To a solution of 1-ethynyl-4-iodobenzene 6 (0.908 g, 3.98 mmol) in THF (20 mL) at −78° C. was added ethylmagnesium bromide (3M in ether, 1.39 mL, 4.18 mmol). After 10 minutes the cooling bath was removed and the solution was allowed to stir at room temperature for 1 hour. The reaction mixture was then re-cooled to 0° C. and added to a solution of N-(tert-butoxycarbonyl)-L-proline N′-methoxy-N′-methylamide 2 (0.970 g, 3.76 mmol) in THF (10 mL). The reaction mixture was warmed to room temperature and stirring was continued for 12 hours before the mixture was quenched with saturated NH4Cl. The mixture was diluted with ethyl acetate/H2O, the layers separated and the aqueous phase was re-extracted with ethyl acetate (2×). The combined organic layers were washed (H2O, brine), dried (Na2SO4), and filtered, and the solvent was removed in vacuo. The resulting residue was purified by flash chromatography (hexane:ethyl acetate, 4:1) to give (S)-tert-butyl 2-(3-(4-iodophenyl)propioloyl)pyrrolidine-1-carboxylate 7 (0.908 g, 71%) as a yellow oil which solidified on standing. 1H NMR (400 MHz, CDCl3) δ 7.72-7.76 (m, 2H), 7.26-7.30 (m, 2H), 4.49 (dd, J=8.8, 4.3 Hz, 0.3H), 4.29 (dd, J=8.5, 5.5 Hz, 0.7H), 3.59 (app t, J=6.7 Hz, 2H), 2.20-2.33 (m, 1H), 1.85-2.10 (m, 3H), 1.45, 1.40 (s, 9H, rotamers in 2:3 ratio). LCMS: Anal. Calcd. for C18H20INO3: 425. found: 326 (M+H-Boc)+.
