A solution containing 1.5 g of 5-benzyloxy-3-[1-tert-butoxycarbonyl-5-(2-chloroethoxy)-1H-indol-2-yl]indazole-1-carboxylic acid tert-butyl ester prepared according to procedure J, 1 g of potassium carbonate, 600 mg of potassium iodide and 761 μl of ethylamine in 75 ml of acetonitrile is heated at 80° C. for 18 hours. After this period of time, 1.5 ml of ethylamine are added and the reaction is continued for a further 18 hours at 80° C. This operation is repeated after a further 18 hours and the reaction mixture is then evaporated under reduced pressure. The brown oil obtained is taken up in a mixture of ethyl acetate (80 ml) and of water (80 ml). After separation by settling out and extraction with ethyl acetate (80 ml), the organic extracts are combined, washed with water (100 ml) and with brine (100 ml), dried over magnesium sulfate and then evaporated under reduced pressure to obtain 1.15 g of 5-benzyloxy-3-[1-tert-butoxycarbonyl-5-(2-diethylaminoethoxy)-1H-indol-2-yl]indazole-1-carboxylic acid tert-butyl ester, which is used as it is in the subsequent stage.
