Browsing by Author "Şahin, Yeşim"

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Open Access
Precious metal-Free LaMnO3 perovskite catalyst with an optimized nanostructure for aerobic C–H bond activation reactions: alkylarene oxidation and naphthol dimerization
(American Chemical Society, 2021-02-03) Şahin, Yeşim; Sika-Nartey, Abel Tetteh; Ercan, Kerem Emre; Koçak, Yusuf; Senol, Sinem; Özensoy, Emrah; Türkmen, Yunus Emre
In this article, we describe the development of a new aerobic C–H oxidation methodology catalyzed by a precious metal-free LaMnO3 perovskite catalyst. Molecular oxygen is used as the sole oxidant in this approach, obviating the need for other expensive and/or environmentally hazardous stoichiometric oxidants. The electronic and structural properties of the LaMnO3 catalysts were systematically optimized, and a reductive pretreatment protocol was proved to be essential for acquiring the observed high catalytic activities. It is demonstrated that this newly developed method was extremely effective for the oxidation of alkylarenes to ketones as well as for the oxidative dimerization of 2-naphthol to 1,1-binaphthyl-2,2-diol (BINOL), a particularly important scaffold for asymmetric catalysis. Detailed spectroscopic and mechanistic studies provided valuable insights into the structural aspects of the active catalyst and the reaction mechanism.
Open Access
Rapid access to hydroxyfluoranthenes via a domino Suzuki–Miyaura/intramolecular Diels–Alder/ring-opening reactions sequence
(American Chemical Society, 2022-04-07) Ahmadli, Dilgam; Şahin, Yeşim; Çalıkyılmaz, Eylül; Şahin, Onur; Türkmen, Yunus E.
In this work, we developed an efficient method for the rapid construction of fluoranthene skeleton to access a variety of substituted hydroxyfluoranthenes. The 1-iodo-8-alkynylnaphthalene derivatives, which serve as substrates for the key fluoranthene-forming step, were prepared via selective monoalkynylative Sonogashira reactions of 1,8-diiodonaphthalene. The domino reaction sequence which involves a sequential Suzuki–Miyaura coupling, an intramolecular Diels–Alder reaction, and an aromatization-driven ring-opening isomerization has been shown to give substituted hydroxyfluoranthenes in up to 92% yield. This work demonstrates the utility of designing new domino reactions for rapid access to substituted polycyclic aromatic hydrocarbons (PAHs).
Open Access
Transition metal catalysis for aerobic C-H oxidation reactions and for the synthesis of fluoranthene derivatives
(2021-01) Şahin, Yeşim
Within the past two decades, a powerful class of new reactions that introduces oxidized functionality to (sp3) C-H bonds has emerged and gained tremendous attention since it can revolutionize the chemical industry by placing reactive functional groups directly in a molecule. Usually, precious metals (e.g., Pd, Pt, Ru etc.) are used for the activation of C-H bonds, and finding alternative ways that use less expensive and less toxic first row transition metals to replace precious metal catalysts is necessary. In this work, we have developed a reductive pretreatment system to increase the activity of precious metal-free LaMnO3 perovskites for C-H oxidation reactions of alkylarenes to ketones or oxidative dimerization of naphthols under mild conditions. Furthermore, a bimetallic nickel-manganese based hydroxide catalyst was synthesized as well and it was proven to oxidize a variety of alkylarenes and alcohols. Using molecular oxygen as the sole oxidant in C-H oxidation reactions is another advantage of our method since it is green, inexpensive and readily available in nature. In the second part, two novel methods have been developed for the synthesis of fluoranthenes which are important polycyclic skeletons. They can be found in many natural products, organic electronics, dyes and various materials. These methods employ Pd-catalyzed cross-coupling reactions such as Suzuki-Miyaura and Sonogashira reactions in the first steps using 1,8-dihalonaphthalenes and then use intramolecular Diels-Alder reactions for the formation of tetracyclic ring in the fluoranthene core. Our methods also provide a modular pathway for the synthesis of multi-substituted fluoranthene derivatives from simple molecules because it is designed as a three-component system and each component can be readily prepared or functionalized allowing easy modification.
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Yurtsever Ailesi’nin Ardino (Eğridere) Kasabası’ndan Türkiye’ye göçü
(Bilkent University, 2017) Şahin, Yeşim; Yurtsever, Ayberk; Erkan, Meltem; Şener, Hazal; Morova, Işık Buğra