Abstract
Trityl ethers are chemoselectively deprotected to the corresponding alcohols in high yields by a catalytic amount of indium tribromide in aqueous acetonitrile. The method is compatible with various functional groups such as acetonides, acetates, benzoates, olefins, carbamates, esters and ethers present in the substrate.
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19.General procedure: A mixture of trityl ether (5 mmol) and InCl3 or InBr3 (0. 25 mmol) in acetonitrile: water (1:1, 10 ml) was stirred under reflux for an appropriate time (Table 1). After completion of the reaction as indicated by TLC, the reaction mixture was diluted with water (10 ml) and extracted twice with ethyl acetate (2 × 15 ml). The combined organic layers were dried over anhydrous Na2SO4, concentrated in vacuo and purified by column chromatography on silica gel (Merck, 100–200 mesh, ethyl acetate – hexane, 2:8) to give pure alcohol. Spectral data for compound 1a: 1H NMR (CDCl3): δ 2.05 (m, 4H), 3.30 (t, 2H, J = 6.8 Hz), 3.70 (t, 2H, J = 6.8 Hz), 4.50 (s, 2H), 7.25–7.35 (m, 15H), 7.45-7.55 (m, 5H). 2a: 1H NMR (CDCl3): δ 1.75 (m, 4H), 3.05 (brs, OH), 3.55 (t, 3H, J = 6.8 Hz), 3.65 (t, 3H, J = 6.8 Hz), 4.50 (s, 2H), 7.35–7.45 (m, 5H). 1b: 1H NMR (CDCl3): δ 1.95 (m, 4H), 2.05 (s, 3H), 3.20 (t, 2H, J = 7.0 Hz), 4.25 (t, 2H, J = 7.0 Hz), 7.25–7.35 (m, 10H), 7.45-7.55 (m, 5H). 2b: 1H NMR (CDCl3): δ 1.80 (m, 4H), 2.05 (s, 3H), 3.05 (brs, OH), 3.30 (t, 2H, J = 7.0 Hz), 4.25 (t, 2H, J = 7.0 Hz).