Bipyridylium quaternary salts and related compounds. Part IV. Pyridones derived from paraquat and diquat

Abstract

The 1′,2′-dihydro-1,1′-dimethyl-2′-oxo-4,4′-bipyridylium cation (IV) and 1,1′-dimethyl-4,4′-bipyridyl-2,2′-dione (V), thought to be possible products of the action of alkali on paraquat, have been synthesised by treatment of paraquat with alkaline ferricyanide. The action of other alkaline oxidising agents was also investigated. 6,7-Dihydro-4-oxodipyrido[1,2-a:2′,1′-c]pyrazinium ion (VII) and 6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazine-4,9-dione (VIII) have been prepared and the former was confirmed as a photochemical decomposition product of diquat.