Hydrogen Bromide → 2-Bromo-2-(4-methylthiophenyl)-1-(4-methylphenyl)ethanone

Participants

Reaction Steps

A 500 mL round-bottomed flask equipped with a pressure-equalizing addition funnel and provisions for magnetic stirring was charged with 2-(4-methylthiophenyl)-1-(4-methylphenyl)ethanone from Step 2 (10.0 g, 39.0 mmol), 33% HBr in acetic acid (70 mL) and glacial acetic acid (100 mL). Over approximately 20 minutes, a solution of bromine in acetic acid (1M, 39 mL) was added to the suspension, and the reaction was held at room temperature for one hour. Any undissolved solids were removed by filtration, and the reaction was concentrated in vacuo, to a residue. The residue was dissolved in methylene chloride (100 mL), washed with 5% Na2S2O5 (2×100 mL), dried over MgSO4, filtered, and concentrated in vacuo to a colorless oil. The oil was held under vacuum for 16 hours, yielding 2-bromo-2-(4-methylthiophenyl)-1-(4-methylphenyl)ethanone (8.38 g, 64%) as a dirty white solid: mp 97°-98° C. 1H NMR (CDCl3) 300 MHz 7.86 (d, J=8.46 Hz, 2H), 7.80(d, J=8.26 Hz, 2H), 7.33-7.16(m, 4H), 5.88(s, 1H), 2.43(s, 3H), 2.36(s, 3H).

Provenance & Evidence