반응 #69952

반응 방정식

trimethyl borate

sodium carbonate

butyl lithium

hexane

triphenylphosphine

4-chloro-iodobenzene

3,5-dibromo-2-ethyl-thiophene

→

3-bromo-5-(4-chlorophenyl)-2-ethyl-thiophene

수율 75.0%

용매

THF

diethyl ether

반응 조건

후처리

1. 1
   workup.STIRRINGThe reaction is stirred at −78° C. for 30 minutes
2. 2
   온도to warm to room temperature
3. 3
   workup.STIRRINGstirred for a further 60 minutes
4. 4
   온도the reaction is heated
5. 5
   온도to reflux for 3 hours
6. 6
   기타The cooled reaction mixture
7. 7
   기타is partitioned between ether (250 ml) and water (300 ml)
8. 8
   기타The organic layer is separated
9. 9
   건조dried over magnesium sulphate
10. 10
    여과filtered
11. 11
    기타evaporated under reduced pressure
12. 12
    기타The residue is therefore purified by flash chromatography on silica gel

실험 절차

To a solution of 3,5-dibromo-2-ethyl-thiophene (3.28 g, 12.15 mmol) in diethyl ether (50 ml) at −78° C. under N2 is added, slowly, 2.5M butyl lithium in hexane solution (4.86 ml, 12.15 mmol) over 10 minutes and the reaction stirred at −78° C. for a further 30 minutes. The reaction is then cooled to −78° C. before the dropwise addition of trimethyl borate (1.64 ml, 14.6 mmol) over 5 minutes. The reaction is stirred at −78° C. for 30 minutes, then allowed to warm to room temperature and stirred for a further 60 minutes. Palladium acetate (68 mg, 0.3 mmol), triphenylphosphine (314 mg, 1.2 mmol) and 4-chloro-iodobenzene (4.9 g, 12.15 mmol) is then added to the reaction, followed by THF (50 ml) and 1N sodium carbonate solution (20 ml) and the reaction is heated to reflux for 3 hours. The cooled reaction mixture is partitioned between ether (250 ml) and water (300 ml). The organic layer is separated, dried over magnesium sulphate, filtered and evaporated under reduced pressure. The residue is therefore purified by flash chromatography on silica gel to give 3-bromo-5-(4-chlorophenyl)-2-ethyl-thiophene as a white solid (2.75 g).

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