UBC Theses and Dissertations

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UBC Theses and Dissertations

Development of heteroatom radical based synthetic strategies Wickenden, Jason


This thesis presents investigations of carbo- and heterocycle formation using radical relay cyclization reactions initiated by alkoxy radicals, cyclic imine formation using substoichiometric stannane and photodeoxygenation reactions involving benzotriazole-borane complexes. Chapter 1 describes our investigations and development of radical relay cyclization reactions initiated by alkoxy radicals that provided carbo- and heterocyclic compounds. Pairing N-alkoxyphthalimides as alkoxy radical precursors with the slow addition of radical initiator provided a wide range of carbocycles. Incorporation of functionality into the linear backbone provided substituted heterocyclic compounds in excellent yield. Chapter 2 describes the cyclization of aminyl radicals onto silyl enol ethers. The rate acceleration imparted by the silyl enol ether allowed for high yielding pyrrolidine formation. Investigations focused on an unexpected cyclic imine product that was observed in our previous studies. We sought to both optimize our conditions to provide this imine in the highest possible yield, and investigated the mechanism by which this imine product may be formed. Chapter 3 describes the development of a photodeoxygenation reaction using benzotriazole-borane complexes. The coordination of a benzotriazole ligand with commercially available borane-tetrahydrofuran provides the benzotriazole-borane complex as a bench stable white powder. DFT calculations suggested these benzotriazoleborane complexes could behave a radical chain deoxygenation reaction. Irradiation of a variety of xanthates provided the deoxygenated products in excellent yield. Furthermore, our work suggests that the benzotriazole ligand may be catalytic in these deoxygenation reactions.

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