7-Bromo-4H-1-benzopyran-4-one → 7-bromo-3,4-dihydro-2H-1-benzopyran-4-one

Participants

Reaction Conditions

Reaction Steps

A solution of 7-bromo-4H-chromen-4-one (26 g, 116 mmol) in dry THF (500 mL) under nitrogen for 1 hr, cooled to −80° C., and 173 mL of diisobutylaluminium hydride (2M in Toluene) was added over 30 minutes. The reaction was stirred at the same temperature for 30 min, quenched with a SiO2 (52 g)/water (52 mL) suspension, and allowed to warm to 0° C. The solution was filtered, the SiO2 washed with EtOAc, and the combined filtrate was concentrated to dryness. The residue was dissolved in CHCl3 (400 mL), washed with 1N NaOH (300 mL), dried over Na2SO4 and concentrated. Purification by chromatography on SiO2 (60-120 mesh) EtOAc/Pet ether (gradient elution 0-15%) afforded 7-bromochroman-4-one 18.1 g (69%) a pale yellow solid. LCMS 229.0 (M+2H); 1H NMR (DMSO-d6) 7.64-7.67 (d, 1H), 7.32 (s, 1H), 7.22-7.25 (d, 1H), 4.53-4.57 (t, 2H), 2.76-2.80 (t, 2H).

Provenance & Evidence