Münchnone (synonyms: 1,3-oxazolium-5-oxide; 1,3-oxazolium-5-olate; anhydro-5-hydroxy-1,3-oxazolium hydroxide; 5-hydroxy-1,3-oxazolium hydroxide, inner salt; oxido-oxazolium) is a

mesoionic In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be rep ...

heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

, with the molecular formula C₃H₃NO₂. The name refers to the city of

Munich Munich ( ; german: München ; bar, Minga ) is the capital and most populous city of the German state of Bavaria. With a population of 1,558,395 inhabitants as of 31 July 2020, it is the third-largest city in Germany, after Berlin and ...

, Germany (), where the compound and its derivatives were first discovered and studied.

Synthesis and reactivity

The first preparation of a münchnone derivative was reported in 1959 by Lawson & Miles by cyclodehydration of 2-pyridone-''N''-acetic acid with acetic anhydride. The

azomethine ylide Azomethine ylides are nitrogen-based 1,3-dipoles, consisting of an iminium ion next to a carbanion. They are used in 1,3-dipolar cycloaddition reactions to form five-membered heterocycles, including pyrrolidines and pyrrolines. These reactions a ...

reactivity of münchnones, and their reaction with

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

s in the synthesis of

pyrrole Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4 H4 NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-meth ...

s, was first published by Huisgen et al. The Huisgen group followed up with a thorough investigation of the chemical properties, reactivity, and utility of münchnones towards the synthesis of many other products.Gribble, G. W. In ''Oxazoles: Synthesis, Reactions, and Spectroscopy'', A; Palmer, D. C., Ed.; Wiley: New York, 2003; Vol. 60. () As such, they are typically credited for the discovery of the münchnone class of molecules. While certain substituted münchnones are stable and easily isolated under ambient conditions, the majority are unstable, including the parent münchnone itself. Münchnones are typically used as 1,3-dipolar cycloaddition substrates in the synthesis of

s by their

in situ ''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...

generation in the presence of

References

{{DEFAULTSORT:Munchnone Oxazolines Simple aromatic rings Lactones

Synthesis and reactivity

See also

References