Recent advances on the synthesis and chemistry of carbaporphyrins and related porphyrinoid systems

Synthetic methods have been developed for the efficient synthesis of meso-unsubstituted carbaporphyrinoid systems, including oxybenziporphyrins, benzocarbaporphyrins, tropiporphyrins, and azuliporphyrins. In addition, meso-tetrarylporphyrinoids are available by using modified Lindsey-Rothemund reaction conditions. These porphyrin analogs show a broad spectrum of aromatic properties that range from nonaromatic benziporphyrins to highly diatropic systems such as benzocarbaporphyrins. Carbaporphyrinoid systems exhibit unusual reactivity and are often capable of generating organometallic derivatives under mild conditions. Many of the trends observed in the carbaporphyrinoid series were also evident for an expanded series of carbasapphyrins as well. Syntheses of dicarbaporphyrinoids have been investigated but it remains to be seen whether these studies will eventually lead to the formation of hydrocarbon analogs of the porphyrins.