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Paper | Regular issue | Vol 78, No. 8, 2009, pp.1955-1976
Published online, 1st April, 2009
DOI: 10.3987/COM-09-11669
Regio and Stereo Selectivity on the α-Aryl-δ-epoxynitrile Anionic Cyclization Reactions: Modulation towards a 5-Endo or 4-Exo Process

Jesús Armando Luján-Montelongo, Adrián Vázquez-Sánchez, and José Gustavo Ávila-Zárraga*

*Facultad de Química, Ciudad Universitaria, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico


Here we present a study focused on the regio and stereoselectivity of the anionic intramolecular cyclization reactions of several 4-(3,3-dimethyloxiran-2-yl)-2-arylbutanonitriles. The first part comprises the exploration of the reaction varying the temperature/solvent as well as the base counter-ion; switching between Li, Na and K that companies hexamethyldisilylamide anion. This is a well-known base used widely. In the second part, we provide a pair of methodologies that lead almost exclusively to pentacarbocycles through a 5-endo pathway, although is known to be a non-favored process in many cases. We found that both the metal counter-ion and the temperature have an important effect on the regioselectivity of the reaction and, independently of the pathway presented, the preferred diastereoselectivity is trans.