To a solution of the product of Step 1 (1.00 g, 2.43 mmol), PPh3 (1.00 g, 3.71 mmol) and diisopropylethylamine (1.3 mL, 7.28 mmol) in CH3CN (30 mL) was added hexachloroethane (0.812 g, 3.43 mmol) as a solid, portion-wise. The mixture was allowed to stir for 12 hours. TLC (3:1 hexanes:ethyl acetate) indicated the presence of starting material. Therefore, additional PPh3 (0.65 g, 2.43 mmol) and hexachloroethane (0.575 g, 2.43 mmol) were added and stirring continued for 4 hours. The solvent was removed in vacuo, the residue diluted with ethyl acetate-H2O and the layers separated. The aqueous phase was extracted twice with ethyl acetate and the combined organic layers were washed (H2O, brine), dried (Na2SO4), and filtered. The solvent was removed in vacuo and the residue purified by flash column chromatography (3:1 hexanes:ethyl acetate) to provide (S)-tert-butyl 2-(5-(4-bromophenyl)oxazol-2-yl)pyrrolidine-1-carboxylate (0.605 g, 63%). 1HNMR (400 MHz, DMSO-d6) δ 7.60-7.68 (m, 5H), 4.80-4.91 (m, 1H), 3.46-3.51 (m, 1H), 3.33-3.39 (m, 1H), 2.18-2.31 (m, 1H), 1.84-1.99 (m, 3H), 1.36 (s, 4H), 1.15 (s, 5H). LCMS: Anal. Calcd. for C18H21BrN2O3: 392. found: 393 (M+H)+.
