From Enynyl Esters to Functionalized Polycyclic Derivatives via Cycloisomerization and Post-Functionalization

International audienceThe post-functionalization of ketone products originating from the PtCl2-catalyzed cycloisomerization of enynyl esters is described. Postfunctionalization has been accomplished via diastereoselective alkylation, regioselective cyclopropane opening and regioselective Baeyer Villiger and Beckmann rearrangements to provide functionalized polycycles

Synthesis of Allenes Bearing Phosphine Oxide Groups and Investigation of Their Reactivity toward Gold Complexes

International audienceA collection of phosphine oxide allenes has been prepared. Their coordination to gold(I) has been studied giving new coordination complexes when a pendant pyridine moiety was present. Alternatively, their gold(I)-catalyzed cycloisomerization has proven to be quite efficient. An almost complete axial-to-central chirality transfer in the cyclization process was observed, opening the potential access to valuable enantiopure phosphorus derivatives

Bis-phosphine allene ligand: coordination chemistry and preliminary applications in catalysis

International audienceA 1,3-bis-diphenylphosphine allene can give rise to new coordination complexes with palladium, platinum and gold metals. These complexes were fully characterized by NMR, HRMS and X-ray diffraction analysis. For gold(I), the corresponding dinuclear complex has been used in a series of diagnostic catalytic reactions and gave promising preliminary results in asymmetric catalysis

Combination of gold catalysis and Selectfluor for the synthesis of fluorinated nitrogen heterocycles

We herein report the synthesis of 3-fluoro-2-methylene-pyrrolidine (3a) and -piperidine (3b) from 1,5- and 1,6-aminoalkynes, respectively, using a combination of a gold-catalyzed hydroamination reaction followed by electrophilic trapping of an intermediate cyclic enamine by Selectfluor. Careful attention was paid to the elucidation of the mechanism and Selectfluor was suggested to play the double role of promoting the oxidation of gold(I) to a gold(III) active species and also the electrophilic fluorination of the enamine intermediates

Non-Innocent Ligands: New Opportunities in Iron Catalysis

International audienceIntroduced in the late sixties, non-innocent (or redox) ligands have been extensively studied for their unusual and intriguing chemical behavior. Their ability to delocalize and/or provide electrons to the metal center of organometallic complexes confers them undisputable chemical interest and has proved valuable in the development of novel synthetic methodologies. This review will focus on the chemistry and applications of low-valent iron complexes bearing potentially non-innocent ligands. Because of the elusive nature of these ligands, and whenever possible, theoretical calculations and analysis of spectroscopic data will be presented in an effort to provide insights into the catalytic activity of the complexes

Niobium-Catalyzed Intramolecular Addition of O–H and N–H Bonds to Alkenes: A Tool for Hydrofunctionalization

International audienceA convenient, versatile and easy to handle intramolecular hydrofunctionalization of alkenes (C–O and C–N bonds formation) is reported using a novel niobium-based catalytic system. This atom economic and eco-friendly methodology provides an additional synthetic tool for the straightforward formation of valuable building blocks enabling molecular complexity. Various pyran, furan, pyrrolidine, piperidine, lactone, lactam derivatives as well as spirocyclic compounds are produced in high yields and selectivities

Diastereoselective Synthesis of Chiral Methyl 2-Piperidin-2-ylpropanoates

International audienc

N-Bromosuccinimide-Promoted Cyclization of β-Carboxymethyl Enamino Esters; Synthesis of Functionalized 4-Amino-2(5H)-Furanones

International audienc

Photochemical studies on bis-sulfide and -sulfone tethered polyenic derivatives

International audienceThis study focusses on the [2+2]-photocycloaddition of symmetric polyenic system tethered by an aryl bis-sulfide or sulfone platform. Using direct irradiation or photosensibilization, no expected ladderane product was isolated. In most cases, only tricyclic products including a single cyclobutane moeity were formed. Irradiation of bis-acrylic precursors in water with encapsulation by a host (cyclodextrin or cucurbituril) provided a stereoselective access to valuable cyclobutyl adducts

Indolizy Carbene Ligand. Evaluation of Electronic Properties and Applications in Asymmetric Gold(I) Catalysis

International audienceWe report herein a new family of carbene ligands based on an indolizine-ylidene (Indolizy) moiety. The corresponding gold(I) complexes are easily obtained from the gold(I)-promoted cyclization of allenylpyridine precursors. Evaluation of the electronic properties by experimental methods and also by DFT calculations confirms strong σ-donating and π-accepting properties of these ligands. Cationization of the gold(I) complexes generates catalytic species that trigger diverse reactions of (poly)unsaturated precursors. When armed with a methylene phosphine oxide moiety on the stereogenic center adjacent to the nitrogen atom, the corresponding bifunctional carbene ligands give rise to highly enantioselective heterocyclizations. DFT calculations brought some rationalization and highlighted the critical roles played by the phosphine oxide group and the tosylate anion in the asymmetric cyclization of γ-allenol