Reaction #42732

Reaction equation

bromine

product

6-Acetyl-2,2-dimethyl-4H-benzo[1,3]dioxine

sodium hexamethyldisilazane

trimethylsilyl chloride

→

title compound

6-Bromoacetyl-2,2-dimethyl-4H-benzo[1,3]dioxine

Solvents

THF

THF

Conditions

Workup

1. 1
   workup.WAITAfter another 30 minutes
2. 2
   workup.WAITAfter 10 minutes
3. 3
   Otherthe reaction was quenched
4. 4
   workup.ADDITIONby diluting the reaction mixture with diethyl ether
5. 5
   workup.ADDITIONpouring it onto 500 mL of 5% aqueous Na2SO3
6. 6
   workup.ADDITIONpremixed with 500 mL of 5% aqueous NaHCO3
7. 7
   OtherThe phases were separated
8. 8
   Washthe organic phase was washed with brine
9. 9
   Dryingdried over Na2SO4
10. 10
    Filtrationfiltered
11. 11
    Concentrationconcentrated under reduced pressure

Procedure

To the product of step (b) (23.4 g, 0.113 mol) in 600 mL of THF at −78° C. was added 135 mL of 1.0 M sodium hexamethyldisilazane in THF (Sigma-Aldrich). After 1 hour, trimethylsilyl chloride (15.8 mL, 0.124 mol) was added. After another 30 minutes, bromine (5.82 mL, 0.113 mol) was added. After 10 minutes, the reaction was quenched by diluting the reaction mixture with diethyl ether and pouring it onto 500 mL of 5% aqueous Na2SO3 premixed with 500 mL of 5% aqueous NaHCO3. The phases were separated and the organic phase was washed with brine, dried over Na2SO4, filtered and concentrated under reduced pressure to give the title compound as an oil that solidified upon storage in the freezer.

Source