Reaction #531808

Reaction equation

1-Benzyloxy-4-bromo-2,5-dimethoxybenzene

Triisopropyl borate

→

5b

Yield 62.0%

4-Benzyloxy-2,5-dimethoxyphenylboronic acid

Yield 62.0%

Conditions

Workup

1. 1
   Otherflushed with Ar
2. 2
   workup.ADDITIONDry THF (75 mL) was added
3. 3
   workup.ADDITIONnBuLi (11 mL, 2.5M in hexanes) was added
4. 4
   workup.STIRRINGthe reaction stirred for 2 h at −78° C.
5. 5
   Otherto come to room temperature at which time
6. 6
   Otherto form
7. 7
   workup.STIRRINGAfter stirring for an additional 20 h the reaction
8. 8
   Otherwas quenched with saturated NH4Cl (25 mL)
9. 9
   OtherAfter separating the organic layer the aqueous layer
10. 10
    Extractionwas extracted with ethyl acetate (2×50 mL)
11. 11
    Otherdried
12. 12
    Concentrationconcentrated
13. 13
    OtherThe residue was triturated with hexanes
14. 14
    Filtrationfiltered

Procedure

1-Benzyloxy-4-bromo-2,5-dimethoxybenzene 4 (7.48 g,23.0 mmol) was placed in a dry flask and flushed with Ar. Dry THF (75 mL) was added and the solution was cooled to −78° C. in a dry ice/acetone bath. nBuLi (11 mL, 2.5M in hexanes) was added and the mixture was stirred for 20 min at −78° C. Triisopropyl borate (10.7 mL, 0.463 mol) was added and the reaction stirred for 2 h at −78° C. then allowed to come to room temperature at which time a white precipitate began to form. After stirring for an additional 20 h the reaction was quenched with saturated NH4Cl (25 mL). After separating the organic layer the aqueous layer was extracted with ethyl acetate (2×50 mL). The organic layers were combined, dried and concentrated. The residue was triturated with hexanes and filtered to give 4.1 g (62%) of 5b as a light off-white creamy solid. 1H-NMR (400 MHz, DMSO-d6) dH 3.70 (3H, s, OCH3), 3.79 (3H, s, OCH3), 5.16 (2H, s, CH2Ph), 6.77 (1H, s, ArH), 7.18 (1H, s, ArH), 7.33-7.52 (5H, m, CH2Ph)

Source