To a solution of N-(3,4-dichlorophenyl)-2-chloro-3-nitro-5-trifluoromethylbenzamide (0.76 g; 1 eq.) in dioxane (12 ml) is added piperidine (0.4 ml; 2.2 eq.). After stirring for 18 hours at 25° C., 10 ml of water are added and the product is extracted with ethyl acetate. The organic phase is dried and concentrated. The orange oil obtained is dissolved in 2 ml of ethyl ether and 120 ml of hexane. After 3 days at 0° C., the solid is filtered off by suction and dried. 540 mg of N-(3,4-dichlorophenyl)-3-nitro-2-piperid-1-yl-5-trifluoromethylbenzamide are obtained (m.p.=144° C.).
