Pawlicki Miłosz, Latos-Grazyński Lechosław, Szterenberg Ludmiła
Department of Chemistry, University of Wrocław, 50 383 Wrocław, Poland.
J Org Chem. 2002 Aug 9;67(16):5644-53. doi: 10.1021/jo025773f.
An oxa-analogue of 5,10,15-triarylcorrole, i.e., 5,10,15-triaryl-21,23-dioxacorrole (21,23-O(2)Cor)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 alpha-alpha bond. The replacement of 2-phenylhydroxymethylfuran by 3-phenylhydroxymethylfuran led to a nonaromatic isomer of (21,23-O(2)Cor)H, i.e., (iso-21,23-O(2)Cor)H, which accommodates two furan rings. The protruding furan is built into the macrocycle via beta and beta' carbon atoms with the oxygen atom pointing outward. Crystal structures of the (21,23-O(2)Cor)H(2)[ZnCl(4)] and [(iso-21,23-O(2)Cor)H(2)]Cl have been studied by X-ray crystallography. The complex ZnCl(4)(2-) anion is located in a clam-shell-like cavity formed by two 21,23-dioxacorrole cations of the (21,23-O(2)Cor)H(2)[ZnCl(4)] unit. The 21,23-dioxacorrole cation is only slightly distorted from planarity. In [(iso-21,23-O(2)Cor)H(2)]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-O(2)Cor)H molecule preserves aromaticity of the parental corrole with characteristic downfield positions of furan and pyrrole resonances in (1)H NMR accompanied the NH resonance at the upfield position (-2.53 ppm). The temperature-dependent features detected in (1)H NMR spectra of (21,23-O(2)Cor)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-O(2)Cor)H yields five-coordinate (21,23-O(2)Cor)Ni(II)Cl--the first high-spin nickel(II) in a corrole-like macrocyclic environment.
5,10,15 - 三芳基卟吩的氧类似物，即5,10,15 - 三芳基 - 21,23 - 二氧杂卟吩（21,23 - O₂Cor）H，其中两个吡咯环被呋喃部分取代，它是通过2,5 - 双（芳基羟甲基）呋喃、2 - 苯基羟甲基呋喃和吡咯缩合制备的。2 - 苯基羟甲基呋喃作为合适的合成子来引入具有形成直接吡咯 - 呋喃α - α键能力的呋喃环。用3 - 苯基羟甲基呋喃取代2 - 苯基羟甲基呋喃会生成（21,23 - O₂Cor）H的一种非芳香异构体，即（异 - 21,23 - O₂Cor）H，它含有两个呋喃环。突出的呋喃通过β和β'碳原子构建到大环中，氧原子向外。通过X射线晶体学研究了[(21,23 - O₂Cor)H₂]₂[ZnCl₄]和[(异 - 21,23 - O₂Cor)H₂]Cl的晶体结构。配合物ZnCl₄²⁻阴离子位于[(21,23 - O₂Cor)H₂]₂[ZnCl₄]单元的两个21,23 - 二氧杂卟吩阳离子形成的蛤壳状空腔中。21,23 - 二氧杂卟吩阳离子仅略微偏离平面。在[(异 - 21,23 - O₂Cor)H₂]Cl中，与规则卟啉相比，由于内环收缩了两个碳原子，大环强烈褶皱。氯离子位于大环中心上方，并参与两个分子内（N）H...Cl和两个分子间（C）H...Cl相互作用，被归类为四分叉体系。（21,23 - O₂Cor）H分子保留了母体卟吩的芳香性，在¹H NMR中呋喃和吡咯共振具有特征性的低场位置，同时NH共振位于高场位置（-2.53 ppm）。在（21,23 - O₂Cor）H的¹H NMR光谱中检测到的温度依赖性特征与互变异构平衡的存在一致，该平衡涉及在N(22)或N(24)氮原子上交替质子化的两个互变异构体。密度泛函理论（DFT）已被用于模拟21,23 - 二氧杂卟吩[22 - N, 24 - NH]、[22 - NH, 24 - N]的两个互变异构体的分子和电子结构。使用B3LYP/6 - 31G**//B3LYP/6 - 31G*方法计算的总能量表明互变异构体之间的能量差非常小（1.4 kcal/mol），表明它们在平衡中同时存在。将镍（II）插入（21,23 - O₂Cor）H中得到五配位的（21,23 - O₂Cor）Ni（II）Cl——在类似卟吩的大环环境中的第一个高自旋镍（II）。
