Author: Emmanuel Lerayer

Highly Functionalized Ferrocenes

International audience; Ferrocene is unique among organometallic compounds, and serves notably as a versatile platform towards the production of ligands useful to promote transition metals chemistry. A general limiting aspect of the synthesis of ferrocene derivatives is the efficient access to sophisticated highly functionalized polysubstituted ferrocenes, i. e. bearing four or more substituents replacing hydrogen atoms on the cyclopentadienyl rings. These ferrocene derivatives can bear various functional or/and structuring spectator substituents. Their preparation involves synthetic difficulties resulting from the need of multiple functionalizations coexisting altogether, and satisfying fu…

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Planar-Chiral 1,1 '-Diboryl Metallocenes: Diastereoselective Synthesis from Boryl Cyclopentadienides and Spin Density Analysis of a Diborylcobaltocene

International audience; The reaction of nonsubstituted alkali metal cyclopentadienides with haloboranes leads to similar to 90:10 mixtures of isomeric diene products that can be deprotonated to give simple boryl cyclopentadienides. We extended this transformation to the sterically hindered lithium tert-butylcyclopentadienide 1 using FBMe(s)2 (Mes = 2,4,6-trimethylphenyl) and ClBCy2 as electrophiles. The boryl group is selectively introduced in the remote position to minimize steric congestion. The new boryl dienes are obtained as mixtures of isomers, and subsequent deprotonation with MeLi or LiHMDS affords the lithium 1,3-disubstituted cyclopentadienides Sa,b in yields over 95%. Direct asse…

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A general diastereoselective synthesis of highly functionalized ferrocenyl ambiphiles enabled on a large scale by electrochemical purification

International audience; A general synthesis of highly functionalized ferrocenes, which include (P,B)- and (N,B)-ambiphiles, has been developed at a multigram scale. Diastereoselective stepwise modification of di-tert-butylated ferrocenes included the unprecedented separation of electroactive species. Bulky alkyl groups on ferrocenes ensure planar chirality of ambiphiles and enforce closer proximity of antagonist Lewis functions.

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A sterically congested 1,2-diphosphino-1'-boryl-ferrocene: synthesis, characterization and coordination to platinum.

International audience; A new class of tritopic ferrocene-based ambiphilic compound has been prepared by assembling diphosphino- and boryl-substituted cyclopentadienides at iron. The presence of five sterically demanding substituents on the ferrocene platform induces conformation constraints, as apparent from XRD and NMR data, but does not prevent chelating coordination to platinum. The Lewis acid moiety is pendant in both the free ligand and the platinum complex.

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Nanocatalysts for High Selectivity Enyne Cyclization: Oxidative Surface Reorganization of Gold Sub-2-nm Nanoparticle Networks

International audience; Ultrasmall gold nanoparticles (NPs) stabilized in networks by polymantane ligands (diamondoids) were successfully used as precatalysts for highly selective heterogeneous gold-catalyzed dimethyl allyl(propargyl)malonate cyclization to 5-membered conjugated diene. Such reaction usually suffers from selectivity issues with homogeneous catalysts. This control over selectivity further opened the way to one-pot cascade reaction, as illustrated by the 1,6-enyne cycloisomerization–Diels–Alder reaction of dimethyl allyl propargyl malonate with maleic anhydride. The ability to assemble nanoparticles with controllable sizes and shapes within networks concerns research in sensor…

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Synthèse et caractérisation de phosphine, borane, amine sur plateforme ferrocène polyfonctionnelle

Ferrocene platforms are useful in coordination chemistry and catalysis thanks to their robustness and versatile functionalization. Ferrocene backbone allows the implantation of several key functional groups in a restricted space, inducing close proximity and potential polyfunctional cooperation (see for instance ferrocenyl polyphosphine chemistry). Ansa ferrocene and ferrocene bearing conformational control inducing groups maximizing the proximity of key groups have been widely reported.The first part of this thesis focuses on the synthesis of new borylated cyclopentadienyl, and their use in formation of borylated metallocenes bearing conformational constraints. NMR analysis and DFT calcula…

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