Ethylene Glycol → 3-[2-(2-Benzyloxy-ethyl)-[1,3]dioxolan-2-ylmethyl]-4-(4-chloro-benzenesulfonyl)-5,8-difluoro-chroman

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Reaction Steps

4-Benzyloxy-1-[4-(4-chloro-benzenesulfonyl)-5,8-difluoro-chroman-3-yl]-butan-2-one (10 g, 19.2 mmole), ethylene glycol (20 ml) and toluene sulfonic acid (1 g) were dissolved in 300 ml toluene. The reaction was refluxed for four hours with a Dean-Stark trap. The reaction was cooled to room temperature and 200 ml water and 200 ml EtOAc were added. The organic layer washed with brine (2×50 ml), dried over Na2SO4 and concentrated. The residue was purified by column chromatography (EtOAc/hexane from 0/100 to 50/50 in 55 minute). Yield: 6.3 g, 58%. 1H NMR (CDCl3 400 MHz δ 7.74 (d, J=8.1 Hz, 2H), 7.51 (d, J=8.8 Hz, 2H), 7.20-7.39 (m, 5H), 7.02 (m, 1H), 6.42 (m, 1H), 4.89 (dd, J=11.0 and 2.9 Hz, 1H), 4.84 (s, 1H), 4.40 (d, J=2.0 Hz, 2H), 4.21 (d, J=11.7 Hz, 1H), 3.85 (m, 4H), 3.46 (t, J=5.9 Hz, 2H), 3.03 (d, J=8.1 Hz, 1H), 1.75-1.90 (m, 3H), 1.54-1.61 (m, 1H).

Provenance & Evidence