Fife, Thomas H.; Duddy, Neil W. published the artcile< Intramolecular aminolysis of esters. Cyclization of esters of (o-aminophenyl)acetic acid>, Computed Properties of 30095-98-8, the main research area is kinetics cyclization aminophenylacetate base catalysis; mechanism cyclization aminophenylacetate LFER; oxindole; leaving group effect intramol aminolysis; proton transfer cyclization mechanism aminophenylacetate.
Rate constants are obtained for the cyclization of o-H2NC6H4CH2CO2R [R = Me (I), CF3CH2 (II)], or its protonated analog, to give III. The second order rate constant, kOH, for OH- catalysis of the reaction of I is 100-fold greater than that for the OH- catalyzed hydrolysis of PhCH2CO2Me. The kOH for cyclization of II is 85-fold greater, at 30°, than that of I. The bell shaped log k0 vs. pH profile for II at low pH indicates that the rate-determining step changes with pH and that the cyclization involves a tetrahedral addition product as an intermediate. The curved kobserved vs. buffer concentration plots for the cyclization of I at pH <7 (which indicates a buffer concentration dependence of the rate-determining step) supports this and shows that at pH >4 and low buffer concentration the breakdown of the tetrahedral intermediate is rate-determining The general base catalysis observed in the cyclization reaction of I and II (characterized by Broensted β 0.5 and 0.1, resp.) involves a proton transfer concerted with bond breaking in contrast with similar reactions of o-H2NCH2C6H4CO2Me [in which proton-transfer is rate-determining (β 1.0)]. The decrease in β as the leaving group improves indicates that the general base is partially removing a proton from the neutral tetrahedral intermediate as the C-O bond breaks. Several different mechanisms and/or rate-determining steps are possible (and are observed) in the intramol. aminolysis of aliphatic esters; the key features in these aminolysis reaction mechanisms are the nucleophile pKa, the steric fit of the nucleophile to the CO group, and the ease of C-O bond breaking in the tetrahedral intermediate decomposition to products.
Journal of the American Chemical Society published new progress about Amino esters Role: RCT (Reactant), RACT (Reactant or Reagent). 30095-98-8 belongs to class esters-buliding-blocks, and the molecular formula is C9H9NO4, Computed Properties of 30095-98-8.
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics