Synthesis of Solution-Phase Phosphoramidite and Phosphite Ligand Libraries and Their In Situ Screening in the Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids

Herein, we report the automated parallel synthesis of solution-phase libraries of phosphoramidite ligands for the development of enantioselective catalysts. The ligand libraries are screened in situ in the asymmetric rhodium-catalyzed addition of arylboronic acids to aldehydes and imines. It is shown that the described methodology results in the straightforward discovery of leads for highly efficient enantioselective catalysts.

Ultra-sensitive and selective Hg2+ chemosensors derived from substituted 8-hydroxyquinoline analogues

International audienceNovel analogues of 8-hydroxyquinoline with phosphinate or thiophosphinate functions and styryl fluorophores in the para position to the nitrogen atom were prepared via multi-step syntheses, using phosphorylation and Wittig coupling reactions. A strong affinity between the quinoline analogues and heavy metal ions such as Pb2+, Cd2+ and Hg2+ was highlighted. The interaction of the metal ions with the nitrogen of the styrylquinoline leads to a large red shift of the absorption and emission spectra in agreement with an increase of the photoinduced charge transfer character of the styryl fluorophore. In the presence of metal ions the appearance of a green fluorescence emission is also observed upon excitation at 420 nm or 840 nm, thanks to a significant increase of the two-photon response. Under optimal conditions, a mercury concentration of 15 ppt in a partially aqueous medium can be detected using the thiophosphinate derivative without interference from other metal ions

Synthesis of Polysubstituted 2‑Iodoindenes via Iodonium-Induced Cyclization of Arylallenes

A new chemoselective iodocarbocyclization of allenyl arenes was developed leading to the formation of 2-iodoindenes. In acetonitrile or nitromethane, electrophilic sources of iodine cations react selectively with the C₂–C₃ double bond of 1-arylallenes to give, after <i>anti</i> nucleophilic attack of the aromatic ring, 2-iodoindene products in high yields. Variations of the allenic skeletons revealed the high 5-<i>endo</i> selectivity and some competitive pathways of cyclization. Postfunctionalization reactions of the carbon–iodine bond, via Pd- and Cu-cross-couplings, gave rise to substituted indenes in good to excellent yields

Rhodium-Catalyzed Addition of Arylboronic Acids to Isatins: An Entry to Diversity in 3-Aryl-3-Hydroxyoxindoles

A general method for the catalytic 1,2-addition of aryl and alkenyl boronic acids to isatins is described using a rhodium(I)/triphenylphosphite catalyst. The application of this transformation allows the synthesis of a variety of 3-aryl-3-hydroxyoxindole building blocks in high yields. An enantioselective version of this reaction using a rhodium(I)/phosphoramidite system is also presented.

Rhodium/phosphoramidite-catalyzed asymmetric arylation of aldehydes with arylboronic acids

Phosphoramidites are effective chiral ligands in the rhodium catalyzed addition of arylboronic acids to aldehydes providing up to 75% enantioselectivity and up to 96% isolated yield.

Silver-Catalyzed Domino Hydroarylation/Cycloisomerization Reactions of <i>ortho</i>-Alkynylbenzaldehydes: An Entry to Functionalized Isochromene Derivatives

A Ag-catalyzed versatile and efficient access to 1<i>H</i>,1-arylisochromenes is reported. Starting from <i>ortho</i>-alkynylbenzaldehydes bearing various substitution patterns on the benzaldehyde and alkynyl units, the use of silver triflate (10 mol %) allowed a domino hydroarylation/cycloisomerization reaction process, leading to aryl-functionalized 1<i>H</i>-isochromene (>10 compounds, 80–98% yields). Notably, the reaction conditions were also compatible with benzaldehydes bearing an aliphatic-substituted alkynyl moiety with modest to good yields (34–88%, 10 compounds)

Water-Soluble Gold(I) and Gold(III) Complexes with Sulfonated <i>N</i>‑Heterocyclic Carbene Ligands: Synthesis, Characterization, and Application in the Catalytic Cycloisomerization of γ‑Alkynoic Acids into Enol-Lactones

Zwitterionic imidazolium salts bearing 3-sulfonatopropyl, and 2-pyridyl, 2-picolyl, and 2-pyridylethyl substituents have been synthesized and employed as precursors for the preparation of novel water-soluble Au­(I)- and Au­(III)-NHC complexes of general composition [AuCl­(NHC)] and [AuCl₃(NHC)] (NHC = <i>N</i>-heterocyclic carbene), respectively. These complexes proved to be active, selective, and recyclable catalysts for the intramolecular cyclization of γ-alkynoic acids under biphasic toluene/water conditions, leading to the desired enol-lactones in high yields under mild conditions (r.t.). Remarkably, despite the well-known ability of gold complexes to promote the hydration of CC bonds, the competitive hydration process was not observed, even during the cycloisomerization reactions of 1,6-diynes

Water-Soluble Gold(I) and Gold(III) Complexes with Sulfonated <i>N</i>‑Heterocyclic Carbene Ligands: Synthesis, Characterization, and Application in the Catalytic Cycloisomerization of γ‑Alkynoic Acids into Enol-Lactones

Zwitterionic imidazolium salts bearing 3-sulfonatopropyl, and 2-pyridyl, 2-picolyl, and 2-pyridylethyl substituents have been synthesized and employed as precursors for the preparation of novel water-soluble Au­(I)- and Au­(III)-NHC complexes of general composition [AuCl­(NHC)] and [AuCl₃(NHC)] (NHC = <i>N</i>-heterocyclic carbene), respectively. These complexes proved to be active, selective, and recyclable catalysts for the intramolecular cyclization of γ-alkynoic acids under biphasic toluene/water conditions, leading to the desired enol-lactones in high yields under mild conditions (r.t.). Remarkably, despite the well-known ability of gold complexes to promote the hydration of CC bonds, the competitive hydration process was not observed, even during the cycloisomerization reactions of 1,6-diynes