New Directions in Dendralene Methodology

Abstract

In our current age, synthesizing useful chemicals and materials efficiently has become paramount. Through reduction of step count and utilizing materials that reduce the amount of waste we generate in synthesis, we make chemistry greener and more sustainable in a world with finite resources. Developing new methodology which both reduces step count and the amount of waste improves synthesis as a whole and furthers society's development, and within this thesis are our contributions to achieving this lofty goal.

Chapter Two describes the reactions of dendralenes in cobalt catalyzed formal Diels-Alder reactions. This work demonstrates the combination of [3], [4], [5] and [6] dendralenes and cobalt catalysis in highly regioselective formal [4+2] cycloaddition sequences with electronically neutral/rich alkynes. These adducts may be elaborated into substituted naphthalenes, phenanthrenes, binapthalenes and other polycyclic aromatic hydrocarbons alongside various miscellaneous reactions. The new methodology developed from this work expands the scope of dendralenes further into the realm of polycyclic aromatic hydrocarbons, with fascinating potential applications of these compounds now in the realm of possibility.

Chapter Three showcases a new, unique synthesis for highly substituted butadienyl allenes through couplings between propargylic bromides and allenylic carbonates through a allylic and propargylic transposition and coupling strategy. Our general, modular method accesses substituted butadienyl allenes with up to 7 substituents, allowing a systematic overview of the effects of substituents on their stability and Diels-Alder reactivity. We further conducted preliminary investigations into their potential as intramolecular Diels-Alder reaction precursors for the synthesis of fused, bridged polycyclic systems in efforts to further their scope as natural product precursors.

Chapter Four outlines a modular, robust method for synthesizing parent and substituted 2,3'-cyclo-[3]dendralenes using a 3 step sequence of aldol condensations, dienol triflate formations and cross-couplings starting from commercially available ketone precursors. We thoroughly investigate their Diels-Alder reactivity, and the impact of substitution upon mono and bis-adduct selectivity.