Editing Oxonium ion (section)

==Relevance to natural product chemistry==
Complex bicyclic and tricyclic oxonium ions have been proposed as key intermediates in the biosynthesis of a series of [[natural product]]s by the red algae of the genus ''[[Laurencia]]''.<ref name=":0">{{cite journal |last1=Sam Chan |first1=Hau Sun |last2=Nguyen |first2=Q. Nhu N. |last3=Paton |first3=Robert S. |last4=Burton |first4=Jonathan W. |date=2019-10-09 |others=A full list of references encompassing the contributions from Braddock, Snyder, Murai, Suzuki, Fukuzawa, Burton, Kim, and Fox are available inside. |title=Synthesis, Characterization, and Reactivity of Complex Tricyclic Oxonium Ions, Proposed Intermediates in Natural Product Biosynthesis |journal=Journal of the American Chemical Society |volume=141 |issue=40 |pages=15951–15962 |doi=10.1021/jacs.9b07438 |pmid=31560524 |s2cid=203580092 |issn=0002-7863 |url=https://ora.ox.ac.uk/objects/uuid:0188aa06-1672-434d-a33b-9c6862ff937a}}</ref>
[[File:Oxoniumionlaurencia2.png|center|900x900px]]

Several members of these elusive species have been prepared explicitly by total synthesis, demonstrating the possibility of their existence.<ref name=":0" /> The key to their successful generation was the use of a [[Non-coordinating anion|weakly coordinating anion]] (Krossing's anion, [Al(pftb)<sub>4</sub>]<sup>−</sup>, pftb = perfluoro-''tert''-butoxy) as the counteranion.<ref>{{cite journal |last=Krossing |first=Ingo |date=2001 |title=The Facile Preparation of Weakly Coordinating Anions: Structure and Characterisation of Silverpolyfluoroalkoxyaluminates AgAl(ORF)4, Calculation of the Alkoxide Ion Affinity |journal=Chemistry – A European Journal |volume=7 |issue=2 |pages=490–502 |doi=10.1002/1521-3765(20010119)7:2<490::aid-chem490>3.0.co;2-i |pmid=11271536 |issn=1521-3765}}</ref> As shown in the example below, this was executed by a transannular halide abstraction strategy through the reaction of the oxonium ion precursor (an [[Halocarbon|organic halide]]) with the silver salt of the Krossing's anion Ag[Al(pftb)<sub>4</sub>]•CH<sub>2</sub>Cl<sub>2</sub>, generating the desired oxonium ion with simultaneous precipitation of inorganic [[silver halide]]s. The resulting oxonium ions were characterized comprehensively by [[nuclear magnetic resonance spectroscopy]] at low temperature (−78&nbsp;°C) with support from [[density functional theory]] computation.
[[File:Wiki fig 2.png|center|600x600px]]

These oxonium ions were also demonstrated to directly give rise to multiple related [[natural product]]s by reacting with various [[nucleophile]]s, such as water, bromide, chloride, and acetate.<ref>{{cite journal |last1=Wang |first1=Bin-Gui |last2=Gloer |first2=James B. |last3=Ji |first3=Nai-Yun |last4=Zhao |first4=Jian-Chun |date=March 2013 |title=Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology |journal=Chemical Reviews |volume=113 |issue=5 |pages=3632–3685 |doi=10.1021/cr9002215 |pmid=23448097 |issn=0009-2665 |url=http://ir.yic.ac.cn/handle/133337/9046|url-access=subscription }}</ref><ref>{{cite journal |last1=Zhou |first1=Zhen-Fang |last2=Menna |first2=Marialuisa |last3=Cai |first3=You-Sheng |last4=Guo |first4=Yue-Wei |date=2015-02-11 |title=Polyacetylenes of Marine Origin: Chemistry and Bioactivity |journal=Chemical Reviews |volume=115 |issue=3 |pages=1543–1596 |doi=10.1021/cr4006507 |pmid=25525670 |issn=0009-2665}}</ref><ref>{{cite journal |last1=Wanke |first1=Tauana |last2=Philippus |first2=Ana Cláudia |last3=Zatelli |first3=Gabriele Andressa |last4=Vieira |first4=Lucas Felipe Oliveira |last5=Lhullier |first5=Cintia |last6=Falkenberg |first6=Miriam |date=2015-11-01 |title=C<sub>15</sub> acetogenins from the Laurencia complex: 50 years of research – an overview |journal=Revista Brasileira de Farmacognosia |volume=25 |issue=6 |pages=569–587 |doi=10.1016/j.bjp.2015.07.027 |issn=0102-695X |doi-access=free}}</ref>
[[File:Wiki fig 3.png|center|800x800px]]