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DDC: 540 × Subject: Cyclization ×

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Now showing 1 - 4 of 4
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    Ring-Closure Mechanisms Mediated by Laccase to Synthesize Phenothiazines, Phenoxazines, and Phenazines
    (Washington, DC : ACS Publications, 2020) Hahn, Veronika; Mikolasch, Annett; Weitemeyer, Josephine; Petters, Sebastian; Davids, Timo; Lalk, Michael; Lackmann, Jan-Wilm; Schauer, Frieder
    The green and environmentally friendly synthesis of highly valuable organic substances is one possibility for the utilization of laccases (EC 1.10.3.2). As reactants for the herein described syntheses, different o-substituted arylamines or arylthiols and 2,5-dihydroxybenzoic acid and its derivatives were used. In this way, the formation of phenothiazines, phenoxazines, and phenazines was achieved in aqueous solution mediated by the laccase of Pycnoporus cinnabarinus in the presence of oxygen. Two types of phenothiazines (3-hydroxy- and 3-oxo-phenothiazines) formed in one reaction assay were described for the first time. The cyclization reactions yielded C–N, C–S, or C–O bonds. The syntheses were investigated with regard to the substitution pattern of the reaction partners. Differences in C–S and C–N bond formations without cyclization are discussed.
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    Nickel-catalyzed carbonylative synthesis of dihydrobenzofurans
    (Amsterdam : Elsevier, 2021) Geng, H.-Q.; Wang, W.; Wu, X.-F.
    A nickel-catalyzed carbonylative synthesis of dihydrobenzofurans has been developed. With Mo(CO)6 as the CO source and manganese metal as the reductant, alkyl halides were reacted with aryl iodides to give the desired products in moderate to good yields. © 2020 Elsevier B.V.
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    Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles
    (Frankfurt, Main : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2019) Do, Hoang Huy; Ullah, Saif; Villinger, Alexander; Lecka, Joanna; Sévigny, Jean; Ehlers, Peter; Iqbal, Jamshed; Langer, Peter
    A two-step palladium-catalyzed procedure based on Suzuki–Miyaura cross coupling, followed by a double Buchwald–Hartwig reaction, allows for the synthesis of pharmaceutically relevant benzo[4,5]furo[3,2-b]indoles in moderate to very good yield. The synthesized compounds have been analyzed with regard to their inhibitory activity (IC50) of nucleotide pyrophosphatases h-NPP1 and h-NPP3. The activity lies in the nanomolar range. The results were rationalized based on docking studies. © 2019 Do et al.
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    Mechanistic insight of TiCl4catalyzed formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1,3-dielectrophiles
    (London : RSC Publishing, 2015) Nisa, Riffat Un; Maria, Maria; Wasim, Fatima; Mahmood, Tariq; Ludwig, Ralf; Ayub, Khurshid
    The mechanism of TiCl4 mediated formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 1,3-dielectrophiles is studied at the B3LYP level of density functional theory (DFT) to rationalize the experimental regioselectivity. Methyl and trifluoromethyl substituted 1,3 dielectrophiles are studied theoretically since they show different regioselectivities. Two different mechanisms involving 1,2 and 1,4 addition of 1,3-bis(silyl enol ethers) on 1,3-dielectrophiles are studied for each dienophile. The intramolecular transition metal catalyzed and non-catalyzed dynamic shift of the silyl moiety is also studied. The structure of the 1,3 dienophile and the associated Mulliken charges are the driving forces for different regioselectivities in methyl and trifluoromethyl dienophiles.