Synthesis and Properties of Carbaporphyrin and Carbachlorin Dimethyl Esters Derived from Cyclopentanedialdehydes

Abstract

Norbornenes with two ester substituents were prepared by Diels-Alder cycloadditions of cyclopentadiene with dimethyl fumarate and dimethyl 1,1-ethylenedicarboxylate. Oxidation with potassium permanganate gave good yields of related diols that were oxidatively ring-opened to afford cyclopentane dialdehydes. MacDonald-type "3 + 1" condensations with a tripyrrane, followed by oxidation with DDQ in refluxing toluene, gave carbaporphyrin or carbachlorin products in good yields. The macrocyclic products were highly diatropic and produced porphyrin-like UV-vis spectra. The carbaporphyrin was converted into silver(III) and gold(III) organometallic derivatives. Reaction with methyl iodide in the presence of potassium carbonate gave mono- and dialkylation products, and treatment of the former with Ni(OAc) or Pd(OAc) afforded nickel(II) and palladium(II) complexes. The free base carbaporphyrin and carbachlorin, and the nickel and palladium complexes, were characterized by X-ray crystallography. The carbachlorin also reacted with silver(I) acetate to give a silver(III) derivative. Carbaporphyrins and carbachlorins underwent deuterium exchange at the meso-positions with deuteriated TFA, and this observation indicates that protonation is occurring at the bridging carbons. The new route to carbaporphyrins and carbachlorins has enabled detailed studies on the properties of these systems and provides the foundations for future investigations.

Metalation and Methyl Group Migration in 21-, 22-, and 23-Methylcarbaporphyrins: Synthesis and Characterization of Palladium(II), Rhodium(I), and Rhodium(III) Derivatives

“…The palladium­(II) center resides in an approximately square planar coordination environment with 2.058(2) Å Pd–C21, 2.037(2) Å Pd–N22, 2.066(2) Å Pd–N23, and 2.028(1) Å Pd–N24 bond lengths. In fact, the metal coordination environment is indistinguishable from that of the closely related complex (8,12,13,17-tetraethyl-2,3-bis­(methoxycarbonyl)-7,18,21-trimethyl-21-carbaporphyrinato)­palladium­(II) . Complex 15a has the palladium­(II) ion coordinating η 1 to C21, and as the carbon is alkylated, this leads to the distended 1.491(2) and 1.498(2) Å sp 3 →sp 2 C21–C1 and C21–C4 bond distances, and C21 is clearly separated from the macrocycle’s π-system.…”

“…Benziporphyrins are also dianionic ligands, whereas N-confused porphyrins can act as both dianionic or trianionic ligands . True carbaporphyrins such as 1 and 2 are trianionic ligands and have been shown to form Ag­(III), − Au­(III), Rh­(III), and Ir­(III) derivatives. However, the coordination chemistry can be altered by replacing one of the remaining nitrogens with oxygen, sulfur, or selenium.…”

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

“…Despite this, it is an avenue that has been continually explored. [ 154,155 ] Azuliporphyrins are macrocycles in which one of the pyrrole rings has been replaced with an azulene.…”

Tropylium and Porphyrinoid Character in Carbaporphyrinoid Systems. Relative Stability and Aromatic Characteristics of Azuliporphyrin and Tropiporphyrin Tautomers, Protonated Species, and Related Structures

“…Over the last 20 years, increasing emphasis has been placed on carbaporphyrinoid systems, porphyrin analogues that have one or more carbon atoms instead of nitrogens within the macrocyclic cavity. , These include true carbaporphyrins such as 3 and 4 , − N-confused porphyrins 5 , , neo-confused porphyrins 6 , , and benziporphyrins 7 (Figure ). These systems vary from fully aromatic macrocycles to nonaromatic systems.…”