Master Degree / Yüksek Lisans Tezleri
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Master Thesis Alkenil Epoksitlerin Organoboronlar ile Tepkimelerinin Mekanistik ve Stereokimyasal Çalışmaları ve Ürün Uygulamaları(2024) Ekiyorum, Gamze; Artok, LeventAllilik bileşiklerin uygun ayrılan gruplarla 1,3-substitüsyon reaksiyonları, aril gibi fonksiyonel gruplara sahip alkenil reaktiflerin sentezi açısından organik kimyada temel bir öneme sahiptir. Bu reaksiyonlar genellikle metal katalizörler gerektirir ve farklı substratlar üzerinde regio- ve stereoselektiflik elde etmek önemli bir zorlu süreç olmaya devam etmektedir. Alkenil epoksitler de, allilik elektrofilller olarak, 1,3-substitüsyon tepkimeleri vererek da fonksiyonel allilik alkoller üretebilmektedir.Alkenil epoksitlerin kullanımının önemli bir avantajı, substitüsyon sırasında epoksit halkasının açılmasıyla hidroksil gruplarının oluşması ve allilik alkollerin üretilmesidir. Bu allilik alkoller, organik sentezde önemli ara ürünlerdir. Organoboronlar, aril gruplarının eklenmesi veya alkenilasyon reaksiyonları için birçok çapraz bağlama yönteminde yaygın olarak kullanılmakta olup, çeşitli allilik reaktiflerle çapraz bağlama reaksiyonlarında da kullanılmaktadır. Mevcut çalışmalar organoboronların terminal alkenil epoksitlerle olan reaksiyonlarını incelemiş olurken, literatürde iç alkenil epoksitler için seçimli ve başarılı metodolojilerin eksikliği göze çarpmaktadır.Laboratuvarımız, organoboronlarla iç alkenil epoksitlerin paladyum katalizli reaksiyonlarının, alkenil epoksitin C1 pozisyonunda bir hidroksil grubu içermesi durumunda regio- ve stereoselektif bir şekilde ilerleyerek aril-substitüe alilik alkoller elde edilebileceğini yakın zamanda göstermiştir. Bu yöntem, Pd⁰-AsPh₃ kombinasyonunu kullanmakta ve hafif koşullar altında uygulanmaktadır.Bununla birlikte, önceki çalışmalarda ayrıntılı deneysel veriler veya mekanistik öngörüler rapor edilmemiştir. Bu nedenle, bu tezin temel amacı, ürünlerin bağıl stereomerik yapısını aydınlatmak ve daha kapsamlı deneysel veriler sağlamaktır. Ayrıca, bu metodolojinin doğal olarak oluşan bileşiklerin sentezindeki potansiyel uygulamaları da tartışılmaktadır.Master Thesis Borylation of Petroleum Cracking Olefin Products(01. Izmir Institute of Technology, 2022) Arapoğlu, Mehmet Anıl; Artok, LeventCracking is a process that long-chain hydrocarbons are broken down into more valuable fragments called naphtha cracking products. The olefins formed as a result of this process have various functions such as forming the smallest building blocks of fine and speciality chemicals. It has been foreseen that borylation processes can be applied as a conversion method of these products into valuable intermediate structures. In this context, this thesis describes first time the transition-metal-catalyzed borylation of a number of petroleum cracking olefin products. Borylation reactions have been extensively investigated in the literature and have become one of the popular methods for synthesizing organoboron reagents, which can also be used in the synthesis of functional materials, pharmaceuticals, and agricultural chemicals. In the context of this thesis, petroleum cracking olefinic products were converted into high-value-added organoboron derivatives by metal-catalysed hydroboration and dehydrogenative borylation methods. For this purpose, the experimental conditions were optimized using propene and isobutene reagents. It has been shown in this study that iridium complexes with N-Heterocarbene (NHC) ligands are highly effective catalysts and therefore anti-Markovnikov hydroboration products can be produced in excellent yields even at very low catalyst loadings. On the other hand, alkenyl boron products could be obtained with high yields, which could be performed in the absence of dehydrogenative borylation reactions, ligand, base, and any other additives. The applicability of these methods in internal and terminal alkenes such as cyclohexene, ethene, decene and styrene has been also demonstrated. Finally, these products were converted into a number of intermediates by Suzuki-Miyaura cross-coupling reactions. Thus, in the conversion of alkenes to valuable intermediates, practical and sustainable applications would be possible by using simple, abundant, and cheap reagents instead of expensive and dangerous chemicals.Master Thesis Iridium Catalyzed Boration of Dihydroisoquinoline Derivatives(Izmir Institute of Technology, 2022) Yazıcı, Ece; Artok, LeventTransition metal catalyzed borylation reactions have an important place in organometallic chemistry. In recent years, these reactions have been extensively investigated and have become a versatile tool in the synthesis of new organic materials. C-H bonds can be easily transformed into C-B bonds by borylation reactions. In particular, iridium-catalyzed borylation includes significant advances such as mild reaction conditions, additive-free, high efficiency and being in a single step. In this thesis, the borylation of dihydroisoquinolines with a wide range of biological properties was performed for the first time. Investigating the extent of the reaction has led to the development of optimization studies. Besides, the effects of steric and electronic factors on selectivity are also shown. In this new methodology, C3-borylated products with high regioselectivity and yield were formed with the directing effect of the acyl group. The use of AsPh3 as a ligand is critical to the product selectivity of the method. When the reagent scope was investigated, it was determined that the functional group tolerance of the reactions was quite high. Finally, borylated dihydroisoquinolines have been converted into various intermediates by application studies.Master Thesis Enantio-Pure Synthesis of Enyne Epoxides and Their Iron-Catalyzed Sn2" Reactions With Grignard Reagents(01. Izmir Institute of Technology, 2020) Omur, Cenk; Artok, LeventThe use of transition-metal catalysts in synthetic chemistry has gained a lot of significance in the last decade, by virtue of their selectivity wheather regio-isomerically, or enantiomerically, or both. Besides their superior selectivity, these reactions have also been considered as atom economic and environmental-friendly. Iron-catalyzed reactions gained undeniable attention in regard to their low toxicity and presence in enzymatic reactions. Thus, use of the iron catalyst in the synthesis of biologically important and intermediary chemicals bear great significance. Allene motifs, which exist in vast number of naturally occuring compounds are important intermediates in synthesis of bio-active materials due to their versatile reactivity and instrict chirality. The first transition metal-mediated sythesis of allenes was accomplished by 1,3-substitution reaction of propargylic acetates with stoichiometric amounts of organocuprates (Rona et al.,1968). Later on, Fürstner and co-workers have established a technique that, allows the use of catalytic amounts of iron complexes for the reaction of Grignard reagents with propargylic oxiranes which yields -allenol compounds with different modes of addition (Fürstner et al., 2003). In addition to significant developments in this field, our group has established iron-promoted reactions of enyne acetates and oxiranes with Grignard reagents, producing functionalized vinyl allene structures. (Taç et al., 2017). In that study, reactions proceeded regioselectively in 1,5-substitution (SN2'') manner yielded vinylallenes in good to high yields. However, stereoselectivity of the method was not sufficiently satisfactory. Nevertheless, we disclose herein that the corresponding iron-catalyzed reactions of enyne oxiranes with an endocyclic alkenyl moiety are highly stereoselective; vinyl allene products could be obtained in high diastereomeric ratios by this method. Moreover, the ability to synthesize oxirane substrates in high enantiomeric purity allowed the production of the desired enantiopure vinyl allenes.Master Thesis Palladium Catalyzed Cross Coupling Reactions of Alkenyl Epoxides and Organoboronic Acid Esters(Izmir Institute of Technology, 2018) Eren, Ahmet; Artok, LeventIn organic chemistry, it is a useful method to form a new allylic compounds as a result of 1-3 substitution reactions of allylic compounds which have a good leaving group. These reactions usually require a metal catalyst but one of the most challenging aspects of these applications is the process regio and stereo selectivity for a wide variety of substrate types. Other compounds such as alkenyl epoxides are also useful for 1-3 substitution reactions. An advantage of using alkenyl oxirane compounds is that the oxirane ring is opened in the substitution step to form a hydroxyl group and resulted in the formation of allylic alcohols which are important intermediate product. Metal catalysed and regioselective reactions of terminal alkenyl epoxides with organoborons have been reported in the literature. However, there is no successful method for internal alkenyl oxiranes. Thus, in this study, 1-3 substitution reactions of alkenyl oxiranes were successfully applied, which yielded allylic alcohols with high regio- and stereoselectivity.Master Thesis Palladium-Catalyzed Stereo-Selective 1.2-Addition Reactions of ?,?-Epoxy Esters With Organoborons(Izmir Institute of Technology, 2018) Bilgi, Yasemin; Artok, LeventTransition metal-catalyzed SN2-type addition reactions of allylic compounds having good leaving groups is a valuable reaction procedure in organic chemistry. Vinyl epoxides, as a derivative of allylic compounds, are suitable reagents for substitution reactions with their high reactivity due to the presence of an epoxide ring tensions and a conjugated C-C double bond attached to this ring. The occurrence of a substitution reaction of such reagents over the allylic position allows synthesis of homoallylated alcohols, one of the key building blocks in the synthesis of natural compounds. Organoborans are stable against moisture and air and environmentally friendly compounds and are thought by us to be suitable nucleophiles in these reactions. Within the context of this research, Pd-catalyzed stereo-selective SN2-addition type arylation reactions of γ,δ-epoxy-α,β-unsaturated esters with organoborons were investigated. The reaction mechanism proceeds through formation of π-allylpalladium complex with the help of Pd-AsPh3 combination. The method has enabled to formation of γ-Aryl-δ-hydroxy-α,β-unsaturated esters with high regio- and stereo- selectivity.Master Thesis Coupling Reactions of Enyne Oxiranes With Grignard Reagents(Izmir Institute of Technology, 2016) Aytaç, İsmet Arınç; Artok, LeventLaboratory-synthesized (Z)-2,4-Enyne oxiranes were subjected iron-catalyzed reactions with Grignard reagents. The reactions afforded majorly E-configured vinylallenes with a hydroxyl group on the allylic carbon as the 1,5-(SN2'')-substitution products. However, in some case, along with the desired vinyllallenes products, 1,1- (SN2) and 1,3-substitution (SN2’) by-products were also recovered. Diastereo-selectivity of the method is strictly reliant on the syn/anti mode of the alkylation process. This study provides a new methodology for the synthesis of vinylallenes which are potential building blocks of biological active molecules.Master Thesis Synthesis of Allyl Alcohols by Paladium-Catalyzed 1,3-Substitution Reactions of Alkenyl Epoxides With Organoborons(Izmir Institute of Technology, 2016) Kıbrıs, Erman; Artok, Levent1,3-Substitution reactions of allylic compounds having a good leaving group is a prominent method in Organic Chemistry for the synthesis of new allylic reagents with an exchanged functional group. These reactions usually require the use of metal catalysts and one of the most challenging aspects for these applications is the regio- and stereo-selectivity of the process for a wide range of substrate types. Other compounds such as vinyl epoxides are also acceptable for substitution reactions. An important advantage of using these reagents is that opening of the oxirane ring during the substitution process lead to the generation of a hydroxyl group and as a result affords allyl alcohols which are important intermediaries in organic syntheses. An example of regio-selective metal-catalyzed reactions of vinyl epoxides having a terminal alkenyl group with environmentally benign organoborons was reported in the literature. However, no such success could be achieved with vinyl epoxides with an internal alkenyl group. Therefore, within the context of this method internal vinyl epoxides were successfully subjected to 1,3-substitution reactions with organoborons which yielded arylated allyl alcohols in both a regio- and stereo-selective manner. The method is applicable under quite mild conditions where a palladium-AsPh3 combination is used to activate the process.Master Thesis Thermal and Photodehydrogenation Reactions of Terpenes Over Zeolites(Izmir Institute of Technology, 2003) Tuzcuoğlu, Esra; Artok, LeventIn this thesis study, catalytic activity of cation exchanged (Na+, Li+, Ca2+, K+, Cs+) zeolite Y, especially NaY, and various microporous and mesoporous (Na exchanged, Beta, Mordenite, and NaX, CsNaX, MCM-41, Montmorillonite KSF and amorphous Silica) catalysts was investigated in the dehydrogenation reaction of terpenes to p-cymene.The results suggested that, there are two types of acid sites are present in cation exchanged zeolites from NH4Y, which are Br Bronsted and Lewis sites. a-terpinene, disproportionated by Br Bronsted acid catalysis into 3-p-menthene and p-cymene, and pcymene was also formed by direct dehydrogenation of a-terpinene can possibly occur with the participation of Lewis acid sites in cation exchanged zeolite Y. Best conversion to p-cymene were observed in the NaHY, LiHY and CaHY exchange from NH4Y that have relatively small cations, which more acidic than the larger ones.With the catalysts that have Bronsted acid sites except ion-exchanged zeolite Y, no conversion or only acid catalyzed isomerization reactions occur that shows the Bronsted acidity was not enough to catalyze the dehydrogenation of a-terpinene. Also Lewis acidic character and the structure morphology are the most important factors affecting the conversion. Lewis acidity is influenced from the cation and zeolite type.Master Thesis Acylation of 2-Methoxynaphthalene Over Ion-Exchanged Beta Zeolite(Izmir Institute of Technology, 2002) Kantarlı, İsmail Cem; Artok, LeventFriedel Crafts acylation of 2-Methoxynaphthalene was carried out over various ion-exchanged . zeolites (Mn+., where Mn+: In3+, Zn2+, Al3+, Fe3+, La3+) with various anhydride (acetic, propionic and benzoic anhydrides), or acyl chloride (acetyl, propionyl and benzoyl chlorides) acylating reagents. The results suggested that selectivity towards the 6-substituted products was higher with the larger size anhydrides, propionic and benzoic anhydrides. The metal cation type within the zeolite significantly influenced the extent of conversion and product distribution. That La3+ exchanged zeolite displayed higher selectivity for the 6-position acylated product with anhydrides ascribed mainly to narrowing of channels by the presence of La(OH)2+ ions that leave no room for the formation of more bulky isomeric forms and to enhanced Bronsted acidity of the zeolite. With acyl chlorides, the recovery of ketone products was found to be remarkably low. 1-Acyl-2-methoxynaphthalenes actively underwent deacylation when acyl chlorides were used as the acylation reagent.
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