J. Appl. Cryst.の発刊に際して

I. Introduction: Conceptual vs Fundamental andComputational Aspects of DFT1793II. Fundamental and Computational Aspects of DFT 1795A. The Basics of DFT: The Hohenberg−KohnTheorems1795B. DFT as a Tool for Calculating Atomic andMolecular Properties: The Kohn−ShamEquations1796C. Electronic Chemical Potential andElectronegativity: Bridging Computational andConceptual DFT1797III. DFT-Based Concepts and Principles 1798A. General Scheme: Nalewajski’s ChargeSensitivity Analysis1798B. Concepts and Their Calculation 18001. Electronegativity and the ElectronicChemical Potential18002. Global Hardness and Softness 18023. The Electronic Fukui Function, LocalSoftness, and Softness Kernel18074. Local Hardness and Hardness Kernel 18135. The Molecular Shape FunctionsSimilarity 18146. The Nuclear Fukui Function and ItsDerivatives18167. Spin-Polarized Generalizations 18198. Solvent Effects 18209. Time Evolution of Reactivity Indices 1821C. Principles 18221. Sanderson’s Electronegativity EqualizationPrinciple18222. Pearson’s Hard and Soft Acids andBases Principle18253. The Maximum Hardness Principle 1829IV. Applications 1833A. Atoms and Functional Groups 1833B. Molecular Properties 18381. Dipole Moment, Hardness, Softness, andRelated Properties18382. Conformation 18403. Aromaticity 1840C. Reactivity 18421. Introduction 18422. Comparison of Intramolecular ReactivitySequences18443. Comparison of Intermolecular ReactivitySequences18494. Excited States 1857D. Clusters and Catalysis 1858V. Conclusions 1860VI. Glossary of Most Important Symbols andAcronyms1860VII. Acknowledgments 1861VIII. Note Added in Proof 1862IX. References 1865

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Conceptual density functional theory.

Catalytic dehydrogenative cross-coupling: forming carbon-carbon bonds by oxidizing two carbon-hydrogen bonds

Controlled/living radical polymerization: Features, developments, and perspectives

The site-selective formation of carbon-carbon bonds through direct functionalizations of otherwise unreactive carbon-hydrogen bonds constitutes an economically attractive strategy for an overall streamlining of sustainable syntheses. In recent decades, intensive research efforts have led to the development of various reaction conditions for challenging C-H bond functionalizations, among which transition-metal-catalyzed transformations arguably constitute thus far the most valuable tool. For instance, the use of inter alia palladium, ruthenium, rhodium, copper, or iron complexes set the stage for chemo-, site-, diastereo-, and/or enantioselective C-H bond functionalizations. Key to success was generally a detailed mechanistic understanding of the elementary C-H bond metalation step, which depending on the nature of the metal fragment can proceed via several distinct reaction pathways. Traditionally, three different modes of action were primarily considered for CH bond metalations, namely, (i) oxidative addition with electronrich late transition metals, (ii) σ-bond metathesis with early transition metals, and (iii) electrophilic activation with electrondeficient late transition metals (Scheme 1). However, more recent mechanistic studies indicated the existence of a continuum of electrophilic, ambiphilic, and nucleophilic interactions. Within this continuum, detailed experimental and computational analysis provided strong evidence for novel C-H bond metalationmechanisms relying on the assistance of a bifunctional ligand bearing an additional Lewis-basic heteroatom, such as that found in (heteroatom-substituted) secondary phosphine oxides or most prominently carboxylates (Scheme 1, iv). This novel insight into the nature of stoichiometric metalations has served as stimulus for the development of novel transformations based on cocatalytic amounts of carboxylates, which significantly broadened the scope of C-H bond functionalizations in recent years, with most remarkable progress being made in palladiumor ruthenium-catalyzed direct arylations and direct alkylations. These carboxylate-assisted C-H bond transformations were mostly proposed to proceed via a mechanism in which metalation takes place via a concerted base-assisted deprotonation. To mechanistically differentiate these intramolecular metalations new acronyms have recently been introduced into the literature, such as CMD (concerted metalationdeprotonation), IES (internal electrophilic substitution), or AMLA (ambiphilic metal ligand activation), which describe related mechanisms and will be used below where appropriate. This review summarizes the development and scope of carboxylates as cocatalysts in transition-metal-catalyzed C-H functionalizations until autumn 2010. Moreover, experimental and computational studies on stoichiometric metalation reactions being of relevance to the mechanism of these catalytic processes are discussed as well. Mechanistically related C-H bond cleavage reactions with ruthenium or iridium complexes bearing monodentate ligands are, however, only covered with respect to their working mode, and transformations with stoichiometric amounts of simple acetate bases are solely included when their mechanism was suggested to proceed by acetate-assisted metalation.

Carboxylate-assisted transition-metal-catalyzed C-H bond functionalizations: mechanism and scope.

Which electrophiles react with which nucleophiles? The correlation log k20 °C = s(E + N), in which electrophiles (carbocations, metal-π-complexes, diazonium ions) are characterized by one (E) and nucleophiles are characterized by two parameters (N, s), proved to be applicable for a wide variety of electrophile−nucleophile combinations. Since the introduction of this correlation in 1994 (Angew. Chem., Int. Ed. Engl. 1994, 33, 938−957), numerous new reagents have been characterized, and in 2001 (J. Am. Chem. Soc. 2001, 123, 9500−9512), a new method of parametrization was proposed that facilitates a continuous extension of the data sets without the need for reparametrization of existing data. This Account adjusts the N and s parameters of all presently characterized π-nucleophiles (arenes, alkenes, organometallics) to the new parametrization and illustrates how to employ the resulting reactivity scales for analyzing synthetic and mechanistic problems in organic and macromolecular chemistry. Predictions of ab...

π-Nucleophilicity in Carbon−Carbon Bond-Forming Reactions

Twenty-three diarylcarbenium ions and 38 π-systems (arenes, alkenes, allyl silanes and stannanes, silyl enol ethers, silyl ketene acetals, and enamines) have been defined as basis sets for establishing general reactivity scales for electrophiles and nucleophiles. The rate constants of 209 combinations of these benzhydrylium ions and π-nucleophiles, 85 of which are first presented in this article, have been subjected to a correlation analysis to determine the electrophilicity parameters E and the nucleophilicity parameters N and s as defined by the equation log k(20 °C) = s(N + E) (Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938−957). Though the reactivity scales thus obtained cover more than 16 orders of magnitude, the individual rate constants are reproduced with a standard deviation of a factor of 1.19 (Table 1). It is shown that the reactivity parameters thus derived from the reactions of diarylcarbenium ions with π-nucleophiles (Figure 3) are also suitable for characterizing the nucleoph...

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles

Do general nucleophilicity scales exist

Benzhydrylium ions (Ar 2 CH + ) and structurally related quinone methides are em- ployed as reference electrophiles for comparing the nucleophilicities of a large variety of compounds, e.g., alkenes, arenes, alkynes, allylsilanes, allylstannanes, enol ethers, enamines, diazo compounds, carbanions, transition-metal π-complexes, hydride donors, phosphanes, amines, alkoxides, etc., using the correlation equation log k (20 °C) = s(N + E), where s and N are nucleophile-dependent parameters and E is an electrophilicity parameter. The same equation was employed to derive the electrophilicity parameter E for different types of car- bocations, cationic transition-metal π-complexes, typical Michael acceptors, and electron-de- ficient arenes. The E, N, and s parameters thus obtained can be used for predicting rates and selectivities of polar organic reactions.

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Kinetics of electrophile-nucleophile combinations: A general approach to polar organic reactivity

The concept of hard and soft acids and bases (HSAB) proved to be useful for rationalizing stability constants of metal complexes. Its application to organic reactions, particularly ambident reactivity, has led to exotic blossoms. By attempting to rationalize all the observed regioselectivities by favorable soft-soft and hard-hard as well as unfavorable hard-soft interactions, older treatments of ambident reactivity, which correctly differentiated between thermodynamic and kinetic control as well as between different coordination states of ionic substrates, have been replaced. By ignoring conflicting experimental results and even referring to untraceable experimental data, the HSAB treatment of ambident reactivity has gained undeserved popularity. In this Review we demonstrate that the HSAB as well as the related Klopman-Salem model do not even correctly predict the behavior of the prototypes of ambident nucleophiles and, therefore, are rather misleading instead of useful guides. An alternative treatment of ambident reactivity based on Marcus theory will be presented.

Armin R. Ofial

Papers

π-Nucleophilicity in Carbon−Carbon Bond-Forming Reactions

Reference Scales for the Characterization of Cationic Electrophiles and Neutral Nucleophiles

Do general nucleophilicity scales exist

Kinetics of electrophile-nucleophile combinations: A general approach to polar organic reactivity

Farewell to the HSAB Treatment of Ambident Reactivity