Potassium Carbonate → 4-(4-BROMOPHENYL)-2-BUTANONE

A mixture of 2,4-pentanedione (200 mg, 206 μL, 2 mmol), the 4-bromobenzyl bromide (2 mmol), and anhydrous potassium carbonate (276 mg, 2 mmol) in methanol (10 mL) was heated at reflux temperature for 16 h. The mixture was then cooled to room temperature, methanol was removed under reduced pressure, and the resulting residue was partitioned between ethyl acetate (10 mL) and water (10 mL). The organic layer was separated, and the aqueous layer was extracted further with ethyl acetate (3×10 mL). The combined organic phase was washed with water (10 mL), dried over anhydrous Na2SO4, and then the solvent was removed under pressure. The resulting oil was chromatographed on a silica gel column using hexanes-ethyl acetate as mobile phase to give 4-(4-bromophenyl)-2-butanone as a clear liquid (302 mg, 67%): Rf=0.38 (hexanes-ethyl acetate 3:1 v/v); 1H NMR (400 MHz, CDCl3): δ 2.15 (s, 3H), 2.75 (t, J=7.2 Hz, 2H), 2.86 (t, J=7.2 Hz, 2H), 7.07 (d, J=8 Hz, 2H), 7.40 (d, J=8.4 Hz, 21; 13C NMR (100 MHz, CDCl3): δ 29.2, 30.2, 44.9, 120.0, 130.2, 131.7, 140.2, 207.4; HRMS (ESI) Calcd. for C10H11BrONa: 248.9891 [M+Na+]. Found: 248.9880.