Triphenylphosphine (160 mg, 0.62 mmol), imidazole (42 mg, 0.62 mmol) and iodine (160 mg, 0.62 mmol) were added to a solution of 2-(4-chloro-3,5-diphenyl-1H-pyrazolo[3,4-c]pyridazin-1-yl)ethanol (181 mg, 0.52 mmol) in CH2Cl2 (6 ml). After stirring at ambient temperature for 1 h the reaction was filtered and solvent removed in vacuo. Purification using chromatography (silica gel, gradient 10 to 60% ethyl acetate/isohexane) gave 4-chloro-1-(2-iodoethyl)-3,5-diphenyl-1H-pyrazolo[3,4-c]pyridazine as a clear oil (202 mg) which was used as such in the subsequent step.
