反应详情

A stirred mixture of ethyl 4-oxo-6-methyl-4,5,6,7-tetrahydrobenzofuran-3-carboxylate (15.7 g, 71 mmol) and ammonium acetate (9.54 g, 124 mmol) in N,N,-dimethylformamide (75 mL) was heated at 100° C. for 2 hours. The reaction mixture was concentrated in vacuo, ice water was added, and the precipitate collected, rinsed with water then diethyl ether and dried to give ethyl 4-oxo-6-methyl-4,5,6,7-tetrahydro-1H-indole-3-carboxylate (5.94 g). To this ester was added aqueous 5N sodium hydroxide (50 mL) and ethyl alcohol (10 mL) and the mixture heated at reflux for 40 minutes. The reaction mixture was cooled in an ice water bath, acidified with aqueous hydrochloric acid, and the precipitate collected, rinsed with water then diethyl ether and dried to give 4-oxo-6-methyl-4,5,6,7-tetrahydro-1H-indole-3-carboxylic acid (5.2 g). m.p. 210-211° C.

1. temperaturethe mixture heated
2. temperatureat reflux for 40 minutes
3. temperatureThe reaction mixture was cooled in an ice water bath
4. customthe precipitate collected
5. washrinsed with water
6. dry with materialdiethyl ether and dried