This thesis is focused on the development of new pincer complex-catalyzed transformations. Optimization of the catalytic properties (fine-tuning) was directed to increase the catalytic activity as well as the chemo-, stereo- and enantioselectivity of the complexes. This was achieved by varying the heteroatoms in the terdentate pincer ligand, by changing the electronic properties of the coordinated aryl moiety and by implementing chiral functionalities in the pincer complexes. In the cross-coupling reaction of vinyl epoxides and aziridines with organoboronic acids the chemoselectivity of the reaction could be increased by employment of pincer complexes instead of commonly used Pd(0) catalysts. Furthermore, the introduction of a methoxy substituent in the aromatic subunit of the complex considerably increased the activity of the pincer complex catalyst. Fine-tuning of the enantioselectivity in electrophilic allylation reactions was achieved by using a wide variety of new BINOL- and biphenanthrol-based pincer complexes. The highest enantioselectivity (85% ee) was obtained by applying biphenanthrol-based pincer complexes. Stereoselective pincer complex-catalyzed condensation of sulfonylimines with isocyanoacetate could be achieved under mild reaction conditions. By application of chiral PCP catalysts, 2-imidazolines could be obtained with up to 86% ee. A new pincer complex-catalyzed C-H bond functionalization based reaction between organonitriles and sulfonylimines affords homoallylic amines and beta-aminonitriles in high yields. The asymmetric version of this process affords beta-aminonitriles with up to 71% ee. In the last chapter, a pincer complex-catalyzed redox coupling reaction is described. In this highly regio- and stereoselective process the integrity of the pincer catalysts is fully retained. This catalytic reaction proceeds with a high level of functional group tolerance, as allylic acetate and aryl halide functionalities are retained.

Transition metal catalysis is a powerful tool for the construction of biologically active and pharmaceutically relevant architectures. With the challenge of continually depleting resources that this generation of scientists faces, it is becoming increasingly important to develop sustainable technologies for organic synthesis that utilize abundant and renewable feedstocks while minimizing byproduct formation and shortening the length of synthetic sequences by removing unnecessary protecting group manipulations and functionalizations. To this end, we have developed four new methods that transform inexpensive starting materials to valuable products. This dissertation covers the following key areas: 1) activation of CO2 for a mild and functional group tolerant synthesis of carboxylic acids, 2) oxidative twofold C–H bond activations as a strategy toward biaryls, 3) migratory O- to N-rearrangements in pyridines and related heterocycles for the preparation of N-alkylated heterocycles, and 4) asymmetric hydrogenations of cyclic imines and enamines en route to chiral 1,2- and 1,3-diamines and macrocyclic peptides.

Transition metal catalysis is a powerful tool for the construction of biologically active and pharmaceutically relevant architectures. With the challenge of continually depleting resources that this generation of scientists faces, it is becoming increasingly important to develop sustainable technologies for organic synthesis that utilize abundant and renewable feedstocks while minimizing byproduct formation and shortening the length of synthetic sequences by removing unnecessary protecting group manipulations and functionalizations. To this end, we have developed four new methods that transform inexpensive starting materials to valuable products. This dissertation covers the following key areas: 1) activation of CO2 for a mild and functional group tolerant synthesis of carboxylic acids, 2) oxidative twofold C–H bond activations as a strategy toward biaryls, 3) migratory O- to N-rearrangements in pyridines and related heterocycles for the preparation of N-alkylated heterocycles, and 4) asymmetric hydrogenations of cyclic imines and enamines en route to chiral 1,2- and 1,3-diamines and macrocyclic peptides.

Aquesta tesi és el reflex que de la cooperació entre grups experimentals i grups teòrics s'aconsegueix l'assoliment d'objectius inassolibles de forma individual. A partir de la DFT s'expliquen processos inorgànics i organometàl·lics de gran valor biològic i/o industrial. La tesi està enfocada especialment a l'estudi de complexos mononuclears i binuclears de coure, on té lloc l'activació d'enllaços C-H, C-C, i O-O. L'estudi de complexos octaèdrics de ruteni ha permès dur a terme extensos estudis isomèrics i racionalitzar les propietats espectroscòpiques dels mateixos. A més a més, estudis més puntuals respecte clusters de coure, l'estudi de la reacció de Pawson-Khand, l'estudi d'enllaços Pt-Pt en complexos trimèrics de platí, a més a més de l'estudi de la isomeria de complexos de Ni i Pt. / This thesis shows that the cooperation between experimental and theoretical groups gives as a result the achievement of aims impossible working independently. From DFT calculations inorganic and organometallic problems related to great biological and industrial processes can be explained. This thesis is especially focused on the study of mononuclear and binuclear copper complexes, where a C-H, C-C, and O-O bond activation takes place. The study of octahedral ruthenium complexes has allowed carrying out isomeric studies and the rationalization of spectroscopic properties. Furthermore, other little studies related to copper clusters, the Pawson-Khand reaction, Pt-Pt bond interaction in trimer platinum complexes, and isomerism of Ni and Pt complexes.

Lanthanum (La)-promoted hydrocarbon activation reactions were carried out in a laser vaporization metal cluster beam source. Reaction products were identified by time-of-flight mass spectrometry, and the approximate ionization thresholds of La-hydrocarbon complexes were located with photoionization efficiency spectroscopy. The accurate ionization energies and vibrational frequencies of the La complexes were measured using mass analyzed threshold ionization (MATI) spectroscopy. Their molecular structures and electronic states were investigated by combing the MATI spectroscopic measurements with quantum chemical and Franck-Condon factor calculations. In this dissertation, La-mediated C-H and C-C bond activation reactions were investigated for several small alkynes (acetylene, propyne) and alkenes (propene, 1,3-butadiene, 1-butene). The C-H bond activation was observed for both alkynes and alkenes and the C-C bond activation for alkenes. The metal-hydrocarbon intermediates formed by the C-H or C-C bond cleavage reacted further with one or more parent hydrocarbon molecules to produce larger species by C-C bond coupling reactions. Structural isomers of the intermediates and products were identified within an energy range of several kilocalories per mole. Reaction pathways for the intermediate and product formations were studied by theoretical calculations. The ground electron configuration of La atom is 4d16s2.Upon the hydrocarbon coordination, La atom is excited to a 4d26s1 configuration to facilitate the formation of two La-C bonds. After the metal-hydrocarbon complex formation, only one electron is left in the 6s orbital of the metal center. Therefore, the most stable electronic state of the La complexes studied in this work is in a doublet spin state. Ionization of the doublet state yields a preferred singlet ion state. Although La is in the formal oxidation state of +2, the ionization energies of the metal-complexes are significantly lower than that of the free atom. This observation suggests that the concept of the formal oxidation state widely used in chemistry textbooks is not useful in predicting the change of the ionization energy of a metal atom upon ligation. Moreover, ionization has a very small effect on the geometry of the hydrocarbon fragment in each complex but significantly reduces the La-C distances as a result of an additional charge interaction.

No description available.

The use of small molecule building blocks in, for example, pharmaceutical research and new material development, creates a need for new and improved organic synthesis methods. The use of transition metals as mediators and catalysts opens up new reaction pathways that have made the synthesis of completely new compounds possible as well as greatly improved the synthetic routes to known compounds. Herein, the development of new metal-mediated and catalyzed reactions for construction of vinylic and allylic carbon-carbon and carbon-heteroatom bonds is described.  The use of iodonium salts as coupling partners in Pd-catalyzed Heck type reactions with alkenes is shown to improve the current substrate scope. Results from a mechanistic study indicate that the reaction proceeds via high oxidation state palladium intermediates. The use of IIII reagents is also believed to facilitate a PdII/PdIV catalytic cycle in allylic silylation of alkenes using (SiMe3)2, which, to the best of our knowledge, is the first method developed for metal-catalyzed allylic C-H silylation. The same silyl-source, (SiMe3)2, has previously been used in a Pd-catalyzed allylic substitution reaction in which allylic silanes are formed from allylic alcohols. A detailed mechanistic investigation of this reaction is described in which by-products as well as intermediates, including the resting state of the catalyst, are identified using 1H, 11B, 19F and 29Si NMR spectroscopy. Kinetic experiments are performed that give information about the turn-over limiting step and the mechanism of the analogous borylation using B2pin2 is also investigated. Insights from this study further made it possible to improve the stereoselectivity of this reaction. Additionally, a new method for Cu-mediated trifluoromethylation of allylic halides is presented in which linear products are formed exclusively from both linear and branched allylic substrates at room temperature.  Identification of allylic fluorides as by-products during the reaction also led to the development of a similar Cu-mediated reaction for the fluorination of allylic halides. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

No description available.

The Dong research group is interested in harnessing the power of transition metal catalysis to transform simple molecules and reagents (such as carbon monoxide, hydrogen gas, olefins, and C–H and C–O bonds) into valuable products (such as functionalized heterocycles, chiral carbonyl compounds and natural products). This thesis will describe our continual effort to achieve this goal. Part I describes the Pd-catalyzed functionalization of sp2 and sp3 C–H bonds. Carbon monoxide is used as a stoichiometric reductant in the cyclization of diarylnitroalkenes to afford biologically relevant 3-arylindoles and other N-containing heterocycles with carbon dioxide as the only stoichiometric byproduct. Also, an aryl sulfoxide moiety is shown to direct the arylation of sp3 C–H bonds to afford beta-functionalized amides. Part II describes the Ru-catalyzed sp3 C–O bond activation of alkoxypyridines and related heterocycles. In this transformation, an O- to N-alkyl migratory rearrangement occurs to afford N-alkylated pyridones which are structures found in many natural products and pharmaceutical agents. Part III describes our pursuit of metal-catalyzed asymmetric synthesis. Readily available benzylic bromides are carbonylated with carbon monoxide in alcoholic solvent mixtures. The resulting medicinally relevant 2-arylpropionic esters are obtained with moderate to good enantioselectivities. Preliminary results for the asymmetric hydrogenation of gem-diarylethylenes and novel ligand development are also disclosed. Part IV describes our efforts towards the total synthesis of 6-deoxyerythronolide B. Our retrosynthetic analysis of the macrolide antibiotic involves disconnections at the lactone linkage and between C7 and C8. The two equally complex fragments were prepared via reliable aldol, hydroboration, crotylation and redox chemistry. Rather than the typical macrolactonization method to form the 14-membered ring, we propose an alternative strategy where we plan to cyclize with a metal-catalyzed ring-closing metathesis event. Currently, this step is under investigation by other members in the group.

The Dong research group is interested in harnessing the power of transition metal catalysis to transform simple molecules and reagents (such as carbon monoxide, hydrogen gas, olefins, and C–H and C–O bonds) into valuable products (such as functionalized heterocycles, chiral carbonyl compounds and natural products). This thesis will describe our continual effort to achieve this goal. Part I describes the Pd-catalyzed functionalization of sp2 and sp3 C–H bonds. Carbon monoxide is used as a stoichiometric reductant in the cyclization of diarylnitroalkenes to afford biologically relevant 3-arylindoles and other N-containing heterocycles with carbon dioxide as the only stoichiometric byproduct. Also, an aryl sulfoxide moiety is shown to direct the arylation of sp3 C–H bonds to afford beta-functionalized amides. Part II describes the Ru-catalyzed sp3 C–O bond activation of alkoxypyridines and related heterocycles. In this transformation, an O- to N-alkyl migratory rearrangement occurs to afford N-alkylated pyridones which are structures found in many natural products and pharmaceutical agents. Part III describes our pursuit of metal-catalyzed asymmetric synthesis. Readily available benzylic bromides are carbonylated with carbon monoxide in alcoholic solvent mixtures. The resulting medicinally relevant 2-arylpropionic esters are obtained with moderate to good enantioselectivities. Preliminary results for the asymmetric hydrogenation of gem-diarylethylenes and novel ligand development are also disclosed. Part IV describes our efforts towards the total synthesis of 6-deoxyerythronolide B. Our retrosynthetic analysis of the macrolide antibiotic involves disconnections at the lactone linkage and between C7 and C8. The two equally complex fragments were prepared via reliable aldol, hydroboration, crotylation and redox chemistry. Rather than the typical macrolactonization method to form the 14-membered ring, we propose an alternative strategy where we plan to cyclize with a metal-catalyzed ring-closing metathesis event. Currently, this step is under investigation by other members in the group.