Zinc-catalyzed alkynylation of acetals via oxocarbenium ion intermediates
| Author(s) | Haidzinskaya, Tatsiana | |
| Date Accessioned | 2012-12-14T13:38:26Z | |
| Date Available | 2012-12-14T13:38:26Z | |
| Publication Date | 2012 | |
| Abstract | Reactions that allow the conversion of a simple achiral or racemic starting material into an enantiomerically pure product are of great importance. Such processes are particularly advantageous when they are combined with the formation of a carbon-carbon bond. In the large majority of such reactions, stereoselectivity is controlled by enzymes, chiral auxiliaries, organocatalysts, or transition metal catalysts. In particular, enantioselective transition metal catalysis is a powerful tool in the synthesis of enantioenriched products. The M. Watson group has recently demonstrated a new enantioselective metal-catalyzed strategy for the addition of terminal alkynes to racemic isochroman and chromene acetals. This thesis describes my progress towards establishing this alkynylation strategy for a much broader class of cyclic acetal substrates. The first chapter reviews developments in enantioselective additions of carbon nucleophiles to prochiral cyclic oxocarbenium ions using both organocatalysis and transition metal catalysis. The chapter briefly discusses the addition of carbon nucleophiles to aldehydes and ketones catalyzed by transition metals, as well as enantioselective alkynylation of iminium ions. The second chapter of this thesis describes my work on alkynylation of chroman acetals through cyclic oxocarbenium ions, specifically optimization of reaction conditions and my progress towards an asymmetric version of this reaction. The third chapter discusses diastereoselective alkynylation reactions. In addition to the routes for substrate synthesis for these studies, the alkynylation of several nonbenzopyranyl substrates through aliphatic oxocarbenium ion intermediates has been achieved. This work establishes that the alkynylation strategy previously used for the addition of terminal alkynes to racemic isochroman and chromene acetals can be applied to a much broader class of cyclic acetal substrates, in particular chroman, tetrahydrofuran, and tetrahydropyran acetals. | en_US |
| Advisor | Watson, Mary P. | |
| Degree | M.S. | |
| Department | University of Delaware, Department of Chemistry and Biochemistry | |
| URL | http://udspace.udel.edu/handle/19716/12029 | |
| Publisher | University of Delaware | en_US |
| dc.subject.lcsh | Zinc. | |
| dc.subject.lcsh | Catalysts. | |
| dc.subject.lcsh | Alkynes. | |
| dc.subject.lcsh | Acetals. | |
| Title | Zinc-catalyzed alkynylation of acetals via oxocarbenium ion intermediates | en_US |
| Type | Thesis | en_US |