| 1. |
- Guđmundsson, Arnar, et al.
(författare)
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Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of Amines using a Hybrid Hydroquinone/Cobalt Catalyst as Electron Transfer Mediator
- 2021
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 60:21, s. 11819-11823
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report the first Fe-II-catalyzed aerobic biomimetic oxidation of amines. This oxidation reaction involves several electron transfer steps and is inspired by biological oxidation in the respiratory chain. The electron transfer from the amine to molecular oxygen is aided by two coupled catalytic redox systems, which lower the energy barrier and improve the selectivity of the oxidation reaction. An iron hydrogen transfer complex was utilized as the substrate-selective dehydrogenation catalyst along with a bifunctional hydroquinone/cobalt Schiff base complex as a hybrid electron transfer mediator. Various primary and secondary amines were oxidized in air to their corresponding aldimines or ketimines in good to excellent yield.
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| 2. |
- Manna, Srimanta
(författare)
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Copper-Catalyzed Diastereo- and Enantioselective Borylative Cyclization
- 2022
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 12:7
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Forskningsöversikt (refereegranskat)abstract
- Copper-catalyzed enantioselective borylative cyclization with various electrophiles via difunctionalization of unsaturated hydrocarbons is a powerful tool for the generation of interesting boron-containing carbocycles and heterocycles processes involving a chiral organocopper intermediate. Alkenes, allenes, and alkynes are versatile and easily accessible substrates that can be subjected to a wide range of reactions to produce densely functionalized, enantioenriched products. In this chapter, I discuss copper-catalyzed alkenes, allenes, and alkynes borofunctionalization and enantioselective cyclization via chiral organocopper intermediate. Copper-catalyzed enantioselective borylative cyclization and regiodivergent functionalization of alkenes, allenes, and alkynes, as well as the current mechanistic understanding of such processes, are given special attention in this review.
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| 3. |
- Manna, Srimanta, et al.
(författare)
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Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of N-Heterocycles
- 2021
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 27:55, s. 13725-13729
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Tidskriftsartikel (refereegranskat)abstract
- Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.
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| 4. |
- Manna, Srimanta, et al.
(författare)
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Mechanistic Studies on Iron-Catalyzed Dehydrogenation of Amines Involving Cyclopentadienone Iron Complexes-Evidence for Stepwise Hydride and Proton Transfer
- 2023
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Ingår i: ACS Catalysis. - 2155-5435. ; 13:13, s. 8477-8484
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of dehydrogenation of amines catalyzedby (cyclopentadienone)ironcarbonyl complexes was studied by means of kinetic isotope effect(KIE) measurements, intermediate isolation, and density functionaltheory calculations. The (cyclopentadienone)iron-amine intermediateswere isolated and characterized by H-1 and C-13 NMR spectroscopy as well as X-ray crystallography. The isolatediron-amine complexes are quite stable and undergo a formal beta-hydride elimination to produce imine and iron hydride complexes.The KIEs observed for the iron-catalyzed dehydrogenation of 4-methoxy-N-(4-methylbenzyl)aniline are in accordance with stepwisedehydrogenation. The density functional calculations corroborate astepwise mechanism involving a rate-determining hydride transfer fromamine to iron to yield a metal hydride and an iminium intermediate,followed by a proton transfer from the iminium ion to the oxygen ofthe cyclopentadienone ligand.
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| 5. |
- Manna, Srimanta, et al.
(författare)
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Metal-catalyzed biomimetic aerobic oxidation of organic substrates
- 2021
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Ingår i: Advances in Catalysis. - Cambridge : Academic Press. - 9780128245712 ; , s. 1-57
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Bokkapitel (refereegranskat)abstract
- The use of molecular oxygen (O2) as terminal oxidant in transition metal-catalyzed oxidative reactions is an appealing and challenging approach in organic chemistry. In these oxidations, the reoxidation of the reduced form of the metal catalyst by O2 is the key and challenging step, due to the triplet ground state of O2 and the high energy barrier for electron transfer. Inspired by (i) the electron transfer chain (ETC) in aerobic respiration and (ii) metalloenzymes for oxidations in Nature, organic chemists have developed metal-catalyzed biomimetic oxidations. In this chapter, two biomimetic approaches for transition metal-catalyzed aerobic oxidations are summarized, including: (i) biomimetic oxidation by multistep electron transfer pathways inspired by the respiratory chain and (ii) biomimetic oxidation by rational design of metal complexes that mimic metalloenzymes. The first type of aerobic oxidative transformations discussed include Wacker oxidations, alkyne oxidations, C—H functionalizations, and dehydrogenative oxidations of alcohols and amines. The second type of aerobic oxidations include iron-, copper- and manganese- osmium- and vanadium-catalyzed reactions.
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