Synthesis
The general procedure for the synthesis of 4-formyl-N-CBZ piperidine from N-CBZ-4-piperidine methanol (1-CBZ-4-hydroxymethylpiperidine) was as follows:
Step 3: Synthesis of benzyl 4-formyl-piperidine-1-carboxylate (3);
Oxalyl chloride (59.1 mL, 674 mmol) was dissolved in dichloromethane (500 mL) and the solution was cooled to -78 °C. The solution was then dissolved in dichloromethane (500 mL). Dimethyl sulfoxide (68.3 mL, 963 mmol) was added slowly with stirring and stirring was continued for 15 minutes. Subsequently, benzyl 4-hydroxymethyl-piperidine-1-carboxylate (2) (120 g, 481 mmol) dissolved in dichloromethane (500 mL) was added. The reaction mixture was slowly warmed to -55 °C and kept at this temperature for 15 minutes. After that, the mixture was again cooled to -78 °C and a solution of dichloromethane (250 mL) of triethylamine (205 mL, 1443 mmol) was slowly added. The reaction suspension was allowed to warm slowly to room temperature and the reaction was quenched with glacial acetic acid (100 mL). The reaction solution was washed with water and the aqueous phase was back-extracted with dichloromethane (2 x 200 mL). All organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated to afford benzyl 4-formyl-piperidine-1-carboxylate (119 g, 100% yield).
References
[1] Bioorganic and Medicinal Chemistry Letters, 2001, vol. 11, # 19, p. 2663 - 2666
[2] Patent: WO2007/93603, 2007, A1. Location in patent: Page/Page column 15
[3] Patent: WO2014/22349, 2014, A1. Location in patent: Paragraph 00158
[4] Chinese Chemical Letters, 2012, vol. 23, # 6, p. 661 - 664
[5] Organic and Biomolecular Chemistry, 2017, vol. 15, # 46, p. 9830 - 9836
