Cover Picture Supramolecular Catalysis of a Unimolecular Transformation Aza-Cope Rearrangement within a Self-Assembled Host (Angew. Chem. Int. Ed. 482004)код для вставкиСкачать
Cover Picture Dorothea Fiedler, Robert G. Bergman,* and Kenneth N. Raymond* A supramolecular metal–ligand assembly catalyzes the [3,3]-sigmatropic rearrangement of enammonium guests in aqueous solution. The cover picture shows the proposed catalytic cycle. The space-restrictive host cavity forces the substrates to bind in a reactive chairlike conformation and thus accelerates the rate of rearrangement. Release and hydrolysis of the rearranged product enable catalytic turnover. For more information, see the Communication by R. G. Bergman, K. N. Raymond, and D. Fiedler on p. 6748 ff. Noncovalent Interactions The affinity of a ligand for its receptor depends both on the coordination itself and modification of the noncovalent interactions within the receptor. This phenomenon is described by D. H. Williams et al. in their Review on page 6596 ff. Polymerization Catalysts Epoxides and CO2 undergo copolymerization in the presence of well-defined homogeneous catalysts to produce polycarbonates. The latest developments in this field are summarized by G. W. Coates and D. R. Moore in their Review on page 6618 ff. Water structure The previous assumption that water adsorbs in a uniform monolayer on the surface of zinc oxide is disproved by B. Meyer, C. W6ll, and co-workers in their Communication on page 6641 ff. According to the findings a superstructure is formed that consists of partially dissociated water molecules.