 (s, 1H, furan-H), 8.61 (s, 1H, NH). ESI-MS m/z: 343.0 (M+Clꢀ). 7o: Yield, 52%; Light yellow
crystal; mp 208ꢀ210 8C; 1H NMR (CDCl3, 400 MHz): d 1.64 (s, 9H, t-Bu), 2.78 (s, 3H, thiadiazol-CH3), 7.02 (t, 1H, J = 4.4 Hz, thiophene-H),
7.42 (d, 1H, J = 3.2 Hz, thiophene-H), 7.48 (d, 1H, J = 4.8 Hz, thiophene-H), 8.58 (s, 1H, NH). ESI-MS m/z: 403.1 (M+Clꢀ). 7p: Yield, 38%;
1
Pale yellow crystal; mp 197ꢀ199 8C; H NMR (CDCl3, 400 MHz): d 1.71 (s, 9H, t-Bu), 2.84 (s, 3H, thiadiazol-CH3), 7.10ꢀ7.19 (m, 7H,
naphthalene-H), 8.61 (s, 1H, NH). ESI-MS m/z (%): 403.1 (M+Clꢀ).