Ketone Hydrogenation with Iridium Complexes with “non N–H” Ligands: The Key Role of the Strong Base

Ferrocenyl phosphine thioether ligands (PS), not containing deprotonatable functions, efficiently support the iridium catalyzed ketone hydrogenation in combination with a strong base co-catalyst. Use of an internal base ([Ir(OMe)(COD)]2 in place of [IrCl(COD)]2) is not sufficient to insure activity and a strong base is still necessary, suggesting that the active catalyst is an anionic hydride complex. Computational investigations that include solvent effects demonstrate the thermodynamically accessible generation of the tetrahydrido complex [IrH4(PS)]-and suggest an operating cycle via a [Na+(MeOH)3∙∙∙Ir-H4(PS)] contact ion pair with an energy span of 18.2 kcal/mol. The cycle involves an outer sphere stepwise H-/H+ transfer, the proton originating from H2 after coordination and heterolytic activation. The base plays the dual role of generating the anionic complex and providing the Lewis acid co-catalyst for ketone activation. The best cycle for the neutral system, on the other hand, requires an energy span of 26.3 kcal/mol. This work highlights, for the first time, the possibility of outer sphere hydrogenation in the presence of non deprotonatable ligands and the role of the strong base in the activation of catalytic systems with such type of ligands

A New Synthetic Method and Solution Equilibria for the Chlorotitanate(IV) Anions− Evidence for the Existence of a New Species: [Ti2Cl11]3−

International audienceTiCl3 is oxidized by SOCl2 in the presence of the appropriate amount of [NEt3Bz]Cl or [PPN]Cl [Bz = benzyl; PPN = bis(triphenylphosphanyl)iminium] to afford the corresponding salts of [Ti2Cl9]−, [Ti2Cl10]2− or [TiCl6]2−. The results of cyclic voltammetric and solution IR studies in the Ti−Cl stretching region are interpreted in terms of a rapid chloride-redistribution equilibrium between [Ti2Cl10]2− on one side and a mixture of [Ti2Cl9]− and a previously unreported [Ti2Cl11]3− species on the other side. In the solid state, however, a compound with the [PPN]3[Ti2Cl11] stoichiometry exists as a mixture of [PPN]2[Ti2Cl10] and [PPN]2[TiCl6]. The PPN salt of [Ti2Cl9]− has been structurally characterized by X-ray diffractometry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004

Oxidation of alcohols by TBHP in the presence of sub-stoichiometric amounts of MnO2

AbstractCommercially available activated MnO2 has been investigated as a catalyst for the oxidation of alcohols (phenylethanol, 4-methyl- and 4-methoxybenzyl alcohol, trans-cinnamyl alcohol, cyclohexanol, menthol, perillyl alcohol and myrtenol) by TBHP/decane or TBHP/water in MeCN. The activity is highest for benzylic and allylic alcohols. Secondary alcohols yield ketones with good selectivities, while the aldehydes generated from primary alcohols are further oxidized. The process competes with the TBHP catalyzed decomposition. It thus requires the use of excess TBHP and high catalyst loadings to achieve high conversions. However, the low cost of the reagents makes this new protocol convenient for the oxidation of reactive secondary alcohols. The study also suggests that MnO2 should be proscribed as a reagent to quench excess TBHP in oxidative processes when the synthetic target contains easily oxidizable alcohol functions and when carrying our detailed kinetic monitoring of oxidation processes

Redox-responsive catalysis: fine tuning of chemoselectivity in the intramolecular reaction of diazo compounds catalysed by ferrocene-functionalised dirhodium(II) complexes

International audienceA series of heteroleptic dirhodium(II) complexes (1a–k) of formula [Rh2(OAc)3(L)], where L is a redox-active ferrocenecarboxylate ligand, have been evaluated in the redox-responsive, dirhodium(II)-catalysed decomposition of several diazo substrates prone to chemoselectivity issues. The influence of the counter-anion of chemically oxidised ferrocenyl-containing complexes on the chemoselectivity of the decomposition of the diazo compound 2 has been investigated with complexes 1a–d: bulky, weakly coordinating SbF6− and BArF4− ([(3,5-(CF3)2C6H3)4B]−) result in a greater chemoselectivity difference between the reduced and oxidised versions of the catalyst than BF4−. The correlation between the electronic nature of the ferrocenyl substituents and the extent of the chemoselectivity switch is not obvious, as complex 1a with unsubstituted ferrocene gave the best results upon oxidation among complexes 1a–k. The introduction of a saturated tether in 1j–k drastically decreases the chemoselectivity difference between the reduced and oxidised species. Finally, two additional diazo compounds with various chemoselectivity issues (9 and 10) were evaluated in the presence of complexes 1a and 1a+·SbF6−: the decomposition of diazo complex 9, producing an aromatic C–H insertion product 11 and a cyclopropanation product 12, led to a 42% chemoselectivity difference between 1a and 1a+·SbF6−. This demonstrates that changing the electronic properties of only one ligand on dirhodium, by oxidation of its ferrocenyl part, can have a marked influence on the reaction selectivity

Rhodium-catalyzed aqueous biphasic hydrogenation of alkenes with amphiphilic phosphine-containing core-shell polymers

International audienceThe biphasic aqueous hydrogenation reaction of styrene and 1-octene could be efficiently carried out using phosphine-containing core-shell water-soluble polymers used as nanoreactors in presence of [Rh(COD)Cl]2. The catalytic aqueous phase could be successfully recycled up to six times

New ferrocenyl phenol thiophosphines

International audienc

Real-World Treatment Patterns Among French Patients With Metastatic Castration-Resistant Prostate Cancer Under Abiraterone or Enzalutamide

International audiencePURPOSE: Using large French retrospective study cohort of chemotherapy-naïve metastatic castration-resistant prostate cancer patients (mCRPC; n = 10,308) comparing survival between patients who initiated abiraterone (ABI; 64%) and those initiating enzalutamide (ENZ; 36%), the present objective was to describe treatment patterns in the 2 years following initiation. METHOD: Using the national health data system (SNDS) from 2014 to 2018, we first explored the number of treatment lines, and secondly, patterns of patient management using state sequence analysis; cluster analyses were performed on the 0 to 12 month and 13 to 24 month periods. Age, Charlson score, and duration of androgen deprivation therapy (ADT) were obtained for each cluster in the first year of follow-up. RESULTS: Patients with only 1 treatment line accounted for 52%. In the 0 to 12 month sequence analysis, the main clusters among ABI/ENZ new users involved patients who continued the initial treatment (54% of 65% respectively) and discontinued active treatment (14.5% for both). Less than 2 years exposure to ADT prior to ABI/ENZ initiation was frequently observed for noncontrolled mCRPC, as shown in the death and switch from ABI/ENZ to docetaxel clusters. The clusters for a switch ABI/ENZ to ENZ/ABI involved 6% to 11% of the patients. CONCLUSION: Our study suggested fairly similar patterns between ABI and ENZ initiation. The cluster of patients with active treatment discontinuation needs to be further investigated, as well as factors influencing therapeutic choice. Better understanding for the use of second-generation hormone therapy in mCRPC in real life, could improve its implementation by clinicians in the early stages of prostate cancer

An oxidovanadium(IV) complex with 4,4′-di-tert-butyl-2,2′-bipyridine ligand: Synthesis, structure and catalyzed cyclooctene epoxidation

International audienceThe interaction of vanadium(III) chloride (VCl3) with 4,4'-di-tert-butyl-2,2'-bipyridine (dbbpy) in air resulted in the monomeric oxidovanadium(IV) complex [VOCl2 (dbbpy)(H2O)] (1) in high yield. The complex was characterized by IR and EPR spectroscopies, by elemental analysis, and by single crystal X-ray diffraction analysis. The vanadium atom has a distorted octahedral coordination environment. The EPR spectrum of 1 in CH2Cl2 demonstrates an eight-line signal typical of vanadium(IV) with a d(1) electronic configuration. Complex 1 exhibits catalytic activity in the cyclooctene oxidation with tert-butyl hydroperoxide (TBHP) in CHCl3. Detailed EPR, NMR and GC-MS studies of the reaction revealed a few mechanistic details and the nature of by-products that are generated by involvement of the chloroform solvent

New protocol for the synthesis of S‐thioesters from benzylic, allylic and tertiary alcohols with thioacetic acid

International audienceA new one‐pot solvent‐less reaction to convert benzylic, allylic, ferrocenyl or tertiary alcohols into S‐thioesters, bench‐stable and less odorous precursors of the corresponding thiols, which is based on reactions in neat thioacetic acid in the presence of tetrafluoroboric acid, is presented. Reaction monitoring by NMR and GC of the benzyl alcohol conversion indicated the intermediate formation of benzyl acetate and benzyl thionoacetate (PhCH2OC(S)CH3) prior to the slower conversion to the final S‐benzyl thioacetate product. Increasing the HBF4 concentration enhanced the reaction rate, giving good to excellent yield (up to 99%) for a large scope of alcohols. Control experiments, with support of DFT calculations, have revealed a thermodynamically favorable, though requiring HBF4‐activation, disproportionation of CH3C(O)SH to CH3C(O)OH and CH3C(S)SH, the latter immediately decomposing to H2S and (MeC)4S6 but also generating the hitherto unreported [MeC(O)C(Me)S]2(µ‐S)2. Kinetic investigations demonstrated that the rate of benzyl alcohol conversion is second‐order in [PhCH2OH] and second order in [HBF4], while the rate of conversion of the benzyl acetate intermediate to S‐benzyl thioacetate is second order in [PhCOOMe] and fourth order in [HBF4]. The DFT calculations rationalize the need to two alcohol molecules and two protons to generate the reactive benzyl cation