Scheme 7. Computed mechanisms for E-aryl diene formation as compared to 1,2-dihydronaphthalene formation from allyl-radical intermediate D′.^a DFT-D3 calculated (Turbomole, BP86, def2-TZVP, disp3) mechanisms for [Co(por)]-catalysed 1,2-dihydronaphthalene and E-aryl diene formation from D′ (free energies, , in kcal mol^–1). All energies, including the transition states, are reported with respect to species D′ as the reference point. A cobalt–porphyrin complex without meso-substituents was used as a simplified model of the actual [Co(TPP)] catalyst.