pi-Arene/metal binding: an issue not only of structure but also of reactivity.
A trimethyl-, triethyl-, or triisopropylsilyl group attached to the meta position of toluene retards the rate of permutational hydrogen/metal interconversion with butyllithium in the presence of potassium tert-butoxide by factors of 1.7, 3, and 7, respectively. Although remote from the reaction center, the substituents sterically impede the coordination of potassium to the arene electron sextet. pi-Arene/metal bonding may play a major role in modulating chemical and, by extension, biochemical reactivity.
Masson
Eric
E
Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale, (BCh), Lausanne, Switzerland.
Schlosser
Manfred
M