130 mg (0.50 mmol) of 2-hydroxy-4-methyl-4-phenyl-2-(trifluoromethyl)-pentanal is dissolved in 15 ml of toluene and mixed with 73 mg (0.55 mmol) of 4-amino-indazole and with 0.22 ml of titanium tetraethylate and stirred at 100° C. for 2.5 hours under argon. For working-up, the reaction solution is mixed with 1 ml of saturated sodium chloride solution, and it is stirred for 30 minutes. The suspension is then suctioned off on Celite and washed with 200 ml of ethyl acetate. The organic phase is washed with saturated sodium chloride solution, dried with sodium sulfate and concentrated by evaporation in a vacuum: 246 mg. Column chromatography on silica gel with pentane-ethyl acetate yields 190 mg of the product.
