Steric and Electronic Substituent Effects Influencing Regioselectivity of Tetracene Endoperoxidation

This paper describes the influence of steric and electronic factors in the regioselectivity of endoperoxide formation of tetracene derivatives using O-1(2). A combination of kinetics experiments and product distributions resulting from these photosensitized oxidations demonstrates that, while the steric effect of o-alkyl groups on aryl substituents is highly localized to the substituted ring, the resistance to oxidation based on phenylethynyl substituents is more evenly distributed between the two reactive rings. These results are important for the rational design of highly persistent acenes.