[CH2:1]([O:8][C:9]1[C:10]2[N:11]([CH:15]=[C:16]([CH3:18])[N:17]=2)[CH:12]=[CH:13][CH:14]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.P(Cl)(Cl)(Cl)=O.[C:24](=O)([O-])[OH:25].[K+]>CN(C)C=O>[CH2:1]([O:8][C:9]1[C:10]2[N:11]([C:15]([CH:24]=[O:25])=[C:16]([CH3:18])[N:17]=2)[CH:12]=[CH:13][CH:14]=1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1.[CH:9]([O:8][CH:1]([CH3:2])[CH3:24])([CH3:14])[CH3:10]4.77 g (0.02 mol) of 8-benzyloxy-2-methylimidazo[1,2-a]pyridine are stirred at 60° C. for 2.5 h in a Vilsmeier mixture of 20 ml of dimethylformamide and 2.3 ml of phosphorus oxychloride and the mixture is worked up in a customary manner using ice/water and potassium hydrogen carbonate. 8-Benzyloxy-2-methylimidazo[1,2-a]pyridine-3-carboxaldehyde of m.p. 105°-106° C. (from diisopropyl ether) is obtained. This compound is debenzylated analogously to Kaminski et al., J. Med. Chem. 28, 876 (1985), method H, to give the title compound of m.p. 251°-252° C.
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