Reaktion #2169945

Reaktionsgleichung

butyl lithium

2-Methoxythiophene

thienyl lithium

diethyl oxalate

NH4Cl

→

5-methoxy-2-thiopheneglyoxylic acid ethyl ester

Lösungsmittel

hexane

THF

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturheated
2. 2
   Temperaturat reflux for 1 hr
3. 3
   TemperaturAfter cooling
4. 4
   Sonstigethe clear solution is transferred to a dropping funnel by means of a siphon
5. 5
   workup.STIRRINGAfter stirring 2 hr at -78° C
6. 6
   Sonstigeis brought to -10° C
7. 7
   SonstigeThe aqueous fraction is separated
8. 8
   Extraktionextracted several times with ether
9. 9
   WaschenThe combined ether extracts are washed with water and brine
10. 10
    Trocknendried (MgSO4)
11. 11
    Einengenconcentrated

Vorschrift

2-Methoxythiophene (15.4 g) is dissolved in 100 ml anhydrous THF and butyl lithium (0.135 moles) in hexane is added dropwise. The solution is stirred at room temperature 15 hr and then heated at reflux for 1 hr. After cooling, the clear solution is transferred to a dropping funnel by means of a siphon. The solution of thienyl lithium is added dropwise to a solution of diethyl oxalate (19.7 g) in 150 ml THF at -78° C. After stirring 2 hr at -78° C, the mixture is brought to -10° C and treated with saturated NH4Cl solution. The aqueous fraction is separated and extracted several times with ether. The combined ether extracts are washed with water and brine, dried (MgSO4) and concentrated. Chromatography on silica gel (eluant = benzene) gives 5-methoxy-2-thiopheneglyoxylic acid ethyl ester (2; X1 = CH3O, X2 and X3 = H and R10 = C2H5); mp 136° - 137° C after recrystallization from benzene-hexane.

Quelle