Engaging 1-Alkynyl Triazenes in Transition Metal-Catalyzed and Fluorinative Transformations

Triazenes have garnered great attention for their anti-cancer properties and versatility in organic chemistry. Recently, a novel synthesis of 1-alkynyl triazenes was reported. This thesis describes the compatibility, reactivity and applications of 1-alkynyl triazenes in various transition metal-catalyzed and fluorinative transformations.Chapter 1 provides an introduction to the discovery, biological activities and chemical reactivity of aryl triazenes. The recent procedure on 1-alkynyl triazene synthesis is described, followed by the context for experimental work presented in this thesis.In Chapter 2, we demonstrate Ru-catalyzed [2 + 2 + 2] cyclotrimerizations of 1-alkynyl triazenes to form densely substituted arenes and pyridines. The regioselectively installed triazenyl moiety can be elaborated into a range of useful substituents. The largely unknown coordination chemistry of 1-alkynyl triazenes with Cp*RuCl is investigated, leading to the isolation of several complexes that may provide insights into catalyst design.In Chapter 3, we explore the use of 1-alkynyl triazenes as fluoro alkyne surrogates in Rh-catalyzed olefinic C-H annulations with a rare Lossen rearrangement, leading to 4-fluoro-2-pyridones after a subsequent Wallach fluorination. The triazenyl pyridone intermediates are further transformed into other value-added fluorine-containing functional groups.In Chapter 4, we study the reactivity of 1-alkynyl triazenes in Ag-catalyzed cyclizations with propiolic acids, forming most notably the unreported 6-fluoro pyrones. A mechanistically intriguing 1,5-carbonyl transposition has been unraveled. The triazenyl unit is shown to serve as a traceless activating group for Diels-Alder cycloadditions.Chapter 5 describes perfluorinations and regiodivergent oxyfluorinations of 1-alkynyl triazenes, which provide tunable selective access to 1,1,2,2-tetrafluoro alkyl triazenes, α-difluoro triazenyl ketones and α-difluoro acyl triazenes. Mechanistic investigations of these fluorinative transformations have been subsequently explored.Finally in Chapter 6, we offer an outlook on the potential opportunities with the chemistry of 1-alkynyl triazenes.