| 摘要 |
1. A process for the preparation of substituted pyridinecarboxylic acids by ozonolysis of quinolines, wherein a quinoline of the formula which is substituted in position 2 and/or 3 and/or 4 by R3, and in position 6 and/or 7 by R4, where R1 and R2 are H or a C1 -C3-alkyl group and R3 and R4 are a group which is inert under the reaction conditions, and at least one of the radicals R1 and R2 is not H, is reacted with ozone in aqueous acidic solution at temperatures of from -5 to +40 degree C, the resulting solution is maintained at a temperature of from 0 to 100 degree C for 0.5 to 15 hours with the introduction of oxygen or air for decomposition of the peroxides formed, and the corresponding substituted pyridinecarboxylic acid of the formula in which R3 is as defined above, and R5 and R6 are OH or C1 to C3-alkyl, where at least one of the radicals R5 and R6 is not OH, is isolated from the reaction mixture. 2. The process as claimed in Claim 1 wherein the quinoline of the formula I used is 8-methylquinoline or 3-ethyl-8-methylquinoline. 3. The process as claimed in Claim 1 wherein the aqueous acidic solution used is an aqueous sulfuric acid, nitric acid or phosphoric acid solution. 4. The process as claimed in Claim 1 wherein the reaction with ozone is carried out at 0 to +10 degree C. 5. The process as claimed in Claim 1 wherein the peroxide decomposition is carried out at 50-70 degree C. 6. The process as claimed in Claim 1 wherein oxygen is introduced in the form of pure oxygen or in the form of air. 7. The process as claimed in Claim 1 wherein the substituted pyridinecarboxylic acid is isolated from the reaction mixture by means of extraction. 8. A use of pyridinecarboxylic acids obtained as claimed in Claim 1 for obtaining herbicides. 9. A use of 2-acetylnicotinic acid obtained as claimed in Claim 1 for obtaining herbicides based on substituted semicarbazones. |
