THEORETICAL-STUDIES ON THE CONFIGURATIONS OF BENZHOMOBARRELENE DERIVATIVES

Reaction of 7-carbomethoxy-cycloheptatriene with benzyne resulted in t he formation of only one benzhomobarrelene isomer, 5A. Theoretically, four addition products, 5A-D, can be formed from this reaction. Certai n molecular mechanic calculations (MM2 force field) have been undertak en on these isomers. It has been shown that the isomers 5A and 5C have the lowest energies. The non-existence of 5C has been discussed in te rms of a benzyne approach to a norcaradiene structure. Furthermore, MM 2 calculations on two different conformers of 5A have revealed that th e bisected conformer 5AE has the highest strain energy. However, AM1 s emiempirical calculations of those conformers have shown that the conf ormer 5AE possesses a lower heat of formation than the isomer 5AA.