Yazar "Turkmen, Yunus E." seçeneğine göre listele

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    Aza-Nazarov Cyclization Reactions via Anion Exchange Catalysis
    (Amer Chemical Soc, 2019) Donmez, Selin E.; Soydas, Emine; Aydin, Gokcen; Sahin, Onur; Bozkaya, Ugur; Turkmen, Yunus E.
    A catalytic aza-Nazarov cyclization between 3,4-dihydroisoquinolines and alpha,beta-unsaturated acyl chlorides has been developed to access alpha-methylene-gamma-lactam products in good yields (up to 79%) as single diastereomers. The reactions proceed efficiently when AgOTf is used as an anion exchange catalyst with a 20 mol % loading at 80 degrees C. Computational studies were performed to investigate the reaction mechanism, and the findings support the role of the -TMS group in reducing the reaction barrier of the key cyclization step.
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    Photochemical [2+2] cycloadditions of naphthalene acrylic acids: templated and untemplated photoreactivity, selective homo/heterodimerizations, and conformational analysis
    (Royal Soc Chemistry, 2025) Temel, Merve; Yildiz, Gizem; Ceyhan, Kaan Berkay; Alkan, Fahri; Sahin, Onur; Turkmen, Yunus E.
    Selective homo- and heterodimerization reactions of naphthalene acrylic acids have been achieved in a diastereocontrolled manner with the use of 1,8-dihydroxynaphthalene as a covalent template in photochemical [2 + 2] cycloadditions. When the reactions were run in solution, cycloaddition products were obtained in good yields (64-88%), which were subsequently detached from the template via a transesterification reaction affording the symmetrical and unsymmetrical cyclobutane products in 75-91% yields. A careful examination of the crystal structures of diester 6a and cycloadduct 15a along with detailed powder XRD and ATR-IR spectroscopic studies revealed an intriguing case of conformational isomerism in 15a arising from the different possible orientations of its two ester carbonyls. The rotational barriers between the different conformers of 15a were calculated to be within the range of 4.19-7.10 kcal mol-1, indicative of rapid interconversion between these conformers in solution at room temperature.
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    Polarization-Enhanced Hydrogen Bonding in 1,8-Dihydroxynaphthalene: Conformational Analysis, Binding Studies and Hydrogen Bonding Catalysis
    (Wiley-V C H Verlag Gmbh, 2020) Mammadova, Flora; Hamarat, Busra; Ahmadli, Dilgam; Sahin, Onur; Bozkaya, Ugur; Turkmen, Yunus E.
    In this article, the presence and effects of polarization-enhanced hydrogen bonding in 1,8-dihydroxynaphthalene (1,8-DHN) were investigated in detail through a series of experimental and computational studies. First, the conformation of 1,8-DHN, and its ability to make intra- and intermolecular hydrogen bonds were investigated in solid state by X-ray crystallography, in solution by NMR spectroscopy, and computationally by density functional theory. Second, equilibrium binding constants, which were determined by P-31-NMR titration studies, demonstrated stronger complexation of Ph3PO with 1,8-DHN compared to mono-naphthol derivatives 8-methoxy-1-naphthol and 1-naphthol. In the final section, 1,8-DHN was observed to be an effective catalyst for the Friedel-Crafts-type addition reaction of indoles to beta-nitrostyrenes, and a rationale for this catalytic activity was provided via computational studies. All the findings described in this work support the enhanced hydrogen bond donating ability of 1,8-DHN due to polarization caused by the six-membered intramolecular hydrogen bond present in its structure.
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    Rapid Access to Hydroxyfluoranthenes via a Domino Suzuki-Miyaura/Intramolecular Diels-Alder/Ring-Opening Reactions Sequence
    (Amer Chemical Soc, 2022) Ahmadli, Dilgam; Sahin, Yesim; Calikyilmaz, Eylul; Sahin, Onur; Turkmen, Yunus E.
    In this work, we developed an efficient method for the rapid construction of fluoranthene skeleton to access a variety of substituted hydroxyfluoranthenes. The 1-iodo-8-alkynylnaphthalene derivatives, which serve as substrates for the key fluoranthene-forming step, were prepared via selective monoalkynylative Sonogashira reactions of 1,8-diiodonaphthalene. The domino reaction sequence which involves a sequential Suzuki-Miyaura coupling, an intramolecular Diels-Alder reaction, and an aromatization-driven ring-opening isomerization has been shown to give substituted hydroxyfluoranthenes in up to 92% yield. This work demonstrates the utility of designing new domino reactions for rapid access to substituted polycyclic aromatic hydrocarbons (PAHs).