Munchnones

These are the ring structures of munchnones. It is not easily represented by diagrams because the positive and negative charge are delocalised.

Abstract
A new palladium-catalyzed route to prepare 1,3-oxazolium-5-oxides (i.e., Münchnones) directly from imine, carbon monoxide, and acid chloride building blocks has been developed. This provides a straightforward catalytic synthesis of Münchnones and is amenable to generating a diverse range of products by simple modification of the imine or acid chloride starting materials. Münchnones are vital synthetic intermediates to a variety of heterocyclic and peptide-based molecules. As such, this methodology has been utilized to design a new catalytic synthesis of alpha-amino acid derivatives via a one-pot coupling of imines, carbon monoxide, and acid chloride followed by alcohol. The latter represents the first reported catalytic synthesis of alpha-amino acids directly from imine and carbon monoxide building blocks.

Other Names
In addition to the trivial name **münchnone**, this molecule has also been referred to as a:
 * muenchnone
 * munchnone (umlaut omitted)
 * 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

Discovery and Utility
The first preparation of a münchnone derivative was reported in 1958 by Lawson & Miles by cyclodehydration of 2-Pyridone-//N//-acetic acid with acetic anhydride. [|[1]] The azomethine ylide reactivity of münchnones, and their reaction with [|alkynes] in the synthesis of [|pyrroles], was first published by [|Huisgen] et. al. [|[2]] [|[3]] 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. [|[4]] [|[5]] As such, they are typically credited for the discovery of Münchnones. 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 [|pyrroles] by their [|in situ] generation in the presence of [|alkynes].