Aminopyralid

1918-02-1

150114-71-9

General procedure for the synthesis of 4-amino-3,6-dichloropyridine-2-carboxylic acid from 4-amino-3,5,6-trichloropyridine-2-carboxylic acid: 50.8 g of 4-amino-3,5,6-trichloropyridine-2-carboxylic acid was mixed with 500 ml of water, and 66.7 g of 30% sodium hydroxide solution was added homogeneously, and then after filtration the filtrate was transferred to a 1000 ml high-pressure reactor fitted with a magnetic stirrer, a thermometer, and an exhaust pipe. After filtration, the filtrate was transferred to a 1000-mL high-pressure reactor equipped with a magnetic stirrer, thermometer and exhaust pipe. 2 g of 5% Pd/C catalyst was added to the reactor, the reactor was sealed, replaced with nitrogen three times, and then filled with hydrogen to a pressure of 0.2 MPa. Stirring was initiated and the temperature was raised to 50°C, and the pressure was further increased to 0.3 MPa by filling with hydrogen, and the reaction was confirmed to be complete by HPLC after 20 hours, and then cooled down to room temperature. The reaction solution was decanted out, filtered to recover the catalyst, and the filtrate was adjusted to pH 1-2 with 30% hydrochloric acid, cooled to crystallize and centrifuged, and the precipitate was washed with hot water to obtain 38.8 g of 4-amino-3,6-dichloro-pyridine-2-carboxylic acid, with the product purity of 97.5% and the yield of 91.4%.