反应详情

4-Oxo-pentanoic acid ethyl ester (17.6 ml, 0.124 mol.) and conc. sulfuric acid (10 ml) were added to a solution of 4-fluorophenylhydrazine (20.2 g, 0.124 mol.) in abs. ethanol (90 ml), and the mixture was heated at reflux for 4 h. For working up, the mixture was filtered over silica gel and washed with ethanol (3×20 ml). The solution was poured into 500 ml of ice-water and extracted with ether (3×100 ml). The combined extracts were washed with 2M sodium hydrogen carbonate solution (50 ml), dried, filtered and concentrated. By recrystallisation from EE/cyclohexane (1:1) it was possible to obtain (5-fluoro-2-methyl-1H-indol-3-yl)acetic acid ethyl ester in a yield of 4.5 g (yellow solid, m.p. 61–62° C.).

1. temperatureat reflux for 4 h
2. filtrationthe mixture was filtered over silica gel
3. washwashed with ethanol (3×20 ml)
4. additionThe solution was poured into 500 ml of ice-water
5. extractionextracted with ether (3×100 ml)
6. washThe combined extracts were washed with 2M sodium hydrogen carbonate solution (50 ml)
7. customdried
8. filtrationfiltered
9. concentrationconcentrated
10. customBy recrystallisation from EE/cyclohexane (1:1) it