The ball-mill-based mechanochemical activation of metallic copper powder facilitates solvent-free alkyne-azide click reactions (CuAAC). All parameters that affect reaction rate (i.e., milling time, revolutions/min, size and milling ball number) have been optimized. This new, efficient, facile and eco-friendly procedure has been tested on a number of different substrates and in all cases afforded the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in high yields and purities. The final compounds were isolated in almost quantitative overall yields after simple filtration, making this procedure facile and rapid. The optimized CuAAC protocol was efficiently applied even with bulky functionalized β-cyclodextrins (β-CD) and scaled-up to 10 g of isolated product.

The modification and characterization of porous particles and matrices using cyclodextrins (CD) has attracted a large amount of interest in recent years. In fact, CDs are at the heart of this study which aims to graft β-CD onto silica particles by means of efficient protocols and nonconventional energy sources. In particular, the use of microwave irradiation, benign reaction media and a solvent-free planetary ball mill has provided a high degree of grafting. The inclusive properties of β-CD grafted silica were tested with phenolphthalein and its sorption capacity with 2 methyl orange and both tests confirmed the efficiency of the grafting protocols. Samples were extensively characterized by TGA, elemental analysis, IR, BET and HRTEM. The green protocols herein reported can facilitate access to functionalized silica and pave the way to its use in novel applications.

Silica is an extremely versatile support, which is capable of hosting metal nanoparticles (NPs) and enhancing their stability and reactivity. In this study, a novel cyclodextrin/silica support for Pd NPs, which we have denoted Pd/Si‐CD, has been prepared. The highly efficient and homogeneous impregnation of small palladium nanoparticles on this support has been carried out under conventional conditions, and ultrasound irradiation has been shown to have a beneficial effect on catalyst preparation. The catalyst exhibited excellent activity in ligand‐free C−C Suzuki and Heck couplings with a large number of aryl iodide and bromides, in which microwave irradiation use cuts down reaction time. Pd/Si‐CD have shown high activity and selectivity in the hydrogenation reaction, and the semihydrogenation of phenyl acetylene was also studied with excellent results.

A highly versatile and flexible copper nanoparticle (Cu(0) NPs) catalytic system has been developed for the controlled and selective transfer hydrogenation of nitroarene.Interestingly, the final catalytic product is strongly dependent on the nature of the hydrogen donor source. The yield of nitrobenzene reduction to aniline increased from 20% to an almost quantitative yield over a range of alcohols, diols and aminoalcohols. In glycerol at 130 °C aniline was isolated in 93% yield. In ethanolamine, the reaction was conveniently performed at a lower temperature (55 °C) and gave selectively substituted azobenzene (92% yield). Experimental studies provide support for a reaction pathway in which the Cu(0) NPs catalysed transfer hydrogenation of nitrobenzene to aniline proceeds via the condensation route. The high chemoselectivity of both protocols has been proved in experiments on a panel of variously substituted nitroarenes. Enabling technologies, microwaves and ultrasound, used both separately and in combination, have successfully increased the reaction rate and reaction yield.magnified image

Mechanochemically promoted reduction of nitro and azido derivatives may be successfully performed in stainless steel jars without catalyst addition.