Azobisisobutyronitrile → 4-bromo-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran

To a solution of 6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (6.40 g, 34.18 mmol), title A compound, in carbon tetrachloride (90 mL) was added N-bromosuccinimide (6.69 g, 37.6 mmol). The solution was purged with argon. A solution of Azobisisobutyronitrile (0.4 g, 3.42 mmol) in carbon tetrachloride (10 mL) was added; the reaction was heated at reflux for 30 minutes with irradiation (high intensity visible light). The reaction mixture was concentrated under vacuum and the residue was dissolved in 75 mL ethyl acetate. The solution was washed successively with distilled water (4×75 mL), saturated sodium bicarbonate solution (75 mL), saturated NaCl solution (75 mL), and dried over magnesium sulfate. The solvent was recovered under vacuum to obtain an orange waxy solid which was triturated with cold pentane to provide a beige solid (7.19 g). This was crystallized from ethyl acetate and hexanes (10:90) to yield the title compound (4.60 g) as off-white needles, m.p. 94°-95° C. The mother liquors were combined and chromatographed on silica gel during with hexane/ethyl acetate (19:1) to afford additional product (2.26 g) for a combined yield of 75.4%.

1. customThe solution was purged with argon
2. temperaturethe reaction was heated
3. temperatureat reflux for 30 minutes with irradiation (high intensity visible light)
4. concentrationThe reaction mixture was concentrated under vacuum
5. dissolutionthe residue was dissolved in 75 mL ethyl acetate
6. washThe solution was washed successively with distilled water (4×75 mL), saturated sodium bicarbonate solution (75 mL), saturated NaCl solution (75 mL)
7. dry with materialdried over magnesium sulfate
8. customThe solvent was recovered under vacuum
9. customto obtain an orange waxy solid which
10. customwas triturated with cold pentane

ORD record

ord-1ee52ff17f2d430982176dd585a23685

Source dataset

uspto-grants-1994_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05374643