[CH2:1]([O:3][C:4](=[O:13])[C:5]1[CH:10]=[CH:9][N:8]=[C:7](C=O)[CH:6]=1)[CH3:2].[CH:14]([O:21][CH2:22][CH3:23])([O:18][CH2:19][CH3:20])OCC.Cl.C(=O)([O-])[O-].[K+].[K+]>C(O)C>[CH2:1]([O:3][C:4](=[O:13])[C:5]1[CH:6]=[CH:7][N:8]=[C:9]([CH:14]([O:18][CH2:19][CH3:20])[O:21][CH2:22][CH3:23])[CH:10]=1)[CH3:2]To a solution of 2-formyl-isonicotinic acid ethyl ester (5.0 g, 0.027 mol) in ethanol (9 mL) was added triethyl orthoformate (6.2 mL, 0.037 mol) followed by a solution of 6N hydrochloric acid in ethanol (1.5 mL). The mixture was heated to 110° C. (reflux) for 1.5 h, cooled to rt and solid potassium carbonate (1.80 g) added. The mixture was stirred for 5 min, concentrated in vacuo, and redissolved in diethyl ether (100 mL). The reaction was filtered through silica and the resulting cake washed with diethyl ether (50 mL). The filtrated was concentrated in vacuo to give 2-diethoxymethyl-isonicotinic acid ethyl ester as an oil.
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