Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis.

The bis-ortho-thioether 9,10-bis[(o-methylthio)phenyl]anthracene was synthesized as a syn-atropisomer, as revealed by X-ray diffraction. This alkylaryl thioether ligand (L) formed different macrocyclic complexes by coordination with silver(I) salts depending on the nature of the anion: M2L2 for AgOTf and AgOTFA, M6L4 for AgNO3. A discrete M2L complex was obtained in the presence of bulky PPh3AgOTf. These silver(I) complexes adopted similar structures in solution and in the solid state. As each sulfur atom in the ligand is prochiral, macrocycles L2M2 were obtained as mixtures of diastereoisomers, depending on the configurations of the sulfur atoms coordinated to silver cations. The X-ray structures of the two L2·(AgOTf)2 stereoisomers highlighted their different geometry. The catalytic activity of all silver(I) complexes was effective under homogeneous conditions in two tandem addition/cycloisomerization of alkynes using 0.5-1 mol % of catalytic loading.

Stabilisation of carbon-supported palladium nanoparticles through the formation of an alloy with gold: application to the Sonogashira reaction.

Oh my Gold! Gold atoms stabilise catalytically active palladium nanoparticles when engaged in an alloy heterogenised on carbon. The increased durability makes the Pd-Au/C catalyst more recyclable than the gold-free Pd/C catalyst for the Sonogashira reaction.

Practical synthesis of indoles and benzofurans in water using a heterogeneous bimetallic catalyst.

This paper describes the preparation of indoles, azaindoles and benzofurans in pure water by using a new heterogeneous Pd-Cu/C catalyst through a cascade Sonogashira alkynylation-cyclization sequence. Details of the optimization studies and the substrate scope are discussed. This procedure allows the preparation of heterocycles with good yields and is tolerant to a wide variety of functional groups.