[C:1]1([CH3:15])[CH:6]=[CH:5][CH:4]=[CH:3][C:2]=1[C:7]1[CH:8]=[C:9]([C:12]([OH:14])=O)[S:10][CH:11]=1.[Li]CC[CH2:19][CH3:20].C(I)C.CN([C:27]([O:31][N:32]1N=NC2C=CC=C[C:33]1=2)=[N+](C)C)C.[B-](F)(F)(F)F.CNOC.CCN(C(C)C)C(C)C>C1COCC1.CC(=O)OCC>[CH3:27][O:31][N:32]([CH3:33])[C:12]([C:9]1[S:10][C:11]([CH2:19][CH3:20])=[C:7]([C:2]2[CH:3]=[CH:4][CH:5]=[CH:6][C:1]=2[CH3:15])[CH:8]=1)=[O:14]At −70° C. a solution of 4-o-tolyl-thiophene-2-carboxylic acid (790 mg, 3.62 mmol) in THF (10 mL) is treated with tert.-BuLi (6.5 mL, 1.7 M solution in pentane). The mixture is stirred at −70° C. for 30 min before ethyliodide (1.5 mL) is added. The mixture is warmed to rt and stirring is continued for 16 h. The reaction is quenched by adding sat. aq. NH4Cl and the mixture is extracted with EA. The solvent of the organic extracts is evaporated and the remaining oil (680 mg) is dissolved in dry DCM (10 mL). TBTU (1.24 g, 3.87 mmol), N,O-dimethylhydroxylamine (415 mg, 4.25 mmol) and DIPEA (2 mL) is added and the mixture is stirred at it for 20 h before it is diluted with EA and washed with water. The organic layer is separated, evaporated and the remaining residue is purified by CC on silica gel eluting with heptane:EA 9:1 to 2:1 to give 5-ethyl-4-o-tolyl-thiophene-2-carboxylic acid methoxy-methyl-amide (58 mg) as an oil. This oil is dissolved in THF (4 mL) and treated at 4° C. with methyl magnesiumbromide (0.1 mL, 3 M solution in THF). The reaction mixture is stirred at it for 16 h before another portion of the Grignard reagent (0.2 mL) is added. Stirring is continued for 72 h. The mixture is diluted with water and extracted with EA (50 mL). The solvent of the organic extract is evaporated to give crude 1-(5-ethyl-4-o-tolyl-thiophen-2-yl)-ethanone (58 mg) as a yellow oil; LC-MS: tR=1.05 min, [M+1]+=245.16.
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