Polyhalogenoaromatic compounds. Part VII. Reaction of 4-substituted tetrachloropyridines with n-butyl-lithium, the 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-pyrrolidino0-, and tetrachloro-4-piperidine 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-di-hydro-5,8-epoxyquinoline derivatives expected from the cycloaddition 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.