Sulfuric Acid → HCID 13343680, compound

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Reaction Steps

8-Chloro-3-(o-chlorophenyl)-5,6-dihydrofuro[3,2-f]-1,2-benzisoxazole-6-carboxylic acid (4d) was prepared from (3d) using the procedure above; the product contained a significant impurity, presumably the countercyclized 5-(3-benzisoxazolyl)-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acid. The mixture was dissolved in 200 ml. absolute ethanol and treated with 0.5 ml. concentrated sulfuric acid overnight. The solution was then evaporated to dryness, redissolved in ethyl acetate, washed with brine, dried over anhydrous magnesium sulfate, and re-evaporated. Chromatography of the ester on silica gel with chloroform and n-hexane in a 3:1 ratio gave a solid, m.p. 136° C., which was determined by detailed mass spectral analysis to be the desired isomer. Hydrolysis at 60° C. in 25 ml. absolute ethanol and 200 ml. aqueous 1M sodium hydroxide for 20 minutes furnished a white precipitate which was distributed between ethyl acetate and 4.0 M aqueous hydrochloric acid, washed with brine, dried over anhydrous magnesium sulfate, and evaporated. Recrystallization from ethyl acetate with n-hexane gave (4 d), m.p. 224°-225° C., in 8.1% yield. Analysis (C16H9Cl2NO4) C,H,N,Cl.

Provenance & Evidence