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A general and effective method for the racemoselective synthesis of bis-indenyl-type ansa-zirconocenes was proposed and successfully applied for the synthesis of several C2-symmetric ansa-zirconocenes based on 2-methyl-4-aryltetrahydro-s-indacene. This new racemoselective method relies on ZrCl3NH-tert-Bu as a key reagent. The formation of racemic products was confirmed by NMR studies and single-crystal X-ray diffraction. The novel complexes are potent catalysts for isotactic propylene polymerization and ethylene–propylene copolymerization.

Treatment of the lithium salt of t-BuN(H)PPh2 in THF with CrCl2 (THF)(2) afforded a dinuclear, [(t-BuNPPh2)Cr-2(mu-t-BuNPPh2)(3)]center dot(toluene)(1.5) (1), and a tetrameric cluster, [(t-BuNPPh2)Cr(mu-t-BuNPPh2)(2)Cr(mu-Cl)](2)center dot(toluene)(2) (5), depending on the reagents' stoichiometric ratio. Complex 1 is dimeric with a long intermetallic distance and the ligands adopting an asymmetric and distorted bridging-chelating bonding mode. Complex 5 is instead a symmetry-generated tetramer with two identical dimetallic units, each closely related in geometry to 1, linked by two bridging chlorine atoms. The reactions of 1 with alkyl aluminum activators afforded a series of divalent complexes, [{(mu-AlMe3)(t-BuNPPh2)}(2)Cr]center dot(toluene) (2), [{(mu-AlMe2Cl)(t-BuNPPh2)}(2)Cr]center dot(toluene) (3), and [{(mu-AlEt2Cl)(t-BuNPPh2)}(2)Cr]center dot(toluene) (4), containing organo-aluminum residues. Similarly, reaction of 5 with AlMe3 gave [{(mu-AlMe2)(t-BuNPPh2)(2)}Cr(mu-Cl)(2)center dot(toluene)(1.9) (6), also characterized by an X-ray crystal structure. Finally, the trivalent complex [(t-BuNPPh2)(3)Cr] (7) was readily prepared via reaction of the lithiated ligand with CrCl3(THF)(3). Upon treatment with AlMe3 or Et2AlCl, complexes 2 and [{(mu-AlEtCl2)(t-BuNPPh2)}(2)Cr]center dot(toluene) (8) were isolated and fully characterized. In turn, this indicated that reduction to the divalent state is the primary stage of the activation process of the trivalent species. The catalytic behavior of all of these complexes has been assessed in the presence and absence of cocatalyst and with different solvents. The result showed a pronounced solvent effect, allowing switching from nonselective oligomerization to selective trimerization.

We report here our full results concerning the possibility of generating in situ from a stable and readily available ruthenium(II) source a highly active ruthenium catalyst for C-H bond activation. The versatility of this catalytic system has been demonstrated, as it offers the possibility of modifying the electronic and steric properties of the catalyst by fine-tuning of the ligands, allowing functionalization of various substrates. Aromatic ketones and imines could be easily functionalized by the reaction with either vinylsilanes or styrenes, depending on the electronic and steric nature of the ligand. Moreover, variable-temperature NMR experiments and the isolation of a ruthenium intermediate complex provided some insights into the generation of the active catalytic ruthenium species in this reaction.

The sulfated glucuronosyl paragloboside SO4-3-GlcA(β1-3)Gal-(β1-4)GlcNAc(β1-3)Gal-(β1-4)Glcβ(1-1′)Cer (SGPG) is a specific constituent of the peripheral nervous system involved in human dysimmune neuropathies. Although it is highly immunogenic in human pathology, it is not a major constituent of peripheral nerve in humans. Pure SGPG is very difficult to obtain from natural sources, but is needed for the design of efficient and reproducible immunoassays. We describe a new chemical synthesis of this important glycolipid with a stearic tail, including its complete characterization by mass spectrometry and its use in the detection of autoimmune neuropathies.

The anti-Saccharomyces cerevisiae antibodies (ASCA) are markers for Crohn's disease used for diagnostic, phenotypic characterization and sero-epidemiological studies. Antibody detection is made by different immunoenzymatic tests using S. cerevisiae mannans which are both complex and poorly standardized antigens. Here we construct the major discriminating epitopes comprised within this antigen. When coupled to linker arm and a peptidic carrier to functionalize microtiter plates, they were able to discriminate serological responses between Crohn's disease and ulcerative colitis, another form of inflammatory bowel disease.

Reaction of RN(H)PBr(Ph)(2)N(H)R [R = t-Bu, i-Pr, Ph] with two equivalents of n-BuLi followed by reaction with CrCl2(THF)(2) afforded the divalent chromium complexes [(t-Bu)NP(Ph)(2)-N(t-Bu)]Cr(mu(2)-Cl)(2)Li(THF)(2) (1), (i-Pr)NP(Ph)(2)N(i-Pr)]Cr(mu(2)-Cl)(2)Li(THF)(2) (2), and [{[(Ph)-NP(Ph)(2)N(Ph)]Cr}(2)(mu(2)-Cl)(3)][Li(DME)(3)] (3). The trivalent analogue of 1, {[(t-Bu)NP(Ph)(2)-N-(t-Bu)]Cr(mu(2)-Cl)(3)(mu(2)-Cl)(2)}{Li (THF)(2)} (4), was :obtained in a similar rnahner via treatment of the double deprotonated ligand with CrC13(THP)3. Both-reactions of the -divalent Lortriva/ent 4 with AlMe3 yielded the trivalent and {[(t-Bu)NP(Ph)(2)N(t-Bu)](2)Cr}{Me3Al)(2)Cl)}center dot toluene (5) Upon activation With MAO 1-3 produced produced unprecedented and potentially; useful catalytic systems for nonselective ethylene oligomerization devoid of polymer. Divalent clearly the species responsible for the catalytic behavior, ruling out that nonselective oligomerization proceeds via a redox metallacycle mechanism. The absence of polymer in combination with the record activity makes 1 competitive with the best performing industrially used systems.

We report here our full results concerning the possibility of generating in situ from a stable and readily available ruthenium(II) source a highly active ruthenium catalyst for C-H bond activation. The versatility of this catalytic system has been demonstrated, as it offers the possibility of modifying the electronic and steric properties of the catalyst by fine-tuning of the ligands, allowing functionalization of various substrates. Aromatic ketones and imines could be easily functionalized by the reaction with either vinylsilanes or styrenes, depending on the electronic and steric nature of the ligand. Moreover, variable-temperature NMR experiments and the isolation of a ruthenium intermediate complex provided some insights into the generation of the active catalytic ruthenium species in this reaction.