Hydrogenations constitute fundamental processes in organic chemistry and allow for atom-efficient and clean functional group transformations. In fact, the selective reduction of nitriles, ketones, and aldehydes with molecular hydrogen permits access to a green synthesis of valuable amines and alcohols. Despite more than a century of developments in homogeneous and heterogeneous catalysis, efforts toward the creation of new useful and broadly applicable catalyst systems are ongoing. Recently, Earth-abundant metals have attracted significant interest in this area. In the present study, we describe for the first time specific molecular-defined manganese complexes that allow for the hydrogenation of various polar functional groups. Under optimal conditions, we achieve good functional group tolerance, and industrially important substrates, e.g., for the flavor and fragrance industry, are selectively reduced.
An important goal for nanocatalysis is the development of flexible and efficient methods for preparing active and stable core-shell catalysts. In this respect, we present the synthesis and characterization of iron oxides surrounded by nitrogen-doped-graphene shells immobilized on carbon support (labeled FeOx@NGr-C). Active catalytic materials are obtained in a simple, scalable and two-step method via pyrolysis of iron acetate and phenanthroline and subsequent selective leaching. The optimized FeOx@NGr-C catalyst showed high activity in oxidative dehydrogenations of several N-heterocycles. The utility of this benign methodology is demonstrated by the synthesis of pharmaceutically relevant quinolines. In addition, mechanistic studies prove that the reaction progresses via superoxide radical anions (·O2(-)).
Selective hydrogenations of (hetero)arenes represent essential processes in the chemical industry, especially for the production of polymer intermediates and a multitude of fine chemicals. Herein, we describe a new type of well-dispersed Ru nanoparticles supported on a nitrogen-doped carbon material obtained from ruthenium chloride and dicyanamide in a facile and scalable method. These novel catalysts are stable and display both excellent activity and selectivity in the hydrogenation of aromatic ethers, phenols as well as other functionalized substrates to the corresponding alicyclic reaction products. Furthermore, reduction of the aromatic core is preferred over hydrogenolysis of the C–O bond in the case of ether substrates. The selective hydrogenation of biomass-derived arenes, such as lignin building blocks, plays a pivotal role in the exploitation of novel sustainable feedstocks for chemical production and represents a notoriously difficult transformation up to now.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.