A 200 mL round bottom flask containing 4.92 g (15.5 mmol) of vacuum-dried 2-(4-tert-butyl-2-1,3-dioxinan-2-yl-phenyl)-4,4-dimethyl-4,5-dihydro-oxazole was fitted with a stir bar, septum, and nitrogen inlet. Established and maintained N2 atmosphere. Added 100 mL of anhydrous THF. Cooled the solution to −78° C. Stirred rapidly and added 7.5 mL (19 mmol) of a 2.5 M solution of n-butyllithium in hexane dropwise over 5 minutes. Stirred the clear yellow solution at −17° C. for 3 hr. The solution became a deep red-orange color. Cooled the solution to −78° C. Stirred rapidly and added 5.89 g (18.7 mmol) of N-fluorobenzenesulfonimide dissolved in 30 mL anhydrous THF dropwise over 10 min. Stirred the reaction mixture at −78° C. for 5 min. Stirred at −20° C. for 30 min. Stirred at room temperature for 1 h. Poured the reaction mixture into 150 mL of 50% saturated aqueous NH4Cl and 300 mL Et2O. Separated phases and washed the organic phase with 150 mL water and 150 mL brine. Dried over Na2SO4 and removed the solvent on rotavap. Purified by silica gel flash chromatography using isocratic elution with 25% EtOAc/CH2Cl2. Recrystallized the isolated product from hexane to obtain 1.88 g of the title compound as light amber crystals. MS (ESI) 336 (M+H)+.
