Synthesis of Unsymmetrical Heterobiaryls Using palladium-catalyzed cross-coupling reactions of lithium organozincates

International audienceSeveral unsymmetrical heterobiaryls have been synthesized through palladium-catalyzed cross-coupling reactions of lithium triorganozincates. The latter have been prepared by deprotonative lithiation followed by transmetalation using non hygroscopic ZnCl2*TMEDA (1/3 equiv)

A Convenient Approach to Luminescent Cyclometalated Platinum(II) Complexes with Organometallic π-Bonded Benzenedithiolate

International audienceA family of neutral cyclometalated platinum(II) complexes [(C^N)Pt(η-S^S)] with π-bonded benzenedithiolate {(η-S^S) = Cp*Ru(C6H4S2)} and various cyclometalated ligands, {(C^N) = 2-phenylpyridine (ppy), (2); 2,4-difluorophenylpyridine (F2ppy) (3), benzo[h]quinoline (bzq) (4); dibenzo[f,h]quinoline (dbzq) (5) } were prepared and fully characterized. For comparison purposes the related bipyridine platinum (II) complex [(bpy)Pt(η-S^S)][OTf] (6) was also prepared. The electrochemistry behavior of these complexes was investigated and shows the enhanced stability of these compounds toward oxidation due to the presence of Cp*Ru moiety which is now π-bonded to the benzenedithiolato group. Moreover several complexes were identified by single crystal X-ray molecular structures. To the best of our knowledge these are the first structures to be reported for cyclometalated platinum complexes with a π-bonded benzenedithiolate (bdt) ligand. All of the complexes are luminescent in fluid solution at room temperature and in glassy solution at 77 K; their emission properties can be tuned through ligand variation

Iron(II) catalyzed reductive radical cyclization reactions of bromoacetals in the presence of NaBH4: optimization studies and mechanistic insights

Abstract 5-Exo-trig radical reductive cyclization reactions of bromoacetals are catalyzed by iron in the presence of the reducing agent NaBH4. Both iron(II) and iron(III) were found to effectively mediate these reactions. As shown by cyclic voltammetry, iron(III) can be reduced to an iron(II) precatalyst before passing through an identical reaction mechanism in which monoelectronic activation of the substrate would occur by an anionic hydridoiron(I) complex. Further studies have established that both the substrate (iodo- vs bromo-derivative) and the precatalytic mixture are decisive in determining the reaction outcome

Elucidating dramatic ligand effects on SET processes: iron hydride versus Iron borohydride catalyzed reductive radical cyclization of unsaturated organic halides

An iron(II) borohydride complex ([(η1-H3BH)FeCl(NCCH3)4]) is employed as the precatalyst in iron-catalyzed radical cyclizations of unsaturated organic halides in the presence of NaBH4. Mechanistic investigations have established that the ligand bound to the metal center (acetonitrile versus ethylenebis(diphenylphosphine) (dppe)) plays a crucial role in the structure and reactivity of the active anionic iron(I) hydride ([HFeCl(dppe)2]−) and borohydride ([(η1-H3BH)FeCl(NCCH3)4]−) with unsaturated haloacetals. This work provides new insights into iron(I) hydride and borohydride species and their potential implication in single-electron processes

Transition Metal‐Catalyzed Carbon–Carbon Cross‐Coupling

International audienc

Réactions catalysées par Pd(oAc)2/benzoquinone (un procédé général pour l'activation de liaisons Ar-H, Ar-B et C-H, via une oxydation électrochimique)

Le principal problème lié aux réactions catalysées par le palladium (II) est qu au cours du cycle catalytique, du palladium (0) est libéré, ce qui impose la présence d un oxydant permettant la régénération du Pd(II). Des méthodes de recyclage existantes impliquent généralement l utilisation d oxydants chimiques en quantité stœchiométrique. La formation de produits secondaires, et le caractère souvent toxique de ces composés nous ont poussés à trouver une alternative plus douce, plus économique en atomes et généralisable à diverses réactions. Nous proposons ici une voie électrochimique de recyclage du catalyseur, via l utilisation d une quantité catalytique de p benzoquinone. Cette méthode permet d éviter la présence d oxydants chimiques pouvant être nuisibles à la réaction. Ce procédé a été mis au point pour trois réactions différentes de synthèse organique, qui sont : les réactions de type Heck à partir d arènes, la synthèse de biaryles par homocouplage de dérivés organoborés et enfin, l oxydation d alcools en aldéhydes et cétones.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Etudes mécanistiques de réactions catalysées par des complexes de palladium mettant en jeu des réactifs organoborés (homocouplage et couplage croisé)

PARIS-BIUSJ-Thèses (751052125) / SudocSudocFranceF