Browsing by Author "Tasdemir, Volkan"

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Bio-Catalytic Asymmetric Synthesis of Β-Adrenergic Receptor Blocker Precursor: (r)-2
(Taylor & Francis Ltd, 2020) Tasdemir, Volkan; Kalay, Erbay; Dertli, Enes; Sahin, Engin
Aromatic alpha-halohydrins, particularly 2-haloethanols as significant precursor of drugs, can easily be converted to chiral beta-adrenergic receptor blockers. Eight strains of Lactobacillus curvatus were tested as biocatalysts for asymmetric reduction of 2-bromo-1-(naphthalen-2-yl)ethanone 1 to 2-bromo-1- (naphthalen-2-yl) ethanol 2. The parameters of the bioreduction were optimized using L. curvatus N4, the best biocatalyst found. As a result, (R)-2-bromo-1-(naphthalen-2-yl)ethanol 2, which can be beta-adrenergic receptor blocker precursor, was produced for the first time in high yield and enantiomerically pure form using biocatalysts. Moreover, the gram scale synthesis was performed and 7.54 g of (R)-2 was synthesized as enantiopure form (enantiomeric excess >99%) in 48 h. The important advantages of this process are that it produces of (R)-2 for the first time in enantiopure form, in excellent yield and under environmentally friendly and moderate reaction conditions. This system is of the potential to be applied at a commercial scale.
Copper-Catalyzed Synthesis of Fused Imidazopyrazine N-Oxide Skeletons
(Georg Thieme verlag Kg, 2019) Tasdemir, Volkan; Kuzu, Burak; Tan, Meltem; Genc, Hasan; Menges, Nurettin
N-Propargyl-2-aroylimidazoles synthesized and converted into the corresponding ketoximes. Under various conditions, several mono- and diketoxime imidazole derivatives were formed by converting the carbonyl or carbonyl and propargyl groups into oxime groups. N-Propargyl monooxime imidazole derivatives were cyclized by treatment with CuI to give various imidazopyrazine N-oxides. Several copper salts, such as CuOAc, CuSO (4) , and CuOTf, formed the same cyclization product. This cyclization reaction occurred only in the presence of Cu(I) or Cu(II) salts; other transition metals such as Au, Ag, In, and Fe did not yield cyclic products. The nucleus-independent chemical shift method was used to calculate the aromaticity of the bicyclic rings.
Gold-Catalyzed Cyclization of Non-Conjugated Ynone-Oxime Derivatives: Incorporation of Solvent Molecule
(Wiley-v C H verlag Gmbh, 2020) Tasdemir, Volkan; Menges, Nurettin
Au-iii-promoted cyclization reaction of ynone-oxime derivatives furnished 4H-1,2-oxazine ring under mild reaction conditions. When an alcohol is present in the reaction media, it was attached to the oxazine ring by the second activation of cyclic intermediate with a gold catalyst. Cholesterol, propargyl alcohol, phenol, and some of the different alcohol derivatives with alkyl chain were bonded to the oxazine ring in good yields. While amine derivatives did not attach to the ring under optimized reaction conditions, the molecule with the thiol group deactivated the gold catalyst under the same reaction conditions and did not give any cyclic products. With the obtained cyclization protocol, 11 unknown oxazine derivatives were synthesized and characterized. The proposed cyclization mechanism was drawn according to the two independent control experiments, DFT optimization, and NBO charges.
Gold-Catalyzed Cyclization of Unconjugated Ynone Derivatives for 2h-1,2 and 1-Hydroxypyrrole Skeletons Through One-Pot and Single-Step Strategy
(Springer int Publ Ag, 2023) Tasdemir, Volkan; Menges, Nurettin
Unconjugated ynone derivatives with the 1,3-dicarbonyl structure are synthesized, and they are directly subjected to goldcatalyzed reaction with hydroxylamine without obtaining the oxime derivative. Among the different metal salts investigated, AuCl3 is the best for yielding and obtaining two different heterocyclic skeletons. Thanks to this reaction, two important heterocyclic molecules, 2H-1,2-oxazine and 1-hydroxypyrrole, are obtained as a one-pot and single-step strategy with favorable yields. Eleven different 2H-1,2-oxazine and 6 different 1-hydroxypyrrole derivatives are synthesized using starting compounds containing different substituents, in which steric hindrance and electronic effect are also taken into account. When the same reaction is carried out with the unconjugated ynone derivative containing only one carbonyl group, the only 1-hydroxypyrrole derivative is observed to be formed, and 1,2- oxazine ring is not observed.
A Golden Synthetic Approach To 2-(1 H -Pyrrol and Pyrrolo[1,2-A ]quinoxalines Through a Gold Carbene Intermediate
(Georg Thieme verlag Kg, 2024) Tasdemir, Volkan; Genc, Hasan; Menges, Nurettin
The pyrrolo[1,2-a]quinoxaline skeleton has significant potential for many biological and optical applications. Hence, in this study, unconjugated ynone derivatives were treated with 1,2-diaminoarenes in a gold-catalyzed cyclization to give 2-(1H-pyrrol-1-yl)anilines, which are valuable starting materials, and pyrrolo[1,2-a]quinoxalines by a one-pot and single-step approach. A reaction mechanism for the formation of the pyrrolo[1,2-a]quinoxaline skeleton featuring a key gold carbene intermediate is proposed. On the other hand, the methyl group on the C-2 position of the 2-(1H-pyrrol-1-yl)anilines was oxidized by SeO2 to give the pyrrolo[1,2-a]quinoxaline skeleton, resulting in 14 different pyrrolo[1,2-a]quinoxaline derivatives.
Synthesis of Imidazo-1,4 Derivatives and Investigation of Reaction Mechanism
(Tubitak Scientific & Technological Research Council Turkey, 2021) Tasdemir, Volkan
In this study, nine different C-2 aroyl imidazole derivatives were synthesized in a one pot reaction with two steps, and the reduction reactions of these derivatives with NaBH4 were carried out under mild conditions. Substitution reaction of obtained imidazo methanol derivatives with chloroacetylchloride reagent and ring reaction of substitution products were investigated. It was determined that 1,4-imidazoxazinone derivative was obtained as a result of the cyclization reaction. The intermediate products obtained during the cyclization reaction were isolated, and the path of the reaction under different conditions was discussed.
Synthesis of N-Ureido Pyrrole Derivatives Through Gold-Catalysed Reaction: Solvent and Catalyst Effect
(Wiley-v C H verlag Gmbh, 2024) Tasdemir, Volkan
Substituted pyrroles were obtained as a result of metal-catalyzed cyclization of alpha propargyl acetophenone and alpha-propargyl-beta-ketoesters with semicarbazide. Optimum conditions and general procedures with high yields were established in a single pot. Eleven different N-ureido-pyrrole derivatives were successfully yielded. Different ynone derivatives having various functionalities did not affect the cyclization reaction but except a slight decrease in product yield. Screening of optimum catalyst revealed that gold(III) chloride was the best catalyst for the cyclization reaction. We believe that this is the first time an N-ureido-pyrrole skeleton starting from ynone has been synthesized in the literature. Unconjugated ynone derivatives, which hold several functional groups, are subjected to reaction with semicarbazide in the presence of Gold (III) chloride catalyst. In consequence of the reactions, the synthesis of eleven different N-ureido pyrrole derivatives, which contain amide group attached to the nitrogen atom in the pyrrole ring, will take place. image
Synthesis of Novel Tetra-Substituted Pyrazole Derivatives From 2,3-Furandione
(Bentham Science Publ Ltd, 2019) Genc, Hasan; Tasdemir, Volkan; Tozlu, Israfil; Ogun, Erdal
Synthesis of pyrazole-3-carboxylic acid was progressed via two different protocols, one of which is solid state. Pyrazole-3-carboxylic acid was converted into different derivatives such as ester, urea, amide and nitrile. The amide compound was converted to nitrile using SOCl2 and DMF. Solid state heating of carboxylic acid gave decarboxylated product. Cyclization of tetra-substituted pyrazole with hydrazines resulted in pyrazolopyridazinones. The antimicrobial activities of the synthesized pyrazole derivatives against Bacillus cereus, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, and Saccharomyces cerevisiae were evaluated. One of the pyrazole derivatives which possess nitro group showed antimicrobial activity in only B. cereus, a Gram-positive bacteria, with an MIC of 128 mu g/mL.