Oxidative addition of aryl and benzyl trifluoroacetates to zerovalent palladium complexes with two modes of C-O bond cleavage processes

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 arid triethylamine to yield benzyl phenylacetate.