105650-19-9Relevant academic research and scientific papers
Isothiourea-catalysed transfer hydrogenation of α,β-unsaturated para-nitrophenyl esters
Smith, Andrew D.,Wu, Jiufeng,Young, Claire M.
supporting information, (2020/12/21)
A protocol for the isothiourea-catalysed transfer hydrogenation of α,β-unsaturated para-nitrophenyl esters using Hantzsch ester has been developed. Good to excellent yields are observed using α,β-unsaturated aryl esters bearing electron-withdrawing β-subs
The α-effect in nucleophilic substitution reactions of Y-substituted-Phenyl X-substituted-cinnamates with Butane-2,3-dione monoximate
Kim, Min-Young,Son, Yu-Jin,Um, Ik-Hwan
, p. 2877 - 2882 (2014/01/06)
Second-order rate constants (kOx-) have been measured spectrophotometrically for nucleophilic substitution reactions of 4-nitrophenyl X-substituted-cinnamates (7a-7e) and Y-substituted-phenyl cinnamates (8a-8e) with butane-2,3-dione monoximate (Ox-) in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 °C. The Hammett plot for the reactions of 7a-7e consists of two intersecting straight lines while the Yukawa-Tsuno plot exhibits an excellent linearity with ρX = 0.85 and r = 0.58, indicating that the nonlinear Hammett plot is not due to a change in the rate-determining step but is caused by resonance stabilization of the ground state (GS) of the substrate possessing an electron-donating group (EDG). The Bronsted-type plot for the reactions of Y-substituted-phenyl cinnamates (8a-8e) is linear with βlg = - 0.64, which is typical of reactions reported previously to proceed through a concerted mechanism. The a-nucleophile (Ox-) is more reactive than the reference normalnucleophile (4-ClPhO-). The magnitude of the α-effect (i.e., the kOx-/k4-ClPhO- ratio) is independent of the electronic nature of the substituent X in the nonleaving group but increases linearly as the substituent Y in the leaving group becomes a weaker electron-withdrawing group (EWG). It has been concluded that the difference in solvation energy between Ox- and 4-ClPhO - (i.e., GS effect) is not solely responsible for the α-effect but stabilization of transition state (TS) through a cyclic TS structure contributes also to the Y-dependent a-effect trend (i.e., TS effect).
Structure-reactivity correlations in nucleophilic displacement reactions of Y-substituted-phenyl X-substituted-cinnamates with Z-substituted-phenoxides
Son, Yu-Jin,Kim, Eun-Hee,Kang, Ji-Sun,Um, Ik-Hwan
, p. 2455 - 2460 (2013/09/24)
Second-order rate constants (kN) have been measured spectrophotometrically for the nucleophilic displacement reactions of 4-nitrophenyl X-substituted-cinnamates (4a-4e) and Y-substituted-phenyl cinnamates (5a-5e) with Z-substituted-phenoxide anions in 80 mol % H2O/20 mol % DMSO at 25.0 ±0.1 °C. The Hammett plot for the reactions of 4a-4e with 4-chlorophenoxide (4-ClPhO.) consists of two intersecting straight lines, which might be taken as a change in the rate-determining step (RDS). However, it has been concluded that the nonlinear Hammett plot is not due to a change in the RDS but is caused by stabilization of the ground state of substrates possessing an electron-withdrawing group in the cinnamoyl moiety through resonance interactions, since the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρX = 0.89 and r = 0.58. The Bronsted-type plot for the reactions of 4-nitrophenyl cinnamate (4c) with Z-substituted-phenoxides is linear with βnuc = 0.76. The Bronsted-type plot for the reactions of Y-substituted-phenyl cinnamates (5a-5d) with 4-chlorophenoxides (4-ClPhO.) is also linear with βlg =.0.72. The Hammett plot correlated with σ-. constants for the reactions of 5a-5d results in a much better linear correlation than that correlated with σo constants, indicating that a partial negative charge develops on the O atom of the leaving aryloxide. Thus, the reactions have been concluded to proceed through a concerted mechanism.
MECHANISM OF ESTER AMINOLYSIS IN APROTIC MEDIA AND SPECIFIC SOLVENT EFFECTS
Nagy, Otto B.,Reuliaux, Victor,Bertrand, Nicole,Mensbrugghe, Anne Van Der,Leseul, Jean,Nagy, Janos B.
, p. 1055 - 1074 (2007/10/02)
The n-butylaminolysis of nitro-substituted 4'-nitrophenyl benzoates and cinnamates as well as of phenylacetates in aprotic solvents is governed by a kinetic law implying higher order terms in nucleophile.It is shown that the attacking nucleophile forms a n-? type molecular complex with the substrate before reaching the transition state in the subsequent kinetic step.This molecular complex is a true reaction intermediate as evidenced by the observed negative activation enthalpy.Other nucleophile molecules intervene as general base catalysts.Tertiary amines also catalyse the reaction.Their catalytic activity is linearly related to their hydrogen bond forming ability and it is not a direct function of their proton basicity.By varying the nucleophile structure, an excellent Broensted relationship could be obtained for the first time in aprotic media, the β of which confirms that the catalytic collapse of tetrahedral intermediate is the rate determining step.The reaction of cinnamates turns out to be less sensitive to structural changes of the substrate than is the reaction of benzoates as shown by the corresponding Hammet ? values.The electronic effects of 2-nitro groups are strongly solvent dependent.Once more, it is established that whenever specific solvent effects (?-donor or n-donor ability) are present, they dominate the overall effect.A general reaction mechanism is proposed which not only explains the various roles played by the nucleophile but also accounts successfully for the great variety of kinetic schemes observed in aprotic media.
