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Furanic di-carboxylate derivatives of 5-Hydroxymethylfurfural (HMF) are nowadays important in the polymer industry as they are used as building blocks for bio-based polyesters. The high reactivity of HMF compels to avoid harsh synthetic conditions. Therefore, developing mild catalytic processes for its selective oxidation is a challenging task. Herein, we report the first oxidative esterification of HMF to dimethyl furan-2,5-dicarboxylate (FDCM) under flow conditions using oxygen as oxidant. For that purpose, a new series of nitrogen-doped carbon-supported bimetallic Co/Ru heterogeneous catalysts were prepared and characterized by XRD, XPS and N2 physisorption. These analyses revealed that the porosity of the materials and order of impregnation of the metals to the carbon supports lead to varying catalytic activities. Under optimized conditions the flow reactor showed a 15-fold increase on the production of FDCM compared to batch conditions. �� 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

The development of strategies for the sustainable management and valorization of agricultural waste is of outmost importance. With this in mind, we report the use of rice husk (RH) as feedstock for the preparation of heterogeneous catalysts for hydrogenation reactions. The catalysts were prepared by impregnating the milled RH with a silver nitrate solution followed by carbothermal reduction. The composition and morphology of the prepared catalysts were fully assessed by IR, AAS, ICP-MS, XPS, XRD and STEM techniques. This novel bio-genic silver-based catalysts showed excellent activity and remarkable selectivity in the hydrogenation of nitro groups in both aromatic and aliphatic substrates, even in the presence of reactive functionalities like halogens, carbonyls, borate esters or nitriles. Recycling experiments showed that the catalysts can be easily recovered and reused multiple times without significant drop in performance and without requiring re-activation. © 2021 The Authors. ChemCatChem published by Wiley-VCH GmbH

Herein we report the synthesis of isotactically enriched poly(cyclohexene carbonate) (PCHC) by the bulk alternating copolymerization of meso-cyclohexene oxide and carbon dioxide using dialkylmagnesium compounds as catalyst. These simple achiral catalysts showed good activity for the isoselective copolymerization, with high yield and high carbonate-linkage contents, in a controlled manner under mild conditions and atmospheric CO2 pressure. The triad sequences in the 13C NMR spectra of these polymers were assigned using Bernoullian statistical methods in order to determine the tacticity of the copolymer. Differential scanning calorimetry analysis confirmed the formation of highly isotactic polycarbonate. Furthermore, kinetic studies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry investigations allowed us to shed light on the reaction mechanism of the polymerization process.

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.

A series of heteroleptic copper photosensitizers [(P _ P)Cu(N _ N(SO3Na)2)] + containing sulfonate anchor groups is described. In the presence of titanium dioxide they form composites, which are active photosensitizers in the light driven reduction of protons. Further stabilization of these systems is achieved by encapsulation within a plasma-polymerized allylamine (PPAAm) layer. The resulting PPAAm-CuPS-TiO2-composites exhibit a strong absorption in the visible region of the light. Photocatalytic hydrogen production is performed by using only nonnoble metals. In the presence of an iron reduction catalyst a maximum turnover number of 2452 is obtained.

We have prepared a series of new rhenium complexes containing chiral ferrocenyldiphosphane ligands of the Josiphos family, starting from commercially available rhenium sources. These new ReV oxido and nitrido complexes, several of which have been characterized by X-ray crystallography, are air- and moisture-stable and are active catalysts in the asymmetric transfer hydrogenation of ketones using 2-propanol as the hydrogen source in the presence of substoichiometric amounts of triethylamine (TEA). The reaction proceeds cleanly with good to excellent yields (50–99 %) but with moderate enantioselectivity (up to 58 % ee). A mechanism not involving hydridic species is proposed.

The paramagnetic Re(III) complex [ReCl3(Pigiphos)] (1) ((R)-(S)-Pigiphos = bis{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine) is accessible from [ReCl3(NCMe)(PPh3)2] and the ligand Pigiphos. 1 reacts with an excess of NaBH4, affording the polyhydride complex [ReH5(Pigiphos)] (2), which was shown to be a classic polyhydride (NMR T1(min) = 158 ms). This complex reacts readily with both Bronsted acids and hydride scavengers to give the corresponding cationic tetrahydride species, which was shown to be active in the catalytic hydrogenation of dimethyl itaconate.

New polynuclear zinc complexes containing tridentate Schiff base ligands were successfully synthesized and fully characterized. The solid-state structure of the complexes was determined using single crystal X-ray diffraction. The complexes display a tetranuclear cubane-like core structure [Zn4O4] and sowed good catalytic activity towards the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ɛ-caprolactone (ɛ-CL) under solvent-free conditions. The polylactic acid (PLA) obtained from rac-LA showed isotactic enrichment, as proved by homonuclear decoupled 1H NMR analysis. These complexes also showed good activity and superior control towards the ROP of rac-LA and ɛ-CL in the presence of benzyl alcohol as a co-initiator. Furthermore, Kinetic studies demonstrated that the ROP of rac-LA and ɛ-CL has a first order dependence on both monomer (rac-LA and ɛ-CL) and catalyst concentration. This article is protected by copyright. All rights reserved.