Highly Substituted Dihydroindole Derivatives by Intermolecular Couplings of Samarium Ketyls and Indoles

Samarium diiodide promoted intermolecular reductive couplings of ketones and aldehydes to 3-methoxycarbonyl-substituted indole derivatives afforded dihydroindoles in good yields and with excellent diastereoselectivities. Trapping of the intermediate samarium enolate with allyl iodide furnished tricyclic lactones with good efficacy, thus demonstrating the potential of this method for the construction of structurally complex indole derivatives by a three-component protocol.