Investigation of New Intermolecular and Intramolecular Trapping Reactions of 1,2-Cyclohexadienes.

• Author / Creator

  Lofstrand, Verner Alexander

• Small carbocyclic allenes are one of many reactive intermediates though their use in the formation of strategic bonds in organic chemistry is limited. While a vast literature exists detailing the generation and trapping of these species very little has been dedicated to investigating the synthetic potential. This thesis will discuss several new advancements toward the development of small-carbocyclic allenes as strategic intermediates in the synthesis of heterocyclic compounds. Chapter 1 provides a detailed recount of the generation, trapping, and reactive mechanistic inspection of 1,2-cyclohexadiene and derivatives thereof. This is to act as a comprehensive review of the chemistry associated with six-membered cyclic allenes to contrast with the research results presented in this thesis. Chapter 2 will describe the development and use of a robust method to cyclic allene precursor synthesis using copper mediated nucleophilic silylation. The allylic silanes synthesized were presumed to form cyclic allenes in situ based upon the formation of new and previously described cycloadducts. The cyclic allene precursors were used further in the synthesis of nitrogen containing heterocycles via the reaction of 1,3-dipolar compounds with 1,2-cyclohexadiene and derivatives. The cycloaddition proved to be general for a number of 1,3-dipolar compounds with high regio-, site-, and diastereoselectivity. Chapter 3 then expands upon the formation of nitrogen containing heterocycles by exploring attempts to transfer/conserve the central chirality of allene precursors to cycloadducts via axially chiral cyclic allene intermediates.Within this context we sought to investigate the mechanism of the cycloaddition, with a focus on whether it occurs by a concerted or stepwise process. Chapter 4 discusses the attempts made toward a general intramolecular trapping strategy. Via the Stork-Danheiser alkylation, a number of β-subsituted 2-bromo-2-cyclohexen-1-ones were synthesized, silylated, and subjected to fluoride-mediated elimination conditions. With a number of tethered trapping molecules attached at the β-position the ability to trap a cyclic allene in an intramolecular manner was evaluated. Finally, Chapter 5 discusses some strategy and synthetic efforts toward asphaltene model compounds. The synthetic stratagem relied upon a [2+2+2] cycloaddition of nitriles and 1,2-dipropargylic arenes. Effort towards new archipelago asphaltene model compounds is discussed.

• Subjects / Keywords

  • 1,2–Cyclohexadiene
  • Intermolecular
  • Trapping
  • Generations
  • Intramolecular

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3JQ0T88F

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.