Synthesis Strategies towards Tagged Homogeneous Catalysts To Improve Their Separation

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

Cobalt-Catalyzed Asymmetric Hydrogenation: Substrate Specificity and Mechanistic Variability

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area.

Highly Enantioselective Synthesis of Pharmaceuticals at Chiral-Encoded Metal Surfaces

Enantioselective catalysis is of crucial importance in modern chemistry and pharmaceutical science. Although various concepts have been used for the development of enantioselective catalysts to obtain highly pure chiral compounds, most of them are based on homogeneous catalytic systems. Recently, we successfully developed nanostructured metal layers imprinted with chiral information, which were applied as electrocatalysts for the enantioselective synthesis of chiral model compounds. However, so far such materials have not been employed as heterogeneous catalysts for the enantioselective synthesis of real pharmaceutical products. In this contribution, we report the asymmetric synthesis of chiral pharmaceuticals (CPs) with chiral imprinted Pt-Ir surfaces as a simple hydrogenation catalyst. By fine-tuning the experimental parameters, a very high enantioselectivity (up to 95 % enantiomeric excess) with good catalyst stability can be achieved. The designed materials were also successfully used as catalytically active stationary phases for the continuous asymmetric flow synthesis of pharmaceutical compounds. This illustrates the possibility of producing real chiral pharmaceuticals at such nanostructured metal surfaces for the first time.