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Polyurethanes are synthesized on industrial scale by the reaction of diisocyanates with diols in the presence of catalysts which are commonly based on tin complexes and amines. However, due to the toxicity and volatility of these tin catalysts and amines, there is the need to develop new catalysts that are more environmentally benign. Herein, we report the synthesis of O^N^O pincer‐ligated Mn(III) and Fe(III) complexes that serve as suitable catalysts for urethane formation and are stable to hydrolysis as predicted by computations and observed experimentally. The O^N^O pincer scaffold is vital to the activity of these catalysts, simultaneously ensuring increased solubility in the reaction medium as well as providing a stable framework upon dissociation of co‐ligands in the catalytic cycle. In silico mechanistic investigations for urethane formation show that the stabilization of active species in square‐planar geometries enabled by these O^N^O ligands permit the simultaneous coordination of alcohol and isocyanate in suitable configuration at the metal center. [ABSTRACT FROM AUTHOR]

Chemical recycling, in particular hydrogenative depolymerization, offers a promising way to utilize plastic waste. This report covers the manganese‐catalyzed hydrogenation of polyurethane materials to the corresponding monomeric units. The key to success is a Mn pincer complex as a potent hydrogenation catalyst in combination with elevated temperatures (up to 200 °C) and appropriate solvents to ensure sufficient solubility of the polymers. A wide range of polyurethane samples of varying polyol and isocyanate compositions, some of which feature significant amounts of urea functionalities, are depolymerized, releasing polyetherols and diaminotoluene (TDA) in yields of up to 89 % and 76 %, respectively. [ABSTRACT FROM AUTHOR]

The hydrogenation of (+)‐Sclareolide to (−)‐ambradiol catalyzed by a manganese pincer complex is reported. The hydrogenation reaction is performed with an air‐ and moisture‐stable manganese catalyst and proceeds under relatively mild reaction conditions at low manganese and base loadings. A range of other esters could be successfully hydrogenated leading to the corresponding alcohols in good to quantitative yields using this easy‐to‐make catalyst. A scale‐up experiment was performed leading to 99.3 % of the isolated yield of (−)‐Ambradiol. [ABSTRACT FROM AUTHOR]

The Suzuki–Miyaura coupling reaction of electron-poor aryl chlorides in the synthesis of crop protection-relevant active ingredients in water is disclosed. Optimisation of the reaction conditions allowed running the reaction with 50 ppm of Pd-catalyst loading without an additional organic solvent in the cross-coupling reaction step in short reaction times. The system was optimised for the initial cross-coupling step of the large scale produced fungicides Boscalid, Fluxapyroxad and Bixafen up to 97% yield. It is also shown that the Suzuki–Miyaura reaction can be easily scaled up to 50 g using a simple product separation and purification using environmentally benign solvents in the work-up. To show the usability of this method, it was additionally applied in the three-step synthesis of the desired active ingredients. [ABSTRACT FROM AUTHOR]

Chemical recycling provides a promising solution to utilize plastic waste. Here, a catalytic hydrogenative depolymerization of polyamide 66 (PA 66) and polyurethane (PU) was developed. The system employed Ru pincer complexes at high temperature (200 °C) in THF solution, and even technical‐grade polymers could be hydrogenated with satisfactory yields under these conditions. A comparison of the system with some known heterogeneous catalysts as well as catalyst poisoning tests supported the homogeneity of the system. These results demonstrate the potential of chemical recycling to regain building blocks for polymers and will be interesting for the further development of polymer hydrogenation. [ABSTRACT FROM AUTHOR]

The direct access to dimethoxymethane (DMM) from CO2/H2 in MeOH is an attractive approach, but more active, selective, and robust catalyst systems are still desirable for an application of this system. Herein, we present the performance enhancing effect of additives on ruthenium-triphos catalyst systems for CO2 hydrogenation to DMM. In the presence of PPh3, functioning as both additional ligand and precursor for Lewis-acidic phosphonium salts, increased turnover numbers for DMM are achieved. Moreover, PPh3 significantly diminishes catalyst degradation via carbonylation to cationic [RuH(CO)2(triphos)]OTf, which remains an active species in the synthesis of DMM. Catalyst recycling over up to five runs with minimal loss in catalyst performance underlines the robustness of the system. Both, the recyclability of the system and the suppression of catalyst deactivation pathways encourage for application in sustainable continuous processes. [ABSTRACT FROM AUTHOR]

The direct conversion of ketones into chiral primary amines is a key transformation in chemistry. Here, we present a ruthenium catalyzed asymmetric reductive amination (ARA) of purely aliphatic ketones with good yields and moderate enantioselectivity: up to 99 % yield and 74 % ee. The strategy involves [Ru(PPh3)3H(CO)Cl] in combination with the ligand (S,S)‐f‐binaphane as the catalyst, NH4I as the amine source and H2 as the reductant. This is a straightforward and user‐friendly process to access industrially relevant chiral aliphatic primary amines. Although the enantioselectivity with this approach is only moderate, to the extent of our knowledge, the maximum ee of 74 % achieved with this system is the highest reported till now apart from enzyme catalysis for the direct transformation of ketones into chiral aliphatic primary amines. [ABSTRACT FROM AUTHOR]

Abstract: In this study, known homogeneous and heterogeneous chromium(VI) catalyst systems were investigated with respect to the favored formation of cyclohexanone during the decomposition of cyclohexyl hydroperoxide (CHHP). The focus was on mechanistic studies using different spectroscopic methods as well as DFT calculations to further optimize the reaction conditions. As in previous decomposition studies, a mechanism via the formation of a metal alkylperoxido intermediate is probable. In situ spectroscopic studies revealed that in case of both the soluble and insoluble catalyst, the selective decomposition happens via a non‐radical, non‐redox mechanism at the CrVI stage through the formation of a cyclohexylperoxychromium(VI) complex. The proposed mechanism is supported by thorough DFT calculations. [ABSTRACT FROM AUTHOR]

A commentary on a study which developed a single-step catalyst system for the double carbonylation of butadiene to adipic acid esters with high activity and selectivity, is presented. Topics covered include the consecutive and nonselective carbonylations needed to achieve the desired adipic acid without the nitrous oxide, other alternative approaches for the double functionalization of butadiene to adipic acid and yields and selectivity for the butyl-ester of adipic acid.