Formal radical cyclization onto aromatic rings, cascade intramolecular conjugate displacement and synthetic studies on marinopyrroles

• Author / Creator

  Chen, Zhenhua

• The first chapter of this thesis describes the development of a general method for indirectly effecting radical carbocyclization of an alkyl chain onto an aromatic ring. This process involves a Birch reductive alkylation of aromatic tert-butyl esters, chromium(VI)-mediated oxidation and radical cyclization. The cyclized products are easily oxidized to the corresponding cross-conjugated ketones via Saegusa oxidation. Addition of organolithium or Grignard reagents and treatment with bismuth trichloride affords aromatized benzo-fused carbocycles.
  
  The second chapter describes a method for converting Morita-Baylis-Hillman acetates into unusual seven-membered heterocycles containing both nitrogen and sulfur. N-Deprotection of the MBH acetates and trapping with CS2 affords the desired 2-thioxo-1,3-thiazepines. In a modification of this process, when the original nitrogen is substituted with a carbon chain, an azepine derivative is generated. The ring closures occur by intramolecular conjugate displacement.
  
  The last chapter of this thesis describes synthetic studies towards the marine antibiotic alkaloid, marinopyrrole B. Due to the difficulty of bromination of the pyrrole system, it is known that marinopyrrole B cannot be directly made from marinopyrrole A. Our plan was based on brominating the bottom pyrrole at an early stage and constructing the top pyrrole ring later. Previous studies towards the core structure of marinopyrrole A suggested that the Paal-Knorr reaction is an ideal method for construction of the top ring. Preparation of the precursor for the Paal-Knorr reaction was planned via an intermolecular conjugate displacement between a densely halogenated pyrrole and a Morita-Baylis-Hillman carbonate. However, this approach was unsuccessful and further studies are in hand.

• Subjects / Keywords

  • Marinopyrroles
  • ICD
  • Radical cyclization

• Graduation date

  Fall 2011

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3VM3Z

• 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.