94670-10-7Relevant articles and documents
B(C6F5)3-Catalyzed Tandem Friedel-Crafts and C?H/C?O Coupling Reactions of Dialkylanilines
Zhai, Gaowen,Liu, Xueting,Ma, Wentao,Wang, Guoqiang,Yang, Liu,Li, Shuhua,Wu, Youting,Hu, Xingbang
supporting information, p. 3082 - 3086 (2020/09/09)
Tandem Friedel-Crafts (FC) and C?H/C?O coupling reactions catalyzed by tris(pentafluorophenyl) borane (B(C6F5)3) were achieved without using any other additive in the absence of solvent. This process can be used for the reactions between a series of dialkylanilines and vinyl ethers with good isolated yields of bis(4-dialkylaminophenyl) compounds. Based on combined theoretical and experimental studies, the possible reaction mechanism was proposed. B(C6F5)3 can activate the C=C and C?O bond for FC and C?H/C?O coupling reactions respectively. The FC reaction is slow, which is followed by a fast C?H/C?O coupling.
Equilibrium Constants for the Interconversion of Substituted 1-Phenylethyl Alcohols and Ethers. A Measurement of Intramolecular Electrostatic Interactions
Rothenberg, Marc E.,Richard, John P.,Jencks, William P.
, p. 1340 - 1346 (2007/10/02)
Equilibrium constants for the reactions of ring-substituted 1-phenylethyl alcohols with a series of aliphatic alcohols of pKa 12.4-16 to form the corresponding ethers, and for interconversion of the ethers, have been determined in 50:45:5 HOH/CF3CH2OH/ROH (v/v/v), μ = 0.5 (NaCIO4), at 25 deg C.Formation of ethers from the alcohols is favorable, with values of K = 3-74; replacement of water by methanol is favored by factors of 50-74.Equilibrium constants increase with increasing pKa of the alcohol with values of βeq = δlog K/δpKROH in the range 0.17-0.27.This is attributed to hydrogen bonding of the alcohol to the solvent and to an electrostatic interaction between substituents on the alcohol and the aryl group.The contribution from hydrogen bonding to the solvent is estimated to be β = 0.17; for 90percent HOH it is 0.25.An increase in βeq with electron-withdrawing substituents on the benzene ring and a complementary increase in ρeq with electron-donating substituents on ROH are described by an electrostatic interaction coefficient τ = δβeq/δ? = δρeq/δpKROH = 0.10 +/- 0.01.No change in τ for dipole-dipole interactions was observed with increasing water concentration in the range 50-90percent (v/v).The electrostatic interactions that are described by τ can cause changes in structure-reactivity parameters, such as ρ or β, in the absence of changes in transition-state structure.
Formation and Stability of Ring-Substituted 1-Phenylethyl Carbocations
Richard, John P.,Rothenberg, Marc E.,Jencks, William P.
, p. 1361 - 1372 (2007/10/02)
The solvolysis of 1-phenylethyl derivatives with electron-donating 4-substituents in 50:50 trifluoroethanol:water(v:v) occurs at a rate that is independent of azide concentration but gives yields of the corresponding azide adducts of up to 98percent by trapping a carbocation intermediate.Rate constants for reactions of the cations with solvent range from 2 x 103 s-1 (4-Me2N) to 4 x 109 s-1 (4-Me), assuming a diffusion-controlled rate constant of 5 x 109 M-1 s-1 for their reactions with azide and thiol anions.Correlation of the rate constants following the Yukawa-Tsuno treatment gives ρn = 2.5, ρr = 5.2, and r+ = 2.1 for the reaction with trifluoroethanol, and ρn = 2.7, ρr = 4.9, and r+ = 1.8 for the reaction with water.The reverse reaction, acid-catalyzed cleavage of substituted 1-phenylethyl alcohols to give the corresponding carbocation, follows ρn = -4.9, ρr = -4.4, and r+ = 0.9.This gives values of ρn = -7.6, ρr = -9.3, and r+ = 1.2 for formation of the cations at equilibrium.There is an imbalance in the development of resonance delocalization, analogous to the "nitroalkane anomaly", that is consistent with a dependence of the fraction of maximal resonance delocalization on the fraction of rehybridization or C-X bond cleavage.Solvent effects on carbocation stability in aqueous-organic mixtures are relatively small.They depend mainly on the nucleophilicity of the solvent components and a specific solvent effect of trifluoroethanol on the reactivity of hydroxylic nucleophiles, including trifluoroethanol itself.The "ionizing power" of the solvent has only a small effect on cation stability, and there is little effect of the concentration or nature of added salts.
