NBO analysis provided further insight into the nature of this intermediate. In INT-3d', the former π-system of the alkene remains broken resulting in two separated p-orbitals. The β-carbon appears to be sp 3 hybridized carrying a negative partial charge (-1.10) stabilized through coordination to aluminum. The α-C appears to be sp 2 hybridized forming a resonance structure with the adjacent pyridyl group and thus carries a much lower negative partial charge (-0.46).