Add 1,4-phenylenediisocyanate (5.15 g, 32.2 mmol) to a stirred solution of N-(2-ethynyl-phenyl)-acetamide (2.56 g, 16.1 mmol) and 6-nitro-hexanoic acid ethyl ester (4.56 g, 24.1 mmol) in toluene (200 mL, anhydrous) and stir under N2. Add triethylamine (4.5 mL, 32.2 mmol) and heat to reflux under N2 overnight. Filter mixture through a pad of Celite® and rinse with toluene. Concentrate to get 6.2 g yellow oil. Adsorb on SiO2 and purify the residue by flash chromatography on silica gel eluting with 0-60% EtOAc/hexanes to afford the title compound (4.02 g, 76%). Correct regioisomer is confirmed by NOESY. MS (IS) 331 (M+1)+.
