Due to the electron-withdrawing effect of the nitrogen atom on the ring, electrophilic substitution reactions are generally difficult to occur. However, nucleophilic substitution reactions on the pyridine ring are relatively easy to occur. Taking advantage of this property, a variety of important pyridine compounds can be prepared from 3,4-pyridinedicarboxylic acid and its derivatives. Because they often have good biological activity, they are often used as important raw materials or intermediates for the synthesis of pharmaceuticals and pesticides, playing an important role in the synthesis of pyridine drugs.
white to slightly beige fine crystalline powder
ChEBI: Cinchomeronic acid is a pyridinedicarboxylic acid. It is a conjugate acid of a cinchomeronate(1-).
750 g (5.55 mol) of concentrated sulfuric acid and 1.4 g (0.175 mol) of selenium powder were heated in a four-necked flask equipped with a stirrer, a thermometer, a dropping cylinder, and a large gas outlet tube. Once the temperature reached 275 degrees Celsius, the selenium dissolved in concentrated sulfuric acid. 1 g (0.125 mol) of selenium powder was dissolved in 50 g (0.37 mol) of sulfuric acid, briefly heated to 275 degrees Celsius, cooled to room temperature and then combined with 129.2 g (1 mol) of isoquinoline solution dissolved in 550 g (4.08 mol) of sulfuric acid, and dropped into the sulfuric acid with a dropping cartridge to maintain the temperature of the reaction process at 270-280 degrees Celsius. During implementation, water vapor and sulfur dioxide were passed through a gas discharge tube and extracted through a funnel placed above using a water jet pump. After about 2l /2 hours, the entire solution was added drop by drop and the temperature was maintained between 270 - 280C for another hour. After cooling the mixture to room temperature, 400 ml of water was added and 5 g of activated carbon was added and boiled for a few minutes. The selenium and activated charcoal were filtered off and the cooled orange-yellow solution was carefully adjusted with concentrated ammonia to a pH of 1.5. After standing for a few hours, the precipitate was filtered off and washed with water to obtain 3,4-pyridinedicarboxylic acid.
Crystallise the acid from H2O or dilute aqueous HCl. It has also been purified via the dimethyl ester which is distilled (b 95-100o/1.5mm) and hydrolysed with 3.5N HCl, evaporated and recrystallised. [Armarego & Evans J Appl Chem 12 45 1962, Foye et al. J Med Chem 9 61 1966, Beilstein 22 H 155, 22 I 534, 22 II 106, 22 III/IV 1641, 22/4 V 135.]
