View source for Sydnone

{{more footnotes needed|date=August 2013}}
{{Chembox
|ImageFile=Sydnone circle structure.png
|ImageSize = 120px
|IUPACName=2''H''-Oxadiazol-5-one
|OtherNames=1,2,3-Oxadiazol-5(2''H'')-one
|Section1={{Chembox Identifiers
| CASNo = 534-24-7
| PubChem=12443168
| ChemSpiderID = 65792731
| StdInChI=1S/C2H2N2O2/c5-2-1-3-4-6-2/h1,4H
| StdInChIKey = BIGWXAGEQONZGD-UHFFFAOYSA-N
| SMILES = C1=NNOC1=O
}}
|Section2={{Chembox Properties
|C=2|H=2|N=2|O=2
}}
}}

'''Sydnones''' are [[mesoionic]] [[heterocyclic compound|heterocyclic]] chemical compounds possessing a C5-oxygenated [[Oxadiazole|1,2,3-oxadiazole]] core,<ref>{{GoldBookRef|title=sydnones|file=S06207}}</ref><ref name=Stewart>{{cite journal|last1=Stewart|first1=F. H. C.|title=The Chemistry of the Sydnones|journal=Chemical Reviews|date=1 April 1964|volume=64|issue=2|pages=129–147|doi=10.1021/cr60228a004}}</ref><ref name=Browne>{{cite journal|last1=Browne|first1=Duncan L.|last2=Harrity|first2=Joseph P.A.|title=Recent developments in the chemistry of sydnones|journal=Tetrahedron|date=January 2010|volume=66|issue=3|pages=553–568|doi=10.1016/j.tet.2009.10.085}}</ref> named after the city of [[Sydney]], Australia. Like other mesoionic compounds they are [[Dipolar compound|dipolar]], possessing both positive and negative charges which are delocalized across the ring.

== Discovery ==
N-phenylsydnone was first prepared in 1935 by {{ill|John Campbell Earl|de}} and {{ill|Alan W. Mackney|qid=Q112249660}} by cyclodehydration of N-Nitroso-[[N-Phenylglycine|N-phenylglycine]] with [[acetic anhydride]].<ref>{{cite journal|last1=Earl|first1=J. Campbell|last2=Mackney|first2=Alan W.|title=204. The action of acetic anhydride on N-nitrosophenylglycine and some of its derivatives|journal=Journal of the Chemical Society (Resumed)|date=1935|pages=899|doi=10.1039/jr9350000899}}</ref> Later work showed that this could be applied fairly generally to the [[nitrosamine]]s of N-substituted [[amino acid]]s.<ref name=Stewart/>

The parent compound '''sydnone''' is not synthetically accessible and may not exist.<ref name=Stewart/>{{rp|p=130}}<ref name=Browne/>{{rp|p=554}}

== Chemical structure ==
Sydnones have the following [[resonance structures]].{{citation needed|date=December 2024}}<!--Browne and Harrity (2010) instead list 5 resonance structures--> The [[exocyclic]] oxygen atom (O6) has a significant negative charge.<ref name=Browne/>
[[Image:Sydnone Resonance Structures.svg]]

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."<ref>{{cite journal|last1=Simas|first1=Alfredo|title=Are mesoionic compounds aromatic?|journal=Canadian Journal of Chemistry|date=1998|volume=76|issue=6 |pages=869–872|doi=10.1139/v98-065}}</ref>

==Examples==
* [[Cefanone]] ([[Cephanone]])
* [[Ipramidil]]
* 3-Thiomorpholino-sydnonimine {{US patent|4332801}}
* The reaction between methyl 3-benzyl-sydnone-4-acetate and diphenylacetylene is described in Ex1 of {{Cite patent|country=GB|number=1387306}} gives an analog of [[Bufezolac]].
* Synthesis and Biological Evaluation of Coumarinyl Sydnone Derivatives.<ref name="PatelPatel2011">{{cite journal|last1=Patel|first1=Keshav C.|last2=Patel|first2=Himanshu D.|title=Synthesis and Biological Evaluation of Coumarinyl Sydnone Derivatives|journal=e-Journal of Chemistry|volume=8|issue=1|year=2011|pages=113–118|issn=0973-4945|doi=10.1155/2011/705856|doi-access=free}}</ref>

==Related compounds==
A [[sydnone imine]] in which the [[ketone|keto]] [[functional group|group]] of sydnone (=O) has been replaced with an [[imine|imino]] (=NH) group can be found as a substructure in the stimulant drugs [[feprosidnine]] and [[mesocarb]].

== See also ==
* [[List of chemical compounds with unusual names#Named after geographic regions|Chemical compounds with unusual names]]
* [[Montréalone]]
* [[Münchnone]]
* [[Sydnone imine]]

==References==
{{reflist}}
* {{cite journal
 | title =  Sydnone anions and abnormal N-heterocyclic carbenes of O-ethylsydnones. Characterizations, calculations and catalyses.
 |author1=S. Wiechmann |author2=T. Freese |author3=M. H. H. Drafz |author4=E. G. Hübner |author5=J. C. Namyslo |author6=M. Nieger |author7=A. Schmidt | journal =  Chem. Commun.
 | volume = 50
 | pages = 11822–11824
 | year = 2014
 |issue=80 | doi = 10.1039/C4CC05461J  |pmid=25156208 | doi-access =free}}
* {{cite journal
 | title =  Synthesis of Sydnones and Sydnone Imines
 |author1=Claude V. Greco |author2=Wayne H. Nyberg |author3=C. C. Cheng  | journal =  Journal of Medicinal Chemistry
 | volume = 5
 | issue = 4
 | pages = 861–865
 | year = 1962
 | doi = 10.1021/jm01239a022   |pmid=14056419 }}
* {{cite journal
 | title =  Meso-ionic compounds
 |author1=Wilson Baker |author2=W. D. Ollis | journal =   Quarterly Reviews, Chemical Society
 | volume = 11
 | pages =  15–30
 | year =  1957
 | doi = 10.1039/QR9571100015   |s2cid=96888271 }}
* {{cite journal
 | title =  The Preparation of Substituted Hydrazines. I. Alkylhydrazines via Alkylsydnones
 |author1=Joseph Fugger |author2=Jack M. Tien |author3=I. Moyer Hunsberger  | journal = [[J. Am. Chem. Soc.]]
 | volume = 77
 | issue = 7
 | pages = 1843–1848
 | year =  1955
 | doi = 10.1021/ja01612a039   }}
* {{cite journal
 | title =  The Preparation of Substituted Hydrazines. II.1 3-Pyridylhydrazine via the Phototropic N-(3-Pyridyl)-sydnone
 |author1=Jack M. Tien  |author2=I. Moyer Hunsberger
  | journal =  [[J. Am. Chem. Soc.]]
 | volume = 77
 | issue = 24
 | pages = 6604–6607
 | year = 1955
 | doi = 10.1021/ja01629a052   }} 88, 178 (1961);
* {{cite journal
 | title = Sydnones. III. Preparation and Interconversion of Mercurated Derivatives of N-(3-Pyridyl)-sydnone1-3a
 |author1=Jack M. Tien  |author2=I. Moyer Hunsberger
  | journal =  [[J. Am. Chem. Soc.]]
 | volume = 83
 | issue = 1
 | pages = 178–182
 | year = 1961
 | doi = 10.1021/ja01462a035  }}
* {{cite journal
 | author = [[Alan R. Katritzky]]
 | journal = Chem. Ind. 
 | pages = 521 
 | year = 1955
 }}, ();
* {{cite journal
 | title = Some new mesoionic compounds
 |author1=Alexander Lawson  |author2=D. H. Miles
  | journal = J. Chem. Soc. 
 | pages = 2865–2871
 | year = 1959
 | doi = 10.1039/JR9590002865   }}
* {{cite journal
 | title =  A Kinetic Study of the Reaction of a "Meso-ionic" Compound (Dehydrodithizone) with Haloacetates
 |author1=J. Ogilvie |author2=V. K. Miyamoto |author3=Thomas C. Bruice | journal =  [[J. Am. Chem. Soc.]]
 | volume = 83
 | issue = 11
 | pages = 2493–2495
 | year = 1961
 | doi = 10.1021/ja01472a017   }}
* {{cite journal
 | title =  A New Class of Central Nervous System Stimulants
 | author = LEMONT B. KIER, LAURETTA E. FOX, D. DHAWAN & I. W. WATERS
 | journal =  Nature
 | volume = 195
 | issue = 4843
 | pages =  817–818
 | year = 1962
 | doi = 10.1038/195817a0
 | pmid =  14455827 |bibcode = 1962Natur.195..817K | s2cid = 1683698
 }}

== External links ==
* [https://goldbook.iupac.org/terms/view/S06207 IUPAC Goldbook entry]
* [https://books.google.com/books?id=OQrIk2rlduAC&dq=mesoionic+sydnone&pg=PA86 Dictionary of Organic Compounds]

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[[Category:Oxadiazoles]]
[[Category:Simple aromatic rings]]
[[Category:Lactones]]