Chloroacetaldehyde → Imidazo[1,2-a]pyridin-5-amine
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[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([NH2:8])[N:3]=1.O.C(=O)(O)[O-].[Na+].Cl[CH2:16][CH:17]=O>[Na+].[Cl-].CCO>[N:1]1[CH:16]=[CH:17][N:3]2[C:4]([NH2:8])=[CH:5][CH:6]=[CH:7][C:2]=12[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([NH2:8])[N:3]=1.O.C(=O)(O)[O-].[Na+].Cl[CH2:16][CH:17]=O>[Na+].[Cl-].CCO>[N:1]1[CH:16]=[CH:17][N:3]2[C:4]([NH2:8])=[CH:5][CH:6]=[CH:7][C:2]=12To a solution of 2,6-diaminopyridine (5.00 g, 45.8 mmol) in 1:1 H2O:EtOH (10 mL) were added sodium bicarbonate (5.00 g, 59.5 mmol) and chloroacetaldehyde (4.31 g, 27.5 mmol). The reaction mixture was heated to 70° C. overnight, then cooled to rt, diluted with saturated aqueous NaCl (100 mL), and extracted with n-butanol (3×200 mL). The organic layers were combined, dried (MgSO4), and concentrated. The crude residue was purified (FCC, 2 N NH3 in MeOH/DCM) to give imidazo[1,2-a]pyridin-5-ylamine (1.32 g, 22%). MS (ESI+): calcd for C7H7N3 m/z 133.06, found 134.1 (M+H)+. 1H NMR (d6-DMSO): 8.23-8.21 (m, 1H), 7.91 (d, J=1.3, 1H), 7.50 (dd, J=8.8, 7.4, 1H), 7.22 (d, J=8.8, 1H), 6.97 (br s, 2H), 6.37 (dd, J=7.4, 0.9, 1H).
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