We investigated the site selectivity switch in BF3-catalyzeddual skeletal rearrangements of cyclobutene-fused diarylhomobenzoquinones by changing the stoichiometric amountof acid concentration. From the lower to the higher equivalency of BF3·Et2O, the branching product ratios (path A/pathB) obeyed nonlinear sigmoid curves against the equivalencyof BF3·Et2O. The observed selectivity profiles were simulatedto elucidate factors that govern thermodynamic aspects(binding affinity K of each carbonyl function with acid) andkinetic aspects (rate constants k for the cyclobutene-ringcleavage).