title: Diastereoselective access to polyoxygenated polycyclic spirolactones through a rhodium-catalyzed [3+2] cycloaddition reaction: experimental and theoretical studies.
abstract: The synthetic utility of γ-alkylidenebutenolides is demonstrated as highly competent dipolarophile partners in both intra- and intermolecular rhodium(II)-catalyzed 1,3-dipolar cycloaddition reactions. The strength of this approach lies in the formation of spiro[6,4]lactone moieties with the concomitant construction of quaternary spiro stereocenters. Typically, the construction of spirolactones involves an esterification step, which has often been reported as a "biosynthetic pathway", and often occurs either as or near to the final step of a total synthesis. Furthermore, a convergent and versatile route is reported for the formation of the (5,7) skeleton of molecules that were isolated from the Schisandra genus. Computational studies were performed to provide an overall picture of the mechanism of the intermolecular [3+2] cycloaddition between 2-diazo-1,3-ketoester and protoanemonin and to rationalize the empirical observations. In particular, we have demonstrated for the first time that the rhodium center plays an important role during the cyclization step itself and reacts with the dipolarophile as a complex with the ylide.
authors.affiliation: Aix-Marseille Université, Institut des Sciences Moléculaires de Marseille iSm2, UMR AMU-CNRS 7313, service 532, Campus scientifique de Saint Jérôme, 13397 Marseille cedex 20, France.
authors.forename: Fabien
authors.initials: F
authors.lastname: Rodier
authors.forename: Michel
authors.initials: M
authors.lastname: Rajzmann
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Parrain
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Chouraqui
authors.forename: Laurent
authors.initials: L
authors.lastname: Commeiras
mesh_terms: D061565:Cycloaddition Reaction; D007783:Lactones / Q000737:chemistry*; D008024:Ligands; D008962:Models, Theoretical; D015394:Molecular Structure; D011083:Polycyclic Compounds / Q000737:chemistry*; D012238:Rhodium / Q000737:chemistry*; D013141:Spiro Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D007783:Lactones; D008024:Ligands; D011083:Polycyclic Compounds; D013141:Spiro Compounds; D012238:Rhodium