Efficient Synthesis of β-Alkynylcorroles

The introduction of alkynyl groups at the β-pyrrolic positions of dibrominated corrole derivatives was attempted by using both Sonogashira and Stille coupling methodologies. An efficient bromination protocol was developed by using a silver corrolate, which enabled the regioselective preparation of the 3,17-Br2 isomer in high yield. Whereas unsatisfactory results were obtained by applying Sonogashira reaction conditions, the Stille methodology produced, for the first time, novel 3,17-diphenylethynylcorrole derivatives in good to excellent yields. A mild demetalation protocol of the silver complex led to the corresponding corrole free base, opening the way for the preparation of different metal complexes and further elaboration of the corrole platform by using alkyne chemistry. Regioselective dibromination of corrole and subsequent Stille cross-coupling allow the successful preparation of triarylcorroles functionalized at the β positions with alkynyl substituents. These derivatives represent a novel approach to modulate the macrocycle properties, opening the way for corrole-based molecular architectures featuring extensive π conjugation.