[CH:1]([C:3]1[S:7][C:6]([C:8]([OH:10])=[O:9])=[C:5]2[CH2:11][CH2:12][C:13]([CH3:16])([CH3:15])[CH2:14][C:4]=12)=[O:2].CO>C(O)(=O)CC(CC(O)=O)(C(O)=O)O.[Cl-].[Na+].O>[OH:2][CH2:1][C:3]1[S:7][C:6]([C:8]([OH:10])=[O:9])=[C:5]2[CH2:11][CH2:12][C:13]([CH3:16])([CH3:15])[CH2:14][C:4]=12To a solution of crude 3-formyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophene-1-carboxylic acid (2.38 g, 10 mmol) in methanol (20 mL) NaBH4 (756 mg, 20 mmol) is added in portions. The mixture is stirred at rt for 15 min, diluted with 10% aq. citric acid and brine and extracted with TBME. The organic extract is dried over Na2SO4 and the solvent is removed under reduced pressure to give 3-hydroxymethyl-5,5-dimethyl-4,5,6,7-tetrahydro-benzo[c]thiophene-1-carboxylic acid (2.30 g) as a beige foam; LC-MS: tR=0.83 min, [M+1]=241.22; 1H NMR (CDCl3): δ 4.69 (s, 2H), 3.00 (t, J=7.0 Hz, 2H), 2.32 (s, 2H), 1.50 8t, J=7.0 Hz, 2H), 0.94 (s, 6H).
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