Free radical domino reactions in the synthesis of small ring compounds: multiple annulation of cyclopropane-containing polycycles

摘要

Free radical approach to fused vinylcyclopropane derivatives is described. Homolytic decomposition of Barton esters 4a-f in the presence of activated alkynes affords bicyclo[3.1.-]hex-2-ene derivatives 5a-g in moderate yields (18-52%). The propagation sequence comprise: intermolecular addition/5-exo-cyclization/3-exo-cyclization/#beta#-elimination, and allows for a one-pot synthesis of bicyclic cyclopropane derivatives starting from two acyclic, unsaturated compounds.