Samarium(II) iodide has been employed to promote a tandem intramolecular nucleophilic acyl substitution/intramolecular Barbier cyclization sequence, generating bicyclic and tricyclic ring systems in excellent yield and high diastereoselectivity. Additionally, a highly versatile ring expansion-cyclization sequence allows entry into several different naturally occurring tricyclic ring systems containing seven- and eight-membered rings.