POLYHALOGENOAROMATIC COMPOUNDS .7. REACTION OF 4-SUB-STITUTED TETRACHLOROPYRIDINES WITH N-BUTYL-LITHIUM, GENERATION OF 2-PYRIDYNES, AND THEIR TRAPPING AS ADDUCTS WITH FURAN

The reactions of n-butyl-lithium with 2,3,5,6-tetrachloro-4-dimethylamino-, tetrachloro-4-pyrrolidino-, and tetrachloro-4-piperidino-pyridine lead to the corresponding 2,5,6-trichloro-4-dialkylamino-3-pyridyl-lithiums. The same reaction with 2,3,5,6-tetrachloropyridine gives tetrachloro-4-pyridyl-lithium; Reaction with tetrachloro-4-methylpyridine gives (tetrachloro-4-pyridyl)methyl- lithium; And reaction with 3-bromo-2-chloropyridine gives 2-chloro-3-pyridyl- lithium. In the presence of furan, the 2-chloro-3-pyridyl-lithium compounds gave the 5,8-dihydro-5,8-epoxyquinoline derivatives expected from the cycloaddrtion of the corresponding 2-pyridynes to furan. Some other derivatives of the 2-pyridynes, formed by cycloaddition or by addition of organolithium compounds, are described. The evidence for 2-pyridyne intermediates is discussed.