N([CH2:3]NC(N)=O)=O.[OH-].[K+].[Cl:10][C:11]1[N:19]=[CH:18][CH:17]=[C:16]([Cl:20])[C:12]=1[C:13]([OH:15])=[O:14]>C(OCC)C.CO>[Cl:10][C:11]1[N:19]=[CH:18][CH:17]=[C:16]([Cl:20])[C:12]=1[C:13]([O:15][CH3:3])=[O:14]Nitrosomethyl urea (8 g, 78.16 mmol), taken in diethyl ether (30 ml) was cooled to 0° C. and 25% aqueous KOH solution was added slowly under cooling. The ether layer was collected, dried over KOH and added dropwise to a stirring solution of 2,4-Dichloronicotinic acid (3 g, 15.62 mmol) in methanol (5 mL) at 0° C. The reaction mixture was allowed to come to room temperature within 1 hour. The organic solvent was removed under reduced pressure and the crude residue was purified by column chromatography (5-10% EtOAc in hexane) to obtain the pure methyl 2,4-dichloronicotinate (3.00 g, 99%) as colorless oil. 1H NMR (400 MHz, CDCl3): δ 8.34 (d, J=5.3 Hz, 1H), 7.33 (d, J=5.4 Hz, 1H), 3.99 (s, 3H).
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