Synthesis
General procedure for the synthesis of N-(5-chloro-2-pyridinyl)-5-methoxy-2-nitrobenzamide from N-(5-chloro-2-pyridinyl)-5-methoxy-2-aminobenzamide: N-(5-chloro-2-pyridinyl)-5-methoxy-2-nitrobenzamide (30 g, 1.0 eq.) was suspended in methanol (300 ml, 10 v/v) and added with ferric chloride (1.58 g, 0.1 eq.) and heated to reflux. Subsequently, hydrazine hydrate (80%, 24.4 g, 4.0 eq.) was slowly added dropwise and the reaction was kept under reflux conditions for 6 hours. The reaction was monitored by HPLC until the peak area of the feedstock was less than 0.3%. After completion of the reaction, most of the solvent was removed by concentration under reduced pressure and cooled to room temperature. Ethyl acetate was added and stirred for 1 hour. The organic phase was washed sequentially with water and saturated brine, separated and dried over anhydrous sodium sulfate. Finally, concentrated to dryness under reduced pressure to obtain a light yellow solid product. The purity of the product was greater than 98% and the yield was 93%.
References
[1] Patent: CN108586325, 2018, A. Location in patent: Paragraph 0021; 0030-0036
[2] Patent: US2007/112039, 2007, A1. Location in patent: Page/Page column 10-11
[3] Patent: WO2008/57972, 2008, A1. Location in patent: Page/Page column 32-33; 45-46
[4] Patent: US2008/153876, 2008, A1. Location in patent: Page/Page column 24-25
[5] Patent: WO2011/84519, 2011, A1. Location in patent: Page/Page column 38-39
