Phosphoric Acid → Methyl 2-(5-acetylthiophen-2-yl)acetate
Reaktionsgleichung
[CH3:1][O:2][C:3](=[O:10])[CH2:4][C:5]1[S:6][CH:7]=[CH:8][CH:9]=1.[C:11](OC(=O)C)(=[O:13])[CH3:12].OP(O)(O)=O>>[CH3:1][O:2][C:3](=[O:10])[CH2:4][C:5]1[S:6][C:7]([C:11](=[O:13])[CH3:12])=[CH:8][CH:9]=1Komponenten
4
Versuchsvorschrift
A mixture of 2-thienylacetic acid methyl ester, 1.41 g. (0.01 mol) and acetic anhydride, 4.2 g. (0.04 mol) was heated at 70°-80° C. and 0.2 g. of 85% H3PO4 was added dropwise with mechanically stirring. The reaction was somewhat exothermic but cooling was not necessary. The mixture was maintained between 70°-80° C. for 3 hours, and then, poured onto ice-water followed by extraction with ether. Organic layer was washed with water several times, dried over anhyd. MgSO4 and evaporated. The residue was distilled at 2mmHg and a fraction between 160° C. and 172° C. was collected. This material was gradually crystallized and could be recrystallized from the mixture of light-petroleum and benzene. m.p. 43°-44° C. Yield; 1.39 g. (76.5%)