59658-06-9Relevant articles and documents
Heterogeneous Suzuki-Miyaura coupling of heteroaryl ester: Via chemoselective C(acyl)-O bond activation
Ma, Hongpeng,Bai, Chaolumen,Bao, Yong-Sheng
, p. 17266 - 17272 (2019/06/24)
A site-selective supported palladium nanoparticle catalyzed Suzuki-Miyaura cross-coupling reaction with heteroaryl esters and arylboronic acids as coupling partners was developed. This methodology provides a heterogeneous catalytic route for aryl ketone formation via C(acyl)-O bond activation of esters by successful suppression of the undesired decarbonylation phenomenon. The catalyst can be reused and shows high activity after eight cycles. The XPS analysis of the catalyst before and after the reaction suggested that the reaction might be performed via a Pd0/PdII catalytic cycle that began with Pd0.
Comparison of aminolysis of 2-pyridyl and 4-pyridyl x-substituted benzoates in acetonitrile: Evidence for a concerted mechanism involving a cyclic transition state
Um, Ik-Hwan,Bae, Ae-Ri,Um, Tae-Il
, p. 1206 - 1212 (2014/03/21)
A kinetic study on reactions of 2-pyridyl X-substituted benzoates (6a-i) with a series of cyclic secondary amines in MeCN is reported. The Hammett plot for the reaction of 6a-i with piperidine consists of two intersecting straight lines while the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρX = 1.28 and r = 0.63, indicating that the nonlinear Hammett plot is not caused by a change in the rate-determining step but rather by resonance stabilization of substrates possessing an electron-donating group (EDG) in the benzoyl moiety. The Bronsted-type plots are linear with βnuc = 0.59 ± 0.02, which is typical of reactions reported to proceed through a concerted mechanism. A cyclic transition state (TS), which forces the reaction to proceed through a concerted mechanism, is proposed. The deuterium kinetic isotope effect of 1.3 ± 0.1 is consistent with the proposed mechanism. Analysis of activation parameters reveals that ΔH? increases linearly as the substituent X changes from an electron-withdrawing group (EWG) to an EDG, while TΔS ? remains nearly constant with a large negative value. The constant TΔS? value further supports the proposal that the reaction proceeds through a concerted mechanism with a cyclic TS.
A kinetic study on aminolysis of 2-pyridyl X-substituted benzoates: Effect of changing leaving group from 4-nitrophenolate to 2-pyridinolate on reactivity and mechanism
Lee, Jong Pal,Bae, Ae Ri,Im, Li-Ra,Um, Ik-Hwan
experimental part, p. 3588 - 3592 (2011/10/02)
Second-order rate constants (kN) have been measured spectrophotometrically for nucleophilic substitution reactions of 2-pyridyl X-substituted benzoates 8a-e with a series of alicyclic secondary amines in H2O at 25.0 ± 0.1 °C. The kN values for the reactions of 8a-e are slightly smaller than the corresponding reactions of 4-nitrophenyl X-substituted benzoates 1a-e (e.g., kN 1a-e/kN8a-e = 1.1 3.1), although 2-pyridinolate in 8a-e is ca. 4.5 pKa units more basic than 4-nitrophenolate in 1a-e. The Bronsted-type plot for the aminolysis of 8c (X = H) is linear with βnuc = 0.77 and R2 = 0.991 (Figure 1), which is typical for reactions reported previously to proceed through a stepwise mechanism with breakdown of a zwitterionic tetrahedral intermediate T± being the rate-determining step (RDS), e.g., aminolysis of 4-nitrophenyl benzoate 1c. The Hammett plot for the reactions of 8a-e with piperidine consists of two intersecting straight lines (Figure 2), i.e., ρ = 1.71 for substrates possessing an electron-donating group (EDG) while ρ = 0.86 for those bearing an electron-withdrawing group (EWG). Traditionally, such a nonlinear Hammett plot has been interpreted as a change in RDS upon changing substituent X in the benzoyl moiety. However, it has been proposed that the nonlinear Hammett is not due to a change in RDS since the corresponding Yukawa-Tsuno plot exhibits excellent linear correlation with ρ = 0.85 and r = 0.62 (R2 = 0.995, Figure 3). Stabilization of substrates 8a-e in the ground state has been concluded to be responsible for the nonlinear Hammett plot.