反应详情

3-Hydroxy-2-methyl-4-pyrone (22.2 g) in methanol (225 ml) is added to aqueous sodium hydroxide (25 ml H2O containing 7.5 g NaOH). Benzyl chloride (25.5 g) is added and the mixture is refluxed for 6 hours and is then allowed to cool overnight. The bulk of the methanol is removed under vacuum and the residue is treated with water (50 ml). The mixture is extracted into dichloromethane (3×25 ml). The extracts are combined, washed with 5% w/v NaOH (2×25 ml), then water (2×25 ml) and dried over magnesium sulphate. Evaporation of the solvent gives crude 3-benzyloxy-2-methyl-4-pyrone (35 g, 92%) which is purified by distillation in nitrogen under reduced pressure to yield a colourless oil (28 g) of b.p. 148° C./0.2 mm.

1. temperaturethe mixture is refluxed for 6 hours
2. temperatureto cool overnight
3. customThe bulk of the methanol is removed under vacuum
4. additionthe residue is treated with water (50 ml)
5. extractionThe mixture is extracted into dichloromethane (3×25 ml)
6. washwashed with 5% w/v NaOH (2×25 ml)
7. dry with materialwater (2×25 ml) and dried over magnesium sulphate
8. customEvaporation of the solvent
9. customgives crude 3-benzyloxy-2-methyl-4-pyrone (35 g, 92%) which
10. distillationis purified by distillation in nitrogen under reduced pressure