Novel aspects of the chemistry of 1,19-diunsubstituted a,c-biladienes

Cyclization of a,c-biladienes in alcoholic solution gives corroles. When the same reaction is carried out in CHCl3 a completely different outcome is observed, and the product of the reaction is the corresponding open-chain biliverdin. The critical step for the cyclization to corrole is the formation of the fully conjugated 22,24-dihydro-a,b,c-bilatriene cation, which is allowed in methanol and appears to be prevented in CHCl3. The presence of substituents at the 10-position of the a,c-biladiene is also critical for the reaction; while a phenyl group strongly enhances the formation of corrole, in the case of alkyl groups the formation of both corrole and biliverdin is prevented. This result can reasonably be attributed to the failure to give a fully conjugated 22,24-dihydro-a,b,c-bilatriene structure for 10-alkyl substituted a,c-biladienes. Carrying out the a,c-biladiene cyclization in acidic methanol permits a new one-pot preparation of beta-alkylcorroles. Copyright (C) 2003 Society of Porphyrins & Phthalocyanines

5,10,15-Triphenylcorrole: a product from a modified Rothemund reaction

One-pot synthesis of 5,10,15-triphenylcorrole has been achieved by reaction of benzaldehyde with an excess of pyrrole; the triphenylphosphinocobalt complex of 5,10,15-triphenylcorrole has been structurally characterized using X-ray crystallography