To a stirred suspension of the product of Stage (ii) (18.0 g) in 2N hydrochloric acid (36.6 ml) at -5° was added to a solution of sodium nitrite (5.05 g) in water (11 ml) keeping the temperature below 0°. After stirring for a further 15 min, the solution was added to a stirred solution of sodium sulphite (23.05 g) and sodium acetate (9.95 g)in water (220 ml) at -5°. A solid deposited and the mass was stirred at -5° for a further 15 min, then warmed to room temperature over 1 h. Concentrated hydrochloric acid (25 ml) was added, the solution was heated at 75° for 30 min and then allowed to cool. The solid which had deposited was collected by filtration, washed with 2N hydrochloric acid (50 ml) followed by ethanol (50 ml) and dried in vacuo to give the title compound as a powder (18.18 g), m.p. 280°-281°.
