Methanol → 4H-1-Benzopyran-2-carboxylic acid, 4-oxo-, methyl ester
Reaction equation
[O:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[C:4](=[O:11])[CH:3]=[C:2]1[C:12]([OH:14])=[O:13].S(=O)(=O)(O)O.[CH3:20]O>>[CH3:20][O:13][C:12]([C:2]1[O:1][C:10]2[C:5]([C:4](=[O:11])[CH:3]=1)=[CH:6][CH:7]=[CH:8][CH:9]=2)=[O:14]Participants
4
Procedure
Combine chromone-2-carboxylic acid (2.0 g, 10.5 mmol) and methanol (25 mL). Add sulfuric acid (2.5 mL) and heat to reflux. After 2 hours pour the reaction mixture into ice water and filter. Rinse the filter cake with water and a cold dilute aqueous solution of sodium bicarbonate. Chromatograph on silica gel eluting with tetrahydrofuran to give a residue. Recrystallize the residue from methanol to give the title compound as a solid: mp; 120°-122° C.
Workup
- filtrationfilter
- washRinse the filter cake with water