58367-46-7Relevant academic research and scientific papers
Reactions of aryl phenylacetates with secondary amines in MeCN. Structure-reactivity relationship in the ketene-forming eliminations and concurrent E2 and E1cb mechanisms
Cho, Bong Rae,Kim, Yong Kwan,Yoon, Choon-Ock Maing
, p. 691 - 697 (2007/10/03)
Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol% MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol% MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.
Rapid Acid-catalysed and Uncatalysed Hydration of Ketenimines
McCarthy, Daniel G.,Hegarty, Anthony F.
, p. 579 - 591 (2007/10/02)
The rates of hydration of a series of ketenimines (9) have been examined in water (μ 1.0; 25 deg) over the pH range 2-13.Three mechanisms of hydration to the amides (8) were noted: (a) general acid catalysis by proton transfer from H3O(1+) in the pH range 2-7 (giving kH3O(1+)/kD3O(1+) 2.65); (b) general acid catalysis by H2O at pH > 7 (where kH2O/kD2O = 4.8); (c) rate determining HO(1-) attack.The last mechanism was only shown by N-arylketenimines, e.g. (9e); other N-alkylketenimines continue to react by rate-determining proton transfer from water even at pH 13.This result is confirmed by the incorporation of just one deuterium when (9a) reacted in acidic or basic D2O, while the deuteriated ketenimine (9f) does not loose the label on the reaction in water.Substituent effects are parallel for reactions involving H(1+) transfer from H3O(1+) or H2O; the major effects are obtained on changing substituents at carbon (the protonation site).For example, replacement of C-H by C-Me reduces the reactivity by 10-20-fold, while replacement of C-Me by C-Ph reduces the rate of hydration by >100-fold.Ammonium ions also generally react with ketenimines by rate-determining H(1+) transfer to the ketenimine followed by trapping of the nitrilium ion formed by the free amine.Only with the strongest amine base studied (piperidine) does direct nucleophilic attack on the ketenimine compete.
