Calculations on the normal singlet, triplet and open-shell singlet of hypostrophene, its BCO- analogues and the theoretical transition states for the Cope rearrangement at the B3P86/6-311＋G** level have been done with G03W program. By discussing the geometries of the hypostrophene and its BCO-analogues, nucleus independent chemical shifts (NICS), the Cope barriers and the molecule orbitals, we got some interesting information. The transition state for the hypostrophene was the first neutral tetrahomoaromaticity case in recent papers. In the hypostrophene system, the replacements of CH by BCO caused theoretical transition states to be delocalized and aromatic energy minimized, resulting in enhancement of delocalization, aromaticity and stability of both reactants and transition states, which confirmed the BCO stabilization effects further.

Key words: configuration, aromaticity, reaction barrier, molecular orbital