title: Tandem catalysis: generating multiple contiguous carbon-carbon bonds through a ruthenium-catalyzed ring-closing metathesis/Kharasch addition.
abstract: Tandem catalysis can offer unique and powerful strategies for converting simple starting materials into more complex products in a single reaction vessel while generating less waste and minimizing handling. In this regard, Grubbs' ruthenium alkylidene (Cy3P)2Cl2Ru=CHPh is shown to catalyze two mechanistically distinct transformations to offer a unique protocol that effects multiple bond changes in a single operation. A tandem ruthenium-catalyzed olefin ring-closing metathesis (RCM)/Kharasch addition allows for the facile preparation of bicyclic [3.3.0], [4.3.0], and [5.3.0] ring systems in one step from the appropriately functionalized acyclic precursors. For substrates where the intramolecular Kharasch addition fails, an intermolecular Kharasch addition is possible. By combining the intra- and intermolecular Kharasch additions with RCM, three new contiguous carbon-carbon bonds with multiple stereocenters can be generated by the ruthenium catalyst in a controlled fashion in one operation through two mechanistically distinct pathways.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Seigal
authors.forename: Cristina
authors.initials: C
authors.lastname: Fajardo
authors.forename: Marc L
authors.initials: ML
authors.lastname: Snapper