Study On Synthesis Of Quinoline-2-carboxylic Acid, Pyridine-2-carboxylic Acid And Their Methyl Esters

Quinoline and pyridine are homoeomorphous heterocyclic compounds. Quinoline, pyridine and their derivatives are all fine chemical products which possess high added value. With the advancement of science and technology and the development of national economy, the application of them is expanding, and the demand for them is increasing in recent years.Quinoline-2-carboxylic acid, quinoline-2-carboxylic acid methyl ester, quinoline -3-carboxylic acid methyl ester, pyridine-2-carboxylic acid and pyridine-2-carboxylic acid methyl ester are four important pyridine derivatives. The synthetic routes of them are studied, and the problems of synthetic routes of quinoline-2-carboxylic acid, quinoline-3-carboxylic acid methyl ester and pyridine-2-carboxylic acid are solved in the paper. Then the synthetic routes of 2-(methoxycarbonyl)quinoline-3-carboxylic acid, 3-(methylcarbamoyl)quinoline-2-carboxylic acid and 2-methyl-1H-pyrrolo[3,4-b]quinoline-l,3(2H)-dione are discussed.Quinoline-2-carboxylic acid was synthesized by reduction reaction of 2-nitroben-zaldehyde and FeSO₄, and then the cyclization hydrolysis reaction with methyl pyruvate. The total yield of reduction reaction was 51.2%, and the total yield of cyclization hydrolysis reaction was 87.3%.Quinoline-3-carboxylic acid methyl ester was synthesized using quinoline-2,3-d-icarboxylic acid as raw material through decarboxylation, chlorization, alcoholysis reactions, and the total yield was 85.6 %. The product was characterized, and the decarboxylation mechanism of the first step reaction was discussed.Pyridine-2-carboxylic acid was synthesized using 2-methylpyridine as raw material in water through oxidation by KMnO₄ and recrystallization by ethanol, and the total yield was 79.7%. Pyridine-2-carboxylic acid methyl ester was synthesized by the esterification reaction of concentrated sulfuric acid-methanol whose yield was 86.1%, and thionyl chloride-methanol whose yield was 80.3% using pyridine-2-carboxylic acid as raw material. These synthetic routes mentioned in this paper are some referential significance for the synthesis of pyridine heterocyclic compounds. Each synthetic route is suitable for industrial production, and shows great industrial value since it is low-cost and easy operation.This paper characterizes all the reaction products and provides the detailed atlas and datas.