To 1 kg of N-{3-[(2-chloro-5-methoxyphenyl)amino]quinoxalin-2-yl}-3-nitrobenzenesulfonamide, add a catalytic amount of platinum sulfide on carbon (Pt(S)C), 6 volumes of THF, 0.16 volume of water and 2 volumes of ethanol. The reaction mixture is stirred and heated to reflux. An aqueous potassium formate solution (1.4 volume of water+0.69 kg of potassium formate) is added. The reaction mixture is stirred at reflux until completion of the reaction and cooled down at 50° C. After the addition of 10 volumes of methanol and a one hour stirring, the catalyst is filtered off and washed with 3.4 volumes of methanol. The filtered solution is cooled down at 20° C. 0.62 kg of HCl are added. The reaction mixture is stirred at 20° C., cooled down at 5° C. and filtered. The cake is washed with methanol (6 volumes) and dried under vacuum.
