CON(C)[C:4]([C:6]1[S:7][C:8]([C:17]([F:20])([F:19])[F:18])=[C:9]2[CH2:14][C:13]([CH3:16])([CH3:15])[CH2:12][CH2:11][C:10]=12)=[O:5].[CH3:22][Li].Cl>C(OCC)C>[CH3:15][C:13]1([CH3:16])[CH2:12][CH2:11][C:10]2=[C:6]([C:4](=[O:5])[CH3:22])[S:7][C:8]([C:17]([F:20])([F:19])[F:18])=[C:9]2[CH2:14]1A solution of 5,5-dimethyl-3-trifluoromethyl-4,5,6,7-tetrahydro-benzo[c]thiophene-1-carboxylic acid methoxy-methyl-amide (14 g, 44 mmol) in diethyl ether (400 mL) is treated at rt with methyl lithium (80 mL, 1.6 M in diethyl ether). Upon complete addition, the mixture is stirred at rt for 15 min before it is poured onto water/ice and neutralized with aq. HCl. The ether phase is separated and the aq. phase is extracted two more times with diethyl ether (2×100 mL). The organic extracts are washed with brine, dried over MgSO4, filtered and evaporated. The crude product is purified by CC on silica gel eluting with heptane containing 20-30% of DCM to give 1-(5,5-dimethyl-3-trifluoromethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone (9.1 g) as a yellow oil; LC-MS: tR=1.11 min, [M+1+CH3CN]=318.34; 1H NMR(CDCl3): δ 3.04 (t, J=7.0 Hz, 2H), 2.57 (d, J=1.2 Hz, 2H), 2.53 (s, 3H), 1.58 (t, J=7.0 Hz, 2H), 0.99 (s, 6H).
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