[CH2:1]([NH:5][CH2:6][C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH:2]=[CH:3][CH3:4].Cl[C:13]([CH2:18][CH3:19])=[C:14]([CH3:17])[CH:15]=O.C(N(CC)CC)C.CC(C)([O-])C.[K+].[Cl-].[NH4+]>C(O)C>[CH2:1]([N:5]1[C:13]([CH2:18][CH3:19])=[C:14]([CH3:17])[CH:15]=[C:6]1[C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH:2]=[CH:3][CH3:4]
3.74 g (0.024 mole) of ethyl N-(2-butenyl)glycinate were added to a solution of 5.0 g (0.038 mole) of 3-chloro-2-methyl-2-pentenal in 10 ml of ethanol with stirring, and subsequently 6 ml (0.043 mole) of triethylamine were added thereto and stirred at room temperature for 7 hours. After the precipitates deposited were filtered off, 5.35 g (0.048 mole) of potassium tert-butoxide were added to the filtrate by portions and the mixture was stirred for 30 minutes. The reaction mixture was poured into about 150 ml of a saturated aqueous solution of ammonium chloride and extracted with ethyl acetate (once with 100 ml and twice with 50 ml). The combined extracts were washed with a saturated aqueous solution of sodium chloride and dried over anhydrous sodium sulfate, and the solvent was distilled off. The residue was purified by column chromatography through silica gel using a 3:97 mixture of ethyl acetate and hexane as an eluent to give 1.53 g of ethyl 1-(2-butenyl)-5-ethyl-4-methylpyrrole-2-carboxylate (cis/trans=76/24) as an orange oil.
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