Substituent Effect in the Cation Radicals of Monosubstituted Benzenes

In 30 monosubstituted benzene cation radicals, studied at the ωB97XD/aug-cc-pVTZ level, the phenyl rings usually adopt a compressed form, but a differently compressed form—equivalent to an elongated one—may coexist. The computational and literature ionization potentials are well correlated. The geometrical and magnetic aromaticity, estimated using HOMA and NICS indices, show the systems to be structurally aromatic but magnetically antiaromatic or only weakly aromatic. The partial charge is split between the substituent and ring and varies the most at C(ipso). In the ring, the spin is 70%, concentrated equally at the C(ipso) and C(p) atoms. The sEDA(D) and pEDA(D) descriptors of the substituent effect in cation radicals, respectively, were determined. In cation radicals, the substituent effect on the σ-electron system is like that in the ground state. The effect on the π-electron systems is long-range, and its propagation in the radical quinone-like ring is unlike that in the neutral molecules. The pEDA(D) descriptor correlates well with the partial spin at C(ipso) and C(p) and weakly with the HOMA(D) index. The correlation of the spin at the ring π-electron system and the pEDA(D) descriptor shows that the electron charge supplied to the ring π-electron system and the spin flow oppositely.

Structural effects on the bromination rate and selectivity of alkylbenzenes and alkoxybenzenes in aqueous solution

Steric and electronic effects of monosubstituted benzenes influence rates, regioselectivity, and chemoselectivity of electrophilic aromatic substitution involving aqueous brominating agents.

A Study on the Reactivity of Monosubstituted Benzenes in the MW-Assisted Pd(OAc)2-catalyzed Hirao Reaction with Ph2P(O)H and (EtO)2P(O)H Reagents

The reactivity order of “iodobenzene > bromobenzene > phenyl trifluoromethanesulfonate” was established in microwave (MW)-assisted Pd(OAc)2-catalyzed P–C coupling reactions with diphenylphosphine oxide and diethyl phosphite, where the excess of the these >P(O)H reagents served as the reducing agent, and, via its tautomeric >P-OH form, also as the P-ligand. The P–C coupling of Ph2P(O)H with PhBr at 120 °C took place via an induction period, during which the active “P-Pd-P” catalyst was formed from the Pd(II) salt and the >P(O)H species. The lower reactivity of PhBr towards Ph2P(O)H could be promoted by the addition of 20% of KI to the reaction mixture at 120 °C, or utilizing 1 equivalent of KI after a pre-reaction with PhBr at 120-150 °C followed by the P–C coupling at 100 °C. The reactivity of PhOTf and a bromo analogue was compared in competitive couplings with Ph2P(O)H. Beyond this, the reactivity of Ph2P(O)H and (EtO)2P(O)H towards PhOTf was evaluated in another competitive experiment. Increasing the scale of the P–C coupling reaction of (EtO)2P(O)H with PhBr, the quantity for the components of the catalyst could be decreased.

Para-Selective Borylation of Monosubstituted Benzenes Using a Transient Mediator

Herein, we conceptualized a transient mediator approach that has the capability of <i>para</i>-selective C–H functionalization of monosubstituted aromatics. This approach is enabled by in situ generation of a versatile sulfonium salt via highly electrophilic phenoxathiine or thianthrene dication intermediate which can be readily generated from its sulfoxide with trifluoromethanesulfonic anhydride. Preliminary mechanistic study implied that the remarkable <i>para</i> selectivity might be related to the incredible electrophilicity of thianthrene dication intermediate. The versatility of this approach was demonstrated via <i>para</i>-borylation of various monosubstituted simple aromatics combining the sulfonium salt formation with further photocatalyzed transformation.

Para-Selective Borylation of Monosubstituted Benzenes Using a Transient Mediator

Herein, we conceptualized a transient mediator approach that has the capability of <i>para</i>-selective C–H functionalization of monosubstituted aromatics. This approach is enabled by in situ generation of a versatile sulfonium salt via highly electrophilic phenoxathiine or thianthrene dication intermediate which can be readily generated from its sulfoxide with trifluoromethanesulfonic anhydride. Preliminary mechanistic study implied that the remarkable <i>para</i> selectivity might be related to the incredible electrophilicity of thianthrene dication intermediate. The versatility of this approach was demonstrated via <i>para</i>-borylation of various monosubstituted simple aromatics combining the sulfonium salt formation with further photocatalyzed transformation.

Self-assembly of phenyl-bis-(4,5-dihydroxy-2,7-disulfonato-3-naphthyl)methane, tetrasodium salt into a dimer through hydrogen bonding in water: Evidence from its encapsulation of monosubstituted benzenes, phenols, and polyaromatic hydrocarbons in water

Phenyl-bis-(4,5-dihydroxy-2,7-disulfonato-3-naphthyl)methane, tetrasodium salt, self-assembles into a dimer in water. The dimeric form was evidenced by its encapsulation of monosubstituted benzenes, phenols, and polyaromatic hydrocarbons. The stability constants of the inclusion complexes were determined by 1H nuclear magnetic resonance spectroscopy and the complexes formed were of 1:1 host to guest stoichiometry.