[4 + 3] Cycloaddition Reactions of Cyclic Oxyallyls in Natural Product Synthesis

Abstract

The [4 + 3] cycloadditions of oxyallyls and related allyl cations to 1,3-dienes have been widely utilized for the stereocontrolled construction of seven-membered carbocycles. By virtue of the spectator skeleton, the key variant of utilizing cyclic oxyallyls, i.e., by embedding an oxyallyl function in cyclic compounds, provides a conceptually attractive and operationally efficient route to other medium-sized carbocycles and heterocycles in addition to seven-membered rings. The resulting architecturally complex, polycyclic cycloadducts contain not only sufficient functionality, but also well­ defined facial differentiation useful for subsequent elaboration.