Radical 4-exo cyclization of bicyclo[2.2.2]octene derivatives: Construction of tricyclo[3.3.1.02,7]nonane skeleton

[Display omitted] An unexpected radical 4-exo cyclization of rigid bicyclo[2.2.2]octene derivatives is described. Radical reaction of norbornene compounds has been known to induce ring-closing and ring-opening reactions. In this work, we focused on a radical reaction of bicyclo[2.2.2]octene. The radical reaction unexpectedly provided a highly condensed tricyclo[3.3.1.02,7]nonane skeleton having a cyclobutane, which occurs in natural products.