Thesis advisor: James P. Morken / Described herein are three distinct projects centered on the formation and use of carbon-boron bonds. In the first, the enantioselective platinum-catalyzed 1,4-diboration of trans-1,3-dienes is advanced in both selectivity and scope through the development of a novel class of electron rich chiral monodentate phosphines. Under the action of the new ligands, highly selective diboration is maintained at reduced loadings of catalyst. Secondly, enantioenriched 1,2-bis(pinacol boronates) are engaged in regioselective Suzuki-Miyaura cross-coupling with aryl and vinyl electrophiles. A tandem diboration cross-coupling sequence is successfully implemented to afford homobenzylic and homoallylic pinacol boronates directly from terminal olefins, which subsequently undergo oxidation, amination or homologation of the remaining carbon-boron bond to arrive at a range of enantioenriched products. Lastly, aryl electrophiles containing tethered allylboronate units undergo efficient intramolecular coupling in the presence of a chiral palladium catalyst to give enantioenriched carbocyclic products. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Homogeneous organometallic species serve as useful catalysts for a vast number of chemical transformations. Ancillary ligands which bind to the metal center are employed to modulate the reactivity of the metal, and have been key to the discovery and improvement of most types of transition metal-mediated reactions. This thesis describes the design and application of P,N-ligands in platinum group-catalyzed reactions, specifically the Ru- and Ir-catalyzed ketone transfer hydrogenation (TH) and the Pd-catalyzed cross-coupling of aryl (pseudo)halides and N-H containing substrates. A zwitterionic Ru-species featuring a donor substituted P,N-indenide ligand was found to be an excellent catalyst for ketone TH, providing turnover frequencies (TOFs) as high as 300 000 h-1, while related cationic Ru-complexes ligated by P,N-indene ligands were found to be rather poor catalysts. Ir-complexes supported by either indene or indenide P,N-ligands were also found to be active TH catalysts (TOFs ~30 000 h-1), however phenylene P,N ligands, specifically (o-tBu2P-C6H4)NMe2, displayed optimal catalytic performance, allowing for rapid ketone reduction (TOFs of >100 000 h-1), at low catalyst loadings (as low as 0.004 mol% Ir). Enantioselective TH was achieved by employing the suitably substituted, commercially available P,N-ligand, Cy-Mandyphos in combination with [Ir(COD)Cl]2 and NaPF6. The use of P,N-ligands in Pd-catalyzed C-N cross coupling, specifically (o-R2P-C6H4)NMe2 (R = tBu or 1-Ad), allowed for the development of a highly versatile catalyst system for this reaction. In combination with [Pd(allyl)Cl]2 or [Pd(cinnamyl)Cl]2, the above described ligands enabled the cross-coupling of aryl and heteroaryl chlorides and bromides to a diverse range of amine and related substrates such as primary alkyl- and arylamines, cyclic and acyclic secondary amines, N-H imines, hydrazones, lithium amide, and ammonia. Reactions could be performed at low catalyst loadings (0.5-0.02 mol% Pd) with excellent functional group tolerance and chemoselectivity. The ligand N-[2-di(1-adamantylphosphino)phenyl]morpholine in combination with [Pd(cinnamyl)Cl]2 was found to provide excellent reactivity for the cross-coupling of ammonia to aryl chlorides with catalyst loadings of 0.3-5 mol% Pd. Sterically unbiased substrates containing electron-donating groups were tolerated with minimal competing diarylation. Aryl tosylates could be coupled with ammonia at room temperature and chemoselective ammonia arylation in the presence of other amine functionality was well tolerated. Pd-catalyzed cross-coupling of hydrazine with aryl chlorides and tosylates was achieved employing N-[2-di(1-adamantylphosphino)phenyl]-morpholine as the ligand. Good yields of the desired, mono-functionalized aryl hydrazine product was observed for a range of substrates at 5 mol% Pd. Selective hydrazine coupling was observed in the presence of other NH-functionality and NH-indazoles could be prepared by the tandem cross-coupling/condensation of hydrazine with 2-chlorobenzaldehydes.

Herein I describe a model study to determine the feasibility of organic hydride donors as a source of hydride in the regeneration of ammonia borane. Hydride transfer was observed in the model system comprised of Hantzsch ester and several analogues, as the organic hydride donor, and tris(pentafluorophenyl)boron, as the boron-based hydride acceptor akin to BBr3. Side reactions could be minimized by varying the reaction conditions. We determined that a Lewis acid-base adduct was forming between the carbonyls of the donor and the hydride acceptor, that this adduct was dynamic in the case of Hantzsch ester and that it could be inhibited by bulkier ester groups or promoted by reducing the steric bulk at the carbonyl in the case of a methyl ketone. The thermodynamics of the hydride transfer reaction with an N-substituted analogue were probed via variable temperature NMR and compared to two differently substituted analogues. In addition, the scope of the sp2-sp3 Suzuki-Miyaura cross-coupling previously developed in our lab was extended to include 2-(1,2-diaryl)ethane pinacolborane scaffolds. In order to access this asymmetric scaffold, reaction conditions for the cross-coupling of a primary boronic ester in the presence of a secondary one were developed. Yields achieved for the linear cross-coupling were in the 70 % range and varied from 42 % to 69 % for the secondary position. These latter yields are in the same range as the hydroborated styrene scaffolds described in our first account demonstrating the broad scope of these reaction conditions. / Thesis (Master, Chemistry) -- Queen's University, 2011-09-30 14:43:02.652

Creating new carbon-carbon bonds is one of the most important and challenging reactions in organic synthesis. Metal-catalyzed cross-coupling reactions have emerged as one of the preferred methods of producing new carbon-carbon bonds, and this work led to the 2010 Nobel Prize in Chemistry. This thesis was aimed at expanding the current research in the area of metal-catalyzed cross-coupling reactions to include new applications with dithiolane and dithiane protecting groups. 1,3-Dithiolane and 1,3-dithiane derivatives are particularly interesting molecules in that they can be deprotonated by a strong base to form anions, which can then be used for carbon-carbon bond synthesis. This thesis describes the investigation into the use of dithiolanes and dithianes in metal-catalyzed cross-coupling reactions, as well as some of the challenges faced in performing this sulfur-based chemistry.

Creating new carbon-carbon bonds is one of the most important and challenging reactions in organic synthesis. Metal-catalyzed cross-coupling reactions have emerged as one of the preferred methods of producing new carbon-carbon bonds, and this work led to the 2010 Nobel Prize in Chemistry. This thesis was aimed at expanding the current research in the area of metal-catalyzed cross-coupling reactions to include new applications with dithiolane and dithiane protecting groups. 1,3-Dithiolane and 1,3-dithiane derivatives are particularly interesting molecules in that they can be deprotonated by a strong base to form anions, which can then be used for carbon-carbon bond synthesis. This thesis describes the investigation into the use of dithiolanes and dithianes in metal-catalyzed cross-coupling reactions, as well as some of the challenges faced in performing this sulfur-based chemistry.

In the last centuries, transition metal chemistry beсome one оf the mоst іmportant tооls for synthesis of valuable organic compounds and different chemical transformations. In particular, transition metal catalysis are capable of forming novel cross coupling bonds. In this background, photocatalysis was developed later to create new chemical transformations by the irradiation with visible light. In this regard, the combination of transition metal catalysis and photochemistry is a breakthrough in catalysis that has provided impossible transformations in organochemistry. One of the widely available reactants in synthesis are alkyl chlorides. However, it is hard to activate chemically stable C(sp3 )-Cl bond at room temperature. In this study, we overcome this limitation by excited-state palladium catalysis under mild conditions. The reaction goes through the hybrid alkyl-Pd radical as a key intermediate. The procedure provides the synthesis of oxindole and isoquinolinedione derivatives mainly from alkyl chlorides via annulation overcoming its chemical limitations. This work will focus on the generation of alkyl radicals from unactivated C(sp3 )-Cl using simple palladium catalysis

The stereochemical course of the Pd–catalyzed Suzuki-Miyaura cross-coupling of α-substituted, enantioenriched allylic boronic esters with phenyl iodide has been examined. The secondary boronic esters were prepared in both racemic and enantioenriched forms via borylationof a lithiated carbenoid with a geometrically defined vinyl boronic ester. The geometric purities were determined to be >99% and the enantiomeric excesses of stereodefined secondary boronic esters were found to exceed 98:2. In total, 8 allylic boronic esters were successfully cross-coupled, providing arylated products with high regioselectivities (>90:10) and complete enantiospecificities (>99%). The cross-coupling of a sterically and electronically unbiased, deuterated substrate confirmed that fully equilibrated π-allylic intermediates are not involved. Additionally, correlating the absolute configurations of the allylic boronic ester and the cross-coupling product allowed us to confirm that the transmetalation step of the reaction proceeded through a closed transition state via a syn-SE’ mechanism, which further suggests the importance of the distinct Pd-O-B bond linkage. Further, the cross-coupling of vinyl iodides to secondary boronic esters was investigated. / Thesis (Master, Chemistry) -- Queen's University, 2013-11-12 19:05:19.488

Little attention has been given to the formation of the putative PdL2 species required for Pd-catalyzed cross-coupling reactions. Active species are generally difficult to store due to air-sensitivity and are therefore formed in situ at unknown rates and in unknown yields via a variety of palladium precatalysts. Commonly employed Pd(0) and Pd(II) precatalysts are often relatively ineffective because they generate only low concentrations of the bis(phosphine) species PdL2 under most reaction conditions. This thesis describes the use of the easily synthesized and easily handled Pd(η3-1-Ph-C3H4)(η5-C5H5) (I) as a superior precursor than any other documented system for the in situ formation of PdL2. Rapid and quantitative formation of active catalyst solutions allow us to demonstrate that I is also the best precatalyst known for PdL2-catalyzed crosscoupling reactions. We discuss the Suzuki-Miyaura reaction of 4-bromoanisole with phenylboronic acid and demonstrate that, under mild reaction conditions, higher initial rates and higher conversions with I can be obtained compared with other common precatalysts (Pd(OAc)2, Pd(PPh3)4, Pd2dba3, etc.) containing a variety of phosphine ligands. This methodology has also been extended to other cross-coupling reactions, as we demonstrate that higher initial rates and higher conversions with I can be obtained for a variety of Mizoroki-Heck arylations and Buchwald-Hartwig aminations. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-06-25 11:53:06.75

No description available.

Due to its unique properties and high surface area, Graphene has become a good candidate as an effective solid support for metal catalysts. The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene". Microwave-assisted synthesis of various metallic nanostructured materials was investigated for CO oxidation applications. These metallic nanostructured materials were used to convert CO to CO2 as an effective approach for carbon monoxide elimination due to its harmful effect on health and environment. In particular, this dissertation is focusing on palladium as a transition metal that has a unique ability to activate various organic compounds to form new bonds. The prepared graphene-supported metallic nanostructured materials were successfully used to investigate Suzuki cross-coupling reaction as an important reaction in the field of pharmaceutical applications. In this research, nanostructured materials were used as solid support catalysts which showed remarkable improvements in the aspects of size, surface structure, catalytic selectivity, shape and recyclability. The nano porous structure and superparamagnetic behavior of (Fe3O4) nano particles that were used as an effective ingredient in graphene-supported palladium catalyst improved the catalytic activity and the catalyst recyclability simply by using an external magnetic field. This research has been divided into two main categories; the first category is to investigate other metal oxides as a solid support for palladium to be used in CO oxidation catalysis. The second category will focus on improving of solid support systems of palladium – magnetite catalyst to increase recyclability. The final stage of this investigation will study the use of these solid supported metal catalysts in continuous heterogeneous processes under flow reaction conditions. The structural, morphological and physical properties of graphene-based nanocomposites described herein were studied using standard characterization tools such as TEM, SEM, X-ray diffraction, XPS and Raman spectroscopy.