Synthetic investigations on new calixsalens and modified thiacalixarenes

Habashneh, Almeqdad (2008) Synthetic investigations on new calixsalens and modified thiacalixarenes. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

“Calix”-compounds have “cup”- or “basket”-like shapes which make them attractive synthetic targets for host-guest studies and for many other potential applications. The research described in this thesis deals with two sets of objectives, (a) The synthesis and characterization of new generation of calixsalens; and (b) The study of the reactions of thiacalix[4]arene 1,3-bistriflate and the chemistry of thiacalix[2]phenoxathiins. -- Calixsalens are dimeric compounds in which the two salen units are connected by methylene, ethylene or sulfonyl linking groups, and are usually prepared under Schiff-base macrocyclizations of bis-salicylaldehydes with diamines. Chiral Mn(III)-calixsalen complexes have been designed to serve as enantioselective epoxidation catalysts which act via a host-guest catalytic mechanism in which reactants can be included within the chiral cavities of the new complexes. New calixsalen ligands with large (chiral) cavities were synthesized by incorporating new linking groups between the two salen units. Modified low mol% Pd Suzuki conditions efficiently produced the desired targeted bis-salicylaldehydes which were used as the precursors for the desired calixsalen compounds. -- The second part of this thesis describes the attempted modification of thiacalix[4]arene to form the narrow rim-functionalized arylethynyl derivative, using the Sonogashira reaction. However, the reactions employed produced instead an unexpected new pheoxathiin product under Cu(I)-catalyzed conditions. A host-guest complexation study was conducted with the new phenoxathiin and its de-tert-butylated analogue and both were shown to be moderate receptors for Ag⁺ and Hg²⁺ ions but not at all with the neutral Ca₆₀ and Ca₇₀ fullerenes.

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