Cesium carbonate → 3-(Di-tert-butoxycarbonylamino)-1-methylpiperidine

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3-(Bromomethyl)-1-methylpiperidine (1.5 g, 7.81 mmoles) (from Preparative Example 244, Step A above) and di-tert-butyliminodicarboxylate (1.697 g, 7.81 mmoles) were dissolved in anhydrous acetonitrile (25 mL). Cesium carbonate (5.1 g, 15.6 mmoles) and lithium iodide (52 mg, 0.391 mmoles) were added and the mixture was stirred at 70° C. for 20 h. The mixture was evaporated to dryness and the residue was partitioned between dichloromethane and saturated aqueous sodium bicarbonate. The organic layer was dried (MgSO4), filtered and evaporated to dryness. the residue was chromatographed on a silica gel column (30×5 cm) using 3% methanol in dichloromethane as the eluant to give 3-(di-tert-butoxycarbonylamino)-1-methylpiperidine (1.331 g, 52%): FABMS: m/z 329.2 (MH+); HRFABMS: m/z 329.2438 (MH+). Calcd. for C17H33N2O4: m/z 329.2440; δH (CDCl3) 1.10 (1H, m, CH2), 1.54 (18H, s, —COOC(CH3)3), 1.86 (2H, m, CH2), 2.01 (1H, m, CH2), 2.19 (1H m, CH), 2.34 (2H, bm, CH2), 2.59 (3H, —NCH3), 3.19 (2H, m, CH2) and 3.52/3.52 ppm (2H, —CH2N—); δC (CDCl3) CH3: 28.5, 28.5, 28.5, 28.5, 28.5, 28.5, 47.2; CH2: 25.4, 28.3, 50.4, 56.8, 60.8; CH: 37.2; C: 83.0, 83.0, 153.5, 153.5.

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