Transition Metal-Free Intermolecular alpha-C-H Amination of Ethers at Room Temperature

We describe a new method for the intermolecular amination of the alpha-C-H bonds of ethers. A hypervalent iodine reagent was used as oxidant to enable the amination of cyclic and acyclic alkyl ethers with a wide range of amides, imides, and amines. The amination occurred at room temperature and without a transition metal catalyst. The method could be used to synthesize the anti-cancer prodrug Tegafur and its analogues

Synthesis and Reactivity of Mononuclear Iron Models of [Fe]-Hydrogenase that Contain an Acylmethylpyridinol Ligand

[Fe]-hydrogenase has a single iron-containing active site that features an acylmethylpyridinol ligand. This unique ligand environment had yet to be reproduced in synthetic models; however the synthesis and reactivity of a new class of small molecule mimics of [Fe]-hydrogenase in which a mono-iron center is ligated by an acylmethylpyridinol ligand has now been achieved. Key to the preparation of these model compounds is the successful C[BOND]O cleavage of an alkyl ether moiety to form the desired pyridinol ligand. Reaction of solvated complex [(2-CH2CO-6-HOC5H3N)Fe(CO)2(CH3CN)2]+(BF4)− with thiols or thiophenols in the presence of NEt3 yielded 5-coordinate iron thiolate complexes. Further derivation produced complexes [(2-CH2CO-6-HOC5H3N)Fe(CO)2(SCH2CH2OH)] and [(2-CH2CO-6-HOC5H3N)Fe(CO)2(CH3COO)], which can be regarded as models of FeGP cofactors of [Fe]-hydrogenase extracted by 2-mercaptoethanol and acetic acid, respectively. When the derivative complexes were treated with HBF4⋅Et2O, the solvated complex was regenerated by protonation of the thiolate ligands. The reactivity of several models with CO, isocyanide, cyanide, and H2 was also investigated

Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO2 reduction

Reduction of CO2 by electrochemical and photoelectrochemical methods to produce carbon-rich fuels is a heavily pursued research theme. Most of the current efforts are focused on the development of transition-metal-based catalysts. In this tutorial review, we present an overview of the development of organic molecules as mediators and catalysts for CO2 reduction. Four classes of organic molecules are discussed: tetraalkylammonium salts, aromatic esters and nitriles, ionic liquids, and pyridinium derivatives. It is shown that reactions mediated or catalyzed by these organic molecules can be competitive compared to their metal-catalyzed counterparts, both in terms of product selectivity and energy efficiency

Electronic Elements Governing the Binding of Small Molecules to a [Fe]-hydrogenase Mimic

[Fe]-hydrogenase, one of three types of hydrogenases, activates molecular hydrogen. Here, using DFT computations, we examine the electronic elements governing the binding of small ligands to a recently synthesized [Fe]-hydrogenase biomimic. Computed reaction free energies indicate that anionic species, such as CN- and H-, and acceptors, such as CO, bind favourably with the Fe centre. Ligands such as H2O, CH3CN, and H-2, however, do not bind iron. Protonation of an adjacent thiolate ligand on the mimic significantly increases the energies of ligand binding. Additional computational analysis reveals that the degree of electron donation from the ligand to the mimic correlates strongly with overall binding ability. The results give insights into the electronic elements of iron-small-molecule interaction in these model complexes

Recent developments of molybdenum and tungsten sulfides as hydrogen evolution catalysts

Recent work shows that nanoparticulate and amorphous molybdenum and tungsten sulfide materials are active catalysts for hydrogen evolution in aqueous solution. These materials hold promise for applications in clean hydrogen production technologies. In this perspective, the syntheses, structures and catalytic activities of nanoparticulate MoS2 and WS2, incomplete cubane-type [Mo3S4]4+ and amorphous MoSx films are summarized, compared, and discussed

Room temperature C(sp(2))-H oxidative chlorination via photoredox catalysis

Photoredox catalysis has been developed to achieve oxidative C-H chlorination of aromatic compounds using NaCl as the chlorine source and Na2S2O8 as the oxidant. The reactions occur at room temperature and exhibit exclusive selectivity for C(sp(2))-H bonds over C(sp(3))-H bonds. The method has been used for the chlorination of a diverse set of substrates, including the expedited synthesis of key intermediates to bioactive compounds and a drug

Mechanistic Insights into Nickamine-catalyzed Alkyl-Alkyl Cross-coupling Reactions

Within the last decades the transition metal-catalyzed cross-coupling of non-activated alkyl halides has significantly progressed. Within the context of alkyl-alkyl cross-coupling, first row transition metals spanning from iron, over cobalt, nickel, to copper have been successfully applied to catalyze this difficult reaction. The mechanistic understanding of these reactions is still in its infancy. Herein we outline our latest mechanistic studies that explain the efficiency of nickel, in particular nickamine-catalyzed alkyl-alkyl cross-coupling reactions

Anion Exchange Membranes for Hydrogen Technologies: Challenges and Progress

Anion exchange membrane fuel cells (AEMFCs) are considered one of the most promising and efficient hydrogen conversion technologies due to their ability to use cost-effective materials. However, AEMFCs are still in the early stage of development and the lack of suitable anion exchange membranes (AEMs) is one major obstacle. In this review, we highlight three major challenges in AEMs development and discuss recent scientific advancements that address these challenges. We identify current trends and provide a perspective on future development of AEMs

Molybdenum boride and carbide catalyze hydrogen evolution in both acidic and basic solutions

Molybdenum boride (MoB) and carbide (Mo2C) are excellent catalysts for electrochemical hydrogen evolution at both pH 0 and pH 14