SEQUENCED REACTIONS WITH SAMARIUM(II) IODIDE - SEQUENTIAL INTERMOLECULAR CARBONYL ADDITION INTRAMOLECULAR NUCLEOPHILIC ACYL SUBSTITUTION FOR THE PREPARATION OF 7-MEMBERED, 8-MEMBERED, AND 9-MEMBERED CARBOCYCLES

Samarium(II) iodide has been employed to promote a tandem intermolecul ar carbonyl addition/intramolecular nucleophilic acyl substitution seq uence, generating seven- through nine-membered monocyclic, bicyclic, a nd tricyclic ring systems with good yields and high diastereoselectivi ties. This tandem reaction consists of an intermolecular reaction foll owed by an intramolecular ring expansion that results in a formal [m n] cycloaddition, starting from extremely simple, readily available s ubstrates. The regioselectivity and stereoselectivity of the process a rise from a tuning of the reducing power of samarium(II) iodide with n ickel(II) iodide in the first step and irradiation with visible light in the second. By using this method, a variety of structural motifs ha ve been assembled rapidly in good yields.