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Synlett 2010(12): 1825-1828  
DOI: 10.1055/s-0030-1258105
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Microwave Irradiation for Accelerating Synthesis of [1,2,4]Triazole[4,3-a]-pyrimidines Based on Isoflavones

Zun-Ting Zhang*, Juan Xie, Mu-Lin Zhu, Dong Xue
Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude Drugs in Northwest of China, and School of Chemistry and Materials Science, Shaanxi Normal University, Xi’an 710062, P. R. of China
Fax: +86(29)85303940; e-Mail: zhangzt@snnu.edu.cn;
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Publication History

Received 9 February 2010
Publication Date:
30 June 2010 (online)

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Abstract

Microwave irradiation was used to accelerate the cyclocondensation of isoflavones and 3-amino-1,2,4-triazoles in the presence of sodium methoxide to produce 6,7-diphenyl[1,2,4]-triazolo[4,3-a]pyrimidines in good to moderate yields.

Key words

isoflavone - triazole - [1,2,4]triazolo[4,3-a]pyrimidine - microwave

    References and Notes

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18

6-Phenyl-7-(2-hydroxy-4-isopropoxyphenyl)[1,2,4]-triazolo[4,3- a ]pyrimidine (3a)
Mp 228-230 ˚C. IR (KBr): ν = 3083, 2982, 2679, 2586, 1610, 1504, 1440, 1381, 1292, 1264, 1180, 1115, 989, 921, 846, 791, 757, 703, 652, 573, 506, 461 cm-¹. ¹H NMR (300 MHz, DMSO-d 6): δ = 1.26 (d, J = 5.9 Hz, 6 H), 4.56 (m, 1 H), 6.39 (d, J = 8.2 Hz, 2 H), 7.03 (d, J = 8.2 Hz, 1 H), 7.33 (m, 5 H), 8.60 (s, 1 H), 8.95 (s, 1 H), 9.86 (s, 1 H) ppm.
¹³C NMR (75 MHz, DMSO-d 6): δ = 21.8, 69.4, 102.6, 106.4, 118.7, 125.0, 127.8, 128.3, 129.4, 131.6, 134.4, 144.2, 154.3, 155.5, 155.9, 156.9, 160.2 ppm. MS (EI): m/z (rel intensity) = 369 (62) [M + Na], 347 (100) [M + 1], 305 (66). Anal. Calcd for C20H18N4O2: C, 69.35; H, 5.24; N, 16.17. Found: C, 69.18; H, 5.31; N, 16.25.

19

Representative Procedure for the Preparation of 6-Phenyl-7-(2-hydroxy-4-isopropoxy-phenyl)[1,2,4]-triazolo[4,3- a ]-pyrimidine (3a) and 3-Hydroxy-6-phenyl-7-(2-hydroxy-4-isopropoxyphenyl)[1,2,4]triazolo[4,3- a ]pyrimidine (3s)
The ipriflavone (1a, 1.5 mmol, 420 mg), 2a (2.1 mmol, 118 mg) and NaOMe (4.5 mmol, 3 equiv) were mixed in DMSO (8 mL). The mixture was heated by the microwave irradiation (output 240 W, 100 ˚C) for 10 min. Reaction was monitored by TLC, in which the disappearance of 1a indicated the completeness of reaction. The mixture was added into H2O (30 mL) and adjusted to neutrality with the solution of 5% HCl. Precipitate appeared and was filtered. Finally, 3a (374mg, 72%) was obtained by purifying the precipitate on silica gel column chromatography (PE 60-90-EtOAc = 2:1); 3s was obtained by the same way, except that the equivalent of NaOMe (6.0 mmol, 4 equiv) was different when 2b was instead of 2a.