28987-52-2Relevant articles and documents
The effect of the leaving group in n-heterocyclic carbene-catalyzed nucleophilic aromatic substitution reactions
Yasui, Kosuke,Kamitani, Miharu,Fujimoto, Hayato,Tobisu, Mamoru
, p. 1424 - 1429 (2020)
We report here that the reactivity order of the leaving group is F > Cl 2 Br > I in N-heterocyclic carbene-catalyzed CSNAr reactions of aryl halides bearing an α,β-unsaturated amide. Based on a qualitative Marcus analysis, the nature
Nonpolar solvent a key for highly regioselective SNAr reaction in the case of 2,4-difluoronitrobenzene
Sythana, Suresh Kumar,Naramreddy, Surendra R.,Kavitake, Santosh,Kumar,Bhagat, Pundlik R.
, p. 912 - 918 (2014/08/05)
A practical and highly regioselective aromatic nucleophilic substitution reaction for the substrate 2,4-difluoronitrobenzene is demonstrated with various O/S/N-nucleophiles. Solvent screens substantiate the role of a nonpolar solvent in ortho-selective nucleophilic substitution through a six-membered polar transition state.
The influence of nucleophile substituents on the orientation in the reaction between 2,4-difluoronitrobenzene and lithium phenoxides in liquid ammonia
Politanskaya, Larisa,Malykhin, Evgenij,Shteingarts, Vitalij
, p. 405 - 411 (2007/10/03)
The dependence of the orientation of aryloxydefluorination of 2,4-difluoronitrobenzene (1) (o/p ratio) by the action of X-substituted lithium phenoxides 2 (X = p-OMe, p-Me, p-Et, p-iPr, p-tBu, m-Me, H, p-F) in liquid ammonia in the temperature range from -55 to -35 °C has been investigated. The enthalpic preference for ortho-fluorine substitution decreases with weakening substituent electron-donating capability in the order: p-OMe > p-Me ≈ p-Et > m-Me > H ≥ p-F. The predominant fluorine substitution at the ortho position for X = p-Me, p-Et turns into a preference for substitution at the para position when X = p-iPr, and this increases further on going to X = p-tBu, PM3, AM1 and MNDO MO calculations showed greater stability of the intermediate anionic σ-complexes formed on nucleophile addition at the para position, thus suggesting that the predominant ortho substitution manifested for X = p-OMe, m-Me, H, p-F and p-Alk = Me, Et is due to control over orientation by the charge distribution in the substrate. The substrate electronic structure, as a controlling factor, is probably changed by the relative stability of intermediate anionic σ-complexes on going to p-Alk = iPr, tBu, as a consequence of an enhancement of the substituent's electron-withdrawing nature with the increase in alkyl group polarizability in the order: p-Me ≈ p-Et p-iPr p-tBu.
