Samarium(II)-Mediated Reactions of γ,δ-Unsaturated Ketones. Cyclization and Fragmentation Processes

On treatment with samarium(II) iodide, γ,δ-unsaturated ketones undergo very different processes depending upon the nature of the reaction conditions. Employing samarium(II) iodide and MeOH, functionalized <i>syn</i>-cyclopentanol products are obtained stereoselectively. Mechanistic studies suggest that this cyclization occurs via a sequential reduction/intramolecular aldol reaction. With samarium(II) iodide and HMPA, products of a 4-<i>exo</i>-<i>trig</i> cyclization and of an interesting fragmentation reaction are observed.