Metalations facilitated by hydrocarbon solvents: Activation provided by opposing-p-resonance in aryl substrates

ORGN 127

D. W. Slocum, Melody Taylor, Scott Brown, Seth Dumbris, B. D. Woosley, Phillip Shelton, and R. W. Holman. Department of Chemistry, Western Kentucky University, Bowling Green, KY 42101
Hydrocarbon solvents do not deoligomerize n-BuLi. In the presence of an aryl substrate possessing a substituent with non-bonding electron pair(s), coordination to n-BuLi is detected. As coordination occurs to n-BuLi only within the tetramer and dimer oligomeric forms, it is inferred that deoligomerization of the hexameric n-BuLi has been enabled by the substrate. Moreover, enhancement of this coordination and extents of aryl metalation by suitably oriented electron-donating substituents on the aryl substrates has been observed. Based on 13C data, a cyclohexane solution of anisole at 25°C formed less than 1% complex with n-BuLi after 3h and only 7% complex after 24h. In contrast, p-dimethoxybenzene afforded 33% complex with n-BuLi in 3h as well as a significantly increased rate and extent of metalation. Similar observations for p-tetramethylphenylenediamine, p-methoxydimethylaniline and p-methylanisole will be reported. Our conjectures regarding the influence of substituents suitably oriented on an aromatic ring will be presented. A conclusion to be advanced from our studies is that there exist electronic effects in certain aromatic substrates that influence the process of directed ortho-metalation.

 

Asymmetric Reactions and Syntheses, Metal-Mediated Reactions, Materials, Molecular Recognition
8:00 PM-10:00 PM, Sunday, August 22, 2004 Pennsylvania Convention Center -- Hall D, Poster

Division of Organic Chemistry

The 228th ACS National Meeting, in Philadelphia, PA, August 22-26, 2004