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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 ]
2-Pyrone 4-Pyrone. Pyrones or pyranones are a class of heterocyclic chemical compounds. They contain an unsaturated six-membered lactone ring, which has one oxygen atom and an adjacent ketone functional group. [1] There are two isomers denoted as 2-pyrone and 4-pyrone.
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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Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. [1] It was first described by Eduard Buchner and Theodor Curtius in 1885 [ 2 ] and later by Fritz Schlotterbeck in 1907. [ 3 ]
The Knorr pyrrole synthesis is a widely used chemical reaction that synthesizes substituted pyrroles (3). [1] [2] [3] The method involves the reaction of an α-amino-ketone (1) and a compound containing an electron-withdrawing group (e.g. an ester as shown) α to a carbonyl group (2). [4] The Knorr pyrrole synthesis