[F:1][C:2]1[C:7]([O:8][CH:9]([CH3:11])[CH3:10])=[CH:6][CH:5]=[C:4]([F:12])[C:3]=1[OH:13].[CH2:14]([O:16][C:17](=[O:21])[C:18]#[C:19][CH3:20])[CH3:15].N12CCCN=C1CCCCC2>O1CCCC1>[CH2:14]([O:16][C:17](=[O:21])/[CH:18]=[C:19](/[O:13][C:3]1[C:4]([F:12])=[CH:5][CH:6]=[C:7]([O:8][CH:9]([CH3:11])[CH3:10])[C:2]=1[F:1])\[CH3:20])[CH3:15]To a stirred mixture of 2,6-difluoro-3-isopropoxy-phenol (5.74 g, 0.031 mol) and ethyl-2-butynoate (6.85 g, 0.061 mol) in tetrahydrofuran (50 mL) was added 1,8-diazabicyclo[5.4.0]undec-7-ene (4.64 g, 0.030 mol) slowly. After addition was complete the mixture was stirred at reflux for 6 h. 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 which afforded (E)-3-(2,6-difluoro-3-isopropoxy-phenoxy)-but-2-enoic acid ethyl ester as a brown oil (6.85 g, 75%) and used without further purification.
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