C([C:3]1[C:8]([Br:9])=[CH:7][C:6]([Br:10])=C[N:4]=1)#N.[C:11]([OH:14])(=[O:13])[CH3:12].S(=O)(=O)(O)O>O>[Br:10][C:6]1[C:12]([C:11]([OH:14])=[O:13])=[N:4][CH:3]=[C:8]([Br:9])[CH:7]=12-Cyano-3,5-dibromopyridine (prepared in the above (2)) 3.27 g is added to a mixture of acetic acid 14 ml, sulfuric acid 14 ml and water 14 ml, and the mixture is refluxed at 140° C. for 4 hours. The reaction mixture is cooled and water is added thereto. The resulting precipitate is filtered and washed with water. The precipitate is dissolved in ether, washed and dried. The solvent is removed in vacuo and crystallized from a mixture of ether and hexane to give 3,5-dibromopyridine-2-carboxylic acid. mp 170–171° C.
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