1-tert-butoxycarbonyl-2-methyl-4-piperidone vinyl acetal (6.00 g) was used as starting material and dissolved in acetone (150 mL). To this solution, p-toluenesulfonic acid monohydrate (4.40 g) was slowly added under ice bath cooling and stirring conditions. After addition, the reaction mixture was gradually warmed to room temperature with continuous stirring overnight. Upon completion of the reaction, the reaction mixture was diluted with ethyl acetate and the organic layer was subsequently washed with saturated sodium bicarbonate solution and saturated aqueous sodium chloride solution sequentially. The organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure to remove the solvent to afford 1-tert-butoxycarbonyl-2-methyl-piperidone (2.40 g, 48% yield) as a yellow oil. Its 1H NMR (500 MHz, CDCl3) data were as follows: δ 1.18 (3H, d, J=7.0 Hz), 1.49 (9H, s), 2.20-2.30 (1H, m), 2.30-2.40 (1H, m), 2.45-2.55 (1H, m), 2.65-2.70 (1H, m), 3.25-3.35 ( 1H, m), 3.90-4.05 (1H, m), 4.20-4.30 (1H, m).
![1,4-Dioxa-8-azaspiro[4.5]decane-8-carboxylic acid, 7-Methyl-, 1,1-diMethylethyl ester](/CAS/GIF/126503-08-0.gif)
