[CH3:1][C:2]1[O:3][C:4]2[C:11]([CH:12]([N:22]([CH2:25][CH3:26])[CH2:23][CH3:24])[CH2:13][O:14][Si](C(C)(C)C)(C)C)=[CH:10][CH:9]=[CH:8][C:5]=2[C:6]=1[CH3:7].O.O.O.[F-].C([NH3+])(C)(C)C.O>O1CCCC1>[CH3:1][C:2]1[O:3][C:4]2[C:11]([CH:12]([N:22]([CH2:25][CH3:26])[CH2:23][CH3:24])[CH2:13][OH:14])=[CH:10][CH:9]=[CH:8][C:5]=2[C:6]=1[CH3:7]2.77 g (7.68 mmol) of 2,3-dimethyl-7-(1-diethylamino-2-[tert-butyldimethylsilyloxy]ethyl)benzofuran and 30 ml of tetrahydrofuran are introduced into a 250 ml round-bottomed flask. The reaction mixture is cooled to 0° C. by an ice bath and a solution of 2.9 g (9.21 mmol) of tert-butylammonium fluoride trihydrate in 10 ml of tetrahydrofuran is added. The reaction mixture is stirred at 0° C. for 1 hour and at room temperature for 16 hours. 150 ml of water are added and extraction is carried out with ethyl ether (3×200 ml). The organic phases are combined, dried over magnesium sulphate and concentrated under vacuum. The residue is purified by chromatography on a silica column (elution solvent: 5% methanol in dichloromethane). 1.6 g (Yield: 80%) of 2,3-dimethyl-7-(1-diethylamino-2-hydroxyethyl)benzofuran are obtained in the form of an oil.
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