[OH:1][C:2]1[CH:7]=[C:6]([N:8]2[CH2:12][CH2:11][CH2:10][CH2:9]2)[C:5]([CH3:13])=[CH:4][C:3]=1[CH:14]([CH3:22])[C:15](N1CCCC1)=[O:16].Cl.C1(N=C=NC2CCCCC2)CCCCC1>C(O)(=O)C>[CH3:22][CH:14]1[C:3]2[CH:4]=[C:5]([CH3:13])[C:6]([N:8]3[CH2:12][CH2:11][CH2:10][CH2:9]3)=[CH:7][C:2]=2[O:1][C:15]1=[O:16]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°.
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