Cl.[CH3:2][C:3]1[N:4]([NH2:16])[C:5]2[C:14]3[CH:13]=[CH:12][CH:11]=[CH:10][C:9]=3[N:8]=[CH:7][C:6]=2[N:15]=1.[C:17]1(C)[CH:22]=CC(S(O)(=O)=O)=C[CH:18]=1.O.CO>COC(OC)(C)C>[C:17](=[N:16][N:4]1[C:5]2[C:14]3[CH:13]=[CH:12][CH:11]=[CH:10][C:9]=3[N:8]=[CH:7][C:6]=2[N:15]=[C:3]1[CH3:2])([CH3:22])[CH3:18]A suspension of 2-methyl-1H-imidazo[4,5-c]quinolin-1-amine hydrochloride (1.79 g, 7.62 mmol) in 30 mL of 2,2-dimethoxypropane was treated with 90 mg of p-toluenesulfonic acid. The reaction mixture was heated to 100° C. overnight. The reaction mixture was then treated with 10 mL of H2O and 10 mL of MeOH, and heating was continued for 24 h. The reaction mixture was cooled and concentrated under reduced pressure. The resulting oil was dissolved in 50 mL of CHCl3 and washed with 2% Na2CO3 solution, H2O and brine. The organic portion was dried over Na2SO4, filtered and concentrated to give N-isopropylidene(2-methyl-1H-imidazo[4,5-c]quinolin-1-yl)amine (1.82 g) as a yellow solid.
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