One-pot synthesis of meso-alkyl substituted isocorroles: the reaction of a triarylcorrole with Grignard reagent.

The reaction of 5,10,15-tritolylcorrole with EtMgBr opens the way for novel functionalizations of the corrole ring. DDQ oxidation of the macrocycle, followed by addition of the Grignard reagent, led to the formation of 5- and 10-alkyl substituted isocorroles in satisfying yields. Together with the one-pot formation of these isocorrole isomers, the use of such a nucleophile evidenced the competitive reactivity of the macrocycle β-positions, leading to the formation of 2-bromo- and 3-bromo-5,10,15-tritolylcorrole. While the formation of these monobromocorrole derivatives is not unprecedented, this is the first time the isomers have been separated and fully characterized. Furthermore, the higher yields of the 2-substituted species highlight a useful regioselectivity for the substitution reaction.