MODIFIED ULLMANN COUPLING OF 2-CHLORO-3-TRIFLUOROMETHYLPYRIDINE

The application of the modified Ullmann reaction to 2-chloro-3-trifluoromethylpyridine furnishes 5,5'-bis(trifluoromethyl)-2,2'-bipyridine as the primary product, accompanied by small amounts of the expected 3,3'-bis(trifluoromethyl)-2,2'-bipyridine, 2-benzyl-3-(trifluoromethyl)pyridine, bibenzyl, 3-trifluoromethylpyridine, 3-methylpyridine, 2-hydroxyethyl-(3-trifluoromethylpyridyl) ether and 2-hydroxyethyl-(3-methylpyridyl) ether. For comparison purposes, a sample of 3,3'-bis-(trifluoromethyl)-2,2'bipyridyl was prepared by the treatment of 2,2'-bipyridyl-3,3'-dicarboxylic acid with sulfur tetrafluoride. The formation of all but two compounds mentioned above can be rationalized on the basis of the single-electron-transfer process.