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-endo-trig, a 4-exo-dig, and a final 1,6-H transfer allows the diastereoselective 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 cascade have been delineated.