Browsing by Author "Sari, Ozlem"

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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.
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 Benzoxazole-2 Derivatives: Electronic- and Position-Effect of Functional Groups and Computational Modeling of the Selectivity for Oxazole Ring
(Wiley-v C H verlag Gmbh, 2021) Kuzu, Burak; Sari, Ozlem; Erdem, Safiye Sag; Algul, Oztekin; Menges, Nurettin
In this study, Mitsunobu reagent, DEAD (diethyl azodicarboxylate) and PPh3, and ethyl-oxalamide derivatives of 2-aminophenol were reacted under mild reaction conditions. As a result of the cyclization reaction, benzoxazole derivatives bearing an ester group in the C-2 position were obtained in a one-pot protocol. It was observed that the electron-donating groups at the C-5 position and the electron-withdrawing groups at the C-6 position of the benzene ring increased the yield of the cyclic product. It was found that the cyclization does not occur when the carboxylic acid group is substituted in the benzene ring. The cyclization reaction we performed preferred the 5-endo-trig reaction instead of the 6-exo-trig. This experimental result was examined in detail with density functional theory (DFT) calculations as well. A computational exploration is presented herein that elucidates the detailed mechanism for Huisgen zwitterion's reaction with ethyl-oxalamide derivatives of 2-aminophenol. Potential alternative mechanisms were modeled with DFT calculations via CPCM/M06-2X/6-311++G(d,p)//B3LYP/6-31+G(d,p) level method in tetrahydrofuran to understand shed light on the mechanism. Our computational results are in good agreement with experimental findings that benzoxazole derivatives are the sole products in this reaction.