Application of intramolecular Heck reactions to the preparation of steroid and terpene intermediates having cis A-B ring fusions. Model studies for the total synthesis of complex cardenolides

Article abstract of DOI:10.1016/S0040-4020(01)80759-6

The cis-fused tricyclic dienone 13 is the major product formed from intramolecular Heck cyclization of the dienyl triflate 12 (Scheme I). Similarly, the cis-hexahydrophenanthridine 22 is formed in good yield from Heck cyclization of the aryl triflate 21.