Demetallation of <i>meso</i>-substituted porphyrins

A mild and efficient method for the acid-promoted demetallation of functionalized metalloporphyrins is described. In contrast to the normally harsh conditions required, a variety of Cu porphyrins were rapidly demetallated in excellent yields using methanesulfonic acid in a chlorinated hydrocarbon solvent at room temperature or under microwave heating. Some Co, Ni, and Ag porphyrins could also be efficiently demetallated. Notably, the presence of a small amount of a coordinating solvent in the reaction mixture either completely inhibited the demetallation or significantly slowed it down. Electron withdrawing functionality also slowed down the demetallation time.