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Metal-Free Synthesis of 1,2,4-Triazines via a Coupled Domino Process in One-Pot

[ Vol. 21 , Issue. 2 ]

Author(s):

Jing Wang, Dong Tang, Zhuo-Mei Li, Ping Wu, Xu Meng, Ya-Feng Liu, Guo-Qiang Lu and Bao-Hua Chen   Pages 183 - 188 ( 6 )

Abstract:


Background: 1,2,4-Triazine is a prominent structural core system present in numerous natural and synthetic biologically active compounds. The existing synthetic methodologies have mostly focused on 3,6- disubstituted-1,2,4-triazines and 3,5,6-trisubstituted-1,2,4-triazines. However, until now only a few methods have been developed for making 3,5-disubstituted-1,2,4-triazines.

Objective: The primary objective of the study was to find an efficient and simple way to construct 3,5- disubstituted-1,2,4-triazines.

Method: The arylethene (0.24 mmol), I2 (0.22 mmol), IBX(0.24mmol.) and DMSO (2 mL) were added to a round-bottomed flask equipped with a magnetic stirring bar. The reaction mixture was agitated at 110°C under air for 3h, then amidrazone (0.2 mmol) was added to the mixture and the reaction continued at 110°C for another 1.5h. Afterwards, water (20mL) was added and the reaction mixture was extracted with ethyl acetate (3 × 50mL). The organic phases was combined and concentrated under reduced pressure to distill ethyl acetate. The residue was further purified by column chromatography on a silica gel column with petroleum / ethyl acetate (5:1) as eluent to obtain the desired products.

Results: We developed an operationally simple way of regioselectively synthesizing 3,5-disubstituted-1,2,4- triazines by a coupled domino strategy with terminal aryl alkenes and amidrazones in one-pot. The overall process involves three different reactions: iodination, Kornblum oxidation and condensation.

Conclusion: The strategies exhibit high performance with moderate to high yields, using simple and readily available terminal aryl alkenes and amidrazones, representing a powerful tool for the formation of potentially biologically active derivatives.

Keywords:

1, 2, 4-Triazines, domino strategy, aryl alkenes, amidrazones, Kornblum oxidation, metal-free.

Affiliation:

State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Gansu Lanzhou, 730000, P. R. China, and Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou, 730000, P. R. China.

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