Tetrahydrofuran → 5-methoxy-3,4-dihydro-2H-1-benzopyran-3-one
Reaction equation
[H-].[Na+].Br[C@H:4]1[C@H:9](O)[C:8]2[C:11]([O:15][CH3:16])=[CH:12][CH:13]=[CH:14][C:7]=2[O:6][CH2:5]1.[O:17]1CCCC1>>[CH3:16][O:15][C:11]1[C:8]2[CH2:9][C:4](=[O:17])[CH2:5][O:6][C:7]=2[CH:14]=[CH:13][CH:12]=1Participants
4
Procedure
To a suspension of 5.0 g sodium hydride in 100 ml of dry tetrahydrofuran is added with stirring a solution of 13 g of trans-3-bromo-4-hydroxy-5-methoxy-3,4-dihydro-2H-[1]-benzopyran in 150 ml of dry tetrahydrofuran in a dropwise fashion. After 30 minutes stirring at room temperature, the reaction mixture is filtered through filter-cel and the solvent is removed in vacuo. The residue is dissolved in 150 ml of toluene, 1.0 g of anhydrous zinc iodide is added and the mixture is refluxed for 15 minutes. The reaction mixture is filtered through 120 g of silica gel with methylene chloride as the eluent to afford 5-methoxy-3,4-dihydro-2H-[1]-benzopyran-3-one (5-methoxychroman-3-one) as an oil.