Phenyltrimethylammonium bromide dibromide → 2-Bromo-1-(3,5,5-trimethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone

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Reaction Steps

To a solution of 1-(3,5,5-trimethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone (1.18 g, 5.31 mmol, Example C) in THF (60 mL) and methanol (6 mL), phenyltrimethylammonium bromide dibromide (2.0 g, 5.31 mmol) is added in portions. Upon complete addition, the mixture is stirred at rt for 30 min before the solvent is evaporated. The crude product is purified by prep. HPLC (Grom-Sil 120 ODS-4-HE, 30×75 mm, 10 μm, 20-95% acetonitrile in water containing 0.5% formic acid) to give 2-bromo-1-(3,5,5-trimethyl-4,5,6,7-tetrahydro-benzo[c]thiophen-1-yl)-ethanone (1.28 g) as a colourless oil; 1H NMR (CDCl3): δ 4.24 (s, 2H), 3.03 (t, J=7.0 Hz, 2H), 2.36 (s, 3H), 2.30 (s, 2H), 1.54 (t, J=7.0 Hz, 2H), 0.98 (s, 6H).

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