Ammonium hypoiodite

{{Short description|Type of chemical compound}}

Ammonium hypoiodites are a class of reactive intermediates used in certain organic oxidation reactions. They consist of either ammonium itself or an alkylammonium with various substituents as cation, paired with a hypoiodite anion as the active oxidant. The hypoiodite is generated in situ from the analogous iodide reagent using peroxides, oxone, peracids, or other strong oxidizing agents.{{cite journal |doi= 10.1016/j.reffit.2015.06.001 |title= Iodine catalysis: A green alternative to transition metals in organic chemistry and technology |date= 2015 |last1= Yusubov |first1= Mekhman S. |last2= Zhdankin |first2= Viktor V. |journal= Resource-Efficient Technologies |volume= 1 |issue= 1 |pages= 49–67 |bibcode= 2015RETec...1...49Y }} The hypoiodite is then capable of oxidizing various organic substrates. The iodide is regenerated, meaning the reaction runs with the iodide/hypoiodite as a catalyst in the presence of excess of the original strong oxidizing agent.

Ammonium hypoiodites are capable of oxidizing benzylic methyl groups,{{cite journal |doi= 10.1002/chem.202402528 |title= Syntheses of Diarylmethanes Via an Oxidative Benzylic Functionalization of P-Alkyl Phenol Derivatives Under Quaternary Ammonium Hypoiodite Catalysis |date= 2024 |last1= Pollheimer |first1= David |last2= Mairhofer |first2= Christopher |last3= Waser |first3= Mario |journal= Chemistry – A European Journal |volume= 30 |issue= 54 |pages= e202402528 |pmid= 39054252 |doi-access= free }} initiating oxidative dearomatization,{{cite journal |doi= 10.1021/acscatal.9b04322 |title= High-Performance Ammonium Hypoiodite/Oxone Catalysis for Enantioselective Oxidative Dearomatization of Arenols |date= 2019 |last1= Uyanik |first1= Muhammet |last2= Kato |first2= Takehiro |last3= Sahara |first3= Naoto |last4= Katade |first4= Outa |last5= Ishihara |first5= Kazuaki |journal= ACS Catalysis |volume= 9 |issue= 12 |pages= 11619–11626 }} and oxidative decarboxylation of β-ketolactones.{{cite journal |doi= 10.1039/D2OB00463A|title= Oxidative decarboxylative ammonium hypoiodite-catalysed dihydrobenzofuran synthesis|date= 2022|last1= Röser|first1= Katharina|last2= Scheucher|first2= Anna|last3= Mairhofer|first3= Christopher|last4= Bechmann|first4= Matthias|last5= Waser|first5= Mario|journal= Organic & Biomolecular Chemistry|volume= 20|issue= 16|pages= 3273–3276|pmid= 35363244|doi-access= free}} Similar to the β-ketolactone reaction, oxidative ether formation can be performed at the alpha position of various ketones. Using chiral ammonium cations can give high enantioselectivity of the alpha-etherification reaction, an example of an efficient chiral metal-free organocatalysis process.{{cite journal |doi= 10.1126/science.1188217|title= Quaternary Ammonium (Hypo)iodite Catalysis for Enantioselective Oxidative Cycloetherification|date= 2010|last1= Uyanik|first1= Muhammet|last2= Okamoto|first2= Hiroaki|last3= Yasui|first3= Takeshi|last4= Ishihara|first4= Kazuaki|journal= Science|volume= 328|issue= 5984|pages= 1376–1379|pmid= 20538945|bibcode= 2010Sci...328.1376U}}{{cite journal |doi= 10.1126/science.1254976|title= High-turnover hypoiodite catalysis for asymmetric synthesis of tocopherols|date= 2014|last1= Uyanik|first1= Muhammet|last2= Hayashi|first2= Hiroki|last3= Ishihara|first3= Kazuaki|journal= Science|volume= 345|issue= 6194|pages= 291–294|pmid= 25035486|bibcode= 2014Sci...345..291U}}

Several guanidinium hypoiodites can also be used in the various oxidative-coupling reactions. The guanidinium cation has the added benefit of forming multiple ionic interactions or hydrogen bonds to the substrates.{{cite journal |doi= 10.1002/tcr.202300030 |title= Exploring Guanidinium Organocatalysts for Hypoiodite-Mediated Reactions |date= 2023 |last1= Odagi |first1= Miami |last2= Nagasawa |first2= Kazuo |journal= The Chemical Record |volume= 23 |issue= 7 |pages= e202300030 |pmid= 36949010 }} The conjugate acid of triazabicyclodecene is especially effective.