Process for the preparation of pure 2,3-pyridinedicarboxylic acids of the formula I
1
which are substituted in position 4 and/or 5 and/or 6 by R
1
, where R
1
is hydrogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, C
1
-C
4
alkoxy-C
1
-C
4
alkyl, halogen, hydroxyl or nitro, from quinolines of the formula II
2
in which R
1
is as defined above, and which are substituted in position 6 and/or 7 by R
2
, where R
2
is hydrogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, C
1
-C
4
alkoxy-C
1
-C
4
alkyl, halogen, hydroxyl, nitro or amino, which are reacted in the first step in aqueous sulfuric acid or nitric acid solution with ozone in the ratio of from 1:2 to 1:3 at temperatures from 0 to +50° C., and the resulting peroxide solution is then reacted at temperatures of from +0 to +100° C. in the presence of 0.5-4.0 mol of oxidizing agent per mole of ozonolysis product formed, after which the pH of the reaction solution is adjusted to 0.2 to 3, the mixture is cooled to 0 to 30° C., and the precipitated pyridinedicarboxylic acid is isolated.
式 I 的纯 2,3-
吡啶二
羧酸的制备工艺
1
其中第 4 和/或 5 和/或 6 位被 R
1
其中 R
1
是氢、C
1
-C
4
烷基
1
-C
4
烷氧基、C
1
-C
4
烷氧基-C
1
-C
4
烷基、卤素、羟基或硝基,从式 II 的
喹啉中提取
2
其中 R
1
如上定义,且在第 6 和/或 7 位被 R
2
其中 R
2
是氢、C
1
-C
4
烷基
1
-C
4
烷氧基、C
1
-C
4
烷氧基-C
1
-C
4
烷基、卤素、羟基、硝基或
氨基,第一步在
硫酸或
硝酸水溶液中以 1:2 至 1:3 的比例在 0 至 50 摄氏度的温度下与
臭氧反应、然后,在每摩尔
臭氧分解产物中加入 0.5-4.0 摩尔氧化剂的情况下,在 0 至 100 摄氏度的温度下对生成的过氧化物溶液进行反应,之后将反应溶液的 pH 值调节至 0.2 至 3,将混合物冷却至 0 至 30 摄氏度,分离出沉淀的
吡啶二
羧酸。