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4-Pyrone (γ-pyrone or pyran-4-one) is an unsaturated cyclic chemical compound with the molecular formula C 5 H 4 O 2.It is isomeric with 2-pyrone. Preparation [ edit ]
4-Pyridone exists a keto-enol tautomerism with its enol tautomer 4-hydroxypyridine. In solution, the keto tautomer is favoured, [4] and the enol tautomer only becomes important in very dilute solutions or solutions of non-polar solvents. However, the enol tautomer is dominant in the gas phase. [5]
Protein folding problem: Is it possible to predict the secondary, tertiary and quaternary structure of a polypeptide sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions?
There are two isomers denoted as 2-pyrone and 4-pyrone. The 2-pyrone (or α-pyrone) structure is a lactone and is found in nature as part of the coumarin ring system. 4-Pyrone (or γ-pyrone) is found in some natural chemical compounds such as chromone, maltol and kojic acid.
Likewise a 4-hydroxyl pyrylium compound is a γ-pyrone or pyran-4-one (4), to which group belong compounds such as maltol. pyrones. 2-Pyrones are known to react with alkynes in a Diels–Alder reaction to form arene compounds with expulsion of carbon dioxide, for example: [17] Pyrone cycloaddition
The reaction shown below involves an alkyne oxymercuration reaction to generate the requisite ketone. [10] Early investigation into the Nazarov cyclization. Research involving the reaction was relatively quiet in subsequent years, until in the mid-1980s when several syntheses employing the Nazarov cyclization were published.
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The reaction of tertiary alcohols containing an α-acetylenic group does not produce the expected aldehydes, but rather α,β-unsaturated methyl ketones via an enyne intermediate. [ 8 ] [ 9 ] This alternate reaction is called the Rupe reaction , and competes with the Meyer–Schuster rearrangement in the case of tertiary alcohols.