Coumarin-3-carboxylic acids were obtained in high yields with excellent purity from ortho-hydroxybenzaldehydes and Meldrum's acid after a 2 h reflux in ethanol. The less reactive ketones were first reacted with alcoholic ammonia to form ketimines, which were then condensed with Meldrum's acid to generate 4-alkylcoumarin-3-carboxylic acids in moderate yields.
在
乙醇中回流2小时后,从邻羟基
苯甲醛和Meldrum酸以高收率获得了
香豆素-3-
羧酸。反应性较低的酮首先与
乙醇氨反应形成酮
亚胺,然后与Meldrum's酸缩合以生成中等收率的4-烷基
香豆素-3-
羧酸。