Functionalization of Deutero- and Protoporphyrin IX Dimethyl Esters via Palladium-Catalyzed Coupling Reactions

Herein, we report the functionalization of the β-positions of deutero- and protoporphyrin IX dimethyl esters. Initial halogenations were carried out on both deutero- and protoporphyrin IX dimethyl esters. Although previously reported, vastly optimized yields with respect to deuteroporphyrin halogenation were obtained. Methods were developed for the bromination of the vinyl groups of protoporphyin IX dimethyl ester. Subsequent palladium-catalyzed coupling reactions were utilized to modify the periphery of these naturally occurring porphyrin derivatives with a variety of functionalities. The described Suzuki, Sonogashira, and "Click" reactions demonstrate the ease at which these porphyrins may be manipulated and even interchangeable, as will be discussed for one example. X-ray crystallographic analysis successfully determined the structure of two derivatives synthesized. Results identified a unique head-to-tail stacking pattern for 3,8-diphenyldeuteroporphyrin IX dimethyl ester, most likely due to the presence of additional aromatic moieties on the periphery of the porphyrin.