Reaction #1379913

Reaction equation

triethylborate

1-bromo-2-ethylbenzene

n-Butyl lithium

→

product

Yield 93.8%

2-Ethylphenyl boronic acid

Yield 93.8%

Solvents

tetrahydrofuran

Conditions

Workup

1. 1
   Otherkept at −78° C.
2. 2
   Otheran oven-dried 3 neck flask
3. 3
   workup.ADDITIONwas added slowly (
4. 4
   Otherthe temperature below −68° C.
5. 5
   Otherthe temperature below −68° C
6. 6
   workup.STIRRINGThe reaction was stirred for an additional 40 minutes
7. 7
   Otherthe dry ice bath was removed
8. 8
   workup.ADDITIONwas poured into 300 mL of ice cold saturated ammonium chloride solution
9. 9
   workup.ADDITION200 mL of ice cold ethyl acetate was added
10. 10
    workup.STIRRINGthe mixture stirred for another 30 min
11. 11
    OtherThe layers were separated
12. 12
    WashThe organic layer was washed with water, and brine
13. 13
    DryingIt was then dried over magnesium sulfate
14. 14
    Concentrationconcentrated

Procedure

To a solution of 25 g (135 mmol) of 1-bromo-2-ethylbenzene in 280 mL of dry tetrahydrofuran, kept at −78° C. in an oven-dried 3 neck flask, was added slowly (keeping the temperature below −68° C.) 67.5 mL of 2.5N n-Butyl lithium in hexanes solution (169 mmol, 1.25 eq.). The reaction was stirred for an additional 1 h, and then 69 mL (405 mmol, 3 eq.) of triethylborate was added slowly, keeping the temperature below −68° C. The reaction was stirred for an additional 40 minutes and then the dry ice bath was removed, the reaction was allowed to warm up to room temperature, and then was poured into 300 mL of ice cold saturated ammonium chloride solution. 200 mL of ice cold ethyl acetate was added, and the mixture stirred for another 30 min. The layers were separated. The organic layer was washed with water, and brine. It was then dried over magnesium sulfate, and concentrated to give 19 g (92% yield) of product. The boronic acid was used without purification in the next step.

Source