Concerted Nucleophilic Aromatic Substitution Reactions

Rohrbach, Simon; Sutherland-Smith, Andrew J.; Pang, Jia; Poole, Darren L.; Tuttle, Tell; Chiba, Shunsuke; Murphy, John A.

doi:10.1002/anie.201902216

Cited by 192 publications

(140 citation statements)

References 138 publications

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“…The generally assumed Whelandi ntermediate was not observed. [32] An activation free energy barrier of DG°= 21.9 kcal mol À1 was calculated [29] for PhGeEt 3 ,w hich is in line with the high experimental reactivity observed for ArGeEt 3 at room temperature.F or comparison, the corresponding aryl silane is predicted to react with ab arrier of DG°= 25.2 kcal mol À1 ,inline with the exclusive selectivity for Ge-functionalization.…”

Section: Forschungsartikelsupporting

confidence: 55%

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

2020

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While halogenation is of key importance in synthesis and radioimaging,t he currently available repertoire is largely designed to introduce as ingle halogen per molecule.T his report makes the selective introduction of several different halogens accessible.S howcased here is the privileged stability of nontoxicaryl germanes under harsh fluorination conditions (that allows elective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations,o utcompeting silanes or boronic esters under rapid and additive-free conditions.M echanistic experiments and computational studies suggest ac oncerted electrophilic aromatic substitution as the underlying mechanism.

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Section: Forschungsartikelsupporting

confidence: 55%

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

2020

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“…Nucleophilic substitutions on aromatic systems can proceed via several different reaction mechanisms. 1 Of these, the most fundamental is the bimolecular nucleophilic aromatic substitution (S N Ar) as described in the landmark review by Bunnett et al 2 As detailed more recently, 3 the widely accepted stepwise energy profile of the S N Ar reaction appears not to be the only possible route. In fact, over the last decades, more and more reports accumulated in the literature that suggested certain S N Ar reactions to follow a concerted pathway.…”

Section: Introductionmentioning

confidence: 99%

Computational Study on the Boundary Between the Concerted and Stepwise Mechanism of Bimolecular S_NAr Reactions

2020

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The text-book mechanism of bimolecular nucleophilic aromatic substitutions (S N Ar) reactions is a stepwise process that proceeds via a so-called Meisenheimer intermediate. Only recently the alternative, concerted version of this mechanism has gained acceptance as more and more examples thereof have been reported. But so far only isolated examples of concerted S N Ar reactions have been described and a coherent picture of when a S N Ar reaction proceeds via a stepwise and when via a concerted mechanism has not yet been established. Here key factors are identified that influence the mechanistic choice of S N Ar reactions. Moreover, the electron affinity is used as a simple descriptor to make a prediction on whether a given aryl fluoride substrate favors a concerted or stepwise mechanism.

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“…[11e, 16, 17] A similar concerted S N Ar (cS N Ar) mechanism has also been advanced by Fernandez and Cabrera-Trujillo for arene CÀH activation in benzene and extended arenes by aluminyl reagents. [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.…”

Section: Zuschriftenmentioning

confidence: 99%

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

et al. 2020

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The reactivity of the electron-rich anionic Al I aluminyl compound K 2 [(NON)Al] 2 (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) towards mono-and disubstituted arenes is reported. C À H activation chemistry with n-butylbenzene gives exclusively the product of activation at the arene meta position. Mechanistically, this transformation proceeds in a single step via a concerted Meisenheimer-type transition state. Selectivity is therefore based on similar electronic factors to classical S N Ar chemistry, which implies the destabilisation of transition states featuring electron-donating groups in either ortho or para positions. In the cases of toluene and the three isomers of xylene, benzylic C À H activation is also possible, with the product(s) formed reflecting the feasibility (or otherwise) of competing arene CÀH activation at a site which is neither ortho nor para to a methyl substituent.

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Concerted Nucleophilic Aromatic Substitution Reactions

Cited by 192 publications

References 138 publications

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

Computational Study on the Boundary Between the Concerted and Stepwise Mechanism of Bimolecular S_NAr Reactions

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

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Concerted Nucleophilic Aromatic Substitution Reactions

Cited by 192 publications

References 138 publications

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

Computational Study on the Boundary Between the Concerted and Stepwise Mechanism of Bimolecular SNAr Reactions

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

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Computational Study on the Boundary Between the Concerted and Stepwise Mechanism of Bimolecular S_NAr Reactions

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