反应详情

A reaction vessel charged with 0.5 gram (0.03 mole) of 3,4-dihydro-7-fluoro-4-hydroxy-2H-1-benzopyran and 0.02 gram (catalyst) of p-toluenesulfonic acid in 50 mL of toluene was fitted with a Soxhlet extractor containing molecular sieves (3-4 angstrom). The stirred contents of the reaction vessel was heated at reflux for 90 minutes, during which time the water by-product was collected on the molecular sieves. The reaction mixture was combined with the reaction mixture of another preparation of this compound and concentrated under reduced pressure to a residue. The residue was subjected to column chromatography on silica gel, with 1:9 ethyl acetate:hexane as the eluant. The product-containing fractions were combined and concentrated under reduced pressure, yielding 0.6 gram of 7-fluoro-2H-1-benzopyran. The NMR spectrum was consistent with the proposed structure. This reaction was repeated several times.

1. customwas fitted with a Soxhlet extractor
2. additioncontaining molecular sieves (3-4 angstrom)
3. temperatureThe stirred contents of the reaction vessel was heated
4. customwas collected on the molecular sieves
5. additionThe reaction mixture was combined with the reaction mixture of another preparation of this compound
6. concentrationconcentrated under reduced pressure to a residue
7. concentrationconcentrated under reduced pressure