56000-35-2

4755-77-5

62135-58-4

The general procedure for the synthesis of ethyl [1,2,4]triazolo[1,5-a]pyridine-2-carboxylate from ethyl [1,2,4]triazolo[1,5-a]pyridine-2-carboxylate using 2,4-trimethylbenzenesulfonate 1,2-diaminopyridinium (10.9 g, 35.2 mmol) and ethyl monooxynitrate of oxalyl chloride (9.62 g, 7.84 mL, 70.5 mmol) was as follows: at room temperature, ethyl monooxynitrate of oxalyl chloride was added slowly to a light red solution of 2,4-trimethyl benzenesulfonic acid 1,2-diaminopyridinium pyridine (50 mL) in a light red solution, noting that the reaction is exothermic. The color of the solution changed from light red to dark red. Subsequently, the reaction mixture was heated to 100 °C with continuous stirring overnight. After completion of the reaction, the solvent was removed by evaporation and the black residue obtained was ground with saturated aqueous sodium carbonate solution (300 mL) for 30 minutes. The reaction mixture was extracted with dichloromethane (4 x 250 mL), the organic layers were combined and dried with anhydrous magnesium sulfate. After drying, the organic phase was concentrated in vacuum to give 6.64 g of crude product. The crude product was suspended in ether (30 mL), filtered and washed with ether. The resulting precipitate was dried under vacuum to give the light brown solid product ethyl [1,2,4]triazolo[1,5-a]pyridine-2-carboxylate (6.1 g, 31.9 mmol, 90.6% yield). Mass spectral analysis showed M = 192.2 (M + H)+.