Oxidative Addition of Aryl and Benzyl Trifluoroacetates to Zerovalent Palladium Complexes with Two Modes of C–O Bond Cleavage Processes

Abstract

The aryl trifluoroacetates oxidatively added to a zerovalent palladium complex 2a with acyl-O bond cleavage under mild conditions to give the corresponding trans-(aryloxo)(trifluoroacetyl)palladium complexes 3a—3c. But 4-nitrophenyl trifluoroacetate reacted with 2a to yield cis-[Pd(OC6H4-4-NO2)2(PMe3)2] 3d, which was produced with C–O bond activation followed by disproportionation reaction. In contrast, benzyl trifluoroacetates reacted with the Pd(0) complex with benzyl–O bond fission to form benzyl(trifluoroacetato)palladium complexes 4a—4d. Complexes 4a—4d are in equilibrium in solutions between trans and cis isomers, with the proportion of the cis isomer increasing in polar solvents. Palladium-catalyzed carbonylation of benzyl trifluoroacetate has been achieved in the presence of benzyl alcohol and triethylamine to yield benzyl phenylacetate.

Synthesis of benzylpalladium complexes through C–O bond cleavage of benzylic carboxylates: Development of a novel palladium-catalyzed benzylation of olefins

“…doi:10.1016/j.jorganchem.2007. 10.051 processes using the cleavage of the C-O bond in carboxylic esters and carboxylic anhydrides [4][5][6][7][8].…”

“…Aryl esters such as aryl trifluoroacetates also undergo the oxidative addition involving the acyl-O cleavage to give acylpalladium aryloxide complexes (Scheme 1) [6].…”

Design of catalytic processes based on studies of elementary processes

“…Benzylic carboxylates have properties somewhat similar to allylic carboxylates and undergo the benzyl-O bond cleavage upon interaction with Pd(0) complexes to give benzylpalladium carboxylates [41]. We found recently that the palladium-promoted C-O bond cleavage in benzyl trifluoroacetate can be used for performing the Mizoroki-Heck type benzylation of olefins [42].…”

“…Cleavage of the C-O bond takes place not only with carboxylic anhydride but also with carboxylic esters, particularly with electron-poor esters such as those of fluorinated carboxylic acids [41]. By combining the C-O bond cleavage of perfluorinated carboxylic esters with Pd (0) The mechanism of the trifluoromethyl aryl ketone synthesis from phenyl trifluoroacetate and arylboronic acid is presented in Scheme 9.…”

Insertion of an Alkene into an Ester: Intramolecular Oxyacylation Reaction of Alkenes through Acyl CO Bond Activation

“…[5] We postulated that a chelating group would prevent decarbonylation by stabilizing the acyl metal complex, I. Our approach was akin to stoichiometric acyl C À O bond activation strategies [6][7][8] in which metal chelating groups were used.…”