A solution of 6-methylpyrrolo[2,1-f][1,2,4]triazin-4-amine (500 mg, 3.3 mmol; preparation described in PCT Int. Pat. Appl. WO 2007/056170) in acetic acid (8 ml) was treated with 37% aq. formaldehyde solution (328 μl, 4.04 mmol) and tert-butyl piperazine-1-carboxylate (754 mg, 4.04 mmol). The mixture was stirred at 60° C. overnight. After evaporation, the residue was taken up in ethyl acetate and washed with sat. aq. sodium hydrogencarbonate solution. The aqueous layer was extracted twice with ethyl acetate. The combined organic phases were dried over magnesium sulfate and evaporated affording 1.2 g of the crude product which was used in the next step without further purification.
