- Pyrylium Compounds. XXI. - Structure and Tautomerism of Pseudobases of Unsymmetrically Substituted 2,4,6-Triarylpyrylium Salts
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Hydrolytic ring opening of unsymmetrically substituted 2,4,6-triarylpyrylium salts 11 results in a mixture of two tautomeric pseudobases, the penten-1,5-diones 13 and 14.In crystalline state as a rule one of these tautomers markedly predominates, whereas
- Fischer, Gerhard W.,Herrmann, Michael
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p. 287 - 302
(2007/10/02)
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- Pyrylium Compounds. XXII. 1H-N.M.R. and U.V. Spectroscopic Investigations on the Isomerization of Pseudobases of Unsymmetrically Substituted 2,4,6-Triarylpyrylium Salts
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The kinetics and mechanism of the isomerization of the title compounds, the pentene-1,5-diones 2 and 3, were studied by 1H-n.m.r. and u.v. spectroscopy.The equilibrium constants measured vary little near 1, indicating the small influence of substituents on the equilibrium position.The mutual rearrangement 2(*)3 proved to be a base-catalyzed reaction which is characterized by a strictly linear Hammett correlation between lg k and (*)?p.The results obtained suggest resonance-stabilized anions of type 4 as intermediates. - Pseudobases of 3-alkyl-2,4,6-triarylsubstituted pyrylium salts do not undergo a reversible isomerization.
- Fischer, Gerhard W.,Muegge, Clemens,Fink, Siegfried
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p. 647 - 656
(2007/10/02)
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