Allyl bromide → 7-(Allyloxy)-4-methyl-2H-chromen-2-one

Reaction equation

Br[CH2:2][CH:3]=[CH2:4].[OH:5][C:6]1[CH:15]=[C:14]2[C:9]([C:10]([CH3:17])=[CH:11][C:12](=[O:16])[O:13]2)=[CH:8][CH:7]=1.C(=O)([O-])[O-].[K+].[K+]>CC(C)=O>[CH2:2]([O:5][C:6]1[CH:15]=[C:14]2[C:9]([C:10]([CH3:17])=[CH:11][C:12](=[O:16])[O:13]2)=[CH:8][CH:7]=1)[CH:3]=[CH2:4]

Participants

Procedure

3-Bromo-1-propene (2.95 mL, 34.06 mmol) was added dropwise under argon to a stirred mixture of 7-hydroxy-4-methylcoumarin 1 (2.0 g, 11.35 mmol) and anhydrous potassium carbonate (K2CO3) (2.35 g, 17.03 mmol) in acetone (50 mL). The resulting mixture was then refluxed for 4 h, after which it was allowed to cool, and the K2CO3 filtered off and washed with fresh acetone. The solvent was removed in vacuo and the residue was crystallized from methanol to afford 2 as white-cream crystals (2.36 g, 96%). TLC (hexane/ethyl acetate, 1:3): Rf=0.63. mp 110° C. 1H NMR (CDCl3, 500 MHz) δ 2.39 (s, 3H, CH3), 4.60 (d, J=5.0 Hz, 2H, CH2), 5.33 (d, J=10.5 Hz, 1H), 5.44 (d, J=17.5 Hz, 1H), 6.05 (m, 1H), 6.12 (s, 1H), 6.80 (s, 1H), 6.87 (dd, J=1.5, 9.0 Hz, 1H), 7.49 (d, J=9.0 Hz, 1H). 13C NMR (CDCl3, 125 MHz) δ 18.70, 69.29, 101.84, 112.05, 112.79, 113.75, 118.51, 125.64, 132.31, 152.61, 152.26, 161.26, 161.65. ESIMS calcd for C13H13O3 [M+H]+ 217.1, found 217.1.