Preparation of allyltin reagents grafted on solid support: clean and easily recyclable reagents for allylation of aldehydes

The preparation of polymer-supported allyltin reagents was shown to be possible for both unfunctionalized and functionalized allyl units. These reagents were treated with aldehydes in the presence of cerium(III) or indium(III) salts to afford high yields of homoallylic alcohols, practically uncontaminated with organotin residues (less than 5 ppm). Some mechanism aspects are briefly discussed and the potential for regeneration and reuse of these supported reagents is pointed out.     

Study of the invar effect through ultrasonic measurements of the elastic properties of Fe(64)Ni(36) under pressure

The elastic properties of a polycrystalline sample of invar Fe(64)Ni(36) have been investigated at ambient temperature by ultrasonic experiments up to 7 GPa. The pressure dependence of the bulk modulus is extracted without using any model and discussed in terms of invar anomaly models.     

A General Darling–Erdős Theorem in Euclidean Space

We provide an improved version of the Darling–Erd?s theorem for sums of i.i.d. random variables with mean zero and finite variance. We extend this result to multidimensional random vectors. Our proof is based on a new strong invariance principle in this setting which has other applications as well such as an integral test refinement of the multidimensional Hartman–Wintner LIL. We also identify a borderline situation where one has weak convergence to a shifted version of the standard limiting distribution in the classical Darling–Erd?s theorem.     

Dynamic kinetic resolution of α-chloro β-keto esters and phosphonates: hemisynthesis of Taxotere® through Ru-DIFLUORPHOS asymmetric hydrogenation

The dynamic kinetic resolution (DKR) of racemic α-chloro β-ketoesters and α-chloro β-ketophosphonates through ruthenium-mediated asymmetric hydrogenation is reported. The corresponding α-chloro β-hydroxyesters and α-chloro β-hydroxyphosphonates were obtained in good to high enantio- and diastereomeric excesses using, in particular, the atropisomeric ligand DIFLUORPHOS. This methodology allowed an efficient preparation of the anti phenylisoserine side chain of Taxotere® which has been used for the hemisynthesis of the cancer therapeutic agent itself. In addition, ¹³C NMR in chiral oriented solvents was used to investigate the DKR effect.     

Arborescent polymers and other dendrigraft polymers: A journey into structural diversity

Arborescent polymers are characterized by a dendritic, multilevel branched architecture derived from successive grafting reactions. In spite of their much larger size, these materials display properties analogous to dendrimers and hyperbranched polymers, the two other dendritic polymer families. The distinguishing features of arborescent polymers are their assembly from polymeric building blocks of uniform size and their very high molecular weights attained in few synthetic steps. This article offers an overview of the historical aspects of the development of dendrigraft polymers, starting from our initial efforts on the synthesis of arborescent polystyrenes. Major subsequent developments in the synthetic techniques from our and other research groups allowing the synthesis of dendrigraft copolymers, tailoring of the structural characteristics of the molecules, and further simplifications to their synthesis are also reviewed, with emphasis over the broad range of architectures attainable in these systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3803–3810, 2007     

A regioselective approach to 5-substituted-3-amino-1,2,4-triazines

Nucleophilic displacement of readily available alpha,alpha-dibromoketones with excess morpholine gave the corresponding ketoaminals, which upon condensation with aminoguanidine in MeOH in the presence of AcOH afforded 5-substituted-3-amino-1,2,4-triazines in >95% regioselectivity and 45-76% isolated yield. [reaction: see text]     

Efficient discrimination of transplutonium actinides by in vivo models

Transplutonium actinides are among the heaviest elements whose macroscale chemical properties can be experimentally tested. Being scarce and hazardous, their chemistry is rather unexplored, and they have traditionally been considered a rather homogeneous group, with most of their characteristics extrapolated from lanthanide surrogates. Newly emerged applications for these elements, combined with their persistent presence in nuclear waste, however, call for a better understanding of their behavior in complex living systems. In this work, we explored the biodistribution and excretion profiles of four transplutonium actinides (²⁴⁸Cm, ²⁴⁹Bk, ²⁴⁹Cf and ²⁵³Es) in a small animal model, and evaluated their in vivo sequestration and decorporation by two therapeutic chelators, diethylenetriamine pentaacetic acid and 3,4,3-LI(1,2-HOPO). Notably, the organ deposition patterns of those transplutonium actinides were element-dependent, particularly in the liver and skeleton, where lower atomic number radionuclides showed up to 7-fold larger liver/skeleton accumulation ratios. Nevertheless, the metal content in multiple organs was significantly decreased for all tested actinides, particularly in the liver, after administering the therapeutic agent 3,4,3-LI(1,2-HOPO) post-contamination. Lastly, the systematic comparison of the radionuclide biodistributions showed discernibly element-dependent organ depositions, which may provide insights into design rules for new bio-inspired chelating systems with high sequestration and separation performance.

Transplutonium actinides are among the heaviest elements whose macroscale chemical properties can be experimentally tested.     

Hybrid copolymer latexes cross-linked with methacryloxy propyl trimethoxy silane. Film formation and mechanical properties

We describe in this work the copolymerization reaction of 3-trimethoxysilyl propyl methacrylate (MPS) with styrene (Styr.) and n-butyl acrylate (BuA) monomers through emulsion polymerization. The so-produced hybrid copolymer (P(BuA-co-MPS)) and terpolymer (P(Styr-co-BuA-co-MPS)) latexes were cast into films that displayed a good optical transparency. The copolymers microstructure in the films was characterized by FTIR, ¹³C and ²⁹Si solid state NMR spectroscopies, and was found to be highly dependent on parameters such as the monomer feed composition, the suspension pH and the silane addition profile. The films obtained from the hybrid latexes showed improved dynamic mechanical properties indicating that a reinforcing organo-mineral network had formed in the composite materials. The dynamic modulus of the hybrids increased with increasing silane contents while, concurrently, the tan δ peak shifted to higher temperatures, broadened and decreased in intensity. To cite this article: S. Vitry et al., C. R. Chimie 6 (2003).