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Herein, we report an efficient metal-free system for the transfer hydrogenation of esters and carbonates with ammonia borane as hydrogen donor, by-passing the otherwise ubiquitous formation of transesterification side-products.

Rice husk, one of the main side products in the rice production, and its sustainable management represent a challenge in many countries. Herein, we describe the use of this abundant agricultural bio‐waste as feedstock for the preparation of silver‐containing carbon/silica nano composites with antimicrobial properties. The synthesis was performed using a fast and cheap methodology consisting of wet impregnation followed by pyrolysis, yielding C/SiO2 composite materials doped with varying amounts of silver from 28 to 0.001 wt %. The materials were fully characterized and their antimicrobial activity against ESKAPE pathogens, namely E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, and E. coli, and the pathogenic yeast C. albicans was investigated. Sensitivities of these strains against the prepared materials were demonstrated, even with exceptional low amounts of 0.015 m% silver. Hence, we report a straightforward method for the synthesis of antimicrobial agents from abundant sources which addresses urgent questions like bio‐waste valorization and affordable alternatives to increasingly fewer effective antibiotics., Silver nanoparticles supported on carbon/silica composites have been prepared by a simple method from rice husk. These novel materials display very high antimicrobial activity against ESKAPE pathogens (E. faecium, S. aureus, K. pneumoniuae, A. baumannii, P. aeruginosa, and E. coli) as well as C. albicans. It represents a cheap alternative for the valorization of the overabundant rice bio‐waste with potential direct use in filters for water sanitation or in medical applications.

A convenient method for the hydrogenative depolymerization of silicon-modified polyureas was developed using simple transition metal catalysis. The method is considered sustainable, as it uses H2 as a clean reductant and allows for silicon recycling.

This Focus Review describes state-of-the-art methods for the preparation of antimicrobial silicones. Given the diversity of antimicrobial activity and their mechanisms, the performance of these materials is highly dependent on the characteristics of the polymeric matrix. Therefore, different synthetic routes have been developed, such as 1) physical treatments, 2) chemical transformations, and 3) copolymerization. This classification is not exclusive, so some products belong to more than one class. Herein, we attempt to present a handy overview of the development of antimicrobial silicones, their most important application fields, the most relevant antimicrobial assays, and, as the title suggests, an overview of the most relevant preparation methods.

5-Hydroxymethylfurfural (HMF) has become a benchmark chemical as it can be obtained by the processing of renewable biomass, making its downstream modification an important topic both in industry an...

C-H bond functionalization is a well-developed concept that has been thoroughly studied and gives entry to rather complex molecules without the need for previous derivatization of the substrates. The use of copper complexes in allylic C-H bond functionalization under oxidative conditions as an alternative to the well-established palladium-based methodologies remains largely underdeveloped. Here, we show for the first time a selective cross-dehydrogenative coupling reaction between underivatized allylic substrates and terminal alkynes to produce 1,4-enynes in high yields in a single step, using an in situ synthesized copper catalyst and an oxidant.

Silicones and silicone rubbers are omnipresent in household and industrial products such as lubricants, coatings, sealants, insulators, medical devices, etc. This plethora of applications arises from their unparalleled properties including hydrophobicity, low surface energy, chemical inertness, extreme temperature stability, elasticity, and biocompatibility. Even though silicones have been known for more than five decades, their chemistry is still far from fully understood. Industrially, the vast majority of processes for their synthesis, transformation, and use are based on rather well established, alas outdated technologies, which are frequently empirical and poorly investigated. This review attempts to summarize the different approaches for the synthesis of silicone rubbers by vulcanization or curing of silicone polymers, the catalysts used, and the corresponding reaction mechanisms. Apart from the well-known methods (radical, hydrosilylation, and metal-based condensation), novel approaches such as organo- and bio-catalysis are also addressed.

A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway.

Methyltrioxorhenium acts as a catalyst (5 10 Mol ) for the direct electrophilic trifluoromethylation of various aromatic and heteroaromatic compounds using the hypervalent iodine reagent 1 (trifluoromethyl) 12 benziodoxol 3(1H) one (1). The products are formed in up to 77 yield. Mixtures of regioisomers are obtained in the case of substituted and heteroaromatic substrates. The reaction typically carried out in chloroform solvent at 70 degrees C shows a significant induction period. Monitoring by EPR shows the involvement of radical species. A small kinetic deuterium isotope effect of 1.3 is observed for benzene.

The provision of energy has been listed in the “Top Ten of global concerns” as the single most important issue to be faced to improve quality of life and ultimately to stop, or at least to mitigate, the environmental impact of human activities on the planet. [1] One way in which chemistry can be used to provide more sustainable and benign energy technologies is through the development of artificial photosynthesis systems, which allow for the conversion of the energy of sunlight into useful chemical energy by water splitting. [2] The resulting molecular hydrogen constitutes in principle a clean, renewable, and carbon-free energy source. [3]