Transformations of meso‐Iminofunctionalized Pd(II) and Ni(II)‐Complexes of β‐Alkylsubstituted Porphyrins

Abstract

The meso‐imino derivatives of the palladium (II) and nickel (II) complexes of coproporphyrins I and II and β‐octaethylporphyrin were obtained by the Vilsmeier formylation followed by interaction with amines. The metal complexes of the azomethines obtained were transformed to the corresponding complexes of cyclopentane and cyclopentane‐pyrrolidone fused porphyrin derivatives by thermolysis. The plausible mechanism of such transformations was suggested and substantiated with quantum chemical calculations. Meso‐cyano‐, meso‐hydroxy‐, and meso‐aminocarbonyl derivatives of β‐octaethylporphyrin were obtained by treatment of the corresponding meso‐imino derivatives with bases. Demetalation of the nickel complex of the meso‐ hydroxy‐β‐octaethylporphyrin led to formation of the free base derivative. The structures of new types of the porphyrin derivatives were determined via X‐ray powder diffraction analysis. The obtained types of porphyrins are promising candidates to use as photosensitizers in medicine applications due to their longer wave absorption combined with high stability.

Meso-Formyl, Vinyl, and Ethynyl Porphyrins—Multipotent Synthons for Obtaining a Diverse Array of Functional Derivatives

“…The iminium group of the phosphorus complex is more active to nucleophilic attack compared to the formyl group. Azomethine derivatives of nickel and palladium complexes of various porphyrinoids, including OEP, tetraalkyl esters of coproporphyrins I and II, mesoporphyrin IX, and mesochlorin e6, were obtained by direct interaction of "phosphorus complexes" with amines (Scheme 7) [33][34][35].…”

“…Treatment of the Ni(II) complex of meso-(N-methylimino)-OEP 15Ni with t-BuOK led to the formation of the corresponding meso-nitrile 22, meso-amide 23, and meso-hydroxy 24 derivatives (Scheme 10). The latter was demetalated with sulfuric acid, resulting in phlorin 25 with strong light absorption in the region of 700 nm [35]. Thermolysis of meso-alkylimines of β-substituted metal porphyrins led to the formation of cyclopentane-fused derivatives (Scheme 11) [44][45][46].…”

“…Thermolysis of meso-alkylimines of β-substituted metal porphyrins led to the formation of cyclopentane-fused derivatives (Scheme 11) [44][45][46]. The meso-imines of the tetraalkyl ester of coproporphyrin I (26 and 27) were transformed into a mixture of cyclopentane and cyclopentane-lactam bicycle fused derivatives (28)(29)(30) [35]. Thermolysis of meso-alkylimines of β-substituted metal porphyrins led to the formation of cyclopentane-fused derivatives (Scheme 11) [44][45][46].…”

Modification of β-Octaethylporphyrin via Insertion of Amino and Azino Groups into meso-Positions

“…[39] The trifluoroacylated amino derivative 5 was used as a starting material for the electron acceptor fragment insertion as the trifluoroacyl played a role of a protective group for the reactive amino group. The Vilsmeier-Haack formylation of 5 with POCl 3 /DMF [39][40][41] was initially performed, and the so called intermediate "phosphorus complex" was then subjected to the reaction with hydrazine leading to the hydrazone, which was used in the next step without isolation. Finally, p-nitrobenzaldehyde was added to the reaction mixture containing the hydrazone and the condensation products of the three stage reaction were isolated.…”

Synthesis of β-Octaethylporphyrin Conjugates with Nitrogen and Sulfur Containing Heterocycles

“…[19] The porphyrin with aldehyde group, which is easily accessible by this way, is a versatile building block, [20] often used in diverse transformations inherent to the carbonyl group, [21] in particular, in oxidation, reduction, formation of oximes, semicarbazones, imines and cyanohydrins, condensation with CH-acids, Wittig reaction, as well as reactions with organometallic reagents. [22][23][24] Previously, we have reported on the functionalization of the porphyrins through the formylation, followed by the condensation with nitrogen nucleophiles, leading to insertion of imino, [25][26][27] hydrazono [19,28] and azino [29] groups into the meso-position of the tetrapyrrole macrocycle. In the framework of this work, the formylporphyrin was used in condensation reactions with CH-acids to obtain porphyrin conjugates with heterocycles.…”