尿素法:将次氯酸钠与氢氧化钠按一定比例混合配成溶液,边搅拌边加入尿素与少量高锰酸钾的混合液,直接通蒸汽加热至103~104℃进行氧化反应。反应液中含肼量20g/L,经蒸馏、真空浓缩制得40%水合肼,再经烧碱脱水、减压蒸馏,制得80%水合肼。
氨法:以氨水及次氯酸钠为原料。氨水中加入0.1%骨胶,抑制肼的过度分解。将次氯酸钠按氨与次氯酸钠摩尔比值为(50~60)∶1迅速加入氨水中,在强烈搅拌下于常压或高压下进行氧化反应,先生成氯胺,后继续反应生成肼。反应液经蒸馏回收氨,再经真空蒸馏除去氯化钠及氢氧化钠,蒸发气体冷凝为低浓度肼,再分馏制得不同浓度水合肼。
注意事项:水合肼的热蒸汽与空气接触会引起爆炸,因此包括蒸馏水合肼在内的实验应在氮气流中进行。其蒸气对眼睛、皮肤和呼吸道有刺激作用,应于通风橱内操作。将100g硫酸水合肼和等质量的KOH粉末放入蒸馏烧瓶中,加入5mL水,在通氮气的情况下加热反应至完全。所得水合肼含有水分,可通过分馏除去。
In this study, the synthesis of N-alkyl-3-(indol-3-yl)pyrazoles was carried out from Ag2CO3 catalyzed regioselective aza-Michael addition of 5-(indol-3-yl)-1H-pyrazoles to a, bunsaturated carbonyl compounds. In the presence of 10 mol% of Ag2CO3, the reaction smoothly occurred in dichloroethane (DCE) at 120oC to preferentially afford a series of N-alkyl-3-(indol-3- yl)pyrazoles in high yields with good regioselectivity. It was found that 1-methyl-3-(3-methyl-1Hpyrazol- 5-yl)-2-phenyl-1H-indole, 1-benzyl-3-(3-methyl-1H-pyrazol-5-yl)-1H-indole, a, b-unsaturated ketone, and a, b-unsaturated amide exclusively gave 3-(pyrazol-3-yl)indoles in good yields. This reaction features high regioselectivity, mild reaction conditions, good substrate scope and yields, and a commercially available catalyst. Meanwhile, the reaction was also proven to be quite practical by the gram-scale synthesis of N-alkyl-3-(indol-3-yl)pyrazoles in excellent yields with good regioselectivity.