[S:1]1[CH:5]=[CH:4][CH:3]=[C:2]1[C:6]1[CH:10]=[CH:9][NH:8][N:7]=1.[H-].[Na+].[CH2:13](I)[CH3:14].O>CN(C)C=O.CC(OC)(C)C>[CH2:13]([N:8]1[CH:9]=[CH:10][C:6]([C:2]2[S:1][CH:5]=[CH:4][CH:3]=2)=[N:7]1)[CH3:14].[CH2:13]([N:7]1[C:6]([C:2]2[S:1][CH:5]=[CH:4][CH:3]=2)=[CH:10][CH:9]=[N:8]1)[CH3:14]3-(2-thienyl)-1H-pyrazole (31.6 mmol) was dissolved in 150 mL N,N-dimethylformamide and cooled to 0° C. under argon atmosphere. Sodium hydride (37.9 mmol, 60% dispersion in mineral oil) was added in portions at 0° C. The reaction mixture was allowed to warm to room temperature and was stirred at room temperature for 15 min. After cooling to 0° C. again, ethyl iodide (47.4 mmol) was added dropwise at 0° C. The reaction mixture was stirred at room temperature for 14 h. Water and MTBE were added to the reaction mixture. The phases were separated and the aqueous phase was extracted with MTBE. The combined organic extracts were successively washed with water and brine, dried over MgSO4, filtered and concentrated. The residue was purified by chromatography on silica gel (toluene:ethyl acetate 100:0 to 0:100) to afford 2.50 g 1-ethyl-3-(2-thienyl)-1H-pyrazole (44% yield) and 50 mg of 1-ethyl-5-(2-thienyl)-1H-pyrazole (1% yield).
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