Mechanistically Optimized Intramolecular Catalysis in the Hydrolysis of Esters. Global Changes Involved in Molecular Reactivity

Abstract

The hydrolysis of the 2Ј,2Ј,2Ј-trifluoroethyl monoester of 1,8-naphthalic acid (1) proceeds via the monoanion with the intermediate formation of the corresponding anhydride. The rate constant for the formation of 1,8-naphthalic anhydride (2) is ca 2500 times faster than its rate of hydrolysis. The isotope effect in the plateau region and theoretical calculations at the PM3 level suggest that elimination of the alkoxide is the rate-limiting step for the reaction. Accordingly, decomposition of the isopropyl monoester of naphthalic acid proceeds 10 4 times slower than the spontaneous decomposition of 1. The remarkably high rate of monoester decomposition derives from the special configuration of the substrates and important contributions that arise from relief of torsional strain, which clearly includes electron redistribution due to the decrease in steric hindrance to resonance and the fact that proximity obviates solvation.