A new route to synthesis of 3,6-diaryl-1,2,4-triazolo[3,4-b]1,3,4- oxadiazoles

Article abstract of DOI:10.1002/jccs.200400195

Five new 3,6-diaryl-1,2,4-triazolo[3,4-b]1,3,4-oxadiazole derivatives were synthesized by 9 steps from aromatic acids and evaluated for their activities of anticancer and antibacteria. The structures of all new compounds synthesized were elucidated by MS,

Full text of DOI:10.1002/jccs.200400195

Journal of the Chinese Chemical Society, 2004, 51, 1343-1346
1343
A New Route to Synthesis of
3,6-Diaryl-1,2,4-triazolo[3,4-b]1,3,4-oxadiazoles
Zao-Zao Qiu (
), Chao-Feng Dai (
), Shu-Jun Chao (
),
Peng-Fei Xu* (
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
) and Zi-Yi Zhang (
)
Five new 3,6-diaryl-1,2,4-triazolo[3,4-b]1,3,4-oxadiazole derivatives were synthesized by 9 steps from
aromatic acids and evaluated for their activities of anticancer and antibacteria. The structures of all new com-
pounds synthesized were elucidated by MS, IR, 1HNMR and HRMS.
Keywords: 1,2,4-Triaole; 1,2,4-Triazolo[3,4-b]1,3,4-oxadiazoles; Anticancer and antibacterial test.
INTRODUCTION
Various 1,2,4-triazoles and 1,3,4-thiadiazoles have been
acted with carbon disulfide and potassium hydroxide in boil-
ing ethanol to yield oxadiazole (4). Compound 4 was methyl-
ated in aqueous sodium hydroxide using dimethyl sulfate to
get methyl sulfide (5), then oxidized by potassium permanga-
nate in glacial acetic acid to afford sulfonate (6). Treatment
of compound 6 with hydrazine hydrate in dioxane and ether
afforded 2-hydrazino-oxadiazoles (7). Compound 7 reacted
with acyl chloride to get compound 8. On treatment with
phosphorus oxychloride under refluxing for 5~10 min, the
desired compounds, 1,2,4-triazolo[3,4-b]1,3,4-thiadiazole
derivatives (9) (Scheme I), were yielded.
reported to possess diverse biological activities such as anti-
microbial, insecticidal, herbicidal, and plant growth regula-
tive effects.1-4 In addition to the above biological activities
1,2,4-triazolo[3,4-b]1,3,4-thiadiazole derivatives obtained
by coupling these two bioactive rings together had strong
CNS depressant, mild hypocholesterolemia, and hypotensive
properties.5,6 Some 3,6-disubstituented-1,2,4-triazolo[3,4-
b]1,3,4-thiadiazole derivatives showed anti-HIV-1 activity at
concentrations slightly below cytotoxic levels.7
In the process of preparing compound 9, it is important
to select a suitable refluxing time. It was choosen by such a
method of compound 8 100 mg was added into 4 mL phos-
phorus oxychloride, then stirred and refluxed. After the mix-
ture began to reflux, about 0.3 mL solution was taken out
from the mixture by injector per minute to follow this reac-
tion. The mixture of solution was dropped into 20 g crushed
ice with hard stirring to yield some white or pale yellow sol-
ids. These solids were filtered, washed with water and dis-
solved in THF. We found a suitable time of 5~10 minutes for
this reaction by TLC plate.
1,3,4-Oxadiazole derivatives display quite a broad
spectrum of biological activities too, such as HIV-activity,8
antifungal capability,9 antibacterial,10 plant growth promoter
activities11 and herbicidal effects.12 We thought of coupling
1,2,4-triazoles and 1,3,4-oxadiazoles together and screening
the biological activity of these fused heterocycles.
This ring system was first reported in 196113 and syn-
thesized in 1971.14 There are only a few reports on the synthe-
sis and biological activity research of this ring system due to
the instability of this ring system in acidic and basic condi-
tions, as well as the difficulty of preparing them. Here we
present a new and useful synthesis route and have synthe-
sized five new 1,2,4-triazolo[3,4-b]1,3,4-oxadiazole deriva-
tives.
Compounds 9a~e were screened for their anticancer
and antibacterial activities by testing their inhibitory rate
against cdc25 and eMetAP but no efficient activity was
found.
RESULTS AND DISCUSSION
EXPERIMENTAL
Aromatic acids (1) were esterified to get esters (2) and
All reagents of AR grade were used without purifica-
then hydrazinolysised to give aroylhydrazides (3), which re-
tion. The melting points were determined on a Yanaco MP

1344 J. Chin. Chem. Soc., Vol. 51, No. 6, 2004
Qiu et al.
Scheme I
NH2NH2
H2O
H2SO4
RCOOEt
RCONHNH2
+
EtOH
RCOOH
2
3
1
N
N
N
N
N
(CH3O)2SO2
NaOH
CS2 / KOH, EtOH
reflux
R
SCH3
R
SH
O
O
4
5
N
N
N
NH2NH2
H2O
KMnO4
HOAc
dioxane/ether
R
SO2CH3
R
NHNH2
O
O
7
6
R'
O
R'
N
N
N
O
POCl3
R'COCl
R
Py
N
N
R
NH
O
N
N
H
8
9
1~7 a: R = 4-Br-Ph; b: R = 4-Cl-Ph; c: R = 4-Cl-Ph; d: R = 4-Br-Ph; e: R = Ph
8~9 a: R = 4-Br-Ph, R¢ = Ph; b: R = 4-Cl-Ph, R¢ = 2-Cl-Ph; c: R = 4-Cl-Ph, R¢ = Ph;
d: R = 4-Br-Ph, R¢ = 2-Cl-Ph; e: R = Ph, R¢ = 2-Cl-Ph
Table 1. Inhibition effect of cdc25 and eMetAP by compounds
Preparation of 2-methylsulfonyl-5-aryl-[1,3,4]-oxadiazoles
(6)
9a~e
eMetAP
Dimethyl sulfate (0.1 mol) was added dropwise to a so-
lution of 4 (0.1 mol) in aqueous NaOH (1 M, 200 mL) with
stirring at room temperature for 6 h. The precipitate was fil-
tered, washed with water and recrystallized from ethanol to
give compound 5. To a solution of compound 5 (0.1 mol) in
150 mL glacial acetic acid, 30 g KMnO4 dissolved in 300 mL
water was added slowly. This procedure would last about 1 h.
After KMnO4 was added over, the resulting suspended solid
was stirred for 6 h, cooled to 0 °C and reduced by NaHSO3.
The precipitate was filtered, washed with water, dried and
recrystallized from ethanol to get compound 6. The melting
points of the compounds synthesized here were the same as
those in the literature.17
cdc25
Compd.
(%, C = 250 mM)
(%, C = 500 mM) (%, C = 50 mM)
9a
9b
9c
9d
9e
77.1
6.1
37.7
0
*
36.1
*
90.5
89.4
3.0
-
2.1
30.2
17.9
0
* Not tested because some solid precipitated.
microscropic melting point apparatus and are uncorrected.
Elemental analysis was carried out on a Vario E1 Elementar.
IR spectra were obtained in KBr discs on a Nicolet AVATA
360FT-IR spectrometer. Mass spectra were performed on a
1
HP-5988A spectrometer (EI at 70 ev). H NMR spectra
Preparation of 2-hydrazino-5-aryl-[1,3,4]-oxadiazoles (7)
To a solution of compound 6 (50 mmol) in 50 mL
dioxane and 30 mL ether, 5 equiv. of hydrazine hydrate (85%)
was added with stirring in an ice bath. After 0.5 h there is lots
of white precipitate in this solution which was stirred for an-
other 4 h and filtered. The solid was washed with water and
dried. It needed no futher purification and could be used in
(CDCl3 or DMSO-d6) were recorded on a FT-Ac200M or
FT-Ac80M instrument at room temperature with TMS as an
internal standard. HRMS were run on a FT-ICRMS APEXII
47e spectrometer.
Phosphorus oxychloride was redistilled (b.p. 105 °C).
Compounds 2, 3, and 4 were prepared according to the meth-
ods in the literature.15-16

3,6-Diaryl-1,2,4-triazolo[3,4-b]1,3,4-oxadiazoles
J. Chin. Chem. Soc., Vol. 51, No. 6, 2004 1345
stirring. The solid was filtered and washed with water then
purified by column chromatography using PE-EA (4:1 v/v)
as an eluant to furnish compound 9.
9a Yield 71%; mp 162~164 °C. 1H NMR (DMSO-d6): d
7.53~8.20 (m, 9H). MS: 340 (M+, 26), 342 (28), 215 (37), 217
(37), 181 (27), 183 (31), 102 (31), 103 (32), 105 (14), 77 (32),
36 (100). IR: 1578, 1537, 1467, 1450, 1068, 1044. HRMS
(M+H): 341.0031 (341.0033).
the next step directly.
Preparation of 2-acylhydrazino-5-aryl-[1,3,4]-oxadiazoles
(8)
Acyl chloride (10 mmol) was added dropwise to a mix-
ture of compound 7 (10 mmol) and 10 mL dried pyridine. The
solution was stirred for 0.5 h with an ice bath, and then stirred
at room temperature for 4 h. After the solvent was distilled
under reduced pressure, the residue was poured in 200 mL
water. The precipitate was filtered, washed with water, and
recrystallized from ethanol to give compound 8.
8a Yield 90%; mp 198~200 °C. 1H NMR (DMSO-d6): d
7.51~7.96 (m, 9H), 10.05 (s, 1H), 10.89 (s, 0.4H), 10.97 (s,
0.6H). MS: 358 (M+, 16), 360 (16), 183 (39), 185 (36), 155
(12), 157 (11), 105 (100), 77 (40). IR: 3211, 3040, 1676,
1625. Anal. Calcd. for C15H11N4O2Br: C, 50.16; H, 3.09; N,
15.60; Found: C, 50.11; H, 3.09; N, 15.60.
8b Yield 92%; mp 156~159 °C. 1H NMR (DMSO-d6): d
7.46~7.93 (m, 8H), 10.11 (s, 0.4H), 10.21 (s, 0.6H), 10.81 (s,
0.6H), 10.96 (s, 0.4H). MS: 348 (M+, 13), 350 (7), 313 (2),
179 (4), 139 (100), 141 (33), 111 (29), 113 (9), 75 (16). IR:
3188, 3011, 1675, 1621. Anal. Calcd. for C15H10N4O2Cl2: C,
51.60; H, 2.89; N, 16.05; Found: C, 51.55; H, 2.93; N, 15.96.
9b Yield 65%; mp 214~216 °C. 1H NMR (DMSO-d6): d
7.54~8.19 (m, 8H). MS: 330 (M+, 9), 332 (4), 137 (100), 139
(37), 102 (39), 75 (28). IR: 1583, 1548, 1472, 1426, 1088,
1017, 955, 823, 721. HRMS (M+H): 331.0150 (331.0148).
1
9c Yield 60%; mp 192~194 °C. H NMR (CDCl3): d
7.52~8.28 (m, 9H). MS: 296 (M+, 49), 298 (16), 137 (84), 139
(35), 103 (100), 76 (32). IR: 1582, 1541, 1480, 1456, 1090,
1046, 955, 838, 718. HRMS (M+H): 297.0536 (297.0538).
9d Yield 62%; mp 171~173 °C. 1H NMR (DMSO-d6): d
7.41~8.29 (m, 8H). MS: 374 (M+, 14), 376 (18), 183 (81), 181
(84), 137 (44), 139 (25), 102 (100), 75 (43). IR: 1585, 1545,
1481, 1458, 1071, 1034, 944, 829, 731. HRMS (M+H):
374.9638 (374.9643).
1
9e Yield 58%; mp 165~167 °C. H NMR (CDCl3): d
7.48~8.00 (m, 9H). MS: 296 (M+, 35), 298 (11), 261 (4), 137
(100), 139 (75), 103 (98), 76 (33). IR: 1548, 1539, 1468,
1443, 1061, 1030, 946, 759, 684. HRMS (M+H): 297.0533
(297.0538).
1
8c Yield 86%; mp 216~218 °C. H NMR (CDCl3): d
7.45~7.96 (m, 9H), 10.10 (s, 0.6H), 10.20 (s, 0.4H), 10.83 (s,
0.6H), 10.98 (s, 0.4H). MS: 314 (M+, 8), 316 (3), 139 (74),
141 (23), 111 (33), 113 (10), 105 (100), 77 (77), 75 (26). IR:
3210, 3028, 1675, 1602. Anal. Calcd. for C15H11N4O2Cl: C,
57.24; H, 3.52; N, 17.80; Found: C, 57.13; H, 3.52; N, 17.89.
8d Yield 89%; mp 155~157 °C. 1H NMR (DMSO-d6): d
7.48~7.85 (m, 8H), 10.10 (s, 0.6H), 10.19 (s, 0.4H), 10.79 (s,
0.4H), 10.94 (s, 0.6H). MS: 392 (M+, 2), 394 (3), 357 (1), 359
(1), 196 (3), 198 (3), 183 (23), 185 (19), 139 (100), 141 (28),
111 (19), 75 (18). IR: 3184, 3010, 1675, 1621. Anal. Calcd.
for C15H10N4O2BrCl: C, 45.77; H, 2.56; N, 14.23; Found: C,
45.58; H, 2.50; N, 14.15.
Bioactivity Test
Cdc25 Inhibition Assay
cdc25s phosphate can resolve the phosphate of fluores-
cent substrate OMFP. Excitation wavelength was 485 nm;
emission was monitored at 530 nm. The reaction time was in
proportion to the enhancement of absorbance. Then reaction
beginning speed of enzyme can be tested by the slope of
absorbance enhancement line.18
8e Yield 90%; mp 148~150 °C. 1H NMR (DMSO-d6): d
7.44~7.97 (m, 9H), 10.07 (s, 0.3H), 10.14 (s, 0.7H), 10.79 (s,
0.7H), 10.86 (s, 0.3H). MS: 314 (M+, 8), 316 (3), 279 (2), 139
(100), 141 (29), 111 (23), 105 (40), 77 (25). IR: 3186, 2975,
1701, 1618. Anal. Calcd. for C15H11N4O2Cl: C, 57.24; H,
3.52; N, 17.80; Found: C, 57.18; H, 3.57; N, 17.69.
eMetAP Activity Assay
eMetAP can hydrolysis the thiopeptolide bond of the
Met-S-C-Phe substrate. The product of Met-SH reacts quickly
with excessive DTNB; the 3-hydroxy-4-nitro-thiophenolate
that was generated has an absorbance at 412 nm. We can de-
termine the activity of enzyme by examining the absorbance
change.19
Synthesis of 3,6-dialkyl-1,2,4-triazolo[3,4-b]1,3,4-oxa-
diazoles (9)
ACKNOWLEDGEMENT
A mixture of 1 mmol compound 8 and 5 mL phosphorus
oxychloride was heated to reflux for 5~10 min. The cooled
reaction mixture was poured into 200 g crushed ice with hard
We gratefully acknowledge the Shanghai Institute of

1346 J. Chin. Chem. Soc., Vol. 51, No. 6, 2004
Qiu et al.
7. Paolo, F.; Daniele, S.; Franca, S.; Noemi, P. Farmaco. 1996,
51, 659.
8. Eissa, A. A. H. Bull. Fac. Pharm. 1998, 36, 99.
9. El-Deen, I. M. Pak. J. Sci. Ind. Res. 1993, 35, 261.
10. Zhang, Y.; Qiao, R. Z.; Xu, P. F.; Zhang Z. Y. J. Chin. Chem.
Soc. (Taipei) 2002, 49, 369.
Materia and Medica of the Chinese Academy of Sciences for
the bioactivity test. And we are thankful for the financial sup-
port from the National Nature Science Foundation of the PRC
(No. 20372027) and Gansu Provincial Science Foundation
for middle-young teachers (No. ys-011-A25-001).
11. Zhang, Z. Y.; Feng, X. M.; Liu, H. X. Youji Huaxue. 1989, 9,
355.
Received January 8, 2004.
12. Feng, X. M.; Chen, R.; Cai, S. Y. Org. Prep. Proced. Int.
1992, 24, 492.
13. Potts, K. T. Chem. Rev. 1961, 61, 87.
14. Scott, F. L.; Lambe, T. M.; Butler, R. N. Tetrahedron. Lett,
1971, 1729.
REFERENCES
15. Zhang, Z. Y.; Li, M.; Zhao, L. Youji Huaxue, 1993, 13, 397.
16. Reid, J. R.; Heindel, N. D. J. Heterocyclic Chem. 1976, 13,
925.
17. Madhavan, R.; Srinivasan, V. R. Indian J. Chem. 1969, 7,
760.
18. Hairuo, P.; Wenge, X.; Diane, M. O.; John, P. C.; Randy, T.
M.; Luke, C. H.; Garth, P.; Robert, T. A.; Leon, H. Z. J. Med.
Chem. 2001, 44, 834.
19. Luo, Q. L.; Li, J. Y.; Liu, Z. Y.; Chen, L. L.; Li, J.; Qian, Z.;
Shen, Q.; Li, Y.; Gerald, H. L.; Ye, Q. Z.; Nan, F. J. J. Med.
Chem. 2003, 46, 2631.
1. Eweiss, N. F.; Bahajaj, A. A.; Elsherbini, E. A. J. Hetero-
cyclic Chem. 1986, 23, 1451.
2. Sen Cupta, A. K.; Misra, H. K. Indian J. Chem. 1979, 17B,
185.
3. Booth, D. L.; Rodebaugh, R. M. U.S. 4283543 Chem. Abs.
1981, 95, 187269w.
4. Zhang, L. X.; Zhang, Z. Y. Chem. J. Chin. Univ. 1989, 5,
147.
5. Mody, M. K.; Prasad, A. R.; Ramalingam. T.; Sattur, P. B. J.
Indian Chem. Soc. 1982, 59, 769.
6. Zhang, Z. Y.; Sun, X. W. Heterocycles. 1998, 48, 561.