Hydrochloric Acid → 4-methyl-1-oxo-1H-2-benzothiopyran-3-carboxylic acid

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Reaction Steps

A stirred solution of 2.00 g. (7.17 mM) of the carboxylic acid of Example 13 in 15 ml. of 15% sodium hydroxide is refluxed for 0.75 hour, cooled, and poured into dilute hydrochloric acid, whereupon a precipitate forms. The solid is collected and recrystallized from ethyl acetate-hexane to give a tan solid. This solid is heated briefly to 245°, cooled, and the residue recrystallized from ethyl acetatehexane to give 4-methyl-1-oxo-1H-2-benzothiopyran-3-carboxylic acid as tan crystals, m.p. 247°-248°.

Provenance & Evidence