Reacción #56871

Ecuación de reacción

hydrochloric acid

2-methyl-5-bromo-iodobenzene

isopropylmagnesium chloride

trimethylborate

→

2-methyl-5-bromo-phenylboronic acid

Rendimiento 84.3%

Disolventes

tetrahydrofuran

tetrahydrofuran

Condiciones de reacción

Tratamiento posterior

1. 1
   Temperaturathe mixture was warmed slowly to −20° C.
2. 2
   workup.STIRRINGstirred for 1 hour
3. 3
   TemperaturaAfter cooling again to −78° C.
4. 4
   TemperaturaAfter warming to 0° C.
5. 5
   workup.STIRRINGthe mixture was stirred for 2 hours
6. 6
   Extracciónextracted with ethyl acetate (2×50 ml)
7. 7
   LavadoThe combined extracts were washed with water (50 ml)
8. 8
   Secadodried over sodium sulfate
9. 9
   Concentraciónconcentrated under reduced pressure
10. 10
    Filtraciónfiltered
11. 11
    Lavadowashed with hexane (30 ml)
12. 12
    Otrodried under reduced pressure

Procedimiento

To a solution of 2-methyl-5-bromo-iodobenzene (12 g, 40.4 mmol) in tetrahydrofuran (75 ml), cooled to −78° C., was added a solution of isopropylmagnesium chloride (4.6 g, 44.5 mmol) in tetrahydrofuran (22.2 ml) dropwise over 20 minutes. After stirring at −78° C. for 30 minutes, the mixture was warmed slowly to −20° C. and stirred for 1 hour. After cooling again to −78° C., trimethylborate (8.4 g, 80.8 mmol) was added dropwise. After warming to 0° C., the mixture was stirred for 2 hours, treated with 1 M hydrochloric acid (35 ml), and extracted with ethyl acetate (2×50 ml). The combined extracts were washed with water (50 ml), dried over sodium sulfate, and concentrated under reduced pressure. The residual solid was suspended in hexane (50 ml), filtered, washed with hexane (30 ml) and dried under reduced pressure to provide 2-methyl-5-bromo-phenylboronic acid (7.32 g, 84% yield) as a white solid. 1H NMR (DMSO-d6) δ 7.92 (s, 1H), 7.46 (d, J=8.1 Hz, 1H), 7.13 (d, J=8.1 Hz, 1H), 2.59 (s, 3H).

Fuente