2-(5-Bromo-2,6-dimethyl-4-(4-(trifluoromethyl)piperidin-1-yl)pyridin-3-yl)-2-hydroxyacetate → (S)-isopropyl 2-(5-bromo-2,6-dimethyl-4-(4-(trifluoromethyl)piperidin-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 2-(5-bromo-2,6-dimethyl-4-(4-(trifluoromethyl)piperidin-1-yl)pyridin-3-yl)-2-hydroxyacetate (1.9 g, 4.19 mmol) and 0.4 mL of 70% HClO4 in DCM (20 mL) for 20 min. The reaction mixture was allowed to warm to rt and stirred for 18 h in a pressure sealed vessel, after which it was recooled, and an additional 0.4 mL of 70% HClO4 was added, and the reaction stirred for 24 h at rt. 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 (5-12% EtOAc/hexanes) using an Isolera chromatography station gave (S)-isopropyl 2-(5-bromo-2,6-dimethyl-4-(4-(trifluoromethyl)piperidin-1-yl)pyridin-3-yl)-2-(tert-butoxy)acetate 1.9 g (90%) as a mixture of diastereomers. 1H NMR (500 MHz, DMSO) δ 6.11 (br. s, 1H), 4.93-4.91 (m, 1H), 3.84 (br. s, 1H), 3.209 (br. s, 1H), 3.08 (br. s, 1H), 2.89 (br. s, 1H), 2.53 (s, 3H), 2.44 (br. s, 3H), 1.96 (br. s, 1H), 1.86 (br. s, 2H), 1.64-1.53 (m, 2H), 1.16 (d, J=6.3 Hz, 3H), 1.14 (s, 9H), 1.07 (d, J=6.3 Hz, 3H). UPLC (M+H)=511.4.

Provenance & Evidence