反应详情

Added to 75 ml of dry benzene were 5.3 g (45 mmol) of methylmalonic acid and 11.4 g (0.135 mmol) of 3,4-dihydropyran, followed by the addition of 1 droplet of concentrated sulfuric acid under stirring over a water bath. After one hour, 6 g of sodium hydroxide were added. After the resultant mixture was stirred for 5 minutes, an insoluble material was filtered off. Then, 1.8 g of 60% sodium hydride was added in small portions to the filtrate. After evolution of hydrogen gas subsided, a solution of the acid chloride, which had been prepared from 6.5 g (0.04 mol) of 2,1-benzisoxazole-3-carboxylic acid prepared above in the procedure (1) and 30 ml of thionyl chloride in benzene, was added dropwise under ice cooling. After the resultant solution was stirred for 2 hours at room temperature, 6 ml of acetic acid were added, followed by heating under reflux for 8 hours. After ice cooling, water was added and the reaction product was extracted with ethyl acetate. The extract was purified by silica gel chromatography (eluent: 30:1 n-hexane/ethyl acetate), so that 3-propionyl-2,1-benzisoxazole was obtained as colorless crystals.

1. filtrationan insoluble material was filtered off
2. additionThen, 1.8 g of 60% sodium hydride was added in small portions to the filtrate
3. additionwas added dropwise under ice cooling
4. temperatureby heating
5. temperatureunder reflux for 8 hours
6. extractionthe reaction product was extracted with ethyl acetate
7. customThe extract was purified by silica gel chromatography (eluent: 30:1 n-hexane/ethyl acetate), so that 3-propionyl-2,1-benzisoxazole
8. customwas obtained as colorless crystals