Boron trifluoride etherate → 1-Azido-1-methylcyclopentane

BF3.Et2O (934 mg, 6.23 mmol) was added drop-wise at 20° C. to a stirred solution of 1-methylcyclopentanol (520 mg, 5.19 mmol) and trimethylsilyl azide (716 mg, 6.23 mmol) in 6 mL of toluene. Then the solution was stirred at room temperature for 16 hours. The organic phase was washed with a 10% solution of NaHCO3 (10 mL), water (5 mL) and brine (5 mL), and dried over anhydrous sodium sulfate. The drying agent was removed by filtration and the solvent was evaporated at 35° C. under reduced pressure to give 1-azido-1-methylcyclopentane (720 mg) as a crude product. It was used directly in the next step without further purification.