Thesis advisor: Jason S. Kingsbury / <bold>Chapter 1</bold>: The reaction of diazomethane with simple aldehydes to deliver methyl ketones has a long studied history in the art of organic synthesis. Formyl electrophiles have also been homologated with trimethylsilyldiazomethane, diazoacetates, and aryl-diazomethanes that very rarely proceed with catalytic activation. Due to the stigma of handling non-stabilized diazoalkanes this history is limited to examples utilizing &alpha;diazoesters and entirely missing are examples of tertiary &alpha;substituted ketone synthesis beginning with disubstituted (internal) diazoalkanes. This work describes a general catalytic procedure for convergent ketone production using non-stabilized, mono- and disubstituted diazomethanes. The method involves mild reaction conditions, produces molecular nitrogen as the only byproduct, and includes six examples of chiral ketone synthesis from various aryl, heteroaryl, or aliphatic aldehydes. The latter feature, together with new evidence that the catalytic reaction mechanism invokes a stereospecific, intramolecular C-H migration, sets the stage for an enantioselective synthesis of acyclic ketones by asymmetric carbon insertion. The remarkable tolerance of this transformation to steric crowding in either reaction partner is showcased in a simple, five-step construction of the complete carbon framework in achyrofuran, a complex dibenzofuranoid. <bold>Chapter 2</bold>: Paraformaldehyde is an inexpensive and readily available source of carbon (~30 USD/kg). Upon heating, the polymer thermally depolymerizes to yield gaseous formaldehyde that can be bubbled through reactions or stored in solution at low temperature. In this work, a new and general strategy for complex ketone synthesis is described based on Sc-catalyzed, double diazoalkyl C-H insertion reactions with formaldehyde as a 1-C source. The method forms di-, tri-, and even tetrasubstituted acetones efficiently, and it has streamlined a synthesis of the <underline>Erythroxylon</underline> alkaloid (-)-dihydrocuscohygrine in which absolute stereochemistry in a proline-based starting material is preserved. <bold>Chapter 3</bold>: Use of geminally-substituted diorganometallics often gives new forms of reactivity that are unavailable to their monosubstituted counterparts. With the expanding use of boronic acids in many areas of synthetic organic methodology, an underappreciated research area has been full development of disubstitited <italic>gem</italic> diboronic ester derivatives for use in tandem reactions, olefination methods, metal catalyzed coupling reactions, and transmetallations to mixed <italic>gem</italic> diorganometallics. The nature of molecular boron is routinely engaged through its Lewis acidic vacant <italic>p</italic>-orbital, and, after metalation, this orbital interaction is enlisted to stabilize &alpha;-carbanion or &alpha;-carbanion like species to allow dependable reactivity in various applications. The platinum-catalyzed geminal diboration of diazoalkanes provides reliable and efficient access to a full range of disubstitited <italic>gem</italic> diboronic esters enabling the exploration of novel methodologies. / Thesis (PhD) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Jason Kingsbury / Recent findings have led to the discovery that the Sc-catalyzed addition of substituted diazoalkanes to aldehydes elegantly affords a net carbon insertion into the C-H bond, delivering the requisite ketone in one simple step with no need for a readjustment in oxidation state. This chemistry is much improved over the century old diazomethane chemistry which requires stoichiometric amounts of a promoter and is limited in both application and scope. The new catalytic method has now been utilized as the key step in the synthesis of the pseduosymmetric precursor to the natural product achyrofuran, which has been named “pre-achyrofuran.” Subsequently, a related project was pursued involving the desymmetrization of bicyclic β-diketones by catalytic carbon insertion with trimethylsilyldiazomethane as the reagent. Preliminary developments in this area are disclosed. / Thesis (BS) — Boston College, 2010. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Chemistry Honors Program. / Discipline: Chemistry.

The use of transition metal catalysts - either homogeneous (discrete well-defined metal complexes) or heterogeneous (more poorly-defined metal surfaces) - play an important role in the transformations of small substrates into larger, value-added compounds. Although heterogeneous catalysts have the greater industrial applicability, there has been enormous interest in homogeneous transition metal systems for effecting selective transformations of small substrate molecules. The bulk of these homogeneous systems are mononuclear. Perhaps surprisingly, very little research has focuses on systems with adjacent metal centres. Binuclear systems possess adjacent metals that may interact and possibly lead to transformations not observed in monometallic systems. It is this opportunity for adjacent metal involvement in substrate activation that is the focus of this dissertation. the goal of this research is to gain an increased understanding of metal-metal cooperativity and adjacent metal involvement in substrate transformations; how can adjacent metal involvement lead to substrate activation not seen in monometallic counterparts, and what role does each metal play in these interactions, particularly when the two metals are different. Throughout this dissertation examples of transformation unique to systems with at least two metals are presented and examined with a particular focus on the roles of the two metals and any associated binding modes in these transformations. In addition, by comparing the RhOs, RhRu and IrRu systems, the influence of metal substitution is also examined. For example, diazoalkane activation and C-c bond formation promoted by the Rh-based systems is investigated, the roles of the adjacent metals of the IrRu system in the conversion of methylene groups to oxygenates is examined, and the unusual geminal C-H bond activation of olefinic substrates is explored. Overall, the work presented within this thesis adds to the growing understanding of adjacent metal cooperativety, leading us toward a more rational approach to the design of homogeneous homo- and heterobimetallic catalysts, heterogeneous catalyst and nanoparticle catalysts for selective substrate transformations.

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