[Br:1][C:2]1[C:3]([F:9])=[C:4]([OH:8])[CH:5]=[CH:6][CH:7]=1.[CH2:10]([O:12][C:13](=[O:17])[C:14]#[C:15][CH3:16])[CH3:11].N12CCCN=C1CCCCC2>O1CCCC1>[CH2:10]([O:12][C:13](=[O:17])/[CH:14]=[C:15](/[O:8][C:4]1[CH:5]=[CH:6][CH:7]=[C:2]([Br:1])[C:3]=1[F:9])\[CH3:16])[CH3:11]To a stirred mixture of 3-bromo-2-fluoro-phenol (19.5 g, 0.102 mol) and ethyl-2-butynoate (22.0 g, 0.196 mol) in tetrahydrofuran (100 mL) was added 1,8-diazabicyclo[5.4.0]undec-7-ene (15.6 g, 0.102 mol) slowly. After addition was complete the mixture was stirred at reflux for overnight. Upon completion of the reaction the tetrahydrofuran was removed in vacuo and the residue was diluted in diethyl ether and washed first with 1N aqueous hydrochloric acid, then 10% aqueous sodium hydroxide solution, a saturated sodium chloride solution and dried over magnesium sulfate. The mixture was filtered and evaporated, and the residue dried under high vacuum which afforded (E)-3-(3-bromo-2-fluoro-phenoxy)-but-2-enoic acid ethyl ester as a brown oil (21.5 g, 69%) and used without further purification.
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