Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Palladium-Catalyzed Alkoxycarbonylation Reactions of (e)-2 Carbonates(Izmir Institute of Technology, 2013) Karagöz, Ezgi Şule; Artok, LeventTransition metal-catalyzed carbon-carbon bond formation reactions are well-rounded methods to synthetic organic chemistry. One type of these reactions is the alkoxycarbonylation reactions performed in the presence of a transition metal catalyst, an alcohol and carbon monoxide atmosphere. Investigations on palladium-catalyzed alkoxycarbonylation reaction of allylic compounds leading to β,γ-unsaturated esters have been performed. Moreover propargyl derivatives are prominent reactants for palladium-catalyzed alkoxycarbonylation reactions to yield allene esters which proceed through a σ-allenylpalladium intermediate. Palladium-catalyzed alkoxycarbonylation reaction of some enantio-enriched propargylic derivatives that facilitate unique centre-to-axis chirality transfer is still inadequate and essential. In this study, the palladium-catalyzed alkoxycarbonylation reaction of E-configured 2,4-enyne carbonates which afforded exclusively ester functionalized (E)-configured vinylallenes through the formation of σ-vinylallenylpalladium species was performed. Moreover the chirality transfer of the proposed method was also surveyed over an enantio-enriched E-enyne carbonate.Master Thesis Short-Time Suzuki Reactions of Arly Halides Catalyzed by Palladium-Loaded Nay Zeolite Under Aerobic Conditions(Izmir Institute of Technology, 2006) Durgun, Gülay; Artok, LeventThe palladium-catalyzed Suzuki cross-coupling reaction is a powerful methods used in the synthesis of biaryl compounds.In this study, the Suzuki reactions of aryl bromides and chlorides with arylboronic acid were carried out over a Pd(NH3)42+-loaded NaY type zeolite. On the basis of our results, the Pd(NH3)42+-loaded NaY zeolite was found to be highly active for the Suzuki reactions of wide range of aryl bromides and electron poor aryl chlorides at low Pd concentrations (0.1-0.001mol %Pd), in air and at short times (5-45 minutes). The presence of relatively large amount of zeolite (1-4 g) was crucial for the success of the reactions with aryl chlorides. It was determined that there was a synergistic effect of the water- zeolite pair on the reaction rate.It was found that reactions were catalyzed dissolved palladium species. However,the palladium was largely recovered and only traces of palladium remained within the solution at the end of reaction (<0.8 ppm).Master Thesis Silica Supported N-Heterocyclic Carbenes: Active and Reusable Heterogeneous Catalysts for Mizoroki-Heck Reactions(Izmir Institute of Technology, 2004) Açıkel, Müge; Artok, LeventCarbon-carbon bond formation reactions are among the most important processes in chemistry, as they represent key steps in the synthesis of more complex molecules from simple precursors. This thesis describes mainly the development of novel applications of the mild and versatile palladium-catalyzed carbon-carbon coupling method, commonly known as the Heck reaction. Most of the reactions performed in homogeneous media bearing the difficulty of separation from the reaction mixture. For this reason, N-heterocarbenes (NHCs) that gains scientific interest due to their high catalytic activity and stability were used to combine the practical advantage of a heterogeneous catalyst with the efficiency of a homogeneous system Immobilized Pd(NHC) complex 64 (A) and its modified derivatives (B and C),either with trimethylchlorosilane or with imidazolidinium salt 63, were synthesized. Characterization of the novel materials were performed using elemental analysis, AAS, NMR, DRIFTS and BET analysis. On the basis of the results, catalyst C showed higher activity among the others.The results also verified that the predominant activity of C could be ascribed to direct beneficial effect of imidazolidinium salt by being on the silica surface, in the vicinity of the anchored Pd-NHC complex 64. The catalyst showed high activity and reusability towards the Mizoroki-Heck reactions iodoanisole and bromoarenes (activated, nonactivated and deactivated) with styrene, when reactions at 140 °C in the presence of 1.5 molar equivalent NaOAc.3H2O base and 0.5 % Pd with respect to the aryl halide. The catalyst preserved its original activity for 4-iodoanisole, 4-bromoacetophenone, 4- bromotoluene and even for highly deactivated 4-bromoanisole reagent at least 7 uses.Although the addition of immobilized salt to the catalyst C increased the activity,addition of commonly used Bu4NBr showed no gradual increase in the activity. The catalyst C was also active for 4-chloroacetophenone albeit at higher temperature (170°C). The AAS analysis indicated that the reaction was truly heterogeneous.Master Thesis The Activity of Silica Immobilized Palladium N-Heterocyclic Carbene Complexes Toward Mizoro-Heck Reaction and Their Characterization(Izmir Institute of Technology, 2005) Aksın, Özge; Artok, LeventC-C bond formation reactions are among the important processes in chemistry.A palladium-catalyzed reaction, commonly known as the Mizoroki-Heck (M-H) reaction, is a powerful method in construction of C-C coupling of olefins with aryl and vinyl halides.This thesis describes, mainly development and applications of novel silica anchored saturated molecular Pd-N-heterocyclic carbene (Pd-NHC) catalysts toward the M-H reactions of aryl halides.Characterization of the novel Pd-NHC complexes were performed using elemental analysis, NMR and X-ray crystallography techniques. The synthesized complexes were anchored over an amorphous silica surface through their triethoxy silane groups.On the basis of the results, the silica supported saturated Pd-NHCs were found to be highly active catalyst precursors for Mizoroki-Heck reactions of iodo- and bromoarenes with styrene and butyl acrylate olefins, when reactions were performed at 140 C in the presence of 1.5 molar equivalent Na2CO3 base. The catalyst preserved its original activity for 4-iodoanisole, 4-bromoacetophenone, 4-iodoacetophenone, iodobenzene and 4-iodotoluene reagents at least for 8 uses when Pd concentration, with respect to the aryl halide, was 0.5% in the reaction medium.The higher turnover frequencies were realized at the lower Pd concentrations. The AAS analyses revealed the presence of dissolved Pd species within the reaction medium at the early stages of reaction. Along with this finding, determination of Pd agglomerates onto silica surface by TEM examination indicates that the catalyst acted as a Pd reservoir and reactions were catalyzed homogeneously. In the course of reaction, Pd is liberalized to the solution involved with the reaction cycle and deposited onto silica surface to lead to form less active Pd agglomerates. That no trace of dissolved Pd was detected at the end of reaction by AAS is a positive finding for the purity of product.Master Thesis Palladium Catalyzed Reactions of 2-En Carbonates With Organoboronic Acids(Izmir Institute of Technology, 2011) Üçüncü, Muhammed; Artok, LeventRecently, transition metal catalyzed carbon-carbon bond formation reactions gain numerous importance in organic chemistry. Especially, palladium catalyzed carbon-carbon bond formation reactions provide lots of advantages in organic synthesis. For instance, palladium catalyst is extensively used in many allene formation reactions of various substrates such as propargyl and enyne compounds. This thesis describes the preparation of E-configured aryl or alkenyl functionalized vinylallene structures via the reaction of a 2-en-4-yne carbonates with organoboronic acids in the presence of Pd (0) precursor. This method, which proceeds through formation of s-vinylallenylpalladium intermediate, is applicable for both (E)- and (Z)- configured enyne carbonates and appeared to have wider scope for both organoboronic acids and enyne substrates. The reaction of the carbonate of an enantiomerically enriched enynol reagent with phenylboronic acid under the optimal conditions was proceeded and center-to-axis chirality transfer selectivity was investigated. Complete racemization was observed.Master Thesis Palladium Catalyzed Alkoxycarbonylation Reactions of 2-En Carbonates(Izmir Institute of Technology, 2011) Akpınar, Gürkan Eray; Artok, LeventHomogeneous catalysis relaying on transition metal complexes has led to innovation in organic chemistry. Palladium complexes are the most versatile and used extensively in organic synthesis. One type of these reactions is the carbonylation reactions with palladium complexes in the presence of alcohol and carbon monoxide. Extensive studies have been carried out on palladium-catalyzed carbonylation reactions of allylic and propargylic compounds. Alkynes containing a leaving group in propargylic position undergo alkoxycarbonylation reactions through the involvement of an σ-allenylpalladium as an intermediate to produce allenic esters. On the other hand, allylic compounds usually leads to β,γ-unsaturated esters through the involvement of a π- allylpalladium complex, when subjected to alkoxycarbonylation processes. With the high reactivity of allyl carbonates and propargyl carbonates in mind toward P(0)-catalyzed reactions, we attemped the palladium catalyzed alkoxycarbonylation reaction of Z- or E-configured 2,4-enyne carbonates leading to vinylallene ester structures. The reactions involved 1,5-type substitution and proceeded through formation of σ-vinylallenylpalladium species.