Formation of six-membered palladacycles from phenanthroline Pd(II) bisacetate precursors and phenylisocyanate

Synthesis and characterization of 5a-d. CCDC-221834 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via: www.ccdc.cam.ac.uk/data_request.cif.International audiencePhenylisocyanate reacts with palladium(II) bis-acetate phenanthroline complexes to give six-membered palladacycles in nearly quantitative yields. In this new reaction, the acetate ligands act as decarbonylating agents toward the isocyanate functionality by possibly forming the isolated palladacycles via an intramolecular rearrangement

Addition de carbènes aux alcynes par catalyse au ruthénium. Synthèse de dérivés bicycliques d'acides aminés et de diènes fonctionnalisés

Thèse de Doctorat de l'Université de Rennes 1Jury : E. Dunach, V. Gandon, C. Bruneau, S. Dérie

Addition de carbènes aux alcynes par catalyse au ruthénium (synthèse de dérivés bicycliques d acides aminés et de diènes fonctionnalisés)

Des réactions d'addition de carbènes aux triples liaisons en présence du précatalyseur Cp*Ru(cod)Cl ont été développées. Ces transformations catalytiques ont permis d'accéder à de nouvelles molécules polyfonctionnelles par la formation de liaisons carbone-carbone. La réaction catalytique tandem de métathèse/cyclopropanation découverte au laboratoire, appliquée à des énynes dérivés d'a-aminoacides a permis d'accéder à des dérivés d'alcénylbicyclo[3.1.0]hexanes et d'alcénylbicyclo[4.1.0]heptanes. La réaction a été appliquée sur des énynes obtenus à partir de la glycine, de l'alanine et de la leucine et donne accès, en voie racémique et énantiosélective, à de nouveaux dérivés d'acides aminés bicycliques avec motif cyclopropane. La réaction catalytique tandem a été appliquée à différents 1,6-énynes et 1,7-énynes dérivés d'acides aminés fluorés et a conduit à la formation de dérivés bicyliques d'a-trifluorométhyl-a-aminoesters. L'activation d'un carbonate propargylique disubstitué en présence d'une molécule de diazoalcane a conduit à la formation de diènes conjugués fonctionnalisés par un groupement carbonate. Le diène est obtenu après une 1,2-migration du groupement carbonate sur le carbone du carbène. La réaction appliquée à des carbonates propargyliques non substitués ou mono substitués en position propargylique conduit à la formation de 1,4-bistriméthylsilyl-1,3-butadiènes divers. Les diènes sont obtenus par addition de deux molécules de diazoalcane sur la triple liaison.Addition of carbenes to alkynes in the presence of the catalyst Cp*Ru(cod)Cl has been developed. This catalytic transformation allowed to reach new polyfonctional molecules by formation of carbon-carbon bonds. Metathesis / cyclopropanation tandem reaction discovered in the laboratory has been applied to aminoacids derivatives enynes and allowed to reach alcenylbicyclo[3.1.0]hexanes and alcenylbicyclo[4.1.0]heptanes derivatives. The reaction has been applied to enynes obtained from glycine, alanine and leucine, and gived access, in racemic and enantioselective way, to bicyclic amino acids derivatives with cyclopropane moiety. The catalytic tandem reaction has been applied to different 1,6-enynes and 1,7-enynes derived of amino acids and led to the formation of bicyclic trifluoromethyl-aminoesters. The ectivation of a disubstituted propargylic carbonate in the presence of a molecule of diazoalkane led to the formation of conjugated dienes functionalized by a carbonate group. Dienes are obtained after a 1,2-migration of the carbonate group on the carbon of the carbene. This reaction applied to mono substituted or no substituted propargylic carbonates led to the formation of 1,4-bistrimethylsilyl-1,3-butadienes. These dienes were obtained by addition of two molecules of diazoalkane on the triple bond.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Palladium(0)-catalyzed trimerization of arylisocyanates into 1,3,5-triarylisocyanurates in the presence of diimines: A nonintuitive mechanism

International audienceWe show here that palladium(0) (dibenzylideneacetone) complexes bearing 1,10-phenanthroline constitute efficient catalysts for the cyclotrimerization of aromatic isocyanates. For the first time, the mechanism of this reaction has been investigated experimentally and theoretically with group 10 catalysts. This investigation provides a very consistent picture of the catalytic cycle. Notably, we establish that the reaction does not proceed by stepwise cycloadditions or ring insertions involving metallacyclic intermediates, as might have been anticipated. Rather, in our proposal, the initial steps of the mechanism resemble the chain-growth process operative during the anionic polymerization of isocyanates and feature charge-separated intermediates. These steps are then followed by ring closure on the metal center of the last intermediate formed to yield a seven-membered metallacycle that reductively eliminates the cyclotrimer and re-forms the active species. In addition, we conclusively show that the (known) palladacycles that could be isolated during the experimental investigations are not catalytic intermediates but result from catalyst deactivation. Thus, with Pd(0) diimine catalysts, the actual trimerization mechanism appears to be a blend between the two types of mechanisms proposed thus far for the oligomerization of heterocumulenes with very different catalysts. In conclusion, this work contributes to a better understanding of the reactivity of arylisocyanates in the vicinity of late group 10 metal centers in low oxidation state and sheds some light on the detrimental self-poisoning processes observed during the reductive carbonylation of nitroaromatic substrates catalyzed by related catalysts in non-nucleophilic media

Ruthenium-catalysed synthesis of fluorinated bicyclic amino esters through tandem carbene addition/cyclopropanation of enynes.

International audienceThe reaction of fluorinated 1,6- and 1,7-enynes, containing the moiety N(PG)C(CF(3))(CO(2)R), with diazo compounds in the presence of [RuCl(cod)(Cp*)] (cod=cycloocta-1,5-diene, Cp*=C(5)Me(5) , PG=protecting group) as the catalyst precursor leads to the formation of fluorinated 3-azabicyclo[3.1.0]hexane-2-carboxylates and 4-azabicyclo-[4.1.0]heptane-3-carboxylates. This catalytic transformation was applied to various protecting groups and has proved to be a selective and a general synthetic tool to form constrained proline or homoproline derivatives in good yields. Z stereoselectivity of the created alkenyl group is obtained with N(2)CHSiMe(3), whereas N(2)CHCO(2)Et favours selectively the E configuration for the same double bond. The diastereoselectivity exo/endo depends on the size of the created ring. The X-ray structures of two products have been determined, showing the stereochemistry of the compounds. The reaction can be understood by initial [2+2] addition of the Ru=CHY bond, generated from diazoalkane, with the C≡CH bond of the enyne leading to a key bicyclic ruthenacyclobutane, which promotes the cyclopropanation, rather than metathesis. This selective formation of bicyclic [n.1.0] compounds results from the ruthenium-catalysed creation of three carbon-carbon bonds in a single step under mild conditions

Bifunctional (Cyclopentadienone) Iron-Tricarbonyl Complexes: Synthesis, Computational Studies and Application in Reductive Amination

Reductive amination under hydrogen pressure is a valuable process in organic chemistry to access amine derivatives from aldehydes or ketones. Knolker's complex has been shown to be an efficient iron catalyst in this reaction. To determine the influence of the substituents on the cyclopentadienone ancillary ligand, a series of modified Knolker's complexes was synthesised and fully characterised. These complexes were also transformed into their analogous acetonitrile iron-dicarbonyl complexes. Catalytic activities of these complexes were evaluated and compared in a model reaction. The scope of this reaction is also reported. For mechanistic insights, deuterium-labelling experiments and DFT calculations were undertaken and are also presented

Ruthenium-catalysed synthesis of functional conjugated dienes from propargylic carbonates and silyl diazo compounds.

International audienceRu being served? The reactions of propargylic carbonates with silyl diazo compounds in the presence of [Cp*RuCl(cod)] as a catalyst precursor led to the formation of dienyl carbonates in excellent yields under mild conditions (see scheme; Y = SiMe(3))