5198-87-8

The general procedure for the synthesis of 2-chloro-1,3-thiazole-4-carboxylic acid from ethyl 2-chlorothiazole-4-carboxylate was as follows: 14.0 g (73.1 mmol) of ethyl 2-chlorothiazole-4-carboxylate was slowly added to 11.0 g (0.17 mol, 85% purity) of potassium hydroxide in a solution of ethanol/water (1:3, 200 mL), keeping the reaction temperature at 0 °C. The reaction mixture was stirred at room temperature for 16 hours before being diluted with water and washed twice with ether. Subsequently, the aqueous layer was acidified to pH=5.5 with concentrated hydrochloric acid and stirring was continued at room temperature for three days. The precipitate formed was collected by filtration and dried under vacuum at 40°C to give 7.0 g (56% yield, 95% purity) of 2-chloro-1,3-thiazole-4-carboxylic acid as a brown solid product.

[1] Patent: WO2011/3796, 2011, A1. Location in patent: Page/Page column 126; 127
[2] Helvetica Chimica Acta, 1944, vol. 27, p. 1432,1433
[3] Patent: US5498630, 1996, A
[4] Patent: WO2007/146066, 2007, A2. Location in patent: Page/Page column 152