Disodium → Sodium Hydroxide

To a mixture of the disodium salt of o-mercaptophenylacetic acid (formed by treatment of o-mercaptophenylacetic acid (1.68 g) with sodium hydroxide (0.8 g) in methanol (10 ml) followed by evaporation of half of the resultant solution to dryness and re-dissolution in 10 ml of DMF) and copper-bronze was added a solution of 2,5-dichloropyridine in DMF (5 ml). The reaction mixture was heated to 110°-120° C. for 90 minutes, added to water, acidified, and then extracted (×3) with ether. The combined ether layers were extracted with 2N sodium hydroxide (×1) and the resultant orange aqueous phase was acidified with dilute hydrochloric acid. The resulting suspension was filtered, and the solid was thoroughly washed with water and dried to give [2'-(5"-chloropyridin-2"-ylthio)phenyl]-acetic acid (0.88 g) as a fawn-coloured solid, m.p. 141°-4° C.