C[O:2][C:3]1[CH:8]=[CH:7][C:6](/[CH:9]=[CH:10]/[C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)=[CH:5][CH:4]=1.B(Br)(Br)Br>C(Cl)Cl>[OH:2][C:3]1[CH:4]=[CH:5][C:6](/[CH:9]=[CH:10]/[C:11]2[CH:12]=[CH:13][CH:14]=[CH:15][CH:16]=2)=[CH:7][CH:8]=1To 210 mg (1 mmol) of (E)-4-methoxystilbene (4b) in 7 mL of CH2Cl2 was added 1.28 mL of 1M BBr3 (1.3 mmol) in dichloromethane at −10° C. The mixture was stirred for 4 h at −5° C. and quenched by pouring into cold water. The product was extracted with CH2Cl2, dried over anhydrous MgSO4 and chromatographed using 1:10 CH3OH:CH2Cl2 to afford 85 mg (43%) of 4a. mp 184-185° C.
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