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Thesis advisor: James P. Morken / 1,1-Bis(boronic) esters have attracted significant attention these days due to their unique reactivity. In this thesis, I will show that readily available reagents can undergo deborylative alkylation to deliver synthetically useful primary, secondary and tertiary boronic esters. 1,1-Diboryl alkanes can also engage in base-promoted deborylative cyclization to afford diversified cyclopentane rings with boron motifs attached. This transformation is very appealing because of the prevalence of five-membered rings in natural products. Lastly, it will be showed that geminal bis(boronic) esters can act as an important cornerstone in constructing relatively complicated structures such as natural product Arenolide. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

In this dissertation, we discuss the development of a synthetic method to functionalize various α-haloglycine esters, as key precursors to a large variety of non-proteinogenic α-amino acids (Xaas). At first, we discovered a very practical and high yielding acetyl chloride-mediated cascade reaction to synthesize α-arylated amino esters in one-pot. In this multicomponent reaction (MCR), a primary carbamate was condensed with a glyoxylate, followed by an in situ halogenation which proved essential to trigger the final Friedel−Crafts functionalization. After careful reaction optimization, a plethora of arene nucleophiles were reacted with high regioselectively in CHCl3 at low temperatures (Method A) while less activated arenes reacted more cleanly in CH3CN and at higher temperatures (Method B). To broaden the scope of this reaction to acid sensitive nucleophiles, a one-pot reaction was designed via evaporation of all acid by-products at the α-haloglycine stage. The anion-binding Schreiner’s thiourea catalyst proved to be extremely efficient to promote this complementary approach (Method C) which relies on the chloride leaving group activation by the catalyst to assist the functionalization stage and deliver the α-amino ester product. In the second chapter, some highly practical and efficient preparations of α-haloglycine esters in one-pot have been developed to generate useful precursors of non-proteinogenic α-amino esters. Also, a mild and unique AcOH(cat.)/AcCl system was found to promote an autocatalytic-like condensation/deoxy halogenation and facilitate the multicomponent assembly of non-proteinogenic α-amino esters. Friedel–Crafts reaction between α-chloroglycine and N-methylindole have been studied in details to understand the mechanistic intricacy of this reaction. Our findings through the initial kinetic profiling support that the arylation likely proceeds via a SN1-like (or SN2C+) mechanism. In third chapter, we discuss the development of the most challenging α,α-disubstituted amino esters in a multicomponent fashion. Our results highlight that the MCR proceeds via the formation of an enamide intermediate, which is further tautomerized to corresponding iminium to produce the desired product. In collaboration with Eli Lilly at the Automated Synthesis Laboratory (ASL), we have developed silver (I) salts mediated Friedel–Crafts reaction for synthesis of α-trifluoromethylated α-amino esters on a fully automatized robot. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Thesis (M. Ph.)--Chinese University of Hong Kong. / Bibliography: l. 79-84.

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Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Graduation date: 1999