A solution of 625 mg (85% pure, 0.75 mmol) of E-4-[5-[2-(4-tert-butylbenzyloxy)phenyl]-3-(3,5-difluoro-4-triisopropylsilanyloxybenzyl)pent-4-enyl]benzonitrile in 12 ml of toluene is mixed with 1.76 ml (13.24 mmol) of trimethylsilyl azide and 329.6 mg (1.3 mmol) of di-n-butyltin oxide and stirred at 80° C. for 12 h. After conversion is complete, the mixture is extracted with sodium bicarbonate solution. The aqueous phase is back-extracted twice with ethyl acetate. The combined organic phases are washed with sodium chloride solution, dried over sodium sulfate and concentrated. The resulting residue is purified by flash chromatography on silica gel (mobile phase: cyclohexane/ethyl acetate 1:2→ethyl acetate). 447.3 mg (0.51 mmol, 86% purity, 58% of theory) of the title compound are obtained.
