Nickel catalyzed one pot synthesis of biaryls under air at room temperature

A practical, room temperature catalytic system has been developed for the synthesis of biaryls in one step from the homocoupling of in situ generated Grignard reagents using the nickel(II) complex. Molecular oxygen used as an oxidant makes the system environment friendly. The reaction system is compatible with diverse functionality to afford biaryls in appreciable yields

Substituted BEDT-TTF derivatives: synthesis, chirality, properties and potential applications

The increasing availability of functionalized BEDT-TTF derivatives in both racemic and enantiopure forms opens up great opportunities for preparing multifunctional materials and chiral conducting systems in the form of crystals, thin films and polymers. Functionalities such as amino and carboxyl will allow attachment to other molecular systems, while intermolecular interactions between substituents, e.g. hydrogen bonding and halegon- - - halegon interactions, provides additional tools for designing solid state radical cation structures. In this review the syntheses of substituted derivatives of BEDT-TTF and closely related donors are surveyed, along with the structures and properties of the radical cation salts so far prepared, as a stimulus for future application of these versatile and attractive molecules. Particular attention is paid to the preparation of single enantiomers, and to the stereochemical consequences of the synthetic procedures

Z-Selective Homodimerization of Terminal Olefins with a Ruthenium Metathesis Catalyst

The cross-metathesis of terminal olefins using a novel ruthenium catalyst results in excellent selectivity for the Z-olefin homodimer. The reaction was found to tolerate a large number of functional groups, solvents, and temperatures while maintaining excellent Z-selectivity, even at high reaction conversions

Halide-enhanced catalytic activity of palladium nanoparticles comes at the expense of catalyst recovery

In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr) can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature

An alternative method to access diverse N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications

An alternative synthetic route for the design of N,N′-diquaternised-3,3′-biquinoxalinium “biquinoxen” dications is reported, involving oxidative radical coupling of dithionite reduced quinoxaline quaternary salts. Although the reaction is not regioselective, leading to relatively modest yields (up to 32%), the advantages of this new synthetic protocol lie in a simple potentially gram scale synthesis using inexpensive easily accessible reagents with no metal catalysts and no purification steps. Thus whereas the method reported previously to access the N,N′-dimethyl-3,3′-biquinoxalinium, “methylbiquinoxen” precursor gave higher yield than the new method reported here, this new method avoids the limitation of using scarce oxonium reagents. Overall, the new protocol is a robust synthetic strategy which offers new design possibilities

Supported Au nanoparticles as efficient catalysts for aerobic homocoupling of phenylboronic acid

Au nanoparticles with small sizes (1–4 nm) were effectively formed on Mg–Al mixed oxides (Au/MAO), which showed superior catalytic performances and good recyclability in aerobic homocoupling of phenylboronic acid

Synthesis of highly substituted alkenes by sulfur-mediated olefination of N-tosylhydrazones

Tetraphenylethylenes (TPEs) are well-known for their aggregation-induced emission properties. The synthesis of TPE derivatives, as well as other highly substituted olefins, generally requires the use of hazardous reagents, such as metalorganic compounds, to overcome the high activation energies caused by the sterically congested double bond. Herein, we present an efficient and metal-free procedure for the synthesis of tetraarylethylenes via alkylidene-homocoupling of N-tosylhydrazones, derived from readily available benzophenones, in excellent yields. The method relies only on cheap and benign additives, i.e. elemental sulfur and potassium carbonate, and easily competes with other established procedures in terms of scope, yield and practicability. A mechanistic study revealed a diazo compound, a thioketone and a thiirane as key intermediates in the pathway of the reaction. Based on this, a modified method, which allows for selective alkylidene-cross-coupling, generating a broader scope of tri- and tetrasubstituted olefins in good yields, is showcased as well

Homocoupling of terminal alkynes catalysed by ultrafine copper nanoparticles on titania

Copper nanoparticles on titania effectively catalyse the oxidative homocoupling of terminal alkynes in the presence of piperidine as a base in tetrahydrofuran (THF) or under solvent-free conditions. A wide range of diynes have been synthesised in high yields using low catalyst loading (1 mol-% Cu). The copper catalyst (mainly as Cu2O) has been characterised by different means, is easy to prepare, can be reutilised several times, works either in air or under inert atmosphere and was shown to be superior to other commercially available copper sources.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación [(MICINN) (grant number CTQ2007-65218) and Consolider Ingenio (grant number 2010-CSD2007-00006)], the Generalitat Valenciana (grant no. PROMETEO/2009/039), and the Fondos Europeos para el Desarrollo Regional (FEDER)

A Glycerol-Based Deep Eutectic Solvent as Natural Medium and Organic Reductant for Homocoupling of (Hetero)Aryl Chlorides: a Green Route to 2,2’-Bipyridine and Biaryl Scaffolds

A glycerol-based Deep Eutectic Solvent (DES) enables the Pd-catalyzed activation of (hetero)arylchlorides and promotes the formation of 2,2’-bipiyridines and biaryls through an Ullmann-type homocoupling in smooth experimental conditions (80 °C) with Ca(OH)2 as a green base and Pd/C as heterogeneous catalyst. Noteworthy, the coupling does not need the addition of external reducing agents, like metals, since the glycerol present in the DES acts as a safe and green organic reductant. The heterogeneous catalytic system (DES-Pd/C) showed to be easily recyclable and has been applied to the sustainable synthesis of the Abametapir drug