A solution of (RS)—S-cyclopropyl-S-(4-nitrophenyl)-N-(trifluoroacetyl)sulphoximide in ethanol and THF was admixed with palladium on carbon and hydrogenated for 1 hour under atmospheric pressure at 25° C. Palladium on carbon was added again and the mixture was hydrogenated for a further 4.5 hours at atmospheric pressure. The mixture was filtered, the filtrate was again admixed with palladium on carbon and finally hydrogenated for 45 minutes. The mixture was filtered and concentrated by evaporation (yield: 93%).
