Synthesis
Tert-butyl 4-(2-ethoxy-2-oxoethylidene)piperidine-1-carboxylate (22 g, 81.8 mmol) was added to wet 10% Pd/C (2.2 g) and ethanol (160 mL), and the mixture was degassed and backfilled three times with hydrogen. The reaction mixture was stirred at room temperature for 2 h under the protection of a hydrogen balloon. Upon completion of the reaction, the catalyst was removed by filtration and the filtrate was concentrated to afford tert-butyl 4-(2-ethoxy-2-oxoethyl)piperidine-1-carboxylate (22.5 g, 100% yield). The m/z (M-100) was 172.1 as detected by LRMS, which was consistent with the theoretical value of 172.1.
References
[1] Heterocycles, 2001, vol. 54, # 2, p. 747 - 755
[2] Patent: WO2018/68297, 2018, A1. Location in patent: Page/Page column 135; 136
[3] Patent: WO2018/152329, 2018, A1. Location in patent: Page/Page column 48
[4] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1995, # 6, p. 641 - 644
[5] Chinese Chemical Letters, 2012, vol. 23, # 6, p. 707 - 710
