[Cl:1][C:2]1[C:3]([CH:24](OCC)[O:25]CC)=[N:4][C:5]([C:17]2[CH:22]=[CH:21][C:20]([Cl:23])=[CH:19][CH:18]=2)=[C:6]([F:16])[C:7]=1[N:8]=C1C=CC(=O)C=C1.S(=O)(=O)(O)O.C(#N)C.O>C(Cl)Cl>[NH2:8][C:7]1[C:6]([F:16])=[C:5]([C:17]2[CH:18]=[CH:19][C:20]([Cl:23])=[CH:21][CH:22]=2)[N:4]=[C:3]([CH:24]=[O:25])[C:2]=1[Cl:1]
A mixture of 4-((3-chloro-6-(4-chlorophenyl)-2-(diethoxymethyl)-5-fluoropyridin-4-yl)imino)cyclohexa-2,5-dienone (180 milligrams (mg), 0.401 mmol) and 0.1 molar (M) sulfuric acid (H2SO4; 0.5 mL) in a 1:1 mixture of acetonitrile/water (4 mL) was heated to 80° C. for 1 h. After stirring at room temperature for 2 h, the reaction mixture was added to CH2Cl2 (20 mL). The organic layer was washed with a saturated solution of NaCl and dried (MgSO4), and the solvent was removed leaving 4-amino-3-chloro-6-(4-chlorophenyl)-5-fluoropicolinaldehyde (82 mg, 0.273 mmol, 68% yield) as an off-white solid: mp 166-169° C.; 1H NMR (400 MHz, CDCl3) δ 10.12 (s, 1H), 7.96 (m, 2H), 7.48 (m, 2H), 4.99 (s, 2H); 19F NMR (376 MHz, CDCl3) δ −137.68; ESIMS m/z 285.64 ([M+H]+).
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