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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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    Öğe
    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.