A solution of tert-butyl 2-[2-(5-oxido-1H-imidazo[4,5-c]quinolin-1-yl)ethoxy]ethylcarbamate (4.60 g, 12.4 mmol) in 150 mL of 1,2-dichloroethane was heated to 80° C. and treated with 10 mL of concentrated NH4OH solution. To the rapidly stirred solution was added solid p-toluenesulfonyl chloride (2.71 g, 14.2 mmol) over a 10 min period. The reaction mixture was treated with an additional 2 mL of concentrated NH4OH solution and then sealed in a pressure vessel and heating was continued for 3 h. The reaction mixture was then cooled and treated with 100 mL of CH2Cl2. The reaction mixture was then washed with H2O, 1% Na2CO3 solution (3×) and brine. The organic portion was dried over Na2SO4 and concentrated to give 4.56 g of tert-butyl 2-[2-(4-amino-1H-imidazo[4,5-c]quinolin-1-yl)ethoxy]ethylcarbamate as a light brown foam.
