Lanthanides in Organic Synthesis. 3. A General Procedure for Five- and Six-Membered Ring Annulation

Article abstract of DOI:10.1021/jo00360a025

An improved method for cyclization of 2-(ω-iodoalkyl)cycloalkanones utilizing samarium diiodide (SmI2) has been developed.Both five- and six-membered rings can be constructed in excellent yields for the first time by such a process.The reaction takes place under very mild conditions, allowing toleration of a number of functional groups under the reaction conditions.Stereochemical aspects of the reaction heve been delineated.The reaction has been found to be highly stereoselective when cyclization takes place onto cyclopentanone substrates and when 2-substituted-2-(ω-haloalkyl)cycloalkanone precursors are utilized.