New Sequential Carbon-Carbon Bond Forming Reactions. A Samarium(II) Iodide Mediated Vinylogous Barbier Reaction Followed by an Aldol Reaction

Abstract

Reduction of 4-(3-iodopropyl)cyclopent-2-en-1-ones 1 and 7 with 2.5 equivalents of samarium(II) iodide in tetrahydrofuran containing 10 equivalents of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) produces bicyclic samarium enolates that can be protonated to give simple bicyclo[3.3.0]octan-3-ones, or reacted with aldehydes to give functionalized bicyclo[3.3.0]octan-3-ones. Depending on the structure of the aldehyde, a rapid intramolecular Tishchenko reaction may follow the aldol reaction.