Reaction #487561

Reaction equation

hydrochloric acid

trimethylborate

4-bromo-1-ethyl-2-iodobenzene

isopropylmagnesium chloride

→

5-bromo-2-ethylphenylboronic acid

Yield 87.7%

Solvents

tetrahydrofuran

Conditions

Workup

1. 1
   Temperaturemaintaining a temperature below −60° C
2. 2
   workup.WAITfollowed by an additional hour
3. 3
   workup.STIRRINGof stirring
4. 4
   TemperatureThe solution is re-cooled to −78° C.
5. 5
   Temperatureto warm to room temperature
6. 6
   workup.STIRRINGwith further stirring for 2 hours
7. 7
   Extractionthe crude product is extracted into ethyl acetate (100 ml)
8. 8
   WashThe aqueous phase is washed with ethyl acetate (2×100 ml)
9. 9
   Dryingdried over anhydrous magnesium sulfate
10. 10
    Concentrationthen concentrated in vacuo
11. 11
    Otherto give a light brown solid which
12. 12
    Otheris triturated with hexanes

Procedure

To a solution of 4-bromo-1-ethyl-2-iodobenzene (10.00 g, 32.20 mmol) in anhydrous tetrahydrofuran (60 ml) at −78° C. is added a solution of isopropylmagnesium chloride (16.90 ml, 33.80 mmol, 2M solution in tetrahydrofuran) dropwise, maintaining a temperature below −60° C. After stirring for 20 minutes the reaction mixture is allowed to slowly warm to room temperature followed by an additional hour of stirring. The solution is re-cooled to −78° C. and trimethylborate (7.18 ml, 64.32 mmol) is added dropwise, after which the mixture is again allowed to warm to room temperature with further stirring for 2 hours. Dilute aqueous hydrochloric acid (30 ml) is added, and the crude product is extracted into ethyl acetate (100 ml). The aqueous phase is washed with ethyl acetate (2×100 ml), and all organics are combined, dried over anhydrous magnesium sulfate then concentrated in vacuo to give a light brown solid which is triturated with hexanes to afford 5-bromo-2-ethylphenylboronic acid (6.46 g) as a cream powder.

Source