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以邻甲基苯胺(2)为起始原料,经Sandmeyer法合成7-甲基靛红(4)。4在β-环糊精(β-CD)的催化下与氨基硫脲在水中经环合制得6-甲基-5H-1,2,4-三嗪并[5,6-b]吲哚-3-硫醇(5);后处理简便,β-CD经过滤回收可重复利用,收率也由文献的<30%增至77.9%。再以异丙醇代替毒性较大的水合肼为溶剂,回流条件下5与水合肼反应,反应完毕,直接冷却即可析出纯度较高(93.8%)的3-肼基-6-甲基-5H-1,2,4-三嗪并[5,6-b]吲哚(6)。以异丙醇代替水为溶剂,在乙酸催化下使6与2-乙酰吡啶(7)反应,粗品经乙酸乙酯重结晶,便可得纯度99.3%的VLX600(1),总收率17.0%(以2计)。
Using o-methylaniline (2) as the starting material, 7-methylisatin (4) was synthesized by Sandmeyer method. 4 was cyclized with thiosemicarbazone in water under the catalysis of β-cyclodextrin (β-CD) to prepare 6-methyl-5H-1,2,4-triazino [5,6-b] 3-mercaptan (5). The post-treatment was simple and the β-CD was recovered by filtration. The yield of β-CD was also increased from <30% to 77.9%. Then the isopropanol instead of the more toxic hydrazine hydrate as the solvent, under reflux conditions 5 and hydrazine hydrate reaction, the reaction is completed, the direct cooling can precipitate higher purity (93.8%) 3-hydrazino-6-methyl- 5H-1,2,4-triazolo [5,6-b] indole (6). Using isopropanol instead of water as solvent, 6 and 2-acetylpyridine (7) were reacted under the catalysis of acetic acid. The crude product was recrystallized from ethyl acetate to obtain VLX600 (1) with purity of 99.3%. The total yield was 17.0% (2).