Polystyrenes with chiral phosphoramide substituents as Lewis base catalysts for asymmetric addition of allyltrichlorosilane: enhancement of catalytic performance by polymer effect

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

Achiral polymeric supports can have important positive effects on the activity, stability and selectivity of supported chiral catalysts.

Aminophosphine Oxides: A Platform for Diversified Functions

This review summarizes significant contributions reported on aminophosphine oxides (AmPOs), specifically those containing at least one amino group present as amino substituents on α- and β-carbons including direct P-N bond containing molecules. AmPOs have additional 'N' site(s), including highly basic 'P=O' groups, and these features make favor smooth and unexpected behavior. The most striking manifestations of flexibility of AmPOs are that they are exciting ligand systems for the coordination chemistry of actinides, and their involvement in catalytic organic reactions including enantioselective opening of meso-epoxides, addition of silyl enol ethers, allylation with allyltributylstannane, etc. The diverse properties of the AmPOs and their metal complexes demonstrate both the scope and complexity of these systems, depending on the basicity of phosphoryl group, and nature of the substituents on the pentavalent tetracoordinate phosphorus atom and metal. Two components key to understanding the challenges of actinide separations are detailed here, namely, previously described separation methods, and recent investigations into the fundamental coordination chemistry of actinides. Both are aimed at probing the critical features necessary for improved selectivity of separations. This review leads to the conclusion that, although many AmPOs have already been discovered and developed over the past century, many opportunities nevertheless exist for further developments towards new extraction processes and new catalytic materials by fine tuning the electronic and steric properties of substituents on the central phosphorus atom.

Polystyrene-supportedN-sulfonylated amino alcohols and their applications to titanium(IV) complexes catalyzed enantioselective diethylzinc additions to aldehydes

Crosslinked polystyrene-supported resins 4, 7a, and 7b containing N-sulfonylated beta-amino alcohol in 98, 20, and 40% loadings are prepared. Asymmetric diethylzinc additions to benzaldehyde employing titanium complexes of 10 mol % resins 4, 7a, or 7b are examined and the best performed 7a/Ti(O-i-Pr)4 catalytic system applies to various aldehydes to afford desired secondary alcohols in excellent enantioselectivities up to 95% ee. The resin 7a is reused five times, giving the product with enantioselectivities >or=86% ee and an 81% ee is obtained when the resin is used the sixth time. The used resin 7a is refreshed with 1 M HCl and the asymmetric reaction employing the regenerated resin 7a gives the product in 88% ee.