Conjugate additions, aza-Cope, and dissociative rearrangements and unexpected electrocyclic ring closures in the reactions of 2-(2-pyrrolidinyl)-substituted heteroaromatic systems with acetylenic sulfones.
The reactions of 2-heteroaryl-substituted pyrrolidines with acetylenic sulfones proceeded via two pathways. The first involves conjugate addition of the pyrrolidine to the acetylenic sulfone to afford a zwitterion, followed by dissociation of the C-N bond and recombination of the resulting carbocation and vinyl anion to afford the corresponding azepine derivative. The second comprises a cascade of conjugate addition, aza-Cope rearrangement and anionic 6pi electrocyclic ring-closure steps. The stability of the carbocation intermediate formed by C-N cleavage determines the dominant pathway.
Weston
Mitchell H
MH
Department of Chemistry, University of Calgary, Calgary, AB, Canada, T2N 1N4.
Parvez
Masood
M
Back
Thomas G
TG