反应详情

A mixture of the product from Step A (3.91 g) and p-toluenesulfonic acid (0.2 g) in acetone (150 mL) was heated at reflux temperature for 3 h, cooled and a saturated solution of sodium bicarbonate (50 mL) was added and acetone evaporated. The aqueous mixture was extracted with ethyl acetate (2×10 mL) and the combined extracts were dried (MgSO4) and filtered. DBU (0.3 g) was added to the filtrate and this mixture was heated at reflux temperature for 2 h, cooled and acidified by the addition of 1N HCl. The organic layer was separated, dried (MgSO4) and evaporated to a residue which was purified by column chromatography (silica, 30% ethyl acetate/hexane) to give a viscous oil (1.80 g, 55%).

1. temperaturewas heated
2. temperatureat reflux temperature for 3 h
3. temperaturecooled
4. customacetone evaporated
5. extractionThe aqueous mixture was extracted with ethyl acetate (2×10 mL)
6. dry with materialthe combined extracts were dried (MgSO4)
7. filtrationfiltered
8. additionDBU (0.3 g) was added to the filtrate
9. temperaturethis mixture was heated
10. temperatureat reflux temperature for 2 h
11. temperaturecooled
12. additionacidified by the addition of 1N HCl
13. customThe organic layer was separated
14. dry with materialdried (MgSO4)
15. customevaporated to a residue which
16. customwas purified by column chromatography (silica, 30% ethyl acetate/hexane)