Ketyl−Allene Cyclizations Promoted by Samarium(II) Iodide^†

Samarium(II) iodide has proven to be an effective reagent for intramolecular reductive coupling reactions. Previous investigations of intramolecular ketyl−olefin coupling reactions provided carbocycles in excellent yield and good diastereoselectivity. This method has been extended to ketyl cyclizations with allenes. Substrates leading to both carbocycles and heterocycles in a selective manner are explored.