Hydrochloric Acid → 1,4-Dihydroxy-isoquinoline-3-carboxylic acid butyl ester

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Reaction Steps

4.41 g of sodium (190 mmol) were dissolved in 250 ml of n-butanol with stirring. After the sodium was completely dissolved the solution was allowed to cool to ambient temperature and a solution of 24.0 g (91.9 mmol) of (1,3-dioxo-1,3-dihydro-isoindol-2-yl)-acetic acid butyl ester in 150 ml of butanol was added with stirring. The solution was heated to 100° C. within 30 min and stirred at this temperature for 1 h. Then the mixture was allowed to cool to ambient temperature and was stored at ambient temperature for 18 h. Then the pH of the mixture was adjusted to 2 to 3 by the addition of aqueous 2N hydrochloric acid with stirring. Stirring was continued for 30 min before the solid component was filtered by suction. The filter cake was washed thoroughly with water, and dried in vacuo at 50° C. to give a white solid. 17.75 g of the title compound were obtained; MS-(+)-ion: M+1=262.1 amu.

Provenance & Evidence