79251-23-3Relevant articles and documents
EFFECT OF NEIGHBORING PYRIDINIUM GROUPS ON THE BASIC HYDROLYSIS OF ARYLBENZOATE ESTERS
Engbersen, J. F. J.,Geurtsen, G.,Bie, D. A. De,Plas, H. C. Van Der
, p. 1795 - 1802 (2007/10/02)
Arylbenzoate esters with a quaternary pyridinium group ortho to the ester function exhibit enhanced reactivity towards basic hydrolysis relative to their para analogs in the order pyridinium 4-aminocarbonylpyridinium 3-aminocarbonylpyridinium 3-aminocarbonylquinolium.In contrast, a trimethylammonium group in the ortho position shows a decelerating effect relative to the para analog.It is concluded that the catalytic effect of a neighboring pyridinium group is based upon interaction of the negatively charged transition state of ester hydrolysis with the electron deficient ?-system of the pyridinium ring.For the p-methoxyphenolate ester containing the 3-aminocarbonylpyridinium group in the ortho position this interaction leads to a change in mechanism from rate limiting hydroxide ion attack to hydroxide ion catalyzed expulsion of the leaving group as became apparent from deviation of the Hammett plot and second-order dependence on OH(1-) concentration.For the p-nitrophenolate ester it was observed that decrease of the solvent polarity by addition of dioxane results in an increase of the rate of hydrolysis and a marked increase of the neighboring group effect.
Catalytic Mechanisms of Acyl Transfer Reactions in Dipolar Aprotic Media. 2. Electrophilic Activation of the Carbonyl Group by Quaternary Alkylammonium and Imidazolium Functions
Hajdu, Joseph,Smith, Georgianna M.
, p. 6192 - 6197 (2007/10/02)
Crown ether solvated potassium acetate in dipolar aprotic media readily converts p-nitrophenyl o-toluate to the corresponding acetyltoluyl mixed anhydride.The reaction proceeds at room temperature in quantitative yield.The rate of acyl transfer is 0.0118
