Browsing by Author "Balci, Metin"

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Cettaertalyst-Free Hydrogenation of Alkenes and Alkynes With Hydrazine in the Presence of Oxygen
(Georg Thieme verlag Kg, 2014) Menges, Nurettin; Balci, Metin
A series of alkenes and alkynes was subjected to reduction with hydrazine hydrate in ethanol in the presence of oxygen. An efficient method was developed for the reduction of C-C double bonds and C-C triple bonds with diimide, generated in situ from hydrazine hydrate by oxidation with oxygen. The reduction process proceeded for 24-48 hours with high chemoselectivity and excellent yields. This reduction procedure offers synthetic advantages over metal-catalyzed hydrogenation as well as other systems.
Design and Synthesis of Pyrrolotriazepine Derivatives: an Experimental and Computational Study
(Amer Chemical Soc, 2013) Menges, Nurettin; Sari, Ozlem; Abdullayev, Yusif; Erdem, Safiye Sag; Balci, Metin
The pyrrole derivatives having carbonyl groups at the C-2 position were converted to N-propargyl pyrroles. The reaction of those compounds with hydrazine monohydrate resulted in the formation of 5H-pyrrolo[2,1-d][1,2,5]-triazepine derivatives. The synthesis of these compounds was accomplished in three steps starting from pyrrole. On the other hand, attempted cyclization of a pyrrole ester substituted with a propargyl group at the nitrogen atom gave, unexpectedly, the six-membered cyclization product, 2-amino-3-methylpyrrolo[1,2-a]pyrazin-1(2H)-one as the major product. The expected cyclization product with a seven-membered ring, 4-methyl-2,3-dihydro-1H-pyrrolo[2,1-d][1,2,5]-triazepin-1-one was formed as the minor product and was converted quantitatively to the major product. The formation mechanism of the products was investigated, and the results obtained were also supported by theoretical calculations.
Gold-Catalyzed Formation of Pyrrolo- and Indolo-Oxazin Derivatives: the Key Structure of Some Marine Natural Products
(Beilstein-institut, 2015) Taskaya, Sultan; Menges, Nurettin; Balci, Metin
Various N-propargylpyrrole and indolecarboxylic acids were efficiently converted into 3,4-dihydropyrrolo- and indolo-oxazin-1-one derivatives by a gold(III)-catalyzed cyclization reaction. Some of the products underwent TFA-catalyzed double bond isomerization and some did not. Cyclization reactions in the presence of alcohol catalyzed by Au(I) resulted in the formation of hemiacetals after cascade reactions.
Gold-Catalyzed Oxime-Oxime Rearrangement
(Amer Chemical Soc, 2015) Guven, Sinem; Ozer, Merve Sinem; Kaya, Serdal; Menges, Nurettin; Balci, Metin
The gold-catalyzed reaction of pyrrole and indole oximes having a propargyl group attached to the nitrogen atom was studied. The selective 6-endo-dig mode of cyclization was observed for the terminal alkynes giving rise to the formation of pyrazine N-oxides in the presence of a gold catalyst. However, the reaction with substituted alkyne transferred the oxime functionality intramolecularly from one carbon atom to another via the 7-endo-dig cyclization process. This transformation is unprecedented in the literature and is named an oximeoxime rearrangement.
Intermolecular Heterocyclization of Alkynones With 2-Mercaptoacetaldehyde Under Metal-Free Conditions: Synthesis of 2,3-Disubstituted Thiophenes
(Pergamon-elsevier Science Ltd, 2015) Vatansever, Erol Can; Kilic, Kubra; Ozer, Merve Sinem; Koza, Gani; Menges, Nurettin; Balci, Metin
A concise and regioselective approach for the synthesis of 2,3-disubstituted thiophene derivatives has been developed. The synthetic strategy relies on the reaction of an in situ generated 2-mercaptoacetaldehyde with various alkynones. Furthermore, we calculated the energy gap between the HOMO and the LUMO orbitals of all compounds and observed that the introduction of a strong electron-withdrawing group decreased the HOMO-LUMO energy gap. (C) 2015 Elsevier Ltd. All rights reserved.
Mechanistic Insights Into the Reaction of N-Propargylated Pyrrole- and Indole-Carbaldehyde With Ammonia, Alkyl Amines, and Branched Amines: a Synthetic and Theoretical Investigation
(Wiley-v C H verlag Gmbh, 2019) Sari, Ozlem; Seybek, Ali Fatih; Kaya, Serdal; Menges, Nurettin; Erdem, Safiye Sag; Balci, Metin
The reaction of pyrrole- and indole-carbaldehydes having a propargyl group attached to the nitrogen atom with various amines was studied. The reaction with ammonia formed pyrrolo[1,2-a]pyrazine and pyrazino[1,2-a]indole while the reaction with alkylamines such as methyl, ethyl, hexyl, and benzylamines formed the corresponding pyrazinone derivatives. Unexpectedly, the reaction with allylamine and propargylamine formed pyrazine derivatives in which the allyl and propargyl groups were removed from the molecule. On the other hand, the reaction of N-propargylated pyrrole-carbaldehyde formed indolizine derivatives upon reaction with sterically bulky adamantyl- and tert-butylamines. To understand the main factors causing these differences in reactivity, the reaction mechanisms were studied by means of computational methods. Our calculations showed that bulky amines tend to attack the central carbon of allene formed by the isomerization of N-propargyl functionality, while the attack on the carbonyl carbon by aliphatic amines is more profound.
Synthesis of Indolizines by Dimerization of N-Propargylated Pyrroles Via Allene Intermediates
(Wiley-v C H verlag Gmbh, 2021) Kuzu, Burak; Gul, Sergen; Tan, Meltem; Menges, Nurettin; Balci, Metin
Ten different N-propargyl pyrrole derivatives having various substituents at the C-2 position were synthesized. These derivatives were converted into indolizine derivatives by the [2+2] cycloaddition reaction of pyrrole N-allene, forming in situ, by heating in PrOH in basic medium. The structures were characterized by NMR and X-ray crystallography. The N-propargylated derivatives smoothly underwent intermolecular cyclizations to produce indolizine derivatives in good yields. We proposed a radical mechanism for the dimerization. Reaction of an allene product with butylated hydroxytoluene (BHT), a radical scavenger, did not give any dimerization product. This result supports the radical reaction.
Synthesis of Pyrrole-Fused C,n-Cyclic Azomethine Imines and Pyrazolopyrrolopyrazines: Analysis of Their Aromaticity Using Nucleus-Independent Chemical Shifts Values
(Amer Chemical Soc, 2016) Ozer, Merve Sinem; Menges, Nurettin; Keskin, Selbi; Sahin, Ertan; Balci, Metin
The AgOTf-catalyzed reaction of C-2 substituted pyrrole hydrazones having an N-propargyl group was studied. The selective 6-endo-dig mode of cyclization was observed, giving rise to the formation of pyrrole-fused C,N-cyclic azomethine imine derivatives. The reaction of one azomethine imine derivative with various dipolarophiles resulted in the formation of cycloadducts having a pyrazolopyrrolopyrazine skeleton. The aromaticity of C,N-cyclic azomethine imines as well as that of pyrazolopyrrolopyrazines was determined by calculating of nucleus-independent chemical shifts values.