Cyanogen Bromide → tert-butyl 2-(2-amino-4-chloro-1H-imidazo[4,5-c]quinolin-1-yl)ethylcarbamate

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Reaction Steps

Cyanogen bromide (4.6 g, 44 mmol) was added to a solution of tert-butyl 2-[(3-amino-2-chloroquinolin-4-yl)amino]ethylcarbamate (13.46 g, 39.96 mmol) in ethanol (140 mL), and the reaction was heated at reflux overnight. An analysis by LC/MS indicated the presence of starting material, and additional cyanogen bromide (1.25 g, 12.0 mmol) was added. The reaction was heated at reflux for an additional two hours, and the reaction was still incomplete. Additional cyanogen bromide (1.25 g, 12.0 mmol) was added, and the reaction was heated at reflux for two hours and allowed to cool to room temperature. Most of the solvent was removed under reduced pressure, and aqueous sodium hydroxide (700 mL of 2 N) was added. The mixture was stirred for 30 minutes, and the aqueous portion was decanted away. Ethyl acetate (500 mL) was added, and the mixture was stirred for 20 minutes. The ethyl acetate was then decanted away, and the residue was filtered. The filter cake was washed several times with diethyl ether (1 L total), and the resulting solid was stirred vigorously with diethyl ether (500 mL). The solid was collected by filtration and dried under vacuum overnight to provide 7.02 g of tert-butyl 2-(2-amino-4-chloro-1H-imidazo[4,5-c]quinolin-1-yl)ethylcarbamate as a reddish-brown solid.

Provenance & Evidence