Water → 7-fluoro-2H-chromene
Reaction equation
[F:1][C:2]1[CH:12]=[CH:11][C:5]2[CH:6](O)[CH2:7][CH2:8][O:9][C:4]=2[CH:3]=1.C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C1(C)C=CC=CC=1>[F:1][C:2]1[CH:12]=[CH:11][C:5]2[CH:6]=[CH:7][CH2:8][O:9][C:4]=2[CH:3]=1Participants
Reactant 3
Product 1
Reagents, catalysts & solvents 1
Procedure
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.
Workup
- customwas fitted with a Soxhlet extractor
- additioncontaining molecular sieves (3-4 angstrom)
- temperatureThe stirred contents of the reaction vessel was heated
- customwas collected on the molecular sieves
- additionThe reaction mixture was combined with the reaction mixture of another preparation of this compound
- concentrationconcentrated under reduced pressure to a residue
- concentrationconcentrated under reduced pressure
Sources & evidence
- ORD record
- ord-6d1fadf018ad45ec9fb672dc746cf772
- Source dataset
- uspto-grants-1996_05
- Patent number
- US05521147
Reaction notes
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