Studies Towards the Synthesis of -Annulenes
Blaquiere, Christa S 1991-
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This thesis begins with a historical perspective on aromaticity and benzene, including the discovery and proposed structures for benzene as well as proposed criteria for measuring aromaticity. The history of the synthesis and characterization of -annulene is also discussed. Studies towards the synthesis of an aromatic all-cis--annulene derivative is covered in this dissertation. Two routes that were explored in efforts to obtain a chlorinated all-cis--annulene derivative, 40, are described. The primary route utilizes six chlorine atoms on the hydrocarbon skeleton (R=H) and uses a carbene [2+1] cycloaddition reaction as a key step to incorporate one of the two cyclopropane substituents (Scheme 1.0). The second cyclopropane unit is incorporated through a Diels-Alder reaction between diene 49 and tetrachlorocyclopropene 50, which also established the 10-carbon framework. The cleavage of the central olefin in the 10-carbon skeleton 51 is discussed, as well as difficulties encountered. In attempts to obtain the planar, aromatic -annulene, efforts towards the elimination and oxidation reactions which lead to the aromatization of 55 are also presented. This thesis also discusses an alternative route that incorporates an additional chlorine atom on the carbon framework (R=Cl). The alternative route mirrors the previous pathway; one cyclopropane substituent is incorporated through a carbene [2+1] cycloaddition reaction, whereas the second unit is established via a Diels-Alder reaction (Scheme 1.0). Efforts towards cleaving the olefin in 51 to obtain the carbon skeleton 40 are also discussed. This work concludes with a general discussion and proposal for future directions, with an emphasis on alternative synthetic pathways. This study demonstrates the Diels-Alder reactions and ozonolysis of 51 is a viable strategy to form the functionalized skeleton required for -annulene derivative 40.
DegreeMaster of Science (M.Sc.)
CommitteeHill, Bryan; Krol, Ed; Grosvenor, Andrew
Copyright DateApril 2018