Energy production and storage technologies have attracted a great deal of attention for day-to-day applications. In recent decades, advances in lithium-ion battery (LIB) technology have improved living conditions around the globe. LIBs are used in most mobile electronic devices as well as in zero-emission electronic vehicles. However, there are increasing concerns regarding load leveling of renewable energy sources and the smart grid as well as the sustainability of lithium sources due to their limited availability and consequent expected price increase. Therefore, whether LIBs alone can satisfy the rising demand for small- and/or mid-to-large-format energy storage applications remains unclear. To mitigate these issues, recent research has focused on alternative energy storage systems. Sodium-ion batteries (SIBs) are considered as the best candidate power sources because sodium is widely available and exhibits similar chemistry to that of LIBs; therefore, SIBs are promising next-generation alternatives. Recently, sodiated layer transition metal oxides, phosphates and organic compounds have been introduced as cathode materials for SIBs. Simultaneously, recent developments have been facilitated by the use of select carbonaceous materials, transition metal oxides (or sulfides), and intermetallic and organic compounds as anodes for SIBs. Apart from electrode materials, suitable electrolytes, additives, and binders are equally important for the development of practical SIBs. Despite developments in electrode materials and other components, there remain several challenges, including cell design and electrode balancing, in the application of sodium ion cells. In this article, we summarize and discuss current research on materials and propose future directions for SIBs. This will provide important insights into scientific and practical issues in the development of SIBs.

/pdf/sodium-ion-batteries-present-and-future-gf1bd0vhq4.pdf

Sodium-ion batteries: present and future

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

Functionalizing traditionally inert carbon–hydrogen bonds represents a powerful transformation in organic synthesis, providing new entries to valuable structural motifs and improving the overall synthetic efficiency. C–H bond activation, however, often necessitates harsh reaction conditions that result in functional group incompatibilities and limited substrate scope. An understanding of the reaction mechanism and rational design of experimental conditions have led to significant improvement in both selectivity and applicability. This critical review summarizes and discusses endeavours towards the development of mild C–H activation methods and wishes to trigger more research towards this goal. In addition, we examine select examples in complex natural product synthesis to demonstrate the synthetic utility of mild C–H functionalization (84 references).

Towards mild metal-catalyzed C–H bond activation

2.5. Stabilization of IL Emulsions by Nanoparticles 2623 3. Hydrogenations in ILs 2623 3.1. Hydrogenation on IL-Stabilized Nanoparticles 2623 3.1.1. Hydrogenation of 1,3-Butadiene 2623 3.1.2. Hydrogenation of Alkenes and Arenes 2624 3.1.3. Hydrogenation of Ketones 2624 3.2. Homogeneous Catalytic Hydrogenation in ILs 2624 3.3. Hydrogenation of Functionalized ILs 2625 3.3.1. Selective Hydrogenation of Polymers 2625 3.4. Asymmetric Hydrogenations 2626 3.4.1. Enantioselective Hydrogenation 2626 3.5. Role of the ILs Purity in Hydrogenation Reactions 2628

Catalysis in ionic liquids

The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.1,2 Among all asymmetric catalytic methods, asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines, have become one of the most efficient methods for constructing chiral compounds.3 The development of homogeneous asymmetric hydrogenation was initiated by Knowles4a and Horner4b in the late 1960s, after the discovery of Wilkinson’s homogeneous hydrogenation catalyst [RhCl(PPh3)3]. By replacing triphenylphosphine of the Wilkinson’s catalystwithresolvedchiralmonophosphines,6Knowles and Horner reported the earliest examples of enantioselective hydrogenation, albeit with poor enantioselectivity. Further exploration by Knowles with an improved monophosphine CAMP provided 88% ee in hydrogenation of dehydroamino acids.7 Later, two breakthroughs were made in asymmetric hydrogenation by Kagan and Knowles, respectively. Kagan reported the first bisphosphine ligand, DIOP, for Rhcatalyzed asymmetric hydrogenation.8 The successful application of DIOP resulted in several significant directions for ligand design in asymmetric hydrogenation. Chelating bisphosphorus ligands could lead to superior enantioselectivity compared to monodentate phosphines. Additionally, P-chiral phosphorus ligands were not necessary for achieving high enantioselectivity, and ligands with backbone chirality could also provide excellent ee’s in asymmetric hydrogenation. Furthermore, C2 symmetry was an important structural feature for developing new efficient chiral ligands. Kagan’s seminal work immediately led to the rapid development of chiral bisphosphorus ligands. Knowles made his significant discovery of a C2-symmetric chelating bisphosphine ligand, DIPAMP.9 Due to its high catalytic efficiency in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids, DIPAMP was quickly employed in the industrial production of L-DOPA.10 The success of practical synthesis of L-DOPA via asymmetric hydrogenation constituted a milestone work and for this work Knowles was awarded the Nobel Prize in 2001.3k This work has enlightened chemists to realize * Corresponding author. 3029 Chem. Rev. 2003, 103, 3029−3069

New Chiral Phosphorus Ligands for Enantioselective Hydrogenation

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201510990

Cover Picture: Structurally Defined Molecular Hypervalent Iodine Catalysts for Intermolecular Enantioselective Reactions (Angew. Chem. Int. Ed. 1/2016)

Asymmetric hydrogenation of acetophenone with trans-RuH(η1-BH4)[(S)-tolbinap][(S,S)-dpen] (TolBINAP = 2,2‘-bis(di-4-tolylphosphino)-1,1‘-binaphthyl; DPEN = 1,2-diphenylethylenediamine) in 2-propanol gives (R)-phenylethanol in 82% ee. The reaction proceeds smoothly even at an atmospheric pressure of H2 at room temperature and is further accelerated by addition of an alkaline base or a strong organic base. Most importantly, the hydrogenation rate is initially increased to a great extent with an increase in base molarity but subsequently decreases. Without a base, the rate is independent of H2 pressure in the range of 1−16 atm, while in the presence of a base, the reaction is accelerated with increasing H2 pressure. The extent of enantioselection is unaffected by hydrogen pressure, the presence or absence of base, the kind of base and coexisting metallic or organic cations, the nature of the solvent, or the substrate concentrations. The reaction with H2/(CH3)2CHOH proceeds 50 times faster than that with D2/(...

Mechanism of Asymmetric hydrogenation of ketones catalyzed by BINAP/1,2-diamine-ruthenium(II) complexes

Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd(0)/Pd(II) cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)-promoted reactions at a given point of the catalytic cycle by selective metal oxidation. The resulting higher-oxidation-state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher oxidation state is of significant synthetic potential.

High‐Oxidation‐State Palladium Catalysis: New Reactivity for Organic Synthesis

Palladium catalysis for the intramolecular amination of alkenes is a powerful approach in heterocycle synthesis. The initial common step in this approach consists of an aminopalladation reaction. This tutorial review describes the synthesis of 2-amino alkyl–palladium compounds and renders special attention on the subsequent manipulation of the alkyl-palladium group. By carefully choosing the appropriate conditions, a wide variety of different heterocyclic structures are accessible which arise from reactions such as hydroamination, aza-Heck coupling, aminocarbonylation or oxidative processes such as aza-Wacker reaction and 1,2-difunctionalisation.

Intramolecular aminopalladation of alkenes as a key step to pyrrolidines and related heterocycles

Intramolecular diamination reactions are described which yield cyclic ureas as direct products of an oxidative alkene transformation in the presence of palladium acetate and iodosobenzene diacetate as terminal oxidant. The reaction is truly catalytic in metal catalyst and represents the proof of principle for this elusive type of alkene oxidation.

Kilian Muñiz

Papers

Cover Picture: Structurally Defined Molecular Hypervalent Iodine Catalysts for Intermolecular Enantioselective Reactions (Angew. Chem. Int. Ed. 1/2016)

Mechanism of Asymmetric hydrogenation of ketones catalyzed by BINAP/1,2-diamine-ruthenium(II) complexes

High‐Oxidation‐State Palladium Catalysis: New Reactivity for Organic Synthesis

Intramolecular aminopalladation of alkenes as a key step to pyrrolidines and related heterocycles

Palladium(II)-catalyzed intramolecular diamination of unfunctionalized alkenes.