N#N.[Br:3][C:4]1[CH:5]=[C:6]([C:10](=[O:12])[CH3:11])[CH:7]=[CH:8][CH:9]=1.[CH2:13](O)[CH2:14][OH:15].COC(OC)OC.C([O-])([O-])=O.[Na+].[Na+]>>[Br:3][C:4]1[CH:5]=[C:6]([C:10]2([CH3:11])[O:15][CH2:14][CH2:13][O:12]2)[CH:7]=[CH:8][CH:9]=1In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), a solution of 1-(3-bromo-phenyl)-ethanone (1360 mg, 6.83 mmol) in ethylene glycol (8.00 mL, 143.46 mmol) was treated with trimethylorthoformate (1.50 mL, 13.68 mmol) followed by LiBF4 (131 mg, 1.37 mmol). The reaction mixture was heated at 95° C. for 15 h. Sat. aq. Na2CO3 was added and the mixture was extracted twice with ether and the combined organic extracts were dried over Na2SO4, filtered, and the solvent was removed under reduced pressure. Purification of the residue by FC (20:1 hept-EA) gave the title compound as a pale yellow oil: TLC:rf (10:1 hept-EA)=0.34. LC-MS-conditions 02: tR=1.01 min.
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