Reaktion #71607

Reaktionsgleichung

hydrochloric acid

n-Butyllithium

5-(4-chlorophenyl)-2-ethyl-1-bromobenzene

trimethylborate

→

5-(4-chloro-phenyl)-2-methylphenylboronic acid

Ausbeute 73.0%

Lösungsmittel

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigeis brought to −78° C.
2. 2
   workup.ADDITIONis added dropwise over 30 minutes
3. 3
   workup.STIRRINGthe reaction mixture stirred for two hours
4. 4
   workup.ADDITIONonce the addition
5. 5
   workup.STIRRINGis stirred for two hours
6. 6
   EinengenThe mixture is concentrated
7. 7
   Sonstigeto remove most of the tetrahydrofuran
8. 8
   workup.ADDITIONdiluted with water
9. 9
   Extraktionextracted with diethyl ether
10. 10
    WaschenThe organic extracts are washed with water and brine
11. 11
    Trocknendried over anhydrous sodium sulfate
12. 12
    Filtrationfiltered
13. 13
    Sonstigethe filtrate evaporated in vacuo
14. 14
    SonstigeThe residue is further purified by flash column chromatography on silica gel
15. 15
    Wascheneluting with 7% ethyl acetate in hexane

Vorschrift

5-(4-chlorophenyl)-2-ethyl-1-bromobenzene (10 g, 0.03 mol) is dissolved in THF (250 ml), and the temperature is brought to −78° C. n-Butyllithium (1.33 molar solution in hexanes, 34.6 ml,) is added dropwise over 30 minutes, maintaining the temperature at around −78° C. The reaction mixture is stirred for one and half hours, then trimethylborate (4.9 g, 0.05 mol) is added dropwise and the reaction mixture stirred for two hours. A solution of 2N aqueous hydrochloric acid (100 ml) is added dropwise, and once the addition is complete the mixture is stirred for two hours. The mixture is concentrated to remove most of the tetrahydrofuran, then diluted with water and extracted with diethyl ether. The organic extracts are washed with water and brine, combined, dried over anhydrous sodium sulfate, filtered and the filtrate evaporated in vacuo. The residue is further purified by flash column chromatography on silica gel, eluting with 7% ethyl acetate in hexane to give 5-(4-chloro-phenyl)-2-methylphenylboronic acid (5.4 g).

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