Cyclodimerization of alpha, beta-unsaturated ketones promoted by samarium diiodide

Samarium (II) iodide has been successfully utilized as a strong one-electron on transfer reducing agent for the cyclodimerization of alpha, beta-unsaturated ketones. The absence of any alcohol as proton source is essential. The reaction is regioselective over the competitive carbon-carbon double bond reduction and stereocontrolled. The configuration of the cyclodimerization products, has been confirmed by X-ray analysis.