[NH2:1][C:2]1[C:3]([NH:8][CH2:9][N:10]2[CH2:14][CH:13]([CH2:15][CH2:16][CH3:17])[CH2:12][C:11]2=[O:18])=[N:4][CH:5]=[CH:6][CH:7]=1.[C:19]1(C)C=CC(S(O)(=O)=O)=CC=1.C([O-])(O)=O.[Na+].CCOC(C)=O>C(OC)(OC)OC>[N:1]1[C:2]2[C:3](=[N:4][CH:5]=[CH:6][CH:7]=2)[N:8]([CH2:9][N:10]2[CH2:14][CH:13]([CH2:15][CH2:16][CH3:17])[CH2:12][C:11]2=[O:18])[CH:19]=1
A solution of 1-{[(3-aminopyridin-2-yl)amino]methyl}-4-propylpyrrolidin-2-one x78 (1 eq, 1.6 mmol, 300 mg), and para-toluenesulfonic acid (0.32 mmol, 0.2 eq, 42 mg) in trimethyl orthoformate (15 ml) is allowed to react at room temperature for 3 days. After hydrolysis (20 ml of saturated NaHCO3), extraction with AcOEt (2×10 ml), drying of the cumulated organic layers over MgSO4, and filtration, the volatiles are removed under reduced pressure and the crude material is purified by preparative chromatography affording 250 mg of 1-(3H-imidazo[4,5-b]pyridin-3-ylmethyl)-4-propylpyrrolidin-2-one 268.
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