Cl.[NH2:2][CH2:3][C:4](=O)[CH:5]([CH3:7])[CH3:6].[C:9](OCC)(=O)[CH2:10][C:11]([CH3:13])=O.[C:18]([O-:21])(=O)[CH3:19].[Na+].[OH2:23]>C(O)(=O)C>[CH:5]([C:4]1[C:10]([C:9]([O:21][CH2:18][CH3:19])=[O:23])=[C:11]([CH3:13])[NH:2][CH:3]=1)([CH3:7])[CH3:6]A solution containing 0.32 g of 4-amino-2-methyl-3-butanone hydrochloride, 0.33 g of ethyl acetoacetate and 0.28 g of sodium acetate in 2 ml of 75% acetic acid was heated at 100° C. for 1.5 h. The mixture was poured into 10 ml of water and extracted three times with 10 ml of diethyl ether. Combined extracts were washed three times with 10 ml of saturated sodium hydrogen carbonate and with 10 ml of brine then dried over anhydrous magnesium sulphate, filtered and evaporated. The residue was purified by flash chromatography on silica gel using dichloromethane for the elution to give 0.15 g of ethyl 4-isopropyl-2-methyl-1H-pyrrole-3-carboxylate. Recrystallisation from isohexane gave analytically pure material of melting point 67-68.5° C.; mass spectrum (EI) m/z 195 [M]+.
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