[Br:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[OH:8].[CH2:9]([O:11][C:12](=[O:16])[C:13]#[C:14][CH3:15])[CH3:10].N12CCCN=C1CCCCC2>O1CCCC1>[CH2:9]([O:11][C:12](=[O:16])/[CH:13]=[C:14](/[O:8][C:3]1[CH:4]=[CH:5][CH:6]=[CH:7][C:2]=1[Br:1])\[CH3:15])[CH3:10]To a stirred mixture of 2-bromo-phenol (9.02 g, 0.052 mol) and ethyl-2-butynoate (11.7 g, 0.104 mol) in tetrahydrofuran (50 mL) was added 1,8-diazabicyclo[5.4.0]undec-7-ene (8.05 g, 0.053 mol) slowly. After addition was complete the mixture was stirred at reflux 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-(2-bromo-phenoxy)-but-2-enoic acid ethyl ester as a yellow oil (10.0 g, 67%) and used without further purification.
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