Corrols

Condensed Pyrroles. Pyrroles can be condensed to compounds containing two, three, or four pyrrole nuclei. These are important ia synthetic routes to the tetrapyrroHc porphyrins, corroles, and bile pigments and to the tripyrroHc prodigiosias. The pyrrole nuclei are joiaed by either a one-carbon fragment or direct pyrrole—pyrrole bond. 

Square pyramidal [Co(corrole)(PPh3 )]<= > [Rhl2Me(PPh3)2]... 

Corrole is a tetrapyrrolic macrocycle 1-Norbomyl is a bicyclo[2.2.1]hept-l-yl... 

Originally, 1,19-unsubstituted or 1,19-dicarboxylated biladienes-ac were prepared75 for the synthesis of corroles (See Section 1.6.), but by condensation with formaldehyde they give the corresponding porphyrins, e.g. 14. The method is especially valuable for the introduction of isotopic labels from the formaldehyde moiety.76... 

Copper corrole is a diamagnetic copper(III) complex which at higher temperatures exists in the triplet state and is then best formulated as a copper(II) corrole-n-radical. 

Similarly, the corresponding nickel complex, based on ESR spectroscopy, should be formulated as a nickel(II) corrole-71-radical. The iron corroles exist in the oxidation state + 111 or + IV depending on the nature of additional axial ligands. 

The cobalt corroles are as expected isolated as neutral cobalt(III) complexes with an additional neutral axial ligand, which in most cases is triphenylphosphane or pyridine. 

Schemes based on the acid-catalyzed condensation of a bipyrrole with a dipyrrylmethane are in general unsuccessful for the synthesis of corroles. Thus, the bipyrroles 1 fail to give corroles when reacted with the appropriate dipyrrylmethane 2.10,11 However, cobalt(III) corrole 3 can be prepared in moderate yield by a [2 + 2] approach involving bipyrrole T and dipyrrylmethane 2 bearing formyl groups and carboxylic groups, respectively, and heating initial condensation products, presumably norbilenes, with cobalt(II) acetate and triphenylphosphane in methanol.12...

The most successful general synthesis of corroles 13 involves the light-induced cyclization of l,19-dideoxybiladienes- c 12 under basic conditions in the presence of oxygen.1-2 6,15-16 The yields of corroles 13 arc in the range of 20-70%.17,18... 

Substituted or 1,19-disubstituted octadehydrocorrins are formal tautomers of corroles. When the 1- or 19-substituents are carboxylate residues it is possible to decarboxylatc the esters after hydrolysis.213,15,22... 

The octadehydrocorrins including the corroles are able to stabilize the electron pair liberated by the bond fission between the carboxylic group and the chromophore. 

Protonation and deprotonation reactions of corroles have already been mentioned (see Introduction). Attempts to achieve electrophilic substitution reactions, at the corrole, e.g. Friedel-Crafts acylation, have been unsuccessful.1 Heating corroles with acetic anhydride yields the corresponding 21-acetyl derivatives l.8a,b... 

Alkylation of corrole anions (RI, K2C03, acetone) gives a mixture of A21- and A22-alkylated corroles 2 and 3, respectively, in which the A2 -product predominates.6 8i At elevated temperatures bisalkylated JV.A-dialkyl corroles 4 are formed. 

Metallocorroles (M = Cu, Ni or Pd) can also be alkylated under the same conditions as the metal-free corroles23,24 to give the N2i-alkylated products together with a small amount of C3 alkylated product ( f = Pd). Allyl halides or bulky alkyl halides react with nickel corroles also at the 3-position. 

The name corrphycene for [18]porphyrin(2.1.0.1) is derived from the fact that these compounds combine structural elements from corrins/ corroles, porphyrins and acenes. Two general synthetic strategies have been developed for the final cyclization step of a linear tctrapyrrole leading to the macrotetracycle. 

Chemical transformations at the isocorrole framework are still unknown. The complexation behavior of isocorroles has been found to be similar to that of the corroles and has been reviewed.2... 

Macrocyclic Ligands (Corrins and Corroles) (see also Table 17.10)... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Porphyrins, Hydroporphyrins, Azaporphyrins, Phthalocyanines, Corroles, Corrins and Related Macrocycles... 

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