Mechanism and Substituent Effects of Benzene Arylation via a Phenyl Cation Strategy: A Density Functional Theory Study

Abstract

In this study, density functional theory (DFT) calculations were performed to gain insight into the possible reaction mechanism and substituent effects of benzene arylation at the molecular level. The results showed that both [Me3Si]+[WCA]− and [Et3Si]+[WCA]− promoted the reaction. The whole catalytic cycle generally involved three processes, namely, carbocation formation, Wheland intermediate formation, and catalyst regeneration. For the second process, the stepwise mechanism (C−C coupling followed by proton transfer) was shown to be preferred over the concerted mechanism, with successive [1,2]/[1,4]‐proton transfer as the preferred pathway. C−C coupling, rather than C−H insertion, was shown to be the rate‐determining step of the reaction, which was consistent with the kinetic isotope effect experimental results. Bond dissociation energy calculations showed that the ortho‐TMS substituent played a major role in activating the C−F bond to facilitate phenyl cation formation, leading to the most weakly C−Cl bonded intermediate, which facilitated the C−C coupling. Ortho‐phenyl substituents resulted in more severe steric hindrance of fluoride abstraction and a weaker C−H⋅⋅⋅π interaction in the C−C coupling transition state compared with meta‐phenyl substituents. Better stabilization of the cation center by an electron‐rich meta‐substituent was concluded to be the main reason for the better yield obtained compared with substrates containing an electron‐deficient meta‐substituent.

Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives

“…Similarly, the bidentate interaction in 7 ′( 3b ′) also shows the binding of the cation with the phenyl ring but in this case to the C atom in the para -position. Clearly, these observations reflect the ability of the cation to provoke charge reordering in the molecules despite the deactivating effect of the CF 3 group in the meta -position. , …”

“…Clearly, these observations reflect the ability of the cation to provoke charge reordering in the molecules despite the deactivating effect of the CF 3 group in the metaposition. 147,148 Chemical Synergy of N,N′-Disubstitution. The joining of both substituents to different N atoms results in a new compound, N -( 2-f uroy l)-N ′ -(m -tr ifl uoromethyl)phenylthiourea (4), with new chemical features.…”

NaOH-Mediated Direct Synthesis of Quinoxalines from o-Nitroanilines and Alcohols via a Hydrogen-Transfer Strategy

“…The first reduction of NO 2 to NO has also been verified by DFT calculations, indicating that TS B could be the potential intermediate (see the Supporting Information). 23 Furthermore, MPV-type HT between o-nitrosoaniline and sodium alkoxide C via the intermediate TS D would generate diketone 10 and E, which reacted with the hydroxyl group of the second diol to give A and F. Another redox reaction between A and F would provide benzene-1,2-diamine and α-hydroxy ketone 5a. Finally, the base-induced intermolecular condensation between diamine and 10 would give the desired quinoxaline 4a.…”

Charge-Separated Reactive Intermediates from the UV Photodissociation of Chlorobenzene in Solution

“… 1 They can be produced by thermal decomposition of an aryl diazonium compound, and their reactions include intramolecular cyclization or hydride transfer followed by hydrolysis. 2 − 7 The cyclization reactions can bind adjacent oxygen or sulfur atoms to form alkyldibenzofuranium and alkyldibenzothiophenium species. 8 The phenyl cation, c-C 6 H 5 + , contains a charged benzene ring and has potential use in molecular nitrogen capture to afford diazonium compounds, as observed by mass spectrometry.…”

“…Aryl cations are some of the most reactive intermediates used in organic synthesis . They can be produced by thermal decomposition of an aryl diazonium compound, and their reactions include intramolecular cyclization or hydride transfer followed by hydrolysis. − The cyclization reactions can bind adjacent oxygen or sulfur atoms to form alkyldibenzofuranium and alkyldibenzothiophenium species . The phenyl cation, c-C 6 H 5 + , contains a charged benzene ring and has potential use in molecular nitrogen capture to afford diazonium compounds, as observed by mass spectrometry. , If scalable, this N 2 -capture reaction could provide an alternative to the energy-demanding Haber–Bosch process for extraction of nitrogen from the atmosphere to prepare chemical feedstocks .…”