Effect of transannular interaction on the redox-potentials in a series of bicyclic quinones

• Main Authors: Grigoriy Sereda, Jesse Van Heukelom, Miles Koppang, Sudha Ramreddy, Nicole Collins
• Format: Article
• Language: English
• Published: Beilstein-Institut 2006-12-01
• Series: Beilstein Journal of Organic Chemistry
• Online Access: https://doi.org/10.1186/1860-5397-2-26

Background<p>Better understanding of the transannular influence of a substituent on the redox-potentials of bicyclo[2.2.2]octane-derived quinones will help in the design of new compounds with controlled biological activity. However, attempts to directly relate the reduction potentials of substituted triptycene-quinones to the electronic effects of substituents are often unsuccessful.</p><p>Results</p><p>First and second redox-potentials of a series of bicyclic quinones are compared to computed energies of their LUMO, LUMO+1, and energies of reduction. Transannular influence of substituent on the redox-potentials is rationalized in terms of MO theory. Acetoxy-substituents in the 5,8-positions of the triptycene-quinone system selectively destabilize the product of the two-electron reduction.</p><p>Conclusion</p><p>We have shown that first redox-potentials of substituted bicyclic quinones correlate with their calculated LUMO energies and the energies of reduction. The second redox-potentials correlate with calculated LUMO+1 energies. As opposed to the LUMO orbitals, the LUMO+1 orbital coefficients are weighted significantly on the non-quinone part of the bicyclic system. This accounts for: (1) significantly larger substituent effect on the second redox-potentials, than on the first redox-potentials; (2) lack of stability of the product of two electron reduction of 5,8-diacetoxy-9,10-dihydro-9,10-[1,2]benzenoanthracene-1,4-dione 5.</p>