Regioselective oxidation of carbaporphyrinoid systems

Carbaporphyrins exhibit rich and unique reactivities that form stable organometallic derivatives and unique oxidation reactions. In this review, the regioselective oxidation of carbaporphyrinoids is surveyed. True carbaporphyrins undergo core oxidation to give aromatic carbaporphyrin ketals and weakly aromatic oxycarbaporphyrins, while carbaporphyrin carbaldehydes are converted into aromatic trioxycarbaporphyrins. Azuliporphyrins are easily oxidized to benzocarbaporphyrins and nonaromatic 21-oxyazuliporphyrins. Oxidative metalations are also commonly observed in this system. In addition, other carbaporphyrinoids, including N-confused porphyrins and benziporphyrins, give rise to remarkable oxidation reactions that afford intriguing new structures.