Hydrochloric Acid → Carbamic acid, N-[(1S)-1-(4-chloro-2-pyridinyl)-3-buten-1-yl]-, 1,1-dimethylethyl ester

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Reaction Steps

1B (75 g, 261 mmol) was dissolved in methanol (1500 mL). Hydrochloric acid (6N) (750 ml, 4.5 mol) was added. The reaction was stirred at rt for 2-3 hrs and then was concentrated. The residue was diluted with water (2 L), washed with ethyl acetate (500 ml). The aqueous layer was basified with saturated sodium carbonate solution, extracted into ethyl acetate (3×1 L). The combined organic layers were washed with water (1×1 L) and brine (1×1 L), dried over sodium sulfate, filtered and conc. under vacuum at 50-55° C. to give crude product (43 g, 90%). MS (ESI) m/z: 183.2 (M+H)+. The crude product (42 g, 230 mmol) was dissolved in dichloromethane (420 mL), Et3N (32.1 mL, 230 mmol) was added followed by dropwise addition of BOC2O (53.4 mL, 230 mmol). The reaction was stirred at rt for 2-3 hrs. The reaction was diluted with excess DCM (1 L), washed with water (1×500 ml) and brine (1×500 ml). The organic layer was dried over sodium sulfate, filtered, and concentrated. The crude product was then purified using silica gel chromatography to give 1C (61 g, 86%) as a pale yellow solid. MS (ESI) m/z: 283.2 (M+H)+.

Provenance & Evidence