First X-ray Structure of a<i>N</i>-Naphthaloyl-Tethered Chiral Dirhodium(II) Complex: Structural Basis for Tether Substitution Improving Asymmetric Control in Olefin Cyclopropanation
作者:Ashraf Ghanem、Michael G. Gardiner、Rachel M. Williamson、Paul Müller
DOI:10.1002/chem.200903231
日期:2010.3.15
Good‐ee! The first one‐pot olefincyclopropanation that gives high ee is reported. The optimized catalyst is the 4‐Br‐substitutedchiral paddle‐wheel tetracarboxylatodirhodium(II) complex based on N‐naphthaloyl‐(S)‐tert‐leucinate. X‐ray structural analysis of the parent catalyst reveals a square chiral crown cavity shrouding the axial coordination site (see figure).
Rh(II)-Catalyzed Enantioselective Cyclopropanation of Olefins with Dimethyl Malonate via in Situ Generated Phenyliodonium Ylide
作者:Paul Müller、Ashraf Ghanem
DOI:10.1021/ol048159u
日期:2004.11.1
Olefins are cyclopropanated with dimethyl malonate (1a) iodosylbenzene (PhI=O) and a Rh(II) carboxylate catalyst via an in situ generated phenyliodonium ylide (1c). Enantioselectivities of up to 90% for 4-bromostyrene and 98% for pent-1-ene have been observed with (S)-N-4-bromo-1,8-naphthanoyl-tert-leucine (4c) as the chiral ligand. The same catalyst was effective for olefincyclopropanation with Meldrum's
Highly Enantioselective and Diastereoselective Cycloaddition of Cyclopropanes with Nitrones and Its Application in the Kinetic Resolution of 2-Substituted Cyclopropane-1,1-dicarboxylates