On corrole chemistry. An isomerization study and oxidative cleavage of the corrole macroring to a biliverdin structure

In the present paper, we report the synthesis of free 5- and l0-monophenylcorroles, 4 and 3 respectively as well as the first example of molecular oxygen oxidation of the corrole macrocycle identified as an open chain tetrapyrrole (biliverdin) structure 7. Reaction of 1 and 2 in acetic acid leads to a mixture of two a,c-biladienes 3b and 4b and therefore to a mixture of two corrole isomers 3 and 4. Reaction of 1 and 2 in trifluoroacetic acid leads only to the symmetrical corrole isomer 3 in 41% yield.