Redox catalysis in organic electrosynthesis: basic principles and recent developments.
TL;DR: Progress is described in the field of electroorganic synthesis, a process that can be accomplished more efficiently and purposefully using modern computational tools, and summarizes recent advances.
Abstract: Electroorganic synthesis has become an established, useful, and environmentally benign alternative to classic organic synthesis for the oxidation or the reduction of organic compounds. In this context, the use of redox mediators to achieve indirect processes is attaining increased significance, since it offers many advantages compared to a direct electrolysis. Kinetic inhibitions that are associated with the electron transfer at the electrode/electrolyte interface, for example, can be eliminated and higher or totally different selectivity can be achieved. In many cases, a mediated electron transfer can occur against a potential gradient, meaning that lower potentials are needed, reducing the probability of undesired side-reactions. In addition, the use of electron transfer mediators can help to avoid electrode passivation resulting from polymer film formation on the electrode surface. Although the principle of indirect electrolysis was established many years ago, new, exciting and useful developments continue to be made. In recent years, several new types of redox mediators have been designed and examined, a process that can be accomplished more efficiently and purposefully using modern computational tools. New protocols including, the development of double mediatory systems in biphasic media, enantioselective mediation and heterogeneous electrocatalysis using immobilized mediators have been established. Furthermore, the understanding of mediated electron transfer reaction mechanisms has advanced. This review describes progress in the field of electroorganic synthesis and summarizes recent advances.
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TL;DR: This review discusses advances in synthetic organic electrochemistry since 2000 with enabling methods and synthetic applications analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.
Abstract: Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.
1,930 citations
TL;DR: This work critically address both catalyst-free and catalytic radical reactions through the lens of radical chemistry, using basic principles of kinetics and thermodynamics to address problems of initiation, propagation, and inhibition of radical chains.
Abstract: The area of catalysis of radical reactions has recently flourished. Various reaction conditions have been discovered and explained in terms of catalytic cycles. These cycles rarely stand alone as unique paths from substrates to products. Instead, most radical reactions have innate chains which form products without any catalyst. How do we know if a species added in "catalytic amounts" is a catalyst, an initiator, or something else? Herein we critically address both catalyst-free and catalytic radical reactions through the lens of radical chemistry. Basic principles of kinetics and thermodynamics are used to address problems of initiation, propagation, and inhibition of radical chains. The catalysis of radical reactions differs from other areas of catalysis. Whereas efficient innate chain reactions are difficult to catalyze because individual steps are fast, both inefficient chain processes and non-chain processes afford diverse opportunities for catalysis, as illustrated with selected examples.
843 citations
TL;DR: This review examines the advance in relation to the electrochemical construction of heterocyclic compounds published since 2000 via intra- and intermolecular cyclization reactions.
Abstract: The preparation and transformation of heterocyclic structures have always been of great interest in organic chemistry. Electrochemical technique provides a versatile and powerful approach to the assembly of various heterocyclic structures. In this review, we examine the advance in relation to the electrochemical construction of heterocyclic compounds published since 2000 via intra- and intermolecular cyclization reactions.
810 citations
TL;DR: The developments of the last three decades in electrocatalytic CO2 reduction with homogeneous catalysts are reviewed and important catalyst families are discussed in detail with regard to mechanistic aspects, and recent advances in the field are highlighted.
Abstract: The utilization of CO2 via electrochemical reduction constitutes a promising approach toward production of value-added chemicals or fuels using intermittent renewable energy sources. For this purpose, molecular electrocatalysts are frequently studied and the recent progress both in tuning of the catalytic properties and in mechanistic understanding is truly remarkable. While in earlier years research efforts were focused on complexes with rare metal centers such as Re, Ru, and Pd, the focus has recently shifted toward earth-abundant transition metals such as Mn, Fe, Co, and Ni. By application of appropriate ligands, these metals have been rendered more than competitive for CO2 reduction compared to the heavier homologues. In addition, the important roles of the second and outer coordination spheres in the catalytic processes have become apparent, and metal–ligand cooperativity has recently become a well-established tool for further tuning of the catalytic behavior. Surprising advances have also been made ...
733 citations
TL;DR: In this Outlook, illustrative examples of electrochemical reactions in the context of the synthesis of complex molecules are highlighted, showcasing the intrinsic benefits of electro chemical reactions versus traditional reagent-based approaches.
Abstract: While preparative electrolysis of organic molecules has been an active area of research over the past century, modern synthetic chemists have generally been reluctant to adopt this technology. In fact, electrochemical methods possess many benefits over traditional reagent-based transformations, such as high functional group tolerance, mild conditions, and innate scalability and sustainability. In this Outlook we highlight illustrative examples of electrochemical reactions in the context of the synthesis of complex molecules, showcasing the intrinsic benefits of electrochemical reactions versus traditional reagent-based approaches. Our hope is that this field will soon see widespread adoption in the synthetic community.
674 citations
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TL;DR: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency as mentioned in this paper, and many DSC research groups have been established around the world.
Abstract: Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...
8,707 citations
TL;DR: The phytochemical properties of Lithium Hexafluoroarsenate and its Derivatives are as follows: 2.2.1.
Abstract: 2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313
5,710 citations
TL;DR: In this article, the rate constants of 60 typical electron donor-acceptor systems have been measured in de-oxygenated acetonitrile and are shown to be correlated with the free enthalpy change, ΔG23, involved in the actual electron transfer process.
Abstract: Fluorescence quenching rate constants, kq, ranging from 106 to 2 × 1010 M−1 sec−1, of more than 60 typical electron donor-acceptor systems have been measured in de-oxygenated acetonitrile and are shown to be correlated with the free enthalpy change, ΔG23, involved in the actual electron transfer process
in the encounter complex and varying between + 5 and −60 kcal/mole. The correlation which is based on the mechanism of adiabatic outer-sphere electron transfer requires ΔG≠23, the activation free enthalpy of this process to be a monotonous function of ΔG23 and allows the calculation of rate constants of electron transfer quenching from spectroscopic and electrochemical data.
A detailed study of some systems where the calculated quenching constants differ from the experimental ones by several orders of magnitude revealed that the quenching mechanism operative in these cases was hydrogen-atom rather than electron transfer.
The conditions under which these different mechanisms apply and their consequences are discussed.
3,485 citations
Book•
30 Oct 2006
TL;DR: The role of protection groups in organic synthesis is discussed in this paper, where the authors present several general methods for phosphate Ester formation. But none of these methods are suitable for practical applications.
Abstract: Preface to the Fourth Edition. Preface to the Third Edition. Preface to the Second Edition. Preface to the First Edition. Abbreviations. 1. The Role of Protective Groups in Organic Synthesis. 2. Protection for the Hydroxyl Group, Including 1,2- and 1,3-Diols. Ethers. Esters. Protection for 1,2- and 1,3-Diols. 3. Protection for Phenols and Catechols. Protection for Phenols. Ethers. Silyl Ethers. Esters. Carbonates. Aryl Carbamates. Phosphinates. Sulfonates. Protection for Catechols. Cyclic Acetals and Ketals. Cyclic Esters. Protection for 2-Hydroxybenzenethiols. 4. Protection for the Carbonyl Group. Acetals and Ketals. Miscellaneous Derivatives. Monoprotection of Dicarbonyl Compounds. 5. Protection for the Carboxyl Group. Esters. Amides and Hydrazides. Protection of Boronic Acids. Protection of Sulfonic Acids. 6. Protection for the Thiol Group. Thioethers. Thioesters. Miscellaneous Derivatives. 7. Protection for the Amino Group. Carbamates. Amides. Special -NH Protective Groups. Protection for Imidazoles, Pyrroles, Indoles, and other Aromatic Heterocycles. Protection for the Amide -NH. Protection for the Sulfonamide -NH. 8. Protection for the Alkyne -CH. 9. Protection for the Phosphate Group. Some General Methods for Phosphate Ester Formation. Removal of Protective Groups from Phosphorus. Alkyl Phosphates. Phosphates Cleaved by Cyclodeesterifi cation. Benzyl Phosphates. Phenyl Phosphates. Photochemically Cleaved Phosphate Protective Groups. Amidates. Miscellaneous Derivatives. 10. Reactivities, Reagents, and Reactivity Charts. Reactivities. Reagents. Reactivity Charts. 1 Protection for the Hydroxyl Group: Ethers. 2 Protection for the Hydroxyl Group: Esters. 3 Protection for 1,2- and 1,3-Diols. 4 Protection for Phenols and Catechols. 5 Protection for the Carbonyl Group. 6 Protection for the Carboxyl Group. 7 Protection for the Thiol Group. 8 Protection for the Amino Group: Carbamates. 9 Protection for the Amino Group: Amides. 10 Protection for the Amino Group: Special -NH Protective Groups. 11 Selective Deprotection of Silyl Ethers. Index.
1,989 citations
1,372 citations