ChemInform Abstract: Acetals and Vinyl Ethers of Unsaturated Aldehydes and Ketones in New Syntheses of Heterocyclic Compounds. Part 10. Configurational Z,E Isomerism of 1,3-Bis(6-phenyl-1,3-dioxin-4-ylidene)propan-2-ylium Perchlorates.
Abstract
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ChemInform Abstract
Trimethinecyanines (I) are synthesized from dioxinylium salts using the conventional procedure for methynecyanines. The title salts (I) exist as three configurational Z,E isomers which undergo fast and reversible interconversions at elevated temperature. Quantum-chemical calculations reveal two symmetric and one asymmetric configurations of the carbocation. Terminal carbon atoms of the trimethine bridge which are incorporated into five- or six-membered rings exhibit no Z,E isomerism of trimethinecyanines.
