Hydrochloric Acid → 7-methoxy-3,4-dihydro-2H-1-benzopyran-3-one

Participants

Reaction Conditions

Reaction Steps

7-Methoxy-2H-chromene-3-carboxylic acid (6.07 g, 29.44 mmol) and triethylamine (4.8 ml, 34.48 mmol) were dissolved in dichloromethane (60 ml). Diphenylphosphoryl azide (6.54 ml, 29.44 mmol) was dissolved in toluene (24 ml) and added dropwise to the reaction mixture while slowly increasing the temperature to 60° C. 60 ml of toluene were added and the reaction mixture was stirred at 70° C. for 90 minutes. A 10 molar HCl solution (28 ml) was then added and the reaction mixture was stirred at reflux for 2 hours. After cooling to room temperature the phases were separated. The organic phase was extracted with an aq. NaHCO3 solution. The organic layer was dried over magnesium sulfate, filtered, and the solvent evaporated under reduced pressure. The crude product was purified by chromatography using silica gel with cyclohexane/ethyl acetate (100:0 to 95:5) as eluent, yielding the title product (1.47 g, 24% yield).

Provenance & Evidence