Modified Ullmann coupling of 2-chloro-3-trifluoromethylpyridine

Article abstract of DOI:10.1016/0022-1139(94)03168-Y

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. - Keywords: Ullman coupling; Chlorotrifluoromethylpyridine; Bis(trifluoromethyl)bipyridine; Synthesis; NMR spectroscopy; Mass spectrometry