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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Transition metal catalysed reactions for the synthesis of heteroaromatic compounds

Pelly, Stephen Christopher 22 December 2008 (has links)
The carbazole and 2-isopropenyl-2,3-dihydrobenzofuran structures are widely found in many naturally occurring compounds. For example, the naturally occurring anti-cancer compound, rebeccamycin, contains an indolocarbazole core. Rotenone, which contains an (R)-2-isopropenyl-2,3-dihydrobenzofuran moiety, is widely used today as an effective naturally occurring pesticide. In the carbazole section of this thesis, the synthesis of the naturally occurring furanocarbazole, furostifoline is described. As key steps in this sequence, a Suzuki coupling reaction is utilised to couple appropriately functionalised indole and furan moieties. After further functional group transformations, a metathesis reaction is employed to construct the carbazole system, leading to furostifoline. The synthesis of the unnatural thio-analogue of furostifoline was similarly conducted and is described. Finally, in a somewhat different approach, the synthesis of the indolocarbazole core is described, utilising a Madelung approach initially to form the bis-indole system, 2,2’-biindolyl. After several functional group transformations, a metathesis reaction was once again successfully employed to form the carbazole system, thereby synthesising di(tert-butyl) indolo[2,3-a]carbazole-11,12-dicarboxylate. In the benzofuran section of this thesis, the successful chiral synthesis of two 2- isopropenyl-2,3-dihydrobenzofuran systems is described. As a precursor to rotenone, the synthesis of (R)-2-isopropenyl-2,3-dihydrobenzofuran-4-ol is described starting from resorcinol. The key step in this synthesis is a stereoselective intramolecular Pd π-allyl mediated cyclisation utilising the R,R’-Trost ligand, thereby forming (R)-2-isopropenyl- 2,3-dihydrobenzofuran-4-ol in excellent yield and enantiomeric excess. The alternative enantiomer, (S)-2-isopropenyl-2,3-dihydrobenzofuran-4-ol, was similarly synthesised. Finally, a similar approach was utilised to synthesise both (S)- and (R)-2-isopropenyl-2,3- dihydrobenzofuran, starting from 2-allyl-phenol, and thereby completing a formal synthesis of the naturally occurring compounds, (S)-fomannoxin and (R)-trematone, respectively.

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