2,2,6,6-Tetramethylpiperidine → 2-Fluoro-5-(1-(4-(methylthio)phenyl)ethyl)pyridin-3-ylboronic acid

Participants

Reaction Steps

2-Fluoro-5-(1-(4-(methylthio)phenyl)ethyl)pyridine (1.078 g, 4.359 mmol) and triisopropyl borate (2.50 mL, 10.9 mmol) were dissolved in THF (11.5 mL). In a separate flask, 2,2,6,6-tetramethylpiperidine (1.11 mL, 6.54 mmol) was dissolved in THF (12 mL) and the flask was cooled in an ice water bath. Then, n-butyllithium solution (1.6 M in hexanes, 3.8 mL, 6.1 mmol) was added via syringe, and the yellow solution was stirred under nitrogen for 15 min. Then, the contents were transferred via syringe to the other flask, which was pre-cooled in a dry ice/acetone bath. After completing the transfer, the reaction was stirred under nitrogen at −78° C. for 1 h. Then, the reaction was allowed to slowly warm up to room temperature while being stirred overnight. The reaction was treated with water (30 mL) and stirred for about 30 min. The layers were separated, and the organic phase was extracted with 1 N aqueous NaOH (15 mL). The organic phase was discarded, and the aqueous phase was treated with aqueous 5 N HCl to lower the pH to around 5-6. The aqueous phase was extracted with 10:1 DCM/MeOH. The extracts were combined, concentrated, and dried under high vacuum to afford 2-fluoro-5-(1-(4-(methylthio)phenyl)ethyl)pyridin-3-ylboronic acid (1.2342 g). 1H NMR (400 MHz, CDCl3) δ 8.17-8.05 (m, 2H), 7.25-7.19 (m, 2H), 7.15-7.10 (m, 2H), 4.16 (q, J=7.37 Hz, 1H), 2.47 (s, 3H), 1.66 (d, J=7.24 Hz, 3H). m/z (ESI, +ve ion) 292 (M+H)+.

Provenance & Evidence