反应详情

温度

90 °C

To a 3000 mL three-neck round bottom flask equipped with an overhead stirrer, thermo pocket, addition funnel and nitrogen tube was charged toluene (1000 mL), N-formyl piperidine (3.54 g, 0.031 mol) and thionyl chloride (67 g, 0.559 moles) at 23° C. under nitrogen atmosphere. The resultant reaction mass was heated to 82° C. and to this 8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid (100 g, 0.373 moles) (prepared as in WO 2010/129500) was charged lot wise (5 lots) over a period of 60 min. The walls of the reactor were rinsed with 500 mL toluene. After addition, the resultant reaction mass was stirred at 90° C. for 75 min and the progress of the reaction was monitored by HPLC. For this, 0.5 mL of the reaction mass was diluted with 3 mL of methanol and the formation of acid chloride was analyzed indirectly by detecting its corresponding methyl ester by HPLC). After 2 hours, HPLC analysis indicated about 0.35 a % of unreacted 8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid and about 99.0 a % of 8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid methyl ester. The resultant reaction mass was further heated to 140° C. (oil bath temperature) and distilled at about 109° C. (mass temperature) and 105-107° C. (vapor temperature) at atmospheric pressure over a period of 2.5 hours to remove toluene (about 600 mL) and excess thionyl chloride present in the reaction mass. After distillation, the reaction mass was gradually cooled to 30° C. over a period of 60 min. The concentration of 8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid was about 0.07 a % and the concentration of 8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid methyl ester about 99.2 a % as measured by HPLC at 230 nm.

1. customTo a 3000 mL three-neck round bottom flask equipped with an overhead stirrer
2. additionthermo pocket, addition funnel and nitrogen tube
3. customThe resultant reaction mass
4. additionwas charged lot wise (5 lots) over a period of 60 min
5. washThe walls of the reactor were rinsed with 500 mL toluene
6. additionAfter addition
7. customthe resultant reaction mass
8. waitAfter 2 hours
9. customThe resultant reaction mass
10. temperaturewas further heated to 140° C. (oil bath temperature)
11. distillationdistilled at about 109° C. (mass temperature) and 105-107° C. (vapor temperature) at atmospheric pressure over a period of 2.5 hours
12. customto remove toluene (about 600 mL) and excess thionyl chloride present in the reaction mass
13. distillationAfter distillation
14. temperaturethe reaction mass was gradually cooled to 30° C. over a period of 60 min