The accessibility of functionalized Grignard reagents has opened new dimensions in organic synthesis. One of us has previously demonstrated that treatment of substituted bromoarenes with iPrMgCl·LiCl provides a straightforward access to functionalized aryl Grignard reagents by bromine–magnesium exchange. In accord with the suggested mechanism for these reactions, electron-acceptor groups have been observed to facilitate this conversion. We have now determined the relative rates of such exchange reactions to facilitate a targeted use of these reactions on polyfunctional compounds.