Sodium Hydroxide → 3-(4-Chlorophenyl)-1H-pyrrole-2-carboxylic acid

To a solution of ethyl 3-(4-chlorophenyl)-1H-pyrrole-2-carboxylate [see step 2 ACI-02] (8 g, 32.0 mmol) in DMSO (30 mL) was added NaOH (2.56 g, 64.1 mmol) and the reaction mixture was stirred at 70° C. for 20 h. An additional portion of NaOH (0.5 g, 12.5 mmol) was added and stirring at 70° C. was continued for 30 min. The reaction mixture was cooled in an ice bath and acidified with aqueous 1M KHSO4 (80 mL). The solid was filtered off and washed with aqueous 1M KHSO4 (20 mL), H2O (3×25 mL) and heptane (3×25 mL) and dried on air. The residue was dissolved in EtOAc (600 mL), dried (Na2SO4) and the solvent was removed in vacuo. The product was stirred in i-Pr2O/heptane (1:1, 100 mL). The solid was filtered and off dried in vacuo to give the desired product as a a white solid (6.04 g, 85%).