Cesium carbonate → tert-Butyl 4-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)piperidine-1-carboxylate

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To a solution of 3-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-phenol (10.0 g, 45.4 mmol, 1.0 equiv) in NMP (100 ml) was added Cs2CO3 (44.4 g), 136.3 mmol, 3.0 equiv) and 4-methanesulfonyloxy-piperidine-1-carboxylic acid tert-butyl ester (19.0 g, 68.2 mmol, 1.5 equiv). The reaction mixture was heated to 80° C. and monitored until complete. The reaction mixture was cooled to room temperature, diluted with water and extracted with EtOAc. The organic layer was washed successively with 2N KOH, water, brine, dried (MgSO4), filtered and concentrated under reduced pressure. The target molecule was purified by column chromatography (SiO2), eluted with 5→30% EtOAc-petrol to afford a colourless liquid (9.5 g) that crystallised on standing. 1H NMR (400 MHz, CDCl3): 7.42 (1H, d), 7.37 (1H, d), 7.31 (1H, t), 7.03 (1H, dd), 4.61-4.49 (1H, m), 3.76-3.62 (2H, m), 3.47-3.32 (2H, m), 1.99-1.86 (2H, m), 1.86-1.70 (2H, m), 1.49 (9H, s).

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