Diethyl 3-chloro-4-nitrobenzylphosphonate (2.80 mmol, 0.86 g), tert-butyl 4-oxopiperidine-1-carboxylate (2.80 mmol, 0.557 g) and tetrahydrofuran (4.89 mL) were stirred and sodium hydride (4.19 mmol, 0.168 g) was added. The reaction was stirred overnight at room temperature. Water was added and the reaction extracted with dichloromethane. The organic phase was dried over sodium sulfate and concentrated under vacuum to afford the intermediate tert-butyl 4-(3-chloro-4-nitrobenzylidene)-piperidine-1-carboxylate (0.85 g).
