Hydrochloric Acid → 4-Tridecylpyrrole-2-carboxylic acid

To 10.01 g (32.6 mmol) of methyl 4-tridecylpyrrole-2-carboxylate prepared in Example 32 were added 200 ml of ethanol, 80 ml of water and 5.5 g (131 mmol) of 95% sodium hydroxide and the resulting mixture was heated under reflux for 1 hour. After cooling, 100 ml of water was added thereto. The resulting mixture was acidified with hydrochloric acid and extracted with a mixed solvent of 400 ml of ethyl ether, 100 ml of ethyl acetate and 300 ml of tetrahydrofuran. An aqueous layer was extracted again with 100 ml of ethyl acetate. Then both extracts were combined, washed with a saturated solution of sodium chloride and dried over anhydrous magnesium sulfate. After concentrating the resulting solution under reduced pressure, the recrystallization of the product from a mixed solvent of hexane and tetrahydrofuran gave 7.55 g of 4-tridecylpyrrole-2-carboxylic acid as white crystals, m.p. 150°-151° C.