5.19 Cope, Oxy-Cope, and Anionic Oxy-Cope Rearrangements

Abstract

The Cope rearrangement of all-carbon 1,5-dienes comprises the suprafacial migration of one allyl fragment along another one to furnish an isomerized 1,5-diene with greater thermodynamic stability. One σ- and two π-bonds are established at unambiguously defined locations within the product. The highly stereospecific reaction pathway creating up to two chiral centers makes this process an ideal tool in stereoselective synthesis. This chapter briefly outlines the basic principles and then covers the most relevant advances in this field after the publication of the first edition of Comprehensive Organic Synthesis in 1991. It begins with conjugation-driven reactions and combination with asymmetric enolate-based transformations; strain release Cope rearrangements follow, which are among the best ways to generate medium size and fused medium size rings. In the second part, new applications of the oxy- and in particular anionic oxy-Cope rearrangement reveal their power for the highly stereoselective assembly of very complex polycyclic scaffolds and use in numerous total syntheses of natural products.