Ester hydrolysis catalysed by ortho-palladated aryl oximes

Publisher Website
Google Scholar
Abstract
Hydrolysis of 4-nitro- and 2,4-dinitro-phenyl carboxylates proceeds catalytically in the presence of ortho-palladated aryl oximes 4. The catalytic reaction involves two active species, identified as aquated complexes 4 with protonated (kAH path) and deprotonated (kA path) oximate groups, respectively. Both species contain a weakly basic coordinated hydroxide anion manifested in the kAH path. Other cyclopalladated hydroxo complexes 8, lacking an oxime group, are shown to react with 2,4-dinitrophenyl acetate with rate constants ca. ten times greater than those expected from their basicity. The rate constants kA obey a Brønsted correlation (β ca. 1) with the pKa of the coordinated oxime group. In neutral solution, palladated oximes react with esters ca. 103 times faster than the respective free oximes. The O-acyl oxime intermediate undergoes very fast hydrolysis through intramolecular attack by the coordinated hydroxide. Factors ensuring the combination of fast acylation and deacylation steps are discussed with reference to some related systems.

This publication has 0 references indexed in Scilit: