[N+:1]([C:4]1[CH:5]=[C:6]([CH:14]=[CH:15][CH:16]=1)[CH2:7][S:8]([CH2:11][CH2:12][OH:13])(=[O:10])=[O:9])([O-])=O.C(=O)(O)[O-].[Na+]>Cl.C1COCC1.[Cl-].[Ti+3].[Cl-].[Cl-]>[NH2:1][C:4]1[CH:5]=[C:6]([CH:14]=[CH:15][CH:16]=1)[CH2:7][S:8]([CH2:11][CH2:12][OH:13])(=[O:10])=[O:9]Titanium(III)chloride solution (about 15%) in about 10% hydrochloric acid (MERCK (MDA) INCL SCHUCHARDT, 114 ml) was added to a stirred solution of 2-[(3-nitrobenzyl)sulfonyl]ethanol (9.0 g; 36.7 mmol) in THF (384 ml) at room temperature and the batch was stirred for 18 hours. By adding aqueous sodium bicarbonate solution the pH value of the reaction mixture was raised to 7-8 before the batch was extracted with ethyl acetate (2×). The combined organic phases were washed with brine, dried (Sodium sulfate), filtered and concentrated. The residue was purified by column chromatography (DCM/ethanol 95:5) to give the desired product.
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