Ring transformations of heterocyclic compounds. XVII, 2-(2,4,6-Triarylphenyl) substituted dihydro-1H-imidazolium,dihydrothiazolium and thiazolium salts from 2-methyl derivatives by pyrylium and thiopyrylium ring transformations

The synthesis of hitherto unknown 2-(2,4,6-triarylphenyl) substituted 4,5-dihydro-1H-imidazolium perchlorates 6 , 4,5-dihydrothiazolium perchlorates 8 and thiazolium perchlorates 9 from their 2-methyl derivatives 2 , 4 and 5 , respectively, by a 2,6-C₅+C] ring transformation of 2,4,6-triarylpyrylium and -thiopyrylium salts 1/10 in ethanol in the presence of an appropriate base ( 6 : sodium ethanolate; 8,9 : anhydrous sodium acetate) is reported. Spectroscopic data of the transformation products and structural influences on their formation via anhydrobases of the salts 2 , 4 and 5 are discussed.