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 (x3) with ether. The combined ether layers were extracted with 2N sodium hydroxide (x1) 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.