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Münchnone
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 heterocyclic aromatic chemical compound, with the molecular formula C3H3NO2. The name refers to the city of Munich, 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 reactivity of münchnones, and their reaction with alkynes in the synthesis of pyrroles, 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., ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Montréalone
Montréalone (synonyms: montrealone, phospha-münchnone) is a mesoionic heterocyclic compound, heterocyclic chemical compound. It is named for the city of Montreal, Montréal, Canada, which is the location of McGill University, where it was first discovered. Structure The montréalone parent structure, parent compound has been studied theoretically,Krenske, E. H.; Houk, K. N.; Arndtsen, B. A.; St. Cyr, D. J., Cyclic 1,3-Dipoles or Acyclic Phosphonium Ylides? Electronic Characterization of "Montréalones". ''J. Am. Chem. Soc.'' 2008, ''130'', 10052. () and is unlikely to exist as a stable species. structural analog, Analogs bearing multiple substituents display chemical stability, stability suitable for synthesis, isolation, and characterization.St-Cyr, D. J.; Morin, M. S. T.; Belanger-Gariepy, F.; Arndtsen, B. A.; Krenske, E. H.; Houk, K. N., Phospha-Münchnones: Electronic Structures and 1,3-Dipolar Cycloadditions. ''J. Org. Chem.'' 2010, ''75'', 4261. () Substituted montréalon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 are highly stereo- and regioselective, and have the potential to form four new contiguous stereocenters. Azomethine ylides thus have high utility in total synthesis, and formation of chiral ligands and pharmaceuticals. Azomethine ylides can be generated from many sources, including aziridines, imines, and iminiums. They are often generated ''in situ'', and immediately reacted with dipolarophiles. Structure The resonance structures below show the 1,3-dipole contribution, in which the two carbon atoms adjacent to the nitrogen have a negative or positive charge. The most common representation of azomethine ylides is that in which the nitrogen is positively charged, and the negative charge is shared between the two carbon atoms. The r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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''-methylpyrrole, C4H4NCH3. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme. Pyrroles are components of more complex macrocycles, including the porphyrinogens and products derived therefrom, including porphyrins of heme, the chlorins, bacteriochlorins, and chlorophylls. Properties Pyrrole is a colorless volatile liquid that darkens readily upon exposure to air, and is usually purified by distillation immediately before use. Pyrrole has a nutty odor. Pyrrole is a 5-membered aromatic heterocycle, like furan and thiophene. Unlike furan and thiophene, it has a dipole in which the positive end lies on the side of the heteroatom, with a dipole moment of 1.58 D. In CDCl3, it ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 represented satisfactorily by any one mesomeric structure. Mesoionic compounds are a subclass of betaines. Examples are sydnones and sydnone imines (e.g. the stimulant mesocarb), münchnones, and mesoionic carbenes. The formal positive charge is associated with the ring atoms and the formal negative charge is associated either with ring atoms or an exocyclic nitrogen or other atom. These compounds are stable zwitterionic compounds and belong to nonbenzenoid 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 sat ...s. See also * Mesomer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sydnone Imine
Sydnone imine is a mesoionic heterocyclic aromatic chemical compound. Sydnone imine is the imine of sydnone where the keto functional group of sydnone (=O) has been replaced with an imine (=NH) group. A sydnone imine substructure can be found in the drugs feprosidnine, mesocarb, molsidomine, ciclosidomine, and linsidomine. Chemical structure See also * Montréalone * Münchnone 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 heterocyclic aromatic chemical compound, with the mole ... * Sydnone External links IUPAC Goldbook entryDictionary of Organic Compounds Simple aromatic rings Oxadiazoles Imines ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sydnone Sydnones are mesoionic heterocyclic chemical compounds possessing a 1,2,3-oxadiazole core with a keto group in the 5 position. Like other mesoionic compounds they are di-polar, possessing both positive and negative charges which are delocalized across the ring. Recent computational studies have indicated that sydnones and other similar mesoionic compounds are nonaromatic, "though well-stabilized in two separate regions by electron and charge delocalization." Sydnones are heterocyclic compounds named after the city of Sydney, Australia. A sydnone imine in which the keto group of sydnone (=O) has been replaced with an imino (=NH) group can be found as a substructure in the stimulant drugs feprosidnine and mesocarb. Discovery Sydnone was first prepared in 1935 by Earl & Mackney by cyclodehydration of N-Nitroso- N-phenylglycine with acetic anhydride. Later work |
