Ring transformations of heterocyclic compounds .13. Bis(2,4,6-triarylphenyl) substituted bispyridinium salts from methyl derivatives by double pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 4,4'-bis(2,4,6-triarylphenyl) substituted bispyridinium diperchlorates 3, in which the N-atoms are linked by a carbon chain, a heteroatom containing a carbon chain or a bis(methylene) substituted aromatic/heteroaromatic ring, from 4,4'-dimethylbispyridinium derivatives 2 by a double 2,6-[C-5+C] ring transformation of 2,4,6-triarylpyrylium and 2,4,6-triarylthiopyrylium salts 1/4 is reported. Spectroscopic data of the bispyridinium diperchlorates 3 and their mode of formation are discussed.