Ammonium hypoiodite

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.[1] 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,[2] initiating oxidative dearomatization,[3] and oxidative decarboxylation of β-ketolactones.[4] 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.[5][6]

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.[7] The conjugate acid of triazabicyclodecene is especially effective.

References

1. Yusubov, Mekhman S.; Zhdankin, Viktor V. (2015). "Iodine catalysis: A green alternative to transition metals in organic chemistry and technology". Resource-Efficient Technologies. 1 (1): 49–67. Bibcode:2015RETec...1...49Y. doi:10.1016/j.reffit.2015.06.001.
2. Pollheimer, David; Mairhofer, Christopher; Waser, Mario (2024). "Syntheses of Diarylmethanes Via an Oxidative Benzylic Functionalization of P-Alkyl Phenol Derivatives Under Quaternary Ammonium Hypoiodite Catalysis". Chemistry – A European Journal. 30 (54): e202402528. doi:10.1002/chem.202402528. PMID 39054252.
3. Uyanik, Muhammet; Kato, Takehiro; Sahara, Naoto; Katade, Outa; Ishihara, Kazuaki (2019). "High-Performance Ammonium Hypoiodite/Oxone Catalysis for Enantioselective Oxidative Dearomatization of Arenols". ACS Catalysis. 9 (12): 11619–11626. doi:10.1021/acscatal.9b04322.
4. Röser, Katharina; Scheucher, Anna; Mairhofer, Christopher; Bechmann, Matthias; Waser, Mario (2022). "Oxidative decarboxylative ammonium hypoiodite-catalysed dihydrobenzofuran synthesis". Organic & Biomolecular Chemistry. 20 (16): 3273–3276. doi:10.1039/D2OB00463A. PMID 35363244.
5. Uyanik, Muhammet; Okamoto, Hiroaki; Yasui, Takeshi; Ishihara, Kazuaki (2010). "Quaternary Ammonium (Hypo)iodite Catalysis for Enantioselective Oxidative Cycloetherification". Science. 328 (5984): 1376–1379. Bibcode:2010Sci...328.1376U. doi:10.1126/science.1188217. PMID 20538945.
6. Uyanik, Muhammet; Hayashi, Hiroki; Ishihara, Kazuaki (2014). "High-turnover hypoiodite catalysis for asymmetric synthesis of tocopherols". Science. 345 (6194): 291–294. Bibcode:2014Sci...345..291U. doi:10.1126/science.1254976. PMID 25035486.
7. Odagi, Miami; Nagasawa, Kazuo (2023). "Exploring Guanidinium Organocatalysts for Hypoiodite-Mediated Reactions". The Chemical Record. 23 (7): e202300030. doi:10.1002/tcr.202300030. PMID 36949010.