To gain further insight into the regioselectivity of the arylation processes, we undertook computational studies of the various possible C-H activation steps. Density functional theory (DFT) calculations were carried out with the M06 functional, using the 6-31+G(d) basis set for C, H, N, O and F atoms and the LANL2DZ basis set for Pd. All optimised structures were confirmed by the presence of zero or one imaginary frequencies for minima and transition states respectively, and transition states were shown to link the correct minima through IRC calculations. Calculated free energies were corrected to the reaction temperature of 413 K. Initially, we modelled an adduct Ia in which a palladium atom with a bidentate acetate ligand was chelated by the two nitrogens of a deprotonated molecule of 1a (Scheme 3). Transition states for a concerted metalation-deprotonation (CMD) mechanism could then be located for both methylene and methyl groups (IIa and IIIa respectively; Scheme 3 and Table ). As expected, these calculations indicated that insertion into the methylene group had a much lower energy barrier (G ‡ = 18.1 kJ mol -1 ). A second insertion step was then investigated, starting from the monophenylated adduct VIIa.