Chemical record最新文献

Pyrrole-embedded organic molecules received a considerable importance due to their numerous biological and material applications. Hence, several synthetic strategies have been devised for the construction of diverse pyrrole analogues over the years. Among these, the Clauson-Kaas reaction is one of the most widely used protocols for the synthesis of various N-substituted pyrroles. This review briefly describes the Clauson-Kaas reaction along with modifications and a detailed account on its applications in the various sectors of organic synthesis.

8-Methylquinoline is regarded as an ideal substrate to participate in diversely C(sp³)-H functionalization reactions. The presence of the chelating nitrogen atom enables 8-methylquinoline to easily form cyclometallated complexes with various transition metals, leading to the selective synthesis of functionalized quinolines. Considering the great importance of quinoline cores in medicinal chemistry, in this review article, we have covered the publications related to the C-H activation and functionalization of 8-methylquinoline under transition metal catalysis during the last decade.

Cadmium sulfide (CdS) based heterojunctions, including type-II, Z-scheme, and S-scheme systems emerged as promising materials for augmenting photocatalytic hydrogen (H₂) generation from water splitting. This review offers an exclusive highlight of their fundamental principles, synthesis routes, charge transfer mechanisms, and performance properties in improving H₂ production. We overview the crucial roles of Type-II heterojunctions in enhancing charge separation, Z-scheme heterojunctions in promoting redox potentials to reduce electron-hole (e^-/h⁺) pairs recombination, and S-scheme heterojunctions in combining the merits of both type-II and Z-scheme frameworks to obtain highly efficient H₂ production. The importance of this review is demonstrated by its thorough comparison of these three configurations, presenting valuable insights into their special contributions and capability for augmenting photocatalytic H₂ activity. Additionally, key challenges and prospects in the practical applications of CdS-based heterojunctions are addressed, which provides a comprehensive route for emerging research in achieving sustainable energy goals.

As a significant variant of the Michael reaction, the 1,6-addition reaction has undergone considerable development over the past decade. This effective strategy enables the synthesis of a variety of novel and potentially bioactive functional molecules. In this review, we summarize the recent progress in NHC-catalyzed 1,6-addition reactions, highlighting their efficiency in the rapid synthesis of complex functional molecules. We also provide our perspectives on the future development of this dynamic and highly active research area.

Silicon, due to its abundance, non-toxicity, and cost-effectiveness, is a critical element in the earth's crust with significant industrial applications. In organic chemistry, main group elements, and in particular silicon, are extensively utilized as versatile synthetic intermediates. Despite the current challenges associated with harsh reaction conditions and unsustainable practices in synthesizing crucial organic structural molecules, desilylation reactions have emerged as a facilitative method, offering milder conditions and operational simplicity. This review provides a comprehensive analysis of recent advancements in the synthesis of valuable organic molecules through two distinct desilylation reactions. It systematically presents the synthesis of a variety of derivatives, such as furan, alcohol, N-heterocyclic, and ketone, highlighting the broad substrate tolerance of these reactions. This broad functional group compatibility suggests a promising future for the synthesis of a wide range of bioactive molecules, underscoring the significant potential of desilylation in contemporary organic synthesis.

This report outlines the evolution and recent progress about the different protocols to synthesize the N-heterocycles fused hybrids, specifically [1,2,3]triazolo[1,5-a]quinoline. This review encompasses a broad range of approaches, describing several reactions for obtaining this since, such as dehydrogenative cyclization, oxidative N-N coupling, Dieckmann condensation, intramolecular Heck, (3+2)-cycloaddition, Ullman-type coupling and direct intramolecular arylation reactions. We divided this review in three section based in the starting materials to synthesize the target [1,2,3]triazolo[1,5-a]quinolines. Starting materials containing quinoline or triazole units previously formed, as well as starting materials which both quinoline and triazole units are formed in situ. Different methods of obtaining are described, such as metal-free or catalyzed conditions, azide-free, using conventional heating or alternative energy sources, such as electrochemical and photochemical methods. Mechanistic insights underlying the reported reactions were also described in this comprehensive review.

Restructuring the current energy industry towards sustainability requires transitioning from carbon based to renewable energy sources, reducing CO₂ emissions. Hydrogen, is considered a significant clean energy carrier. However, it faces challenges in transportation and storage due to its high reactivity, flammability, and low density under ambient conditions. Liquid organic hydrogen carriers offer a solution for storing hydrogen because they allow for the economical and practical storage of organic compounds in regular vessels through hydrogenation and dehydrogenation. This review evaluates several hydrogen technologies aimed at addressing the challenges associated with hydrogen transportation and its economic viablity. The discussion delves into exploring the catalysts and their activity in the context of catalysts' development. This review highlights the pivotal role of various catalyst materials in enhancing the hydrogenation and dehydrogenation activities of multiple LOHC systems, including benzene/cyclohexane, toluene/methylcyclohexane (MCH), N-ethylcarbazole (NEC)/dodecahydro-N-ethylcarbazole (H12-NEC), and dibenzyltoluene (DBT)/perhydrodibenzyltoluene (H18-DBT). By exploring the catalytic properties of noble metals, transition metals, and multimetallic catalysts, the review provides valuable insights into their design and optimization. Also, the discussion revolved around the implementation of a hydrogen economy on a global scale, with a particular focus on the plans pertaining to Saudi Arabia and the GCC (Gulf Cooperation Council) countries. The review lays out the challenges this technology will face, including the need to increase its H₂ capacity, reduce energy consumption by providing solutions, and guarantee the thermal stability of the materials.

Proton exchange membrane fuel cells (PEMFCs) have proven to be a promising power source for various applications ranging from portable devices to automotive and stationary power systems. The production of PEMFC involves numerous stages in the value chain, with each stage presenting unique challenges and opportunities to improve the overall performance and durability of the PEMFC stack. These include steps such as manufacturing the key components such as the platinum-based catalyst, processing these components into the membrane electrode assemblies (MEAs), and stacking the MEAs to ultimately produce a PEMFC stack. However, it is also known that the break-in or conditioning phase of the stack plays a crucial role in the final performance as well as durability. It involves several key phenomena such as hydration of the membrane, swelling of the ionomer, redistribution of the catalyst and the creation of suitable electrochemical interfaces – establishment of the triple phase boundary. These improve the proton conductivity, the mass transport of reactants and products, the catalytic activity of the electrode and thus the overall efficiency of the FC. The cruciality of break-in is demonstrated by the improvement in performance, which can even be over 50 % compared to the initial state. The state-of-the-art approach for the break-in of MEAs involves an electrochemical protocol, such as voltage cycling, using a PEMFC testing station. This method is time-consuming, equipment-intensive, and costly. Therefore, new, elegant, and cost-effective solutions are needed. Nevertheless, the primary aim is to achieve maximum/optimal performance so that it is fully operational and ready for the market. It is therefore essential to better understand and deconvolute these complex mechanisms taking place during break-in/conditioning. Strategies include controlled humidity and temperature cycling, novel electrode materials and other advanced break-in methods such as air braking, vacuum activation or steaming. In addition, it is critical to address the challenges associated with standardisation and quantification of protocols to enable interlaboratory comparisons to further advance the field.

The cover picture shows the structure of some three-dimensional small molecular entities, such as highly-functionalized cyclopentanes and saturated azaheterocycles with multiple chiral centers, derived by chemical manipulations of Vince lactam. More details can be found in article number e2024000070 by Melinda Nonn, Santos Fustero, and Loránd Kiss. (DOl: 10.1002/tcr.202400070.