反应详情

A mixture of 1.8 g (6 mmoles) of 2-[2-hydroxy-5-methyl-4-(pyrrolidin-1-yl)-phenyl]-propionic acid pyrrolidide, 2 ml of glacial acetic acid and 2 ml of concentrated hydrochloric acid is boiled under reflux for 40 minutes. The reaction mixture is concentrated by evaporation in vacuo, water is added to the residue, the pH is adjusted to 5 with dilute sodium hydroxide solution and extraction with ether is carried out 3 times. The combined ethereal extracts are dried over sodium sulphate and concentrated in vacuo to 10 ml. 1.2 g (6 mmoles) of N,N'-dicyclohexylcarbodiimide are added thereto and the mixture is left at room temperature for one hour; the residue is filtered off, subsequently washed with ether, and the filtrate is concentrated by evaporation in vacuo. The residue is chromatographed over silica gel with petroleum ether/ether. Subsequent recrystallisation of the pure fractions from ether/petroleum ether yields 3,5-dimethyl-6-(pyrrolidin-1-yl)-benzofuran-2(3H)-one having a melting point of 68°-69°. The starting material can be obtained, for example, as follows:

1. temperatureunder reflux for 40 minutes
2. concentrationThe reaction mixture is concentrated by evaporation in vacuo, water
3. additionis added to the residue
4. extractionthe pH is adjusted to 5 with dilute sodium hydroxide solution and extraction with ether
5. dry with materialThe combined ethereal extracts are dried over sodium sulphate
6. concentrationconcentrated in vacuo to 10 ml
7. filtrationthe residue is filtered off
8. washsubsequently washed with ether
9. concentrationthe filtrate is concentrated by evaporation in vacuo
10. customThe residue is chromatographed over silica gel with petroleum ether/ether
11. customSubsequent recrystallisation of the pure fractions from ether/petroleum ether