ORGN 165 |
| Our published observation of the stability of chlorobenzene to the presence of n-BuLi in cyclohexane has led to several further investigations. In cyclohexane p-chloroanisole (p-ClA) slowly undergoes metalation ortho to the methoxy group. Under identical conditions p-fluoroanisole (p-FA)undergoes ortho-lithiation more rapidly. Little hint of a competing benzyne reaction is observed. The order of metalation reactivity when compared to that of anisole (A) is p-FA >p-CIA> A for a given set of conditions, including elevated T. In addition to a conventional electronegativity rationale for this order, an explanation based on a contribution by an opposing-π-resonance effect will be presented. Several derivatives of these metalated intermediates have been prepared. When ortho-lithiodimethylaniline (o-LiDMA) in cyclohexane is treated with o-IA, the reaction proceeds in the direction shown. o-LiDMA + o-IA → o-IDMA + o-LiA There is little or no evidence of the presence of an equilibrium. Implications regarding the relative neoleophilicity/basicity of o-LiDMA and o-LiA will be discussed. |
|
Process R&D, Physical Organic Chemistry, Heterocycles, Aromatics, Metal-Mediated Reactions
8:00 PM-10:00 PM, Sunday, March 25, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Organic Chemistry |