NUCLEOPHILIC REACTIONS OF PYRIDINES AND IMIDAZOLES WITH VINYL AND AROMATIC HALIDES

The reaction of 4-(dimethylamino)pyridine (DMAP) with hexachlorocyclopentadiene gives two products, 1,2,3,4,5-pentakis(4-(dimethylamino)pyridinium-1-yl)cyclopentadienyl anion (1) and 1-chloro-2,3,4,5-tetrakis(4-(dimethylamino)pyridinium-1-yl)cyclopentadienyl anion(2). The pK(a) of the conjugate acid of 1, with protonation occurring on the cyclopentadienyl ring, is approximately -6. The reaction of DMAP with hexafluorobenzene gives 1,2,4,5-tetrafluoro-3,6-bis(4-(dimethylamino)-pyridinium-1-yl)benzene (3); its X-ray single crystal structure is presented. Upon further treatment of 3 with DMAP, 1-fluoro-2,3,4,5,6-pentakis(4-(dimethylamino)pyridinium-1-yl)benzene (4) is produced. The nucleophiles DMAP, 4-phenylpyridine, 1-methylimidazole, and 1-phenylimidazole were used with 1,2-dichlorotetrafluorocyclobutene to produce, respectively, 1,2-bis(4-(dimethylamino)-pyridinium-1-yl)tetrafluorocyclobutene (5),1,2-bis(4-phenylpyridinium-1-yl)tetrafluorocyclobutene (6),1,2-bis(3-methylimidazolium-1-yl)tetrafluorocyclobutene (7), and 1,2-bis(3-phenylimidazolium-1-yl)tetrafluorocyclobutene (8). The electrochemistry of some of these compounds is described.