Synthesis
General procedure: a mixture of 3,5-dibromopyridine (0.500 g, 2.11 mmol), ethyl 4-piperidinecarboxylate (1.60 g, 10.2 mmol) and cesium carbonate (0.729 g, 2.24 mmol) was placed in a microwave reactor and heated with stirring for 1 hr at 150 °C. After completion of the reaction, the mixture was cooled to room temperature and concentrated. The residue was purified by silica gel column chromatography using hexane/ethyl acetate as eluent to afford ethyl 1-(5-bromopyridin-3-yl)piperidine-4-carboxylate as a yellow oil (0.078 g, 12% yield). The intermediate was further reacted according to the last three steps described in Example 106 to prepare the target compound. The product was structurally confirmed by 1H NMR (500 MHz, CDCl3) and 13C NMR (125 MHz, CDCl3) and analyzed by LCMS showing a purity of >99% with a retention time of 1.19 minutes and a molecular ion peak (M+H+) of 437.3.
References
[1] Patent: WO2005/19200, 2005, A2. Location in patent: Page/Page column 102-103
[2] Patent: WO2014/43068, 2014, A1. Location in patent: Page/Page column 213
