New strategies for the peri lithiation of naphthalamides
Directed metalation reactions are an interesting area of synthetic chemistry. They provide a powerful regiospecific method for functionalizing complex aromatic rings. Presently, directed ortho metalations are well understood. However, there has been very little progress in the remote metalation of naphthalene derivatives. Presently the peri lithiation of naphthalamides is a reaction that has not been solved to a level that allows for it to be deployed in a vast number of synthetic schemes. The processes by which peri functionalized naphthalamides are present obtained required several steps and give poor yields. Previously attempts directed toward the peri lithiation in the Schwan lab have met with little success. Herein experiments were preformed to understand why the pervious attempts failed and other experiments were performed in an effort to acheive the peri lithiation of a specific naphthalamide. The mechanism of previous chemical observations was understood by trapping experiments and clearly demonstrated how problematic acidic sites can interfere with intended directed metalation. The acidic site was sterically hindered by employing strategic protecting groups. However, the steric demand of the protecting groups considered was not sufficient to eliminate the problematic acidic site. This led to the consideration of an alternative strategy for the peri lithiation by removing the acidic center of the specific substrate. This however, resulted in remote addition of lithiating reagents to the naphthalamide and clearly showed that several naphthalamides are not a suitable directed metalation group for the peri lithiation.