Study of a radical cyclizations cascade leading to bicyclo[3.1.1]heptanes

An efficient radical cascade involving a 5-exo-dig, a 1,6-H transfer, a 6-e ndo-trig, a 4-exo-dig, and a final 1,6-H transfer allows the diastereoselec tive construction of bicyclo[3.1.1]heptanes. The size of the R substituent at the propargylic position governs the diastereoselectivity of the 6-endo- trig step. Other parameters (acetylenic substituents, unsaturated partners, ...) have been investigated, and the scope and the limitations of the casc ade have been delineated.