Bistriflamide of (1S,2S)-1,2-Diphenylethylenediamine -- DMAP as Catalyst

1. A solution of (1S,2S)-1,2-diphenylethylenediamine (1.06 g, 5 mmol), triethylamine (2.1 mL, 15 mmol), and DMAP (12.2 mg, 0.1 mmol) in methylene chloride (25 mL) is cooled to -78° C. 
2. To this stirred solution is added trifluoromethanesulfonic anhydride (3.39 g, 12 mmol) dropwise. The cooling bath is removed and flask contents allowed to reach ambient temperature (30 min).
3. The reaction mixture is poured into a 4% sodium bicarbonate solution, the phases separated and the aqueous phase extracted with dichloromethane (15 mL).  The combined organic phases are successively washed with hydrochloric acid (1N) and brine before being dried over anhydrous sodium sulfate.  After filtration, the filtrate is concentrated under reduced pressure and the residue subjected to flash chromatography on silica gel (100 g, eluent ethyl acetate-hexane 15% v/v) to afford the bistriflamide of (1S,2S)-1,2-diphenylethylenediamine (1.64 g, 69%), as colorless crystals, m.p. 213-214°C.