A simple and versatile one-pot synthesis of meso-substituted trans-A2B-corroles

We have developed a new methodology that affords regioisomerically pure trans-A2B-corroles. The corrole formation reaction involves the acid-catalyzed condensation of a dipyrromethane and an aldehyde followed by oxidation with DDQ. Optimal conditions for the condensation were identified after examining various reaction parameters (solvent, acid, concentration, time). The conditions identified (CH2Cl2, [DPM] = 33 mM, [aldehyde] = 17 mM, [TFA] = 1.3 mM (for sterically hindered DPMs) or [TFA] = 0.26 mM (for sterically unhindered DPMs), 5 h, room temperature) resulted in the formation of corroles in 3-25% yield without detectable scrambling. The synthesis is compatible with diverse functionalities: ester, nitrile, ether, fluoro, hydroxy, iodo, nitro, thioacetate, methylsulfoxy. In total 21 corroles of type trans-A2B were prepared. Three exemplary corrole syntheses were successfully carried out at 8 mmol scale. Corroles 23, 30, and 41 (160-600 mg) were obtained in essentially the same yield as in small scale experiments.