[C:1]1([NH:7][C:8]([C:10]2[N:11]=[C:12]3[CH:17]=[CH:16][C:15]([CH:18]=C)=[CH:14][N:13]3[CH:20]=2)=[O:9])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.I([O-])(=O)(=O)=[O:22].[Na+].C(O)(C)(C)C.O>C1COCC1.[Os](=O)(=O)(=O)=O>[CH:18]([C:15]1[CH:16]=[CH:17][C:12]2[N:13]([CH:20]=[C:10]([C:8]([NH:7][C:1]3[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=3)=[O:9])[N:11]=2)[CH:14]=1)=[O:22]A suspension of 150 mg of N-phenyl-6-vinylimidazo[1,2-a]pyridine-2-carboxamide, 232 μL of osmium tetroxide and 167.5 mg of sodium periodate in a mixture of 6 mL of THF, 3 mL of t-butanol and 3 mL of water is stirred for 20 hours at 20° C. and then for a further 48 hours while adding in four portions 100 μL of osmium tetroxide and 80 mg of sodium periodate. The reaction mixture is poured into 50 mL of water and the resulting mixture is extracted twice with 50 mL of ethyl acetate. The combined organic phases are washed with saturated aqueous sodium chloride solution, separated by settling, dried and concentrated to dryness under reduced pressure. The residue is chromatographed on silica, eluting with a mixture of cyclohexane and ethyl acetate (gradient from 0 to 50%) to give 100 mg of 6-formyl-N-phenylimidazo[1,2-a]pyridine-2-carboxamide in the form of a white solid
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