Rationalizing the Al^I‐Promoted Oxidative Addition of C−C Versus C−H Bonds in Arenes

Abstract

The factors controlling the oxidative addition of C−C and C−H bonds in arenes mediated by AlI have been computationally explored by means of Density Functional Theory calculations. To this end, we compared the processes involving benzene, naphthalene and anthracene which are promoted by a recently prepared anionic AlI‐carbenoid. It is found that this species exhibits a strong tendency to oxidatively activate C−H bonds over C−C bonds, with the notable exception of benzene, where the C−C bond activation is feasible but only under kinetic control reaction conditions. State‐of‐the‐art computational methods based on the combination of the Activation Strain Model of reactivity and the Energy Decomposition Analysis have been used to rationalize the competition between both bond activation reactions as well as to quantitatively analyze in detail the ultimate factors controlling these transformations.

Arene C−H Activation at Aluminium(I): meta Selectivity Driven by the Electronics of SNAr Chemistry

“…[18][19][20] That said, the relatively close approach of the H atom of the C À H bond to the aluminium centre in the transition state (ca. 1.8-1.9 ) [16,17] also suggests analogies with a classical oxidative addition pathway featuring a three-centre interaction. [21] With this in mind, we exploited density functional theory to probe the relative energies of the transition states corresponding to ortho, meta and para arene-C À H activation in n-butylbenzene by 1' (i.e.…”

Chemoselective C−C σ‐Bond Activation of the Most Stable Ring in Biphenylene**

“…Activation strain analysis (ASA) was used to interrogate this phenomenon further [38–40] . Similar methodology has been used to explore the factors controlling C−H and C−C bond oxidative addition at an alumanyl anion [41] . The ASA profile derived from TS‐8 was generated (Figure 3 a).…”

Selective cleavage of unactivated arene ring C–C bonds by iridium: key roles of benzylic C–H activation and metal–metal cooperativity

“…Such understanding is currently lacking. The reported mechanistic studies of observed arene C-C cleavage are limited to benzene 16,[20][21][22] or quinoxaline [23][24][25] and are exclusively computational. These DFT calculations focused primarily on C-C scission following reduction or dehydrogenation of the aromatic ring 20,21,[23][24][25] instead of the more fundamentally and synthetically important but little-understood C-C scission in intact arenes.…”

“…These DFT calculations focused primarily on C-C scission following reduction or dehydrogenation of the aromatic ring 20,21,[23][24][25] instead of the more fundamentally and synthetically important but little-understood C-C scission in intact arenes. 14,22,26 Two known computationally identified examples of direct aromatic C-C activation in substituted arenes have never been realized experimentally, illustrating the challenges of integrating experimental and computational approaches in this area. 22,26 As a result, a critical question of the role of substituents on the rate of aromatic C-C cleavage and the selectivity of C-C vs C-H activation (and hence the scope) remains completely unexplored.…”

“…14,22,26 Two known computationally identified examples of direct aromatic C-C activation in substituted arenes have never been realized experimentally, illustrating the challenges of integrating experimental and computational approaches in this area. 22,26 As a result, a critical question of the role of substituents on the rate of aromatic C-C cleavage and the selectivity of C-C vs C-H activation (and hence the scope) remains completely unexplored. We recently reported that simple Cp* iridium complexes cleave the arene ring of a range of industrially important unactivated arenes, including mesitylene, o-, m-, p-xylenes and toluene ( Fig.…”