反应详情

To a stirred solution of ethyl 6-chloro-7-hydroxychroman-4-carboxylate (5.14 g, 20.0 mmol) in glacial acetic acid (50 mL) at ambient temperature was added bromine (1.2 mL, 24 mmol), in six equal portions, waiting 30-60 seconds between each addition for the bromine color to be discharged. Following completion of addition, the solution was concentrated and the residue concentrated from toluene, then partitioned between ethyl acetate (200 mL) and 5% sodium bisulfite (100 mL). The organic was layer dried over sodium sulfate, then stirred with activated charcoal (2 g) at ambient temperature for 20 minutes. The charcoal was removed by filtration through a glass microfibre filter and the filtrate was concentrated to afford ethyl 8-bromo-6-chloro-7-hydroxychroman-4-carboxylate as a light brown oil (6.05 g, 90% yield).

1. additioncompletion of addition
2. concentrationthe solution was concentrated
3. concentrationthe residue concentrated from toluene
4. custompartitioned between ethyl acetate (200 mL) and 5% sodium bisulfite (100 mL)
5. dry with materialdried over sodium sulfate
6. customThe charcoal was removed by filtration through a glass microfibre
7. filtrationfilter
8. concentrationthe filtrate was concentrated