(S)-isopropyl 2-(5-bromo-2,6-dimethyl-4-(4-phenylpiperidin-1-yl)pyridin-3-yl)-2-hydroxyacetate → (S)-isopropyl 2-(5-bromo-2,6-dimethyl-4-(4-phenylpiperidin-1-yl)pyridin-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-2,6-dimethyl-4-(4-phenylpiperidin-1-yl)pyridin-3-yl)-2-hydroxyacetate (1.95 g, 1.5 mmol) and 0.6 mL of 70% HClO4 in DCM (25 mL) for 20 min. The reaction mixture was allowed to warm to rt and stirred for 18 h in a pressure sealed vessel, 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 (5-50% EtOAc/hexanes) using an Isolera chromatography station gave (S)-isopropyl 2-(5-bromo-2,6-dimethyl-4-(4-phenylpiperidin-1-yl)pyridin-3-yl)-2-(tert-butoxy)acetate 970 mg (44.4%) as a mixture of diastereomers. 1H NMR (500 MHz, DMSO-d6) δ 7.36-7.33 (m, 2H), 7.29-7.28 (m, 2H), 7.23-7.20 (m, 1H), 6.26 (s, 1H), 4.95-4.90 (m, 1H), 3.98 (br. s, 1H), 3.41 (br. s, 1H), 3.12 (br. s, 1H), 2.98 (br. s, 1H), 2.71 (br. s, 1H), 2.51 (s, 3H), 2.44 (s, 3H), 1.93 (br. s, 1H), 1.82-1.75 (m, 3H), 1.18 (s, 9H), 1.15 (d, J=6.2 Hz, 3H), 1.07 (d, J=5.9 Hz, 3H). UPLC (M+H)=519.2.

Provenance & Evidence