Mechanistic aspects of the asymmetric rhodium catalyzed hydroboration of vinyl arenes with catecholborane (HBCat) and pinacolborane (HBPin) have been probed. Competition studies conducted with catalysts bearing asymmetric ligands Josiphos or Quinap reveal substituent effects of varying sensitivity correlating to Hammett parameter sigma. In reactions involving the Quinap ligand, rho-values of +1.97 and +1.02 are observed for HBCat and HBPin, respectively. In Josiphos-ligated systems, rho-values of +1.38 and -3.17 are observed, indicating that the reaction proceeds through differing mechanisms depending on the borane employed. Labeling experiments reveal differences in the reversibility of the hydride insertion step of reaction depending on the ligand and borane implemented in hydroboration. A new methodology has been developed for regioselective rhodium-catalyzed hydroboration of internal olefins with pinacolborane. The addition of co-catalytic Lewis acids results in the activation of cationic rhodium catalysts in chlorinated solvents. Increased catalytic activity and regioselectivity are observed under these conditions. For internal alkyl olefins, selectivity for non-isomerized secondary boronate esters was found originate from the non-coordinating solvents employed in the reaction. For aromatic olefins, increased regioselectivity and reaction acceleration are both effects of the Lewis acid additive. Study of the reaction revealed that these properties are linked to Lewis acid-base mediated heterolytic B-H bond cleavage of pinacolborane, and suggests that the reagent is transferred to the rhodium catalyst as borenium ion and hydride moieties. Inhibition studies confirmed that Lewis acid is required throughout the reaction and does not solely act as an initiator. / Thesis (Master, Chemistry) -- Queen's University, 2009-10-12 20:56:41.263

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There is a constant need for robust and highly reactive hydroborating reagents which will be able to yield stable organoborane compounds upon their hydroboration with olefins. These stable organoborane compounds can be used as a starting material in a number of cross-coupling reactions. The objectives of this project were to synthesize heterocyclic borolanes (with mixed donor atoms) and to evaluate the stability and reactivity of such borolanes towards the hydroboration reaction. The second part of the objective was to evaluate the application of arylbenzo-1,3,2-diazaborolane compounds as potential arylating reagent in the copper(II)acetate catalyzed N-arylation of imidazole using the Chan-Lam coupling reaction. Three heterocyclic borolanes were successfully synthesized from the reaction of borane-dimethyl sulfide complex with the corresponding chelating group in yield ranging from 45-96 %. These borolane showed good stability towards atmospheric oxidation and disproportionation due to elevated temperatures. A density functional calculation conducted on these borolanes showed that there was an decrease in the gap energy in the order of benzo-1,3,2-dioxaborolane > benzo-1,3,2-oxothiaborolane > benzo-1,3,2-thiazaborolane > benzo-1,3,2-dithiaborolane > benzo-1,3,2-diazaborolane. The use of benzo-1,3,2-thiazaborolane as a hydroborating reagent showed that this compound was prone to disproportionation. The condensation reaction of boronic acid with 1,2-diaminophenyl, 1,2-dihydroxybenzene and o-aminophenyl mercaptan, resulted in the synthesis of eleven arylbenzo-1,3,2-boronate esters in yields between 66-99 %. The investigation on the use of arylbenzo-1,3,2-diazaboronate ester as N-arylating reagents in the Chan-Lam coupling showed that these compounds were unsuitable arylating reagents and that the boronic acid proved to be better arylating reagent. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Silicon based organic reagents have enjoyed a wealth of applications in the last thirty year. However, the development of organosilanes for asymmetric synthesis has been less prolific. The drawbacks of using 'Si-centred' chiral organosilanes has led to 'C- centred' organosilicon compounds being the substrate of choice. This research has been directed at the synthesis and application of C(_2) symmetric 'C-centred' cyclic organosilicon species and their potential applications in asymmetric synthesis. A variety of synthetic methods have been considered, the most successful of which has been the double asymmetric hydroboration of substituted divinylsilanes. This has allowed the use of unusual boron redistribution chemistry to give access to both acyclic and cyclic rmw-substituted organosilicon compounds with high stereoselectivity. A new method for the synthesis of dichlorosilanes from their diphenyl analogue has been developed and has been shown to occur almost instantaneously and in good yield. Finally, the application of dichlorosilacycles in tethered Diels-Alder reactions has been investigated and has been shown to give enhanced rates of reaction when compared to acyclic silicon tethers.

Thesis advisor: James P. Morken / Detailed within this dissertation are the developments of novel hydroboration and diboration methodologies to access allylboron reagents and efforts towards the application of these methods in the total synthesis of discodermolide. Chapter 1 describes the development of Ni-catalyzed 1,4-hydroboration of 1,3-dienes with pinacolborane. This method provides synthetically useful allylboron intermediates which can be oxidized to stereodefined (Z)-allylic alcohols or used in stereoselective carbonyl addition reactions. Chapter 2 details the development of Ni-catalyzed 1,4-diboration of 1,3-dienes with bis(pinacolato)diboron. This reaction broadens the scope of 1,4-diboration reactions by including internal and sterically hindered dienes, and proceeds with high 1,4- and (Z)-selectivity. The intermediate allylborons can be oxidized to stereodefined 1,4-diols. Chapter 3 describes the development of diastereoselective Ni-catalyzed 1,4-hydroboration of chiral 1,3-dienols. The reaction provides syn-propionate homoallylic alcohols with stereodefined trisubstituted allylborons for the synthesis of polyketide structures. This methodology, among others, was applied towards the total synthesis of discodermolide. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

iii, 192 leaves : ill., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1979

Thesis (Ph.D.) -- University of Adelaide, Dept. of Organic Chemistry, 1979.

Thesis (M.S.)--Rochester Institute of Technology, 1991. / Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 1991. / References : leaves 51-52.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 122-126). Also available via the Internet.