Approach to the synthesis of 8-nitroquinoline-2-carboxylic acid in high yield

Abstract

A synthesis of 8-nitroquinoline-2-carboxylic acid was optimized, using the following basic scheme of transformations: 1) nitration of 2-methylquinoline with subsequent separation of a mixture of isomeric 8-nitroand 5-nitro-2-methylquinolines; 2) oxidation of the methyl group in 2-methyl-8-nitroquinoline (including consecutive steps of bromination and hydrolysis in aqueous sulfuric acid). A new method for the separation of isomeric 8-nitroand 5-nitro-2methylquinolines was suggested. The optimal conditions for the final step of hydrolysis were selected, which gave almost quantitative yield of 8-nitroquinoline-2-carboxylic acid.