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2-Pyrone (α-pyrone or pyran-2-one) is an unsaturated cyclic chemical compound with the molecular formula C 5 H 4 O 2.It is isomeric with 4-pyrone.. 2-Pyrone is used in organic synthesis as a building block for more complex chemical structures because it may participate in a variety of cycloaddition reactions to form bicyclic lactones.
There are two isomers denoted as 2-pyrone and 4-pyrone. The 2-pyrone (or α-pyrone) structure 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.
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 can be obtained by a cyclisation reaction, and converted to 2-pyridone via an exchange reaction with ammonia: Pyridine forms an N-oxide with some oxidation agents such as hydrogen peroxide. This pyridine-N-oxide undergoes a rearrangement reaction to 2-pyridone in acetic anhydride: [21] [22] [23]
The Rothemund reaction. The Rothemund reaction is a condensation/oxidation process that converts four pyrroles and four aldehydes into a porphyrin. It is based on work by Paul Rothemund, who first reported it in 1936. [1] The method underpins more modern synthesis such as those described by Adler and Longo and by Lindsey.
The Trofimov reaction is a powerful reaction for building pyrroles in total synthesis. The starting ketoxime can be prepared simply by condensing hydroxylamine on a ketone. Starting from a ketone allows for a wide range of starting materials as ketones are one of the most common functional groups in organic chemistry.
The Barton–Zard reaction is a route to pyrrole derivatives via the reaction of a nitroalkene with an α-isocyanide under basic conditions. [1] It is named after Derek Barton and Samir Zard who first reported it in 1985.
In organic chemistry, the Paal–Knorr synthesis is a reaction used to synthesize substituted furans, pyrroles, or thiophenes from 1,4-diketones. It is a synthetically valuable method for obtaining substituted furans and pyrroles, which are common structural components of many natural products.