Reaction #168982

Reaction equation

AcOH

trimethyl borate

methyl ether

n-butyllithium

THF

→

6-methoxy-2,3-dihydro-benzo[1,4]dioxin-5-yl-boronic acid

Yield 98.0%

Conditions

Workup

1. 1
   workup.ADDITIONwas added drop-wise
2. 2
   TemperatureAfter 1 h the solution was cooled to −78° C.
3. 3
   TemperatureThe solution was warmed to rt
4. 4
   OtherAfter 16 h the mixture was quenched by the addition of water
5. 5
   Otherresulting mixture
6. 6
   Extractionextracted with ethyl acetate
7. 7
   WashThe combined organics were washed with saturated NaHCO3
8. 8
   Dryingdried with MgSO4
9. 9
   Filtrationfiltered
10. 10
    Concentrationconcentrated in vacuo
11. 11
    OtherThe resulting oil was azeotroped with toluene

Procedure

To a solution of methyl ether X (10.0 g, 60 mmol) in 50 ml THF at −78° C. was added n-butyllithium (36 ml, 90 mmol, 2.5 M in hexanes) was added drop-wise. After 1 h the solution was warmed to rt. After 1 h the solution was cooled to −78° C. and trimethyl borate (13.6 ml, 120 mmol) was added. The solution was warmed to rt. After 16 h the mixture was quenched by the addition of water and resulting mixture was acidified with AcOH and extracted with ethyl acetate. The combined organics were washed with saturated NaHCO3, dried with MgSO4, filtered and concentrated in vacuo. The resulting oil was azeotroped with toluene to afford 6-methoxy-2,3-dihydro-benzo[1,4]dioxin-5-yl-boronic acid (13.72 g, 98%) as an oil.

Source