[Cl:1][C:2]1[C:3]([N:12]2[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]2)=[CH:4][C:5]2[O:9][C:8](=[O:10])[CH2:7][C:6]=2[CH:11]=1.[H-].C([Al+]CC(C)C)C(C)C.S(=O)(=O)(O)O>O1CCCC1.C1(C)C=CC=CC=1.O>[Cl:1][C:2]1[C:3]([N:12]2[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13]2)=[CH:4][C:5]2[O:9][CH:8]([OH:10])[CH2:7][C:6]=2[CH:11]=1A solution of 251 mg (1.00 mmole) of 5-chloro-6-(piperidin-1-yl)-benzofuran-2(3H)-one in 5 ml of absolute tetrahydrofuran is cooled to -78° under a nitrogen atmosphere, 0.84 ml (1.00 mmole) of a 20% diisobutyl aluminium hydride solution in toluene is added and the whole is stirred for 30 minutes at -78°. 2 ml of 2N sulphuric acid are then added and the whole is stirred for 15 minutes at -40°. The reaction mixture is diluted with water and extracted with methylene chloride. The organic phases are washed with water, combined, dried over sodium sulphate and concentrated in a vacuum rotary evaporator. 5-chloro-2-hydroxy-6-(piperidin-1-yl)-2,3-dihydrobenzofuran is obtained in the form of an oil which is used for the following reactions without purification. Rf [silica gel, chloroform/ethyl acetate (3:1)]=0.48.
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