[CH2:1]1[CH2:5][O:4][CH2:3][CH2:2]1.COCC=C.[Br:11][C:12]1[CH:13]=[C:14]([CH:17]=[C:18](Br)[CH:19]=1)[CH:15]=[O:16].C[O-].[Na+]>O.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.Cl[Pd]Cl.[Fe+2]>[Br:11][C:12]1[CH:13]=[C:14]([CH:17]=[C:18]([CH2:2][CH2:1][CH2:5][O:4][CH3:3])[CH:19]=1)[CH:15]=[O:16]To a THF solution (0.3 M) of allyl methyl ether (3.1 eq.) at RT was added borane-methyl sulfide complex (1.0 eq.). The solution was stirred at RT for 30 min. To this solution was then added sequentially 3,5-dibromobenzaldehyde (1.0 eq.), Pd(dppf)Cl2 (0.025 eq.) and solid sodium methoxide (1.5 eq.). The resulting mixture was heated to reflux for 15 h. The cooled reaction mixture was diluted with water and extracted with ether. The combined organic extracts were dried over MgSO4, filtered and the filtrate concentrated in vacuo. Purification of the crude product thus obtained by way of flash chromatography (SiO2, 5:95 (v/v) EtOAc:Hex→7:3 (v/v) EtOAc:Hex) afforded the title compound as a colorless oil.
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