Wydział Chemii

Miłosz Pawlicki

Lechosław Latos-Grażyński

Ludmiła Szterenberg

2002

Journal of Organic Chemistry

67

5644-5653

10.1021/jo025773f

Naukowa

Angielski

Artykuł

An oxa-analogue of 5,10,15-triarylcorrole, i.e., 5,10,15-triaryl-21,23-dioxacorrole (21,23-O₂Cor)H, where two pyrrole rings are replaced by furan moieties, has been produced by condensation of 2,5-bis(arylhydroxymethyl)furan, 2-phenylhydroxymethylfuran, and pyrrole. 2-Phenylhydroxymethylfuran serves as the suitable synthone to introduce a furan ring with the ability create a direct pyrrole−furan α−α bond. The replacement of 2-phenylhydroxymethylfuran by 3-phenylhydroxymethylfuran led to a nonaromatic isomer of (21,23-O₂Cor)H, i.e., (iso-21,23-O₂Cor)H, which accommodates two furan rings. The protruding furan is built into the macrocycle via β and β‘ carbon atoms with the oxygen atom pointing outward. Crystal structures of the [(21,23-O₂Cor)H₂]₂[ZnCl₄] and [(iso-21,23-O₂Cor)H₂]Cl have been studied by X-ray crystallography. The complex ZnCl₄^2- anion is located in a clam-shell-like cavity formed by two 21,23-dioxacorrole cations of the [(21,23-O₂Cor)H₂]₂[ZnCl₄] unit. The 21,23-dioxacorrole cation is only slightly distorted from planarity. In [(iso-21,23-O₂Cor)H₂]Cl, the macrocycle is strongly puckered as the internal ring is contracted by two carbon atoms when compared to regular porphyrin. The chloride anion is located over the center of the macrocycle and is involved in two intra (N)H···Cl and two intermolecular (C)H···Cl interactions to be classified as a tetrafurcate system. The (21,23-O₂Cor)H molecule preserves aromaticity of the parental corrole with characteristic downfield positions of furan and pyrrole resonances in ¹H NMR accompanied the NH resonance at the upfield position (−2.53 ppm). The temperature-dependent features detected in ¹H NMR spectra of (21,23-O₂Cor)H are consistent with the existence of a tautomeric equilibrium which involves two tautomers alternatively protonated on N(22) or N(24) nitrogen atoms. The density functional theory (DFT) has been applied to model the molecular and electronic structure of two tautomers of 21,23-dioxacorrole {22-N, 24-NH}, {22-NH, 24-N}. The total energies calculated using the B3LYP/6-31G**//B3LYP/6-31G* approach demonstrate a very small energy difference (1.4 kcal/mol) between tautomers suggesting their simultaneous presence in equilibrium. Insertion of nickel(II) into (21,23-O₂Cor)H yields five-coordinate (21,23-O₂Cor)Ni^IIClthe first high-spin nickel(II) in a corrole-like macrocyclic environment.

Anions, Aromatic compounds, Macrocycles, Molecular structure, Pyrroles

https://doi.org/10.1021/jo025773f

https://www.acs.org/content/acs/en.html