Browsing by Author "Cooke, Maria Victoria"

Now showing 1 - 6 of 6
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    Metal-free visible-light-promoted C(sp3)-H functionalization of aliphatic cyclic ethers using trace O2
    (Royal Society of Chemistry, 2021) Niu, Ben; Blackburn, Bryan G.; Sachidanandan, Krishnakumar; Cooke, Maria Victoria; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    Presented is a light-promoted C-C bond forming reaction yielding sulfone and phosphate derivatives at room temperature in the absence of metals or photoredox catalyst. This transformation proceeds in neat conditions through an auto-oxidation mechanism which is maintained through the leaching of trace amounts of O2 as sole green oxidant.
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    Photochemical Regioselective C(sp3)-H Amination of Amides Using N-Haloimides
    (American Chemical Society, 2021) Pan, Lei; Elmasry, Joseph; Osccorima, Tomas; Cooke, Maria Victoria; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    A metal-free regioselective C(sp3)-H amination of amides using N-haloimides in the presence of lithium tert-butoxide and visible light is presented herein. This photoexcited approach is straightforward, and it aminates a wide variety of amides under mild conditions without the use of photocatalysts, external radical initiators, or oxidants. A halogen-bonded intermediate between the tert-butoxide base and the N-haloimide is proposed to be responsible for the increased photoreactivity. Calculations show that the formation of this electron donor-acceptor complex presents an exergonic energy profile.
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    Photoinduced C(sp3)-H Chalcogenation of Amide Derivatives and Ethers via Ligand-to-Metal Charge-Transfer
    (American Chemical Society, 2022) Niu, Ben; Sachidanandan, Krishnakumar; Cooke, Maria Victoria; Casey, Taylor E.; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    A photoinduced, iron(III) chloride-catalyzed C-H activation of N-methyl amides and ethers leads to the formation of C-S and C-Se bonds via a ligand-to-metal charge transfer (LMCT) process. This methodology converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido-N,S-acetal derivatives in good yields. Mechanistic work revealed that this transformation proceeds through a hydrogen atom transfer (HAT) involving chlorine radical intermediates.
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    Photoredox Polyfluoroarylation of Alkyl Halides via Halogen Atom Transfer
    (American Chemical Society, 2022) Niu, Ben; Sachidanandan, Krishnakumar; Blackburn, Bryan G.; Cooke, Maria Victoria; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    Polyfluoroarene moieties are of interest in medicinal chemistry, agrochemicals, and material sciences. Herein, we present the first polyfluoroarylation of unactivated alkyl halides via a halogen atom transfer process. This method converts primary, secondary, and tertiary alkyl halides into the respective polyfluoroaryl compounds in good yields in the presence of amide, carbamate, ester, aromatic, and sulfonamide moieties, including derivatives of complex bioactive molecules. Mechanistic work revealed that this transformation proceeds through an alkyl radical generated after the halogen atom transfer.
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    Solvent Anions Enable Photoinduced Borylation and Phosphonation of Aryl Halides via EDA Complexe
    (American Chemical Society, 2022) Pan, Lei; Deckert, Macy M.; Cooke, Maria Victoria; Bleeke, Annika R.; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    We report the synthesis of aryl boronic esters and aryl phosphonate esters promoted by visible-light in the absence of transition-metals or photoredox catalysts. The transformation proceeds at room temperature using sodium hydride, as a non-nucleophilic base, and exhibits functional group tolerance for anilines, amides, and esters. UV-vis spectroscopy, radical trapping experiments, and computational (TD-DFT) calculations suggest an electron-donor-acceptor (EDA) complex between solvent anions and aryl halides as the species responsible for this reactivity.
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    Transition-Metal-Free Photoredox Phosphonation of Aryl C–N and C–X Bonds in Aqueous Solvent Mixtures
    (American Chemical Society, 2022) Pan, Lei; Kelley, Alexandra S.; Cooke, Maria Victoria; Deckert, Macy M.; Laulhé, Sébastien; Chemistry and Chemical Biology, School of Science
    Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using 10H-phenothiazine, an inexpensive commodity chemical, as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in the presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods. The transformation also proceeds under atmospheric conditions, which further differentiates it from current methods that require inert atmosphere. Mechanistic work using fluorescence quenching experiments and radical trapping approaches support the proposed mechanism.