(112a) Mechanistic Studies on the Activation of a Carbon-Carbon Single Bond Via Palladium-Catalyzed β-Alkyl Elimination

The activation and functionalization of carbon-carbon single
bonds presents a significant challenge due to their significant thermodynamic
and kinetic stability.  Miura and coworkers have demonstrated the selective
cleavage of carbon-carbon single bonds followed by functionalization through
coupling with an aryl halide (Journal of Organic Chemistry, 2004,
69, 6942).  Carbon-carbon bond activation is proposed to occur via 
palladium-catalyzed β-alkyl elimination of an aryl group from tertiary
alcohols. 

This work presents the results of the mechanistic study of
β-alkyl elimination.  The nature of the mechanism was more fully
understood through kinetic studies of the palladium-catalyzed coupling of
triphenylmethanol and bromobenzene.  Furthermore, a series of tertiary alcohols
with various substitutions were prepared and tested for the relative rate of
carbon-carbon bond activation.  Intermolecular and intramolecular competition
reactions examined the relative propensity of cleavage of groups containing
differing hybridization, electronic properties, and sterics.  The results of
this study promise to provide additional insight into the process of
carbon-carbon bond activation and facilitate the future development of more
general and selective methodology.