Investigation of New Mild Routes to Substituted and Unsubstituted 1,2-Cycloheptadienes and Their Trapping Reactions

• Author / Creator

  Almehmadi, Yaseen Ahmed

• Strained cyclic allenes are one of many reactive intermediates. They are rare and underutilized chemical species, and their use in the formation of strategic bonds in organic chemistry is limited. Strained cyclic allenes have a unique reactivity that allows useful bond-forming processes to be feasible under mild reaction conditions. In this thesis, I dedicated my time and knowledge to investigate the synthetic potential of these strained, reactive intermediates. We took advantage of the unique reactivity of cyclic allenes to synthesize heterocyclic compounds.
  Chapter 1 provides fundamentals of strained intermediates, especially cyclic allenes. It also presents the most recent advances in the field of strained cyclic allenes whose rings contain eight atoms or fewer. The potential of these reactive species to provide access to useful complex scaffolds in a single step from readily available precursors is discussed.
  Chapter 2 focuses on seven-membered cyclic allenes. 1,2-Cycloheptadiene has been far less-studied when compared to 1,2-cyclohexadienes and six-membered-ring heterocyclic allenes. Medium ring cyclic allenes, composed of seven or eight atoms, are known to undergo rapid dimerization once generated. I report the first trapping processes of 1,2-cycloheptadiene with 1,3-dipoles via mild conditions. These allenes have been generated via a fluoride-mediated desilylative elimination, as reported previously by our group and others. Moreover, I proposed one of the shortest approaches to access seven-membered cyclic allenes from feasible starting materials by a well-established chemistry. This approach tolerates several 1,3-dipolar trapping partners, such as nitrile oxides, nitrones, and azomethine imines, allowing rapid access to fused heterocyclic compounds with high regioselectivity and diastereoselectivity.
  
  Chapter 3 investigates a new approach through the metal–halogen exchange reactions to generate six-, seven-, and eight-membered cyclic allenes. We also examined the trapping process of this new generation. Using this new method, we successfully isolated several cycloadducts with good yields. The advantage of this approach is that readily available precursors are used and can be accessed on a large scale.

• Subjects / Keywords

  • [4+2]-Cycloaddition
  • Cyclic Allenes
  • Reactive Intermediates
  • 1,2-Cycloheptadienes

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-khg2-eh21

• License

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