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International audience; Monocationic complexes of yttrium with various bis-alkyl and bis-allyl ligands Y(CH2SiMe2Ph)2(THF)4][B(C6F5)4], [Y(CH2C6H4NMe2)2(THF)2][B(C6F5)4], and [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4] have been prepared by protonolysis of the corresponding homoleptic tris-alkyl or -allyl complexes using the anilinium borate salt [PhNMe2H][B(C6F5)4]. The resulting ion-pair complexes have been isolated and characterized by different techniques such as elemental analysis, 1H, 13C, and 89Y NMR, and EXAFS for the allyl cationic complex [Y[1,3-(SiMe3)2C3H3]2(THF)2][B(C6F5)4]. More specifically, a 1H-coupled 89Y INEPT sequence has been developed in order to quantify the metal/alkyl ligand stoichiometry of both synthesized neutral tris-alkyl and cationic bis-alkyl yttrium complexes. The activity of the cationic complexes toward ethylene and isoprene homopolymerization has been assessed. In presence of TiBA, polyethylene was produced with activities ranging from 6 to 26 kgPE molY–1 h–1 bar–1. The molar mass of the yielded polymers shows a bimodal distribution. Under similar conditions, polyisoprene was produced up to full conversion of the monomer. The microstructure of the yielded polyisoprene displayed mainly cis-1,4-units (ca. 60–70%) and 3,4-units (ca. 20–30%). Only a few percent of trans-1,4 units was revealed.

International audience; Fast (60 kHz) magic angle spinning solid-state NMR allows very sensitive proton detection in highly paramagnetic organometallic powders. We showcase this technique with the complete assignment of 1 H and 13 C resonances in a high-spin Fe(II) polymerisation catalyst with less than 2 mg of sample at natural abundance.

International audience; Brought to life more than half a century ago and successfully applied for high-value petrochemical intermediates production, nickel-catalyzed olefin oligomerization is still a very dynamic topic, with many fundamental questions to address and industrial challenges to overcome. The unique and versatile reactivity of nickel enables the oligomerization of ethylene, propylene and butenes into a wide range of oligomers that are highly sought-after in numerous fields to be controlled. Interestingly, both homogeneous and heterogeneous nickel catalysts have been scrutinized and employed to do this. This rare specificity encouraged us to interlink them in this review so as to open up opportunities for further catalyst development and innovation. An in-depth understanding of the reaction mechanisms in play is essential to being able to fine-tune the selectivity and achieve efficiency in the rational design of novel catalytic systems. This review thus provides a complete overview of the subject, compiling the main fundamental/industrial milestones and remaining challenges facing homogeneous/heterogeneous approaches as well as emerging catalytic concepts, with a focus on the last 10 years.

International audience; The reactivity of a phenoxy-imine-ether system (FI)TiCl3/MAO was studied toward selective ethylene trimerization. This system was shown to either trimerize or polymerize ethylene depending on the reaction temperature. Its selectivity switches from a significant production of the trimerization product, 1-hexene (85 wt %, 520-450 kg1-hexene gTi-1 h-1) between 30 and 40 °C, to a moderate polyethylene formation (70-80 wt %, 60-70 kgpolyethylene gTi-1 h-1) at higher reaction temperature (T > 60 °C). Polymerization was investigated based on an original "polymer-to-catalyst" strategy aiming at identifying the active species responsible for this side reaction. Using DSC, SEC and high temperature 13 C NMR analyses, polyethylenes were found to exhibit high molar masses (> 10 5 g mol-1) and a low 1-hexene content (< 1 mol %) at any temperature. Kinetic studies support that trimerization and polymerization species are generated from the catalyst precursor at 40 °C but a parallel process may occur at higher temperature. The increase dispersity to 4.6 at 80 °C suggests a change from single to multisite catalysis. The poor comonomer incorporation ability of the active species is reminiscent of a molecular Ziegler Natta or a bulky postmetallocene catalyst.

The use of the dialkene divinyltetramethyldisiloxane (dvtms) allows easy access to the reactive 16-valence-electron complexes [Fe0(L-L)(dvtms)] (L-L = dppe (1,2-bis(diphenylphosphino)ethane; 1), dppp (1,2-bis(diphenylphosphino)propane; 2), pyNMeP(iPr)2 (N-(diisopropylphosphino)-N-methylpyridin-2-amine; 4), dipe (1,2-bis(diisopropylphosphino)ethane; 5)) and [Fe0(L)2(dvtms)] (L = PMe3; 3) by a mild reductive route using AlEt2(OEt) as reducing agent. In contrast, by the same methodology, the 18-valence-electron complexes [Fe0(L-L)2(ethylene)] (L-L = dppm (1,2-bis(diphenylphosphino)methane; 6), dppa (1,2-bis(diphenylphosphino)amine; 7), dppe (8)) were obtained, which do not contain dvtms. In addition, a combined DFT and solid-state paramagnetic NMR methodology is introduced for the structure determination of 5. A comparative study of the reactivity of 1, 2, 4–6, and 8 with 3-hexyne highlights emerging mechanistic implications for C–C coupling reactions using these complexes as catalysts.

International audience; The reduction of [Ni(DME)Cl 2 ] with 2 equiv. of bis(trimethylsilyl)-1,4-tetramethyldihydropyrazine in presence of a ligand L and an excess of olefin cleanly leads to [Ni(L)(alkene) 2 ] complexes. When reduction is done in presence of 1,5-cyclooctadiene (COD), [Ni(COD) 2 ] is obtained. Such approach also allows access to the Ni I dimer [Ni(bis(dicyclohexylphosphino)propane)Cl] 2. Low valent, ligand stabilized (phosphines, N-heterocyclic carbenes = NHC) Ni(0) complexes are important species, being catalytically relevant in many transformations, such as cross coupling processes. 1 Among the known Ni(0) complexes, stable [Ni(L)(alkene) 2 ] or [Ni(L)(bis-alkene)] species (L=phosphines, NHC) are rare because of a lack of efficient, versatile synthetic route or availability of the appropriate precursors. 2 Indeed, [Ni(phosphine)(C 2 H 4) 2 ] have been reported by displacement of the poly-ene ligand from the extremely sensitive [Ni(CDT)] precursor (CDT = 1,5,9-cyclododecatriene), whereas other [Ni(L)(bis-alkene)] species have been prepared from air, light and heat sensitive [Ni(COD) 2 ]. 3-8 In turn, both Ni(0) complexes [Ni(CDT)] and [Ni(COD) 2 ] require the use of pyrophoric alkylaluminium derivatives to be synthesized. It is thus desirable to devise a rational, experimentally simpler, versatile method to access families of Ni(0) species. Recently, bis(trimethylsilyl)-1,4-tetramethyl-dihydropyrazine 1 has been shown to behave as a one or two-electron reducing agent for numerous transition metal complexes. 9,10,11 It was also used to reduce several late transition metal halide precursors to the corresponding metallic nanoparticles in the absence of stabilizing ligand. 12 In the case of Ni, nanoparticles active in carbon-carbon cross coupling process were obtained. We have hypothesized that if the in situ generated reduced Ni center could be efficiently trapped by ligands the aforementioned desirable Ni(0) complexes would be readily accessible. In the present work, we show that from the simple, commercially available, [Ni(DME)Cl 2 ] precursor (DME = dimethoxy-ethane), several Ni(0) complexes could be synthesized in one pot. We also report that with strongly donating bis-phosphine ligands, the reaction leads to Ni(I) complexes instead. Our work started with the synthesis of the emblematic and sensitive [Ni(COD) 2 ] complex. To date it is synthesized by reduction of Ni(acac) 2 with alkylaluminum compounds such as triethylaluminium or DIBAL-H in presence of COD and butadiene at low temperature, followed by low temperature crystallization and filtration to eliminate aluminium side products. 13 The room temperature reduction of [Ni(DME)Cl 2 ] with two equivalents of 1 was carried out in a first stage in THF with the presence of a large excess (20 equiv. of COD). Formation of black precipitate (likely Ni metal) pointed to a fast reduction compared to coordination by COD. The low temperature reduction (-78°C) was attempted to prevent Ni(0) precipitate formation, but the reaction does not proceed at this temperature within a day. The optimized reduction temperature was found to be at-20°C. In this case, we were able to synthesize [Ni(COD) 2 ] as crystalline material in 54% isolated yield, fully characterized by 1 H and 13 C NMR (Scheme 1). The moderate yield can be explained by the remaining formation of nickel black particles during the reduction, which can nevertheless be readily eliminated by filtration prior to crystallization of [Ni(COD)2] from cold toluene. Scheme 1 Synthesis of [Ni(COD) 2 ] by organic reduction of Ni(II) halide Beyond the synthesis of [Ni(COD) 2 ] itself, the reaction proved our hypothesis right, clearly indicating that monometallic Ni(0) can be

International audience; Silver(I) and copper(I) complexes containing neutral bis(N-heterocyclic carbene) (NHC) ligands and coordinated or non-coordinated chloride, bromide, iodide, or tetrafluoroborate anions, were synthesised. The nature of the anions impacts deeply the structural features of the complexes in the solid-state and neutral cubane-, neutral coordination polymer-, or dicationic bridged-type architectures have been characterised. The structures of (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)disilver(I) dichloride (2a), bis(μ-1,3-bis(3′-butylimidazol-2′-ylidene)benzene-κ-C)tetra-μ3-bromotetrasilver(I) (2b), bis(1,3-bis(3′-butylimidazol-2′-ylidene)benzene)disilver(I) tetrafluoroborate (2d) in 2d·CH2Cl2, (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)dicopper(I) dichloride (3a) and (1,3-bis(3′-butylimidazol-2′-ylidene)benzene)dicopper(I) dibromide (3b) were established by X-ray diffraction.

Sulfonamido-phosphorus and aminophosphine ligands self-assemble to readily form active and stable nickel catalysts that are highly selective for the dimerization of ethylene to 1-butene. The self-assembled allyl-nickel complexes are zwitterionic and are stabilized by hydrogen bond interactions between the two ligands. These organometallic cis-diphosphine complexes rearrange under an ethylene atmosphere to give trans-diphosphine catalysts, with one monoanionic P,O METAMORPhos ligand and an aminophosphine.

A new dimension for secondary phosphine oxide (SPOs) ligands is described in this article. Demonstrated on original π-allylic nickel structures, these self-assembled complexes trigger catalytic hydrophosphinylation reactions. Addition of a Lewis acid B(C6 F5 )3 switches the reactivity towards migratory insertion and thus ethylene oligomerization through an unprecedented outer-sphere interaction with the coordinated SPO ligand. NMR experiments and X-ray analyses allowed for the observation of the formation of zwitterionic active species as well as their degradation pathway.

Homogeneous olefin oligomerization plays a pivotal role in the field of petrochemistry. Through catalyst, technology, and process developments, market requirements in terms of productivity, selectivity and sustainability have been addressed. Over more than 50 years, intensive research has been devoted to the design of new Group 4 to Group 10 transition metal complexes and to the study of their reactivity towards olefins leading to several breakthroughs of prime importance for academia as well as for industry. Since the early 1960s, IFPEN contributed to bring innovative industrial solutions to different targets from gasoline production to alpha-olefin on purpose processes with over 100 production units built worldwide. Based on nickel, titanium, zirconium or chromium, the catalytic systems for such processes and their next generation are subject to continuous research where the adaptation of the ligand architecture to the nature of the metal and their mode of activation, play a crucial role to control the reaction selectivity and the catalyst lifetime. Interesting relationships between the complex structure and their reactivity have been drawn and will be discussed in selected examples.

The synthesis of Pd(II) and Ni(II) alcohol-functionalized N-heterocyclic carbene (NHC) complexes was explored to examine the possible influence of the functional arm attached to the NHC backbone on their structure and reactivity and, in the case of a Ni(II) complex, on its catalytic properties in ethylene oligomerization. Starting from the alcohol-functionalized imidazolium salt [ImDiPP(C2OH)]Cl (2), the new functionalized NHC palladium(II) complex [PdCl(acac){ImDiPP(C2OH)-CNHC}] (3) was synthesized and fully characterized. Two byproducts, [PdCl{μ-ImDiPP(C2O)-CNHC,O}]2 (4) and trans-[PdCl2{ImDiPP(C2OH)-CNHC}2] (5), formed during the synthesis of 3, were also fully characterized. Acids promoted the transformation of 3 into the new CNHC-bound complex [PdCl(μ-Cl){ImDiPP(C2OH)-CNHC}]2 (6), unveiling the lability of the acac ligand and the resistance of the Pd-NHC bond to acids. Complex 6 reacted with a base to afford complex 4, in which alkoxide coordination to Pd(II) has occurred to generate a CNHC,O chelate. The stability of 3 was also assessed under basic conditions, and the new complex [Pd(acac){ImDiPP(C2O)-CNHC,O}] (7) was characterized. The new nickel(II) alcoholate-functionalized NHC complex [NiCl{μ-ImDiPP(C2O)-CNHC,O}]2 (8) was synthesized by the reaction of the imidazolium salt 2 with n-BuLi and [NiCl2(dme)]. The reaction of 8 with HCl regenerates the imidazolium and alcohol functions to give [ImDiPP(C2OH)]2[NiCl4] (9). The mixed-metal Ni(II)-Li(I) complexes [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]BF4 (10), [Ni2{μ-ImDiPP(C2O)-CNHC,μ-O}4Li]Cl (11), and [Ni{ImDiPP(C2O)-CNHC,μ-O}2LiBr] (12) were isolated and characterized. However, it was not possible to synthesize a Ni(II) alcohol-functionalized NHC complex in high yield. Small amounts of the square-planar complex [NiCl2{ImDiPP(C2OH)-CNHC}2] (13) could be isolated, and this complex was characterized by single-crystal X-ray diffraction. In 13, only the CNHC atom of the alcohol-functionalized NHC ligand is bound to the metal. The structures of the imidazolium salt 2·2H2O and of the complexes 3, 4, 4-polymorph, 5, 6·CH2Cl2, and 8-13 were established by single-crystal X-ray diffraction.

Despite the progress in the field of dynamic combinatorial chemistry (DCC), dynamic combinatorial catalysis has received considerably less attention. Some first studies, however, have provided proof of principle and demonstrated that DCC-based approaches are also applicable in catalyst development. This provides interesting new tools that are complementary to rational catalyst design and traditional combinatorial strategies. As such, DCC may become highly valuable in the field of dynamic combinatorial catalysis, due also to the practical importance of catalysis. In this review we focus on the principles of dynamic combinatorial catalysis and provide an overview by the introduction of different concept related to the development of libraries and selection procedures in catalysis.

New imino-imidazole ligands bearing a pendant donor function L were synthesized in excellent yields. The corresponding nickel(II) complexes [NiCl2(imino-imidazole-L)]n (L = (CH2)2SMe (2a), (CH2)2OMe (2b), (CH2)2NEt2 (2c), (CH2)2PPh2 (2d), (C6H4)-p-OMe (2e), (CH2)3OMe (2f), (CH2)3CH3 (2g); n = 1, 2) were prepared and characterized by FT-IR spectroscopy and elemental analysis. Furthermore, the coordination geometry around the metal center in the dinuclear complex 2a and the mononuclear complexes 2c and 2e was unambiguously established by single crystal X-ray diffraction. All complexes have been evaluated for the oligomerization of ethylene in the presence of EtAlCl2 or MAO (methylaluminoxane) as cocatalyst, and mostly dimers and trimers were produced. Better activities were observed with EtAlCl2 as cocatalyst than with MAO.

International audience; The new nickel(II) complexes containing NHC ligands N-substituted by a CH2CH2OR ether group (R = Me or Ph) [NiCl2{ImMes(C2OMe)}2] (6), [NiCl2{Imn-Bu(C2OMe)}2] (7), [NiBr2{ImDiPP(C2OMe)}2] (8), [NiBr2{ImMes(C2OMe)}2] (9), [NiBr2{Imn-Bu(C2OMe)}2] (10), NiBr2{ImMes(C2OPh)}2] (18), [NiI2{ImDiPP(C2OMe)}2] (21), [NiI2{ImMes(C2OMe)}2] (22) and [NiI2{Imn-Bu(C2OMe)}2] (23) were synthesized in good yields and fully characterized by NMR spectroscopy and X-ray diffraction analysis. The reaction conditions were optimized and further applied to thioether or non-functionalized NHC ligands, affording [NiBr2{ImDiPP(C2SPh)}2] (19) and [NiBr2{ImDiPP(n-Bu)}2] (20), respectively. Equilibriainvolving syn/anti isomers were unveiled for complexes [NiCl2{ImDiPP(C2OMe)}2] (5), 6−10 and 18−23. Reactions of 6 and 20 with an halide abstractor afforded the dicationic aquo complexes cis-[Ni{ImMes(C2OMe)}2(H2O)2][PF6]2 (27) and cis-[Ni{ImDiPP(n-Bu)}2(H2O)2][PF6]2 (28), in which a cis arrangement of the carbene ligands is evidenced, which contrasts with that in their precursors. These molecules represent rare examples of nickel aquo NHC complexes and of complexes with two cis monodentate NHC ligands. The new complexes reported in this work (15 crystal structures) displayed moderate activities as pre-catalysts forethylene oligomerization and favored dimerization.

Homogeneous olefin oligomerization plays a pivotal role in the field of petrochemistry. Through catalyst, technology, and process developments, market requirements in terms of productivity, selectivity and sustainability have been addressed. Over more than 50 years, intensive research has been devoted to the design of new Group 4 to Group 10 transition metal complexes and to the study of their reactivity towards olefins leading to several breakthroughs of prime importance for academia as well as for industry. Since the early 1960s, IFPEN contributed to bring innovative industrial solutions to different targets from gasoline production to alpha-olefin on purpose processes with over 100 production units built worldwide. Based on nickel, titanium, zirconium or chromium, the catalytic systems for such processes and their next generation are subject to continuous research where the adaptation of the ligand architecture to the nature of the metal and their mode of activation, play a crucial role to control the reaction selectivity and the catalyst lifetime. Interesting relationships between the complex structure and their reactivity have been drawn and will be discussed in selected examples.

Having the tremendous industrial importance of thermoplastics and elastomers in mind, it is not surprising to see a proliferation of studies on a variety of catalytic systems for polymerization and oligomerization of unsaturated hydrocarbons. Over the last 15 years, the development of mid- to late transition metal catalysts has provided significant advances in this area. The availability of iron combined with its low environmental impact and its tolerance to heteroatom functions attracts significant interest from both academia and industry. In the late 1990s, key milestones have been the development of well-characterized bulky bis(imino)pyridine-Fe(II) precatalysts, mainly for the polymerization or oligomerization of ethylene. This chapter provides a brief overview of the key developments reported in the last 5 years in the literature in the field of iron-catalyzed olefin and diolefin polymerization and oligomerization. Emphasis has been placed on ethylene oligomerization and polymerization, with a particular interest in ligand architecture modifications. The advances in characterization and understanding of catalytically active iron species and the corresponding mechanisms are reported. Heterogenization of bis(imino)pyridine iron catalytic systems has been considered for ethylene transformation and will also be covered in this chapter. The interest of iron catalysts for multiple single-site approaches such as reactor blending and tandem catalysis is also described. Finally, iron catalyst systems also present interesting features for diene polymerization even though both activities and selectivities remain far from those observed for conventional catalysts.

International audience; Multinuclear aluminum cocatalysts have been obtained by the reaction of various phenols, alcohols or diois with trimethylaluminum and were used in situ or as isolated, welldefined species, for the activation of an iron(ll) or an iron(lll) precatalyst for the oligomerization of ethylene. The best cocatalyst candidate involves 2,2'-biphenol (10) in a 10/AIMe3 ratio of 2/3.

We report a novel iron(III)-based catalytic system formed by the addition of an anionic N,N,N ligand to an iron(III) precursor. The complex has been characterized by FT-IR, mass spectrometry, and X-ray diffraction. This precatalyst proved to form a stable, active species for the selective oligomerization of ethylene. Up to 66 wt % of butenes was obtained with a selectivity of 98% in 1-butene.

Sulfonamido-phosphoramidite ligands lead to the formation of Rh-Rh dinuclear complexes through the anionic P-N(-) bridging character. The resulting "boat-shaped" dinuclear catalysts activate molecular H(2) through a cooperative dinuclear endocyclic mechanism, resulting in one bridging and one classical hydride on the dinuclear complex. These new complexes are very active hydrogenation catalysts that operate via a new cooperative hydrogenation activation mechanism, as calculated with density functional theory, and they display unequaled high selectivities in the hydrogenation of hindered cyclic acetamidoalkenes.

The new alcohol- and ether-functionalised-NHC silver(I) complexes bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OH)}2]Cl (4), bis(1-(2-hydroxyethyl)-3-mesityl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMes(C2OH)}2]Cl (5), bis(1-(2-hydroxyethyl)-3-methyl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMe(C2OH)}2]Cl (6), bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) tetrafluoroborate, [Ag{ImDiPP(C2OH)}2]BF4 (9), and bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OMe)}2]Cl (13), were synthesized and fully characterized by NMR spectroscopy and single crystal X-ray diffraction. For some complexes, an uncommon heteronuclear coupling (4)J((107/109)Ag-H) was unveiled. Their ability to transfer the NHC ligand to Ni(II) was assessed in the presence of different nickel(II) sources; the bis-NHC Ni(II) complex bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)nickel(II) chloride, [NiCl2{ImDiPP(C2OMe)}2] (15), was obtained from 13 and shown by X-ray diffraction study to have a trans-arrangement of the two NHC ligands. However, in contrast to other Ag(I) NHC complexes the transmetallation reaction failed with the hydroxyl-functionalised silver complexes, possibly due to the acidity of the alcohol OH function, leading overall to reprotonation of the C(NHC) and isolation of the corresponding imidazolium salts.

International audience; Since the discovery that bis(imino)pyridine ligands are able to confer high activities in ethylene oligomerization and polymerization to their iron complexes, considerable attention has been focused on catalyst design for these reactions and this research constitutes an ever-growing area in molecular catalysis. The tuning of the ligand structures and properties, and thus of catalysts, generally represents the basis for subsequent work contributing to process development and industrialization. Significant effort is therefore devoted to generate structural diversity in order to access the required catalyst stability and selectivity. This feature article outlines nitrogen-containing ligands that have been developed for the iron-catalyzed oligomerization of ethylene since the seminal discovery of the properties of bis(imino)pyridine ligands.

International audience; The new molybdenum imido alkylidene complex Mo(N(2,6-iPr2C6H3))(CHCMe2Ph)(NC4H2Me2)(OB(Mes)2) (1;Mes = 2,4,6-MePh) containing both boroxide and pyrrolide ligands is reported. Its formation results from the reaction between bis(mesityl)borinic acid ((Mes)2BOH) and the bis-pyrrolide Schrock-type precursor Mo(N-2,6-iPr2C6H3)(CHCMe2Ph)(NC4H2Me2)2. The complex was fully characterized by 1H, 13C, 11B, and 95Mo NMR spectroscopy, X-ray diffraction, and elemental analysis. Complex 1 proved to be active for homometathesis reactions of 1- and 2-octene at 0.1 mol % loading. The synthesis of mixed pyrrolide boroxide imido molybdenum alkylidene complexes was extended to other borinic acids. The catalytic activity of these new complexes was evaluated in the homometathesis of linear olefins.

H bonds make the catalysts! A single hydrogen bond between ligands coordinated to a rhodium center is critical for the formation of pure supramolecular catalysts for asymmetric hydrogenation reactions. The ester group of the amidite ligand (see scheme) also forms a hydrogen bond with the coordinated substrate. Use of the heterocomplex afforded the highest enantioselectivity reported to date for the hydrogenation of several ester substrates.

Two sets of amino acid based phosphoramidite ligands with either a BINOL backbone (Sb-1a–e and Rb-1a) or a flexible biphenol backbone (2a–c and 2f) were synthesized and evaluated in the rhodium-catalyzed hydrogenation of different functionalized alkenes: dimethyl itaconate (3), methyl 2-acetamidoacrylate (4), methyl α-acetamidocinnamate (5) and N-(3,4-dihydro-2-naphthalenyl)acetamide (6). The amino acid fragment can be modified at three positions (R1–R3) giving rise to modular ligands. Initial experiments varying the R1 position of the amino acid fragment, showed that the valine-based phosphoramidite ligand Sb-1b forms the most selective rhodium catalyst for three of the four substrates of the current study. The modifications at the other positions (R2 and R3) tweaked the ligand structure such that enhanced selectivities were obtained; up to 97 % ee is obtained for the asymmetric hydrogenation of 4 with Sb-1e. For ligands with two sources of chirality match/mismatch effects are observed, the diastereoisomer Sb-1b giving higher selectivity than the diastereoisomer Rb-1b for most of the substrates. The set of phosphoramidite ligands having the flexible and cheap biphenol backbone is developed to study the ability of the amino acid derivatives as the sole source of chirality in the ligand to steer enantioselectivity in rhodium-catalyzed hydrogenation. This study shows their capacity to compete with their BINOL-based analogues and even to outclass them depending on the substrate evaluated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Introduction Breast cancer is the most frequent cancer among women in the U.S., representing 31% of all newly diagnosed cancers in 2006. It is estimated that 75% of breast tumors express the estrogen receptor (ER) in a significant amount of cells. In these cases, it is possible to use hormone therapy as a treatment, alone or as an adjuvant to classical radioor chemotherapy. Hormone therapy can consist of either an ER antagonist (antiestrogen) or an inhibitor of the biosynthesis of estradiol (E2), the most potent endogenous estrogen. This work focuses on the second strategy, with steroid sulfatase (STS) and type 1 17β-hydroxysteroid dehydrogenase (17β-HSD1) as target enzymes. STS, a membrane enzyme widely distributed in the body and often overexpressed in breast tumors, catalyzes the transformation of estrone sulfate, inactive on ER, into estrone (E1), which is active. 17β-HSD1, expressed in aggressive breast tumors, transforms E1 into E2. Arylsulfamates are known irreversible inhibitors of STS and phenols are inhibitors of 17β-HSD1 in addition to being reversible inhibitors of STS. To address the need to rapidly synthesize arylsulfamate and phenols as inhibitors for these enzymes, our laboratory has developed the multidetachable sulfamate linker (see Figure 1) for solid phase synthesis. When treated with an acidic solution, this linker yields arylsulfamates whereas when submitted to a nucleophilic treatment, phenol is obtained. Nine small model libraries, 5 of sulfamates and 4 of phenols, were synthesized using this linker

International audience; In a combined experimental and theoretical study, the activation process of a single site ethylene oligomerization catalyst with aluminum-based activators has been studied. The results put forward a plausible deactivation reaction path of the catalyst for trimethylaluminum, while for methylaluminoxane and a novel phenoxyaluminum-based activator, the experimental catalyst's activity correlates with the energy barrier for the ethylene insertion.