a) N-Boc-4-piperidone (1.0 g, 5.0 mmol) was dissolved in anhydrous ether (10 mL) and cooled to -10°C under nitrogen protection. An ether solution of methylmagnesium bromide (3M, 2.5 mL, 7.5 mmol) was slowly added dropwise, and the reaction mixture was stirred for 5 minutes after the drop was completed. The cooling bath was removed and the reaction mixture was allowed to warm to room temperature and stirring was continued for 2 hours. Upon completion of the reaction, the reaction was quenched with saturated aqueous ammonium chloride solution (10 mL) and subsequently diluted with water (20 mL) and ether (20 mL). The aqueous phase was separated and extracted with ether (2 x 30 mL), and the combined organic phases were washed with brine (50 mL), dried over anhydrous sodium sulfate, and concentrated under reduced pressure to afford N-BOC-4-methyl-4-hydroxypiperidine as a colorless oil (1.05 g, 97% yield).1H NMR (400 MHz, CDCl3) δ 3.76-3.64 (m, 2H), 3.29 -3.16 (m, 2H), 1.66 (s, 1H), 1.45 (s, 9H), 1.25 (s, 3H), solvent peaks were not clearly attributed.
