N-Heterocyclic carbenes (NHCs) have emerged as appropriate replacements for phosphines in transition metal catalyzed cross-coupling chemistry. The advantages of NHCs over phosphines include ease of handling, minimal toxicity, stability and powerful electron donating properties. Improvement of catalytic processes has become increasingly relevant in light of prospective applications of organic transformations in industry as well as in synthetic laboratories. To that end, NHCs represent an important class of catalysts and catalyst modifiers which mandate continued research efforts. Prospective applications of processes catalyzed by NHCs and NHC-metal catalysts provide a strong impetus to develop them and related methodologies. This dissertation focuses on the development of NHCs and NHC ligated metal complexes in various catalytic transformations. NHC ligated palladium catalysts were synthesized in simplified protocols amenable to large-scale industrial applications. The catalysts were utilized in developing different valuable coupling methodologies. Significant advances were achieved in Suzuki-Miyaura, á-arylation of ketones and Kumada-Tamao-Corriu cross coupling reactions. The focus of the work was to make the synthesized catalysts and their activity in these methodologies acceptable to wider range of applications. The strongly nucleophilic nature and easily tunable steric and electronic properties of NHCs have been exploited to mediate organic transformations by utilizing NHCs as catalysts. The metal-free catalysis has an added advantage of being more environmentally friendly. NHCs have proven to be excellent transesterification catalysts for reactions of alcohol and esters. An efficient catalytic system, widening the scope of N-heterocyclic carbenes catalyzed transesterification/acylation reaction of alcohols is described. The methodology has been expanded to include secondary alcohols as well as phosphorus based esters.

Thesis advisor: Kian L. Tan / Thesis advisor: James P. Morken / Described herein are four different research projects spanning over two different research groups. The first two projects describe the development and application of scaffolding catalysts for the (1) site-selective silylation of ribonucleosides and (2) the distal and diastereoselective hydroformylation of homoallylic alcohols. These projects emphasize the effectiveness of scaffolding catalysts to bind a hydroxyl-containing substrate and control the site- or regioselectivity of a reaction using said substrate. The third project describes a hydroxyl-directed diboration of homoallylic and bis-homoallylic alcohols. The hydroxyl-containing 1,2-bis(boronates) are valuable intermediates for further synthetic manipulations. One such manipulation, a hydroxyl-directed Suzuki cross-coupling reaction, is the focus of the final project. This directed cross-coupling reaction forges carbon-carbon bonds in a stereoselective manner, highlighted in the total synthesis of the naturally occurring compound, debromohamigeran E. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: James P. Morken / Internal allyl electrophiles were successfully implemented in a catalytic cross-coupling to allylB(pin) with high regiocontrol to afford multisubstituted 1,5-dienes bearing chemically differentiated olefins. Construction of alkenyl compounds with all carbon quaternary centers and high enantiomeric excess can be achieved in one step without the use of enantiomerically enriched chiral ligands. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: James P. Morken / This dissertation details recent developments in palladium catalyzed carbon-carbon bond formation reactions with two areas of focus: the palladium catalyzed branched and enantioselective allyl-allyl cross-coupling, and the palladium catalyzed carbonylative conjugate addition. Allyl-allyl cross-coupling presents an opportunity to synthesize 1,5-dienes, a scaffold that resembles subunits of terpenes, a critical building block in nature. Chapter I provides an overview of the developments in the allyl-allyl cross-coupling area. Chapter II, III, and IV detail strategies to construct complex substituted asymmetric 1,5-dienes through branched selective and enantioselective allyl-allyl cross-coupling. In chapter V, the palladium catalyzed carbonylative conjugate addition is discussed. This method enables the synthesis of 1,4-dicarbonyl compounds in an atom economical and environmentally friendly fashion, and provides a direct access to five membered heterocycles, a valuable class of chemicals in medicine. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: James P. Morken / This dissertation details the development of several enantioselective or stereospecific transformations involving organoboronic esters. Chapter one will introduce electrophile-induced boronate rearrangements which underpins much of the reactivity that will be discussed in subsequent chapters. In chapter two the conjunctive cross-coupling reaction is presented. Its development and application to the synthesis of non-racemic boronic esters, along with its application to the synthesis of enantioenriched allylic boronic esters, will be discussed. In chapter three the cross-coupling of geminal bis(boronic) esters is introduced and the development of a method to employ them in cross-coupling with alkenyl bromides, affording enantioenriched substituted allylic boronic esters is outlined. In chapter four we highlight the utility of allylic boronic esters, and detail the development of a cross-coupling reaction that involves the use of these substrates and halide electrophiles to furnish enantiomerically enriched products containing all carbon quaternary stereocenters. Finally, in chapter five we describe the development of a metalfree amination reaction of organoboron compounds, which is able to deliver otherwise difficult-to-access enantiomerically enriched α-tertiary amines. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

To address the issue of unnecessary functional group transformations in synthesis, the direct functionalization of carbon-hydrogen (C―H) bonds presents itself as an efficient and atom economical process. In particular, palladium(II)-catalyzed oxidative functionalization of arene C–H bonds were investigated to yield intermolecular and intramolecular arylations. Kinetic studies and characterization of bimetallic palladium(II) complexes led to the discovery of two other palladium(II)-catalyzed processes: arene hydroxylation and selective chlorination of anilides. Realizing the potential of biocatalysis and of transition-metal catalysis, we marriaged these two fundamentally different methods to access complex molecules in rapid and step economical ways and chose popular synthetic target, 6-deoxyerythronolide B to showcase the efficiency of these stereoselective reactions. To form the 14-membered lactone, we employed a transition-metal catalyzed ring-closing metathesis. Two different fragments were assembled via traditional and reliable aldols, oxidations and reductions, crotylations and protective group chemistry.

To address the issue of unnecessary functional group transformations in synthesis, the direct functionalization of carbon-hydrogen (C―H) bonds presents itself as an efficient and atom economical process. In particular, palladium(II)-catalyzed oxidative functionalization of arene C–H bonds were investigated to yield intermolecular and intramolecular arylations. Kinetic studies and characterization of bimetallic palladium(II) complexes led to the discovery of two other palladium(II)-catalyzed processes: arene hydroxylation and selective chlorination of anilides. Realizing the potential of biocatalysis and of transition-metal catalysis, we marriaged these two fundamentally different methods to access complex molecules in rapid and step economical ways and chose popular synthetic target, 6-deoxyerythronolide B to showcase the efficiency of these stereoselective reactions. To form the 14-membered lactone, we employed a transition-metal catalyzed ring-closing metathesis. Two different fragments were assembled via traditional and reliable aldols, oxidations and reductions, crotylations and protective group chemistry.

Enormous efforts have been made to optimize the Pd-catalyzed Suzuki-Miyaura reaction, but there is to date no generally useful protocol and forcing conditions are often required. One reaction variable that has often been neglected is the extent to which the supposed catalysts, bisphosphinepalladium(0) complexes, are actually formed from the variety of popular precatalysts used. There is in fact little evidence that these precursors produce bis-ligated Pd(0) complexes and it is possible that the rate limiting factor may be catalyst formation. If so, then the development of an optimized method for forming these catalytic species would be a significant contribution to this field. The following work describes research efforts to determine the optimum conditions to generate PdL2 (L = PCy3, PMeBut2, PBut3) cleanly and quantitatively from Pd(3-C3H5)(5-C5H5) and Pd(3-1-Ph-C3H5)(5-C5H5). Furthermore, the conditions under which PdL3 species may exist in equilibrium with the PdL2 species are defined. NMR studies indicate that while Pd(PBut3)2 shows no inclination to increase its coordination number, Pd(PCy3)2 and Pd(PMeBut2)2 react with added phosphine to form 3:1 compounds. Equilibrium constants for dissociation of the PdL3 compounds were measured over a range of temperatures, yielding the thermodynamic parameters of dissociation and estimated Pd-P bond dissociation energies. Additionally, the generation of heteroleptic species serve to confirm the existence of 3:1 compounds. A kinetic study of the oxidative addition of PhBr to Pd(PCy3)2 was also performed. It was found that oxidative addition was first order in palladium, but that added bromide had no effect on the rate of oxidative addition. Added PCy3 inhibited oxidative addition, possibly due to the conversion of palladium(0) into the less active 3:1 compound. The formation of the catalytically less active 3:1 compounds has serious implications for many catalytic cross-coupling processes which involve catalyst formation via the slow reduction of palladium(II) in the presence of excess phosphine; for many systems, relatively little of the added palladium may actually be present as the active bisphosphinepalladium(0) compound. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-12-08 13:24:50.825

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23910号 / 工博第4997号 / 新制||工||1780(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 中尾 佳亮, 教授 松原 誠二郎, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Thesis advisor: James Morken / This dissertation details two different alkene difunctionalization strategies that are utilized in the synthesis of three types of organoboron species in racemic and enantioenriched fashion. Chapter one will introduce the carbohydrate and DBU co-catalyzed transition-metal-free enantioselective diboration reactions of unactivated alkenes. Mechanistic insights guided reaction condition design will be discussed. In chapter two, a nickel-catalyzed conjunctive cross-coupling of 9-BBN borane and carboxylic acid derivatives is presented. Its development and detailed mechanistic studies, along with the efforts in asymmetric induction will be covered. Finally, the first enantio- and diastereoselective synthesis of 1,2-anti-silylboronates enabled by palladium-catalyzed conjunctive cross-coupling will be described. The optimization of chemo-, enantio- and diastereoselectivity in the reactions and their following transformations (e.g. oxidation and amination) is demonstrated. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.