Abstract

The Doebner reaction is the chemical reaction of an aniline with an aldehyde and pyruvic acid to form quinoline-4-carboxylic acids. Although Doebner reaction is a simple procedure for synthesis of 4-carboxyquinolines, which the product precipitates from the reaction mixtures with high purity, its yield is not high due to the formation of different reaction by-products. In the present study we found a new by-product (2-methylquinoline-4-carboxilic acid derivative), in Doebner reaction. We synthesized new 2-methylquinoline-4-carboxilic acid derivatives simply by stirring pyruvic acid and aromatic amine in ethanol with high purity. Generally, we found that aniline derivatives possessing electron donating groups are needed for the synthesis of 2-methylquinoline-4-carboxilic acid derivatives in ethanol. ¹H-NMR data of products revealed that this reaction is regioseletive and ring closure occurs on the position with less steric hindrance. The order of mixing of the reactants plays a key role in determining the type of products in the Doebner reaction.

摘要

Doebner 反应是苯胺与醛和丙酮酸形成喹啉-4-羧酸的化学反应。虽然Doebner反应是合成4-羧基喹啉的简单方法，其产物从反应混合物中析出，纯度高，但由于形成不同的反应副产物，其产率不高。在本研究中，我们在 Doebner 反应中发现了一种新的副产物（2-甲基喹啉-4-羧酸衍生物）。我们通过简单地在乙醇中搅拌丙酮酸和芳香胺，合成了新的 2-甲基喹啉-4-羧酸衍生物，纯度高。通常，我们发现在乙醇中合成 2-甲基喹啉-4-羧酸衍生物需要具有给电子基团的苯胺衍生物。¹产物的 H-NMR 数据表明该反应是区域选择性的，并且在空间位阻较小的位置发生闭环。反应物的混合顺序在决定 Doebner 反应中的产物类型方面起着关键作用。