Trifluoroacetic acid → 5-Bromo-4-methylisobenzofuran-1(3H)-one

Participants

Reaction Steps

To a flask charged with (3-bromo-2-methylphenyl)methanol (6.0 g, 30 mmol) was added a 1M trifluoroacetic acid solution of thallium trifluoroacetate (16.2 g, 29.8 mmol). The mixture was stirred at RT overnight. The solvent was removed under vacuum, and the residue was pumped under high vacuum for 30 minutes to ensure complete removal of TFA. To the residue was then added palladium (II) chloride (529 mg, 2.98 mmol), lithium chloride (2.53 g, 59.7 mmol), magnesium oxide (2.41 g, 59.7 mmol), and methanol (150 mL). The reaction was flushed with CO twice, and kept under CO at room temperature. Analysis by LC showed a big product spot within 2 hours. To this solution was added ethyl acetate to precipitate the salts. The black solution was filtered through a Celite® pad, washed with EtOAc, adsorbed onto silica and purified by silica gel chromatography to afford 5-bromo-4-methyl-2-benzofuran-1 (3H)-one. 1H-NMR (500 MHz, CDCl3) δ ppm 7.71 (d, J=8.0 Hz, 1H), 7.58 (d, J=8.0 Hz, 1H), 5.25 (s, 2H), 2.37 (s, 3H).

Provenance & Evidence