反应详情

35.0 g. (0.25 mole) of 5-acetyl-6-methyl -3,4-dihydro-2H-pyrane prepared according to Example 21 are added dropwise into 250 ml. of a 33% solution of of hydrogen bromide in acetic acid, at room temperature, under stirring. The mixture is refluxed for 4 hours, with stirring. After cooling it is poured into 1 kg. of ice water and is then extracted with three 100-ml. portions of chloroform. The combined chloroform solution is washed subsequently with three 50-ml. portions of water, three 50-ml. portions of a 5% aqueous sodium bicarbonate solution and two 50-ml. portions of water, dried over solid anhydrous magnesium sulfate, decoloured with activated carbon and evaporated. The product obtained is purified by fractionated distillation on a short Wigreux column, in vacuum.

1. additionare added dropwise into 250 ml
2. temperatureThe mixture is refluxed for 4 hours
3. temperatureAfter cooling it
4. additionis poured into 1 kg
5. extractionof ice water and is then extracted with three 100-ml
6. washThe combined chloroform solution is washed subsequently with three 50-ml
7. dry with materialportions of water, dried over solid anhydrous magnesium sulfate
8. customevaporated
9. customThe product obtained
10. distillationis purified by fractionated distillation on a short Wigreux column, in vacuum