Polyfunctional catalysis. III. Tautomeric catalysis

Abstract

A tautomeric catalyst is a molecule that repeatedly cycles between two tautomeric states in the course of catalyzing a chemical reaction. The stoichiometries and kinetics for four different tautomeric catalysts-2pyridone, benzoic acid, pyrazole, and 1,2,4-triazole-were examined for the aminolysis of 4-nitrophenyl acetate by «-butylamine and glycine ethyl ester in benzene and 1.5% methanol-benzene. The rate law is third order, rate = ¿[4-nitrophenyl acetate][amine][catalyst], and conforms to a reaction with the following stoichiometry: 4-nitrophenyl acetate + amine + catalyst -amide + 4-nitrophenoI + catalyst. The rate constants at 25 °for the above four tautomeric catalysts are (a) n-butylamine, 17, >2, 0.21, and 0.87 M~sec-1, respectively, and (b) glycine ethyl ester, 0.80, 0.36, 0.0086, and 0.021 M-2 sec-1, respectively. 2-Aminophenol exhibited no catalytic activity for (7) P.

Bonding Analysis of N‐Heterocyclic Carbene Tautomers and Phosphine Ligands in Transition‐Metal Complexes: A Theoretical Study

“…7, concomitant demethylation in the methoxypyridine and the hydroxylation at the C16 position might destroy its chemical stability and consequently non‐enzymatic cyclic reaction occurred, resulting in formation of the cyclic metabolites. O ‐Demethylation from M6 destroyed the aromatic system in pyridine and converted pyridinol into pyridinone [A] with increasing the reactivity at C13 11,12. Then, the dehydration at C16 proceeded [B] and the cyclic reaction was followed by the attack of more reactive C13.…”

The Host/Guest Type of Excited‐State Proton Transfer; a General Review

“…The over all rate is more than 500 times greater when 2-pyridone acts as the cat a lyst than when a sec ond mol e cule of butylamine acts as a gen eral base cat a lyst. 248 In this case, 2-pyridone has been called a bifunctional cat a lyst, since two at oms in the mol e cule are in volved in the pro ton trans fer pro cess. The bifunctional cat a lytic pro cess has also been widely found in bi o log i cal re ac tions.…”

Depsipeptide nucleic acids: prebiotic formation, oligomerization, and self-assembly of a new candidate proto-nucleic acid

“…51,56 Pyrimidine may be produced prebiotically from acrylonitrile. 57 2-Hydroxypyridine (and, by analogy, 2-mercaptopyridine) was chosen for its propensity to act as a bifunctional catalyst in ester aminolysis reactions, 58 which may also enhance the extent of the esterification reaction ( Supplementary Fig. 21).…”