Premium
Carbaporphyrinoids Containing a Pyridine Moiety: 3‐Aza‐ meta ‐benziporphyrin and 24‐Thia‐3‐aza‐ meta ‐benziporphyrin
Author(s) -
Myśliborski Radomir,
LatosGrażyński Lechosław
Publication year - 2005
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500496
Subject(s) - chemistry , pyridine , thiophene , ring (chemistry) , protonation , pyrrole , trifluoroacetic acid , moiety , medicinal chemistry , molecule , crystal structure , aryl , stereochemistry , crystallography , organic chemistry , ion , alkyl
6,11,16,21‐Tetraaryl‐3‐aza‐ m ‐benziporphyrin, an analog of 5,10,15,20‐tetraarylporphyrin with one of the pyrrole units replaced by a pyridine ring pointing outwards, linked at β,β′ positions, was formed by condensation of 3,5‐bis[phenyl(2‐pyrrolyl)methyl]pyridine, pyrrole and p ‐tolualdehyde catalyzed by TFA. The [3+1] approach, which involved a condensation of 3,5‐bis[phenyl(2‐pyrrolyl)methyl]pyridine with 2,5‐bis[hydroxy( p ‐tolyl)methyl]thiophene was applied to afford 6,11,16,21‐tetraaryl‐24‐thia‐3‐aza‐ m ‐benziporphyrin. Introduction of bulky substituents at ortho positions of meso ‐aryl compounds, adjacent to the pyridine ring, resulted in an increase in the yield of condensation. 3‐Aza‐ m ‐benziporphyrins and 24‐thia‐3‐aza‐ m ‐benziporphyrins have the 1 H NMR spectroscopic features of non‐aromatic molecules. Crystal structures of 6,21‐diphenyl‐11,16‐di‐ p ‐tolyl‐3‐aza‐ m ‐benziporphyrin and 6,21‐diphenyl‐11,16‐di‐ p ‐tolyl‐24‐thia‐3‐aza‐ m ‐benziporphyrin were determined by X‐ray crystallography. Both molecules show a similar degree of nonplanarity with the pyridine ring sharply tipped out of the N(23)X(24)N(25) plane, making room for the 6,21‐phenyl groups which are almost coplanar with the macrocycle. The protonation of 6,21‐diphenyl‐11,16‐di‐ p ‐tolyl‐3‐aza‐ m ‐benziporphyrin with trifluoroacetic acid proceeds stepwise, subsequently yielding two dicationic and one tricationic species. Protonated 6,21‐diphenyl‐11,16‐di‐ p ‐tolyl‐24‐thia‐3‐aza‐ m ‐benziporphyrinreacts reversibly with water to give 6‐hydroxy‐6,21‐diphenyl‐11,16‐di‐ p ‐tolyl‐24‐thia‐3‐aza‐ m ‐benziphlorin. The protonation of 6,21‐dimesityl‐11,16‐di‐ p ‐tolyl‐24‐thia‐3‐aza‐ m ‐benziporphyrin initiates an unprecedented process, which converts the non‐aromatic carbaporphyrinoid reversibly into the aromatic 2‐hydroxy‐6,21‐dimesityl‐11,16‐di‐ p ‐tolyl‐24‐thia‐3‐aza‐ m ‐benzichlorin. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)