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

Temperature

-80 °C

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).

1. customquenched with a SiO2 (52 g)/water (52 mL) suspension
2. temperatureto warm to 0° C
3. filtrationThe solution was filtered
4. washthe SiO2 washed with EtOAc
5. concentrationthe combined filtrate was concentrated to dryness
6. dissolutionThe residue was dissolved in CHCl3 (400 mL)
7. washwashed with 1N NaOH (300 mL)
8. dry with materialdried over Na2SO4
9. concentrationconcentrated
10. customPurification by chromatography on SiO2 (60-120 mesh) EtOAc/Pet ether (gradient elution 0-15%)

ORD record

ord-171c7a47b8444c6bbc204f5f4fea7a7f

Source dataset

uspto-grants-2012_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08147818B2