Reactions of Antiaromatic Norcorrole Ni(II) Complex with Carbenes

Oxidative insertion of amines into conjugated macrocycles: transformation of antiaromatic norcorrole into aromatic azacorrole

A new group of aromatic porphyrinoids was obtained by an oxidative insertion of primary amines into the antiaromatic ring of 5,14-dimesityl-norcorrolatonickel(II) activated by iodosobenzene. The substituted 10-azacorroles thus formed were characterized by spectroscopic and electrochemical methods, and XRD analysis. Protonated forms of azacorroles were shown to remain aromatic despite disconnection of the original π-electron delocalization path.

The Effect of Hydrogenation on the Contest between Aromaticity and Antiaromaticity in Norcorrole

Magnetic shielding studies demonstrate that successive hydrogenation of Ni^II norcorrole (NiNc), a stable molecule combining aromatic and antiaromatic features, first weakens and then eliminates the central antiaromatic region, even though the NiNc antiaromatic "core", a 14-membered conjugated cycle with 16 π electrons, is formally preserved throughout the H₂ NiNc-H₈ NiNc series. The differences between aromatic and non-aromatic isotropic shielding distributions and nucleus-independent chemical shift (NICS) values in these hydrogenated porphyrin analogues are highlighted by comparing the results for the members of the H₂ NiNc-H₈ NiNc series to those for the aromatic Ni^II porphyrin complex. The results strongly support the unexpected and counterintuitive conclusion that H₈ NiNc will be nonaromatic, without even a trace of antiaromaticity. Based on these findings, H₈ NiNc is predicted to be the most stable member of the H₂ NiNc-H₈ NiNc series.

From Antiaromatic Norcorrolatonickel(II) to Aromatic and Nonaromatic Zwitterions: Innocent Ligands with Unbalanced Charge of the Core

A three-component reaction of antiaromatic meso-mesityl-3-nitronorcorrolatonickel(II) 1-NO₂ with dialkyl acetylenedicarboxylate and PBu₃ yields aromatic zwitterionic corrole nickel(II) complexes 3-R with one of the meso-substituents comprising a positively charged tributyl phosphonium group and negatively charged coordination core. Reaction of 1-NO₂ with PBu₃ alone resulted in a nonaromatic chiral adduct 5 of a zwitterionic phlorine character with a −PBu₃⁺ group at a pyrrole β-position.

Nucleophilic Aromatic Substitution (SNAr) and Related Reactions of Porphyrinoids: Mechanistic and Regiochemical Aspects

The nucleophilic substitution of aromatic moieties (SNAr) has been known for over 150 years and found wide use for the functionalization of (hetero)aromatic systems. Currently, several "types" of SNAr reactions have been established and notably the area of porphyrinoid macrocycles has seen many uses thereof. Herein, we detail the SNAr reactions of seven types of porphyrinoids with differing number and type of pyrrole units: subporphyrins, norcorroles, corroles, porphyrins, azuliporphyrins, N-confused porphyrins, and phthalocyanines. For each we analyze the substitution dependent upon: a) the type of nucleophile and b) the site of substitution (α, β, or meso). Along with this we evaluate this route as a synthetic strategy for the generation of unsymmetrical porphyrinoids. Distinct trends can be identified for each type of porphyrinoid discussed, regardless of nucleophile. The use of nucleophilic substitution on porphyrinoids is found to often be a cost-effective procedure with the ability to yield complex substituent patterns, which can be conducted in non-anhydrous solvents with easily accessible simple porphyrinoids.

Friedel–Crafts acylation of antiaromatic norcorroles: electronic and steric modulation of the paratropic current

The first ever Friedel–Crafts acylation of an antiaromatic macrocycle was performed for norcorrolatonickel(ii) reacting with aromatic or aliphatic carboxylic acid chlorides in the presence of AlCl₃.

Synthesis and electron-transport properties of a stable antiaromatic NiII norcorrole with the smallest meso-substituent

meso-Dimethylnorcorrole NiII complex exhibited enough stability under ambient conditions despite the distinct antiaromaticity. The small methyl substituents realized a dense and long-range π-stacking in its solid state, which resulted in the superior electron-transporting ability to previously reported NiII norcorroles.