3-NO2-5,10,15-triarylcorrolato-Cu as a versatile platform for synthesis of novel 3-functionalized corrole derivatives

The post-functionalization of Co(iii)PPh3 triarylcorroles through Suzuki-Miyaura couplings and their tunable electrochemically-catalyzed hydrogen evolution and oxygen reduction

The post-functionalization of six novel symmetric and asymmetric meso-expanded Co(iii) corroles through Suzuki-Miyaura coupling reactions has been successfully accomplished and is reported along with their structural characterization. An analysis of the structure-property relationships of the optical and redox properties of the corroles has been carried out by comparing their optical spectra and their electrochemical properties. The results demonstrate that post-functionalized meso-expanded Co(iii) triarylcorroles exhibit enhanced electrocatalyzed oxygen reduction reaction (ORR) activity and that their reactivity can be controlled by modulating the electronic structure, the functionalization and the number of coupled meso-substituents.

Facile Generation of A2B Corrole Radical Using Fe(III) Salts and Its Spectroscopic Properties

A carboxyphenyl-substituted corrole, 5,15-dimesityl-10-(4'-carboxyphenyl)corrole (1), has been synthesized and characterized by UV-vis, fluorescence, ¹H NMR spectroscopy, and electrospray ionization (ESI)-mass spectrometry (MS) techniques. An air-stable corrole radical (1^•) was obtained with the addition of the Fe(III) salt to 1 in dimethyl sulfoxide (DMSO) and characterized by UV-vis, fluorescence, electron paramagnetic resonance (EPR), ESI-MS techniques, and density functional theory studies. The neutral corrole radical (1^•) exhibited a sharp EPR signal at g = 2.006 in DMSO. The reduced bipyrrolic (N-C-C-N) dihedral angle (χ) of 1 from 19.11 to 7.07° leads to the release of angle strain, which is the driving force for the generation of 1^•. Notably, trans-dimesityl groups prevent the dimerization or aggregation of the corrole radical. Further, 1^• was converted to 1 by excess addition of Fe(II) salts in DMSO at 298 K.

Strategies for Corrole Functionalization

This review covers the functionalization reactions of meso-arylcorroles, both at the inner core, as well as the peripheral positions of the macrocycle. Experimental details for the synthesis of all known metallocorrole types and for the N-alkylation reactions are presented. Key peripheral functionalization reactions such as halogenation, formylation, carboxylation, nitration, sulfonation, and others are discussed in detail, particularly the nucleophilic aromatic substitution and the participation of corroles in cycloaddition reactions as 2π or 4π components (covering Diels-Alder and 1,3-dipolar cycloadditions). Other functionalizations of corroles include a large diversity of reactions, namely Wittig reactions, reactions with methylene active compounds, formation of amines, amides, and imines, and metal catalyzed reactions. At the final section, the reactions involving oxidation and ring expansion of the corrole macrocycle are described comprehensively.

Synthesis and functionalization of β-alkyl-meso-triarylcorroles

After the definition of efficient synthetic routes for the preparation of triarylcorroles, the functionalization of these macrocycles is becoming a necessary and challenging field of research. One important synthetic step is the introduction of substituents able to influence the electronic distribution in the macrocyclic ring. A valuable target would be a corrole macrocycle with some β-pyrrole positions occupied by methyl groups, while exploiting other positions to introduce electron-withdrawing substituents. To explore the scope of this approach, we investigated the bromination and the nitration of the corrole ring and the desired products have been obtained in moderate to good yield. The successful preparation of selectively halogenated corroles is particularly interesting since they are suitable substrates for the preparation of more complex partially alkylated structures using modern cross coupling methodologies.

Corrole and nucleophilic aromatic substitution are not incompatible: a novel route to 2,3-difunctionalized copper corrolates

The insertion of a -NO2 group onto the corrole framework represents a key step for subsequent synthetic manipulation of the macrocycle based on the chemical versatility of such a functionality. Here we report results of the investigation of a copper 3-NO2-triarylcorrolate in nucleophilic aromatic substitution reactions with "active" methylene carbanions, namely diethyl malonate and diethyl 2-chloromalonate. Although similar reactions on nitroporphyrins afford chlorin derivatives, nucleophilic attack on carbon-2 of corrole produces 2,3-difunctionalized Cu corrolates in acceptable yields (ca. 30%), evidencing once again the erratic chemistry of this contracted porphyrinoid.