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Iminoxyl radicals vs. tert-butylperoxyl radical in competitive oxidative C-O coupling with β-dicarbonyl compounds. Oxime ether formation prevails over Kharasch peroxidation.

ABSTRACT: Oxidative coupling of oxime and β-dicarbonyl compounds dominates in a β-dicarbonyl compound/oxime/Cu(ii)/t-BuOOH system; in the absence of oxime, oxidative coupling of t-BuOOH and a β-dicarbonyl compound (Kharasch peroxidation) takes place. The proposed conditions for oxidative coupling of oximes with dicarbonyl compounds require only catalytic amounts of copper salt and t-BuOOH serves as a terminal oxidant. The C-O coupling reaction proceeds via the formation of tert-butoxyl, tert-butylperoxyl and iminoxyl radicals. Apparently, tert-butylperoxyl radicals oxidize oxime into iminoxyl radical faster than they react with β-dicarbonyl compounds forming the Kharasch peroxidation product. Iminoxyl radicals are responsible for the formation of the target C-O coupling products; the yields are up to 77%.

SUBMITTER: Krylov IB

PROVIDER: S-EPMC9078167 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Iminoxyl radicals vs. tert-butylperoxyl radical in competitive oxidative C-O coupling with β-dicarbonyl compounds. Oxime ether formation prevails over Kharasch peroxidation.

Krylov I B IB Paveliev S A SA Shumakova N S NS Syroeshkin M A MA Shelimov B N BN Nikishin G I GI Terent'ev A O AO

RSC advances 20180205 11

Oxidative coupling of oxime and β-dicarbonyl compounds dominates in a β-dicarbonyl compound/oxime/Cu(ii)/t-BuOOH system; in the absence of oxime, oxidative coupling of t-BuOOH and a β-dicarbonyl compound (Kharasch peroxidation) takes place. The proposed conditions for oxidative coupling of oximes with dicarbonyl compounds require only catalytic amounts of copper salt and t-BuOOH serves as a terminal oxidant. The C-O coupling reaction proceeds via the formation of t ...[more]

PMID: 35539576

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Project description:Mitochondrial dysfunctions caused by oxidative stress are currently regarded as the main cause of aging. Accumulation of mutations and deletions of mtDNA is a hallmark of aging. So far, however, there is no evidence that most studied oxygen radicals are directly responsible for mutations of mtDNA. Oxidative damages to cardiolipin (CL) and phosphatidylethanolamine (PEA) are also hallmarks of oxidative stress, but the mechanisms of their damage remain obscure. CL is the only phospholipid present almost exclusively in the inner mitochondrial membrane (IMM) where it is responsible, together with PEA, for the maintenance of the superstructures of oxidative phosphorylation enzymes. CL has negative charges at the headgroups and due to specific localization at the negative curves of the IMM, it creates areas with the strong negative charge where local pH may be several units lower than in the surrounding bulk phases. At these sites with the higher acidity, the chance of protonation of the superoxide radical (O2 •), generated by the respiratory chain, is much higher with the formation of the highly reactive hydrophobic perhydroxyl radical (HO2 •). HO2 • specifically reacts with the double bonds of polyunsaturated fatty acids (PUFA) initiating the isoprostane pathway of lipid peroxidation. Because HO2 • is formed close to CL aggregates and PEA, it causes peroxidation of the linoleic acid in CL and also damages PEA. This causes disruption of the structural and functional integrity of the respirosomes and ATP synthase. We provide evidence that in elderly individuals with metabolic syndrome (MetS), fatty acids become the major substrates for production of ATP and this may increase several-fold generation of O2 • and thus HO2 •. We conclude that MetS accelerates aging and the mitochondrial dysfunctions are caused by the HO2 •-induced direct oxidation of CL and the isoprostane pathway of lipid peroxidation (IPLP). The toxic products of IPLP damage not only PEA, but also mtDNA and OXPHOS proteins. This results in gradual disruption of the structural and functional integrity of mitochondria and cells.

Dataset Information

Iminoxyl radicals vs. tert-butylperoxyl radical in competitive oxidative C-O coupling with β-dicarbonyl compounds. Oxime ether formation prevails over Kharasch peroxidation.

Publications

Iminoxyl radicals <i>vs. tert</i>-butylperoxyl radical in competitive oxidative C-O coupling with β-dicarbonyl compounds. Oxime ether formation prevails over Kharasch peroxidation.

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