Boron tribromide → 2,2-dimethyl-3,4-dihydro-2H-1-benzopyran-7-ol

참여 물질

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To a stirred solution of 7-Methoxy-2,2-dimethyl-chroman (4.55 g, 23.7 mmol, from step 1) in anhydrous dichloromethane (50 mL) was added 1M BBr3 (72.86 mL, 47.4 mmol, 2.0 eq ) via cannula over 10 min. The resulting dark brown solution was stirred at rt for 17 h. Saturated solution of NaHCO3 (50 mL) was added and extracted with CH2Cl2 (3×50 mL. The combined organic layers were dried over Na2SO4, filtered and evaporated. The residue was purified on silica gel (flash column chromatography) eluting with 5% ethyl acetate-hexane followed by 20% ethyl acetate-hexane to provide the desired product as white solid (1.76 g, 42%). 1H-NMR (CD3CN) δ 6.89 (d, J=8.5 Hz, 1H), 6.68 (broad, s, 1H, OH), 6.31 (dd, J=2.4, 8.5 Hz, 1H), 6.15 (d, J=2.4Hz, 1H ), 2.69 (t, 2H ), 1.79 (t, 2H), 1.31 (s, 6H). MS LC-MS (MH+=179).

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