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Dications and dianions derived from fused PAHs and hetero‐PAHs were investigated by means of DFT calculations. The electronic, energetic, and structural features of the singlet and triplet electronic states of these doubly charged species were computationally determined and compared with those of the corresponding neutral parent aromatic and heteroaromatic compounds. The aromatic, nonaromatic or antiaromatic character of the studied diions was evaluated via magnetic criteria, namely NICS and 1H NMR chemical shifts, and by the HOMA structural index. Linear correlations were revealed between the computed HOMO‐LUMO gaps and the magnetic parameters which could serve as a guiding tool in the modulation of molecular properties, and for designing new materials derived from this type of compounds. [ABSTRACT FROM AUTHOR]

Dications and dianions derived from fused PAHs and hetero‐PAHs were investigated by means of DFT calculations. The electronic, energetic, and structural features of the singlet and triplet electronic states of these doubly charged species were computationally determined and compared with those of the corresponding neutral parent aromatic and heteroaromatic compounds. The aromatic, nonaromatic or antiaromatic character of the studied diions was evaluated via magnetic criteria, namely NICS and 1H NMR chemical shifts, and by the HOMA structural index. Linear correlations were revealed between the computed HOMO‐LUMO gaps and the magnetic parameters which could serve as a guiding tool in the modulation of molecular properties, and for designing new materials derived from this type of compounds. [ABSTRACT FROM AUTHOR]

Structurally diverse aldoximes were conveniently transformed within minutes to the corresponding nitriles by using tropylium BF4 as organocatalyst, in 1‐butyl‐3‐methylimidazolium ionic liquids (BMIM‐ILs) as solvent, under microwave irradiation. The scope of this convenient, cyanide free, process for nitrile synthesis was explored, and DFT computations were employed to shed light on the mechanistic steps of this catalytic reaction leading to dehydration. [ABSTRACT FROM AUTHOR]

A simple method to obtain ring-closed metacyclophanediene (CPD) from dicyanometacyclophanediene by using diprotonated dinitrile is demonstrated. The method can be applied to design reversible photochromic [pi]-switches.

The synthesis and characterization of 1,4-difluorobenzo[c]phenanthrene (1,4-DFBcPh) was carried to understand its extent of DNA binding by the metabolities of dihydrodiol and diol epoxides. The findings showed that increased molecular distortion decreased metabolic activation to the terminal metabolities and the formation of diol epoxide metabolites was the DNA-damaging species.

A series of new carbocations are generated by low-temperature protonation of substituted benzo[c]-phenanthrenes, B[c]Phs, and their charge delocalization pathways are evaluated by NMR on the basis of the magnitude of [DELTA][delta][super13]C values. It is found that the protonation regioselectivity is strongly controlled by methoxy and hydroxyl substituents, whose directive effects override methyl substitution effects.

Intermediates formed in halogen addition (X = Br, Cl, F) to alkynes (ethyne, propyne, 2-butyne, trifluoromethylethyne, trimethylsilylethyne, and 1-trimethylsilylpropyne) are studied. The solvation effects on the relative stabilities in the resulting bridged halonium, beta-halovinyl, or alpha-halovinyl cations are examined.

A modified mechanistic scheme is proposed in which three intermediates are involved in the electrophilic nitration of aromatics. The proposal is based on insights gained via quantum chemical calculations for the reaction of the nitronium cation with benzene.

The Account describes recent advances, from the authors' laboratories, in the synthesis of diverse libraries of small-molecule building blocks employing ionic liquids (ILs). The ability of ILs to act as catalysts/promoters/solvents for electrophilic and onium ion chemistry, as well as in metal-mediated cross-coupling reactions, and the potential to sequence/hyphenate these methods, have opened up new opportunities for facile assembly of functional small molecules with increased complexity from readily available precursors. While Brønsted acidic IL/IL solvent mixtures are suitable media for carbocation and onium ion chemistry, piperidine-appended IL/IL solvent mixtures can successfully catalyze a variety of base-catalyzed reactions. Several widely practiced transformations including 'name reactions' were adapted and performed efficiently in ILs. 1 Introduction 2 Aryldiazonium Salts and Aryltriazenes as Coupling Partners in Metal-Mediated C–C Cross-Coupling Reactions in ILs 3 Expanding the Scope of Metal-Mediated Cross-Coupling Reactions in ILs 4 Application of ILs in Synthesis and Functionalization of Hetero-cycles 5 Expanding the Scope of Amide Synthesis in ILs 6 Generation and Chemistry of 'Tamed' Propargylic Cations in ILs 7 Newer Nitration Methods for Arenes and Heteroarenes in ILs 8 Halofunctionalization in ILs 9 'Name Reactions'and Other Widely Practiced Synthetic Transformations in ILs 9.1 The Biginelli Reaction 9.2 Nitrile Synthesis by the Schmidt Reaction 9.3 Rupe Rearrangement 9.4 Synthesis of 1,3-Dioxanes via Prins Reaction in [BMIM(SO3 H)][OTf] 9.5 Synthesis of Cyclopropanes and Oxiranes by the Corey–Chaykovsky (CC) Reaction 10 Conclusions and Closing Remarks [ABSTRACT FROM AUTHOR]

Research has been conducted on 1,3-dehydro-silaadamantane dications. The use of density functional theory in investigating these hitherto elusive dications is described and the results of the computed nucleus independent chemical shift values demonstrate three-dimensional heteroaromaticity in the resulting caging dications.

Research has been conducted on the aryl cations. The results of the density functional theory study demonstrate that upon the heteroatom protonation the singlet/triplet energy gap is narrowed but the triplet state is lower in energy.

Research has been conducted on the persistent oxidation dications from fluoranthene-PAHs. Results indicate the charge delocalization mode and tropicity in the resulting nonalternant dications.

Research has been conducted on the dications. The facile generation of dications, the generation of the protonation and the oxidation dications from the 2,7-di-tert-butyl-substituted benzene[e]annelated under mild conditions at low temperature have been carried out and reported.

Research has been conducted on nonalternant polyarenes. The generation and NMR studies of persistent arenium ions from methylene-bridged polycyclic aromatic hydrocarbons are discussed.

This article describes the carbocations derived from the methyl, methoxy-/hydroxy-derivatives of bay-region and fjord-region of polycyclic aromatic hydrocarbons (PAHs). The PAH diol-epoxides binds to DNA. Data discuss the charge delocalization and aromaticity of carbocations in the biological epoxides BgCh, BcPh, and Ch of PAH.

The usage of ionic liquids as solvents for aromatic nitration and its bearing on green chemistry using room-temperature ionic liquids are presented. Research suggests that ionic liquid nitration serves as an alternative to classical nitration in terms of easier product isolation and devoid of acid neutralization protocol.