Reaktion #56871

Reaktionsgleichung

hydrochloric acid

2-methyl-5-bromo-iodobenzene

isopropylmagnesium chloride

trimethylborate

→

2-methyl-5-bromo-phenylboronic acid

Ausbeute 84.3%

Lösungsmittel

tetrahydrofuran

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturthe mixture was warmed slowly to −20° C.
2. 2
   workup.STIRRINGstirred for 1 hour
3. 3
   TemperaturAfter cooling again to −78° C.
4. 4
   TemperaturAfter warming to 0° C.
5. 5
   workup.STIRRINGthe mixture was stirred for 2 hours
6. 6
   Extraktionextracted with ethyl acetate (2×50 ml)
7. 7
   WaschenThe combined extracts were washed with water (50 ml)
8. 8
   Trocknendried over sodium sulfate
9. 9
   Einengenconcentrated under reduced pressure
10. 10
    Filtrationfiltered
11. 11
    Waschenwashed with hexane (30 ml)
12. 12
    Sonstigedried under reduced pressure

Vorschrift

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).

Quelle