Palladium-containing perovskites: recoverable and reuseable catalysts for Suzuki couplings

Palladium-containing perovskites (LaFe0.57Co0.38Pd0.05O3) have been exploited as recoverable and reuseable catalysts in Suzuki coupling reactions; residual levels of Pd after removal of the catalyst by filtration are low (2 ppm) despite evidence that the reaction is occurring via a homogeneous process.     

The synthesis of the anti-malarial natural product polysphorin and analogues using polymer-supported reagents and scavengers

A general asymmetric route to both enantiomers of polysphorin has been developed. The route utilizes polymer-supported reagents, catalysts and scavengers to minimise the need for aqueous work-up and chromatography. This includes application of a method to scavenge 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and a "catch-and-release" procedure to extract the resultant diol following Sharpless asymmetric dihydroxylation. A novel enzymatic selective protection and investigations of a new asymmetric dihydroxylation using microencapsulated osmium tetroxide were also investigated during the course of this study.     

Addition of dithiols to bis-ynones: development of a versatile platform for the synthesis of polyketide natural products

[reaction: see text] The conjugate addition of dithiols to bis-ynones generates a versatile masked 1,3,5-triketone platform. These functional units are useful intermediates for the synthesis of oxygen-containing heterocycles commonly found in polyketide natural products. The tetrahydropyranyl fragments of the marine macrolides Lyngbouilloside and Callipeltoside A have been synthesized with use of this methodology.     

Microencapsulation of osmium tetroxide in polyurea

[reaction: see text] Osmium tetroxide has been microencapsulated in a polyurea matrix using an in situ interfacial polymerization approach. These microcapsules have been effectively used as recoverable and reusable catalysts in the dihydroxylation of olefins     

Large time behavior for some nonlinear degenerate parabolic equations

We study the asymptotic behavior of Lipschitz continuous solutions of nonlinear degenerate parabolic equations in the periodic setting. Our results apply to a large class of Hamilton–Jacobi–Bellman equations. Defining Σ as the set where the diffusion vanishes, i.e., where the equation is totally degenerate, we obtain the convergence when the equation is uniformly parabolic outside Σ and, on Σ, the Hamiltonian is either strictly convex or satisfies an assumption similar of the one introduced by Barles–Souganidis (2000) for first-order Hamilton–Jacobi equations. This latter assumption allows to deal with equations with nonconvex Hamiltonians. We can also release the uniform parabolic requirement outside Σ. As a consequence, we prove the convergence of some everywhere degenerate second-order equations.     

Photoinitiation mechanism of free radical photopolymerization in the presence of cyclic acetals and related compounds

The behavior of six cyclic acetals and related compounds in the photoinitiation step of a radical photopolymerization was investigated. As shown by the photopolymerization kinetic data obtained from FTIR spectroscopy, most of them are efficient coinitiators in the presence of benzophenone (BP) with efficiencies close to a reference amine coinitiator (ethyl dimethylaminobenzoate, EDB). Laser flash photolysis and ESR spin trapping technique were used to study the photochemical mechanisms of the production of initiating radicals and explain the differences in reactivity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010