A pyrylium may be any derivative of the pyrylium cation.Contents 1 Chemical properties 2 Synthesis 3 Pyrones 3.1 Chemical properties 4 Chromenylium ion 5 Flavylium ion 6 See also 7 ReferencesChemical propertiesThe carbon to oxygen double bond is also an oxonium ion, which due to aromatic stabilization is much less reactive than ordinary oxonium ions.
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Being aromatic, pyrylium salts are easily formed from simplestarting materials, and their reactivity towards nuclephiles makesthem useful materials for obtaining other compounds with strongeraromatic character. Thus, pyrylium salts afford pyridines withammonia, pyridinium salts with primary amines, pyridine-N-oxideswith hydroxylamine, phosphabenzenes with phosphine derivatives, salts with hydrogen sulfide,and benzene derivatives with acetonitrile or nitromethane.
Pyrylium Salts Part I. Syntheses - ResearchGate
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The high electronegativity of the oxygen results in the strongest single perturbation of one heteroatom in a six-membered ring.Being aromatic, pyrylium salts are easily formed from simple starting materials, and their reactivity toward nucleophiles makes them useful materials for obtaining other compounds with stronger aromatic character.
Synthesis and reactions of benzo[b]furo[2,3-c]pyrylium ..
SynthesisPyrylium salts with aromatic substituents such 2,4,6-triphenylpyrylium tetrafluoroborate can be obtained from two moles of acetophenone and one mole of benzaldehyde in the presence of tetrafluoroboric acid and an oxidizing agent (Dilthey synthesis).
A pyrylium salt is a salt containing a pyrylium cation or a ..
Abstract: The development of chemical applications of graph theory is reviewed from a personal perspective. Graph-theoretical methods for finding all graphs fulfilling certain mathematical conditions followed by eliminating chemically impossible solutions are equivalent to the ‘Sherlock Holmes principle’. For molecular graphs, this is illustrated by monocyclic aromatic systems and by valence isomers of annulenes. Using dualist graphs for benzenoids and diamond hydrocarbons it was possible to develop simple encoding systems that allowed convenient enumerations of isomers. Starting with the invention of reaction graphs in 1966 that included the Petersen graph which is also the 5-cage (the smallest graph with girth 5) two gaps were filled by discovering the first 10-cage and the unique 11-cage, showing how chemical clues can lead to interesting mathematical developments. Graphs of a third type are represented by synthon graphs that are helping chemical synthesis. Connections between chemical structure and molecular properties allow the design of biologically active substances on the basis of quantitative structure-activity relationships (QSARs). Some of the simplest tools for QSAR are topological indices and they are briefly discussed.
Synthesis of a novel pyrylium salt with chemoselectivity to a ..
Thus, pyrylium salts afford pyridines with ammonia, pyridinium salts with primary amines, pyridine-N-oxides with hydroxylamine, phosphabenzenes with phosphine derivatives, thiopyrylium salts with hydrogen sulfide, and benzene derivatives with acetonitrile or nitromethane.