Studies towards the construction of quaternary indolizidines by [2,3]-sigmatropic rearrangement cocatalyzed by ionic liquid

• Autor(a) principal: Duran-Lara,Esteban F.
• Data de Publicação: 2009
• Outros Autores: Shankaraiah,Nagula, Geraldo,Daniela, Santos,Leonardo S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532009000500002
• topic: Stevens rearrangement; [2,3]-sigmatropic; indolizidines; ionic liquid; co-catalyzed

An efficient enantioselective approach for preparation of quaternary centers from proline 5 building block has been developed through [2,3]-sigmatropic Stevens rearrangement co-catalyzed by ionic liquid. The sigmatropic rearrangement was stereospecific because the [2,3]-migrations were restricted to the same face, and the stereoselectivity arose from the previous N-alkylation step in 8. The approach showed better yields than described in literature. The use of 1-butyl-3-methylimidazolium hexafluorophosphate showed an improvement in the yields of the Stevens rearrangement due to a possible stabilization and/or activatation of zwiterionicspecies in solution by the ionic liquid. Several indolizidine moieties were synthesized from quaternary proline derivative (S)-5.