Reaction Steps
Diethylazodicarboxylate (DEAD, 0.077 mL, 1.15 mmol) was added to a stirred, room temperature suspension of 2,6-Dibromo-4-(dibenzothiophen-1-yl)-phenol (0.250 g, 0.576 mmol), (S)-2-hydroxy-3-phenylpropionic acid, methyl ester (0.208 g, 1.15 mmol), triphenylphosphine (0.302 g, 1.15 mmol) in benzene (3 mL) under a dry nitrogen atmosphere. Dissolution occurred and the solution was heated in an 80° C. oil bath for 16 h. More diethylazodicarboxylate (DEAD, 0.039 mL, 0.576 mmol), (S)-2-hydroxy-3-phenylpropionic acid, methyl ester (0.104 g, 0.576 mmol) and triphenylphosphine (0.151 g, 0.576 mmol) were added and the solution was stirred an additional 4 h. Upon cooling to room temperature, the reaction mixture was diluted with ether and silica gel was added. The reaction mixture was concentrated and the silica adsorbate was flash chromatographed (98:2 petroleum ether:ethyl acetate) to provide the title compound as a white solid (0. 293 g, 85%): NMR (CDCl3): δ 7.89 (dd, J=8, 1 Hz, 1H), 7.85 (ddd., J=8, 1, 1 Hz, 1H), 7.64 (d, J=2 Hz, 1H), 7.63 (d, J=2 Hz, 1H), 7.47 (dd, J=9, 8 Hz, 2H), 7.41-7.17 (m, 8H), 5.13 (dd, J=8, 6 Hz, 1H), 3.71 (s, 3H), 3.55 (dd, J=7, 4 Hz, 1H), 3.53 (dd, J=8, 4 Hz, 1H); MS (EI): [M+], 2 bromine isotope pattern, 594 (20%), 596 (40%) 598 (25%); Anal. Calc. for C28H20Br2O3S: C, 56.39, H, 3.38, N, 0.00. Found: C, 56.27, H, 3.21, N, 0.09.
