ol0480022_si_001.pdf (22 kB)
Buttressing Effects on Haloarene Deprotonation: A Merely Kinetic or Also Thermodynamic Phenomenon?
journal contribution
posted on 2004-11-25, 00:00 authored by Joanna Gorecka, Christophe Heiss, Rosario Scopelliti, Manfred Schlosser(2,6-Dichlorophenyl)- and (2,6-dibromophenyl)trialkylsilanes undergo hydrogen/metal interconversion preferentially at the 4- rather than 3-position.
However, the organometallic species generated by such a "meta metalation" are thermodynamically less stable (i.e., more basic) than those
that would result from an ordinary "ortho metalation". This was demonstrated by equilibration experiments based on permutational halogen/metal interconversion. A new buttressing effect can explain the unprecedented regioselectivity. It is supported by X-ray structures that reveal
marked deformations of the benzene ring in halophenylsilanes.