pi-Annulation reactions of 4-thiazolidinone enaminones in the synthesis of fused bi- and tri-cyclic compounds
Abstract
The a-C position in 4-oxo thiazolidinones functions as one of the three possible nucleophilic sites in these molecules. We used the inherent reactivity of alpha-C of the exocyclic double bond (a so called push pull system) to obtain bicyclic fused thiazolidinones via pi-annulation cyclization. Appropriate reaction conditions to selectively activate this position and secondary nitrogen towards N, pi-annulation were found. Furthermore, the intramolecular vinylogous iminium ion 6-exo-trig cyclization was used to access fused bicyclic precursors for the pi-annulation in order to obtain the novel tricyclic structures stereoselectively.
Keywords:
Thiazolidinones / pi-Annulation / Iminium cyclizations / Enaminones / Push-pull olefinsSource:
Tetrahedron, 2012, 68, 47, 9556-9565Publisher:
- Pergamon-Elsevier Science Ltd, Oxford
Projects:
DOI: 10.1016/j.tet.2012.09.080
ISSN: 0040-4020