(S)-isopropyl 2-(5-bromo-4-(4-methoxy-4-methylpiperidin-1-yl)-2,6-dimethylpyridin-3-yl)-2-hydroxyacetate → (S)-isopropyl 2-(5-bromo-4-(4-methoxy-4-methylpiperidin-1-yl)-2,6-dimethylpyridin-3-yl)-2-(tert-butoxy)acetate

Participants

Reaction Steps

The isobutylene gas was bubbled into a nitrogen purged, cooled (0° C.) solution of (S)-isopropyl 2-(5-bromo-4-(4-methoxy-4-methylpiperidin-1-yl)-2,6-dimethylpyridin-3-yl)-2-hydroxyacetate (1.45 g, 3.38 mmol) and 0.32 mL of 70% HClO4 in DCM (30 mL) for 20 min. The reaction mixture was allowed to warm to rt and stirred for 48 h in a pressure sealed vessel. The reaction was then diluted with DCM, washed with 1M Na2CO3 solution, and dried over MgSO4. The crude product was charged (DCM) to a 80 g ISCO silica gel cartridge and gradient elution (0-30% EtOAc/hexanes) using an Isolera chromatography station gave (S)-isopropyl 2-(5-bromo-4-(4-methoxy-4-methylpiperidin-1-yl)-2,6-dimethylpyridin-3-yl)-2-(tert-butoxy)acetate 1.35 g (82%) as a mixture of diastereomers. 1H NMR (500 MHz, DMSO-d6) δ 6.18 (br. s, 1H), 4.93-4.89 (m, 1H), 4.01 (br. s, 1H), 3.46 (t, J=11.0 Hz 1H), 3.37-3.28 (m, 2H), 3.15 (s, 3H), 2.52 (s, 3H), 2.42 (s, 3H), 1.79-1.51 (series m, 4H), 1.16-1.14 (m, 15H), 1.07 (d, J=6.2 Hz, 3H). UPLC (M+H)=487.4.

Provenance & Evidence