Tuesday, 27 June 2006
Ponderosa (poster/exhibit) (John Ascuaga’s Nugget Casino Resort)
216

Computational and synthetic investigations of dipolar and anionic electrocyclizations for the synthesis of 2-pyrrolines

Amber M. Hibberd, Derrek N. Woodbury, Alina M. Schimpf, and Don L. Warner. Boise State University, Boise, ID

An electrocyclization approach is investigated for the potential regio- and stereo-controlled synthesis of 2-pyrrolines. Traditional cycloaddition methods used in the formation of these azacycles are limited not only by loss of regio- and stereo-control, but also by the presence of stabilizing groups. However, electrocyclic ring closure offers a predictable and controlled route to these same targets. Specifically, electrocyclizations of non-stabilized 1,5-dipoles (vinyl azomethine ylides) and conjugated azaallyl anions have been examined. Destannylation of α-stannyl imines allows for mild access to the 1,5-dipolar and anionic intermediates. As electrocyclization is dependent on dipole/anion geometry, a theoretical investigation of dipole/anion energies and conformational energy barriers has been conducted. Computational results obtained indicate that intermediates substituted at the four position may favor the geometry required for electrocyclization and current experimental efforts are focused on the synthesis of such 4-substituted systems. Additionally, electrocyclizations of 1,7-dipolar systems have been examined and preliminary computational results have revealed, relative to 1,5 systems, decreased energy barriers to interconversion. These and related experimental and computational results will be reported.


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