['According', 'to', 'Fukui', '[', '33', ']', ',', 'reactions', 'can', 'be', 'favorable', 'in', 'the', 'direction', 'of', 'maximal', 'HOMO', '–', 'LUMO', 'overlapping', 'of', 'larger', 'coefficients', 'at', 'the', 'reactive', 'sites', '.']