Synthesis, structural characterization and reactivity of heteroazuliporphyrins

Abstract

A series of hetero-azuliporphyrins have been prepared by the "3 + 1" variant on the MacDonald condensation. Azulitripyrranes with tert-butyl and phenyl substituents reacted with thiophene or selenophene dialdehydes in the presence of TFA to give, following an oxidation step, thia- and selena-azuliporphyrins in 45-55% yield. Two of these compounds gave crystals suitable for X-ray crystallographic analysis and the data were consistent with the presence of a 17-atom delocalization pathway. The hetero-azuliporphyrins have significant diatropic character that is enhanced by the presence of an electron-donating tert-butyl substituent. The aromatic character is further increased in polar solvents such as DMSO, which are believed to stabilize dipolar resonance contributors with 18π electron delocalization pathways. Protonation also greatly increases the diatropic characteristics of these macrocycles. The porphyrinoids underwent an oxidative ring contraction with t-BuOOH-KOH to give moderate yields of benzoheterocarbaporphyrins. Reaction of azulitripyrranes with 2,5-furandicarbaldehyde afforded oxa-azuliporphyrins, a class of carbaporphyrinoids that had previously been inaccessible. These "missing links" in the study of heteroazuliporphyrins were isolated as the dihydrochloride salts. Protonated oxa-azuliporphyrins are stable aromatic compounds, but the free base forms underwent rapid decomposition in solution.

Palladium(II), Ruthenium(II), and Ruthenium(III) Complexes of 23-Thiaazuliporphyrin: The Case of Coordination-Induced Contraction

“…Thus, 5,20-diphenyl-10,15-ditolyl-23-thiaazuliporphyrin maintains borderline aromaticity, comparable to βand 10,15-diaryl-substituted analogues. 10,11 This difference significantly grows upon mono- , respectively (600 MHz, CD 2 Cl 2 , 190 K)]. Two canonical structures of 1 describe the π-electron macrocyclic delocalization (Scheme 4).…”

“…Carbaporphyrinoids − provide an intriguing environment for advanced investigations of organometallic reactivity confined to a unique macrocyclic environment . Azuliporphyrinoids (Scheme ), in which one or more porphyrinic pyrrole rings are replaced by the azulene fragment (β-substituted azuliporphyrins, β-substituted 23-heteroazuliporphyrins (O, S, Se), , 10,15-diaryl-23-heteroporphyrins (S, Se), 5,10,15,20-tetraarylazuliporphyrin, 5,10,15,20-tetraaryl-22,24-diheterodiazuliporphyrin (O, S), , and 5,10,15,20-tetraaryltetraazuliporphyrin tetracation), can be considered as the stimulating class of synthetically readily accessible porphyrinoids designed to explore different facets of organometallic azulene coordination triggered by specific macrocyclic support.…”

Tailor-made aromatic porphyrinoids with NIR absorption

“…Lash et al reported the syntheses of thia/selena azuliporphyrins and oxacarbaporphyrins (Scheme 20). 55 These macrocycles 90 / 91 revealed several moderate bands in the Soret band region at 372, 384, 448, and 477 nm, together with broad absorption bands between 500 and 800 nm (Fig. 20).…”

Metal Complexes of Carbaporphyrinoid Systems

“…[30] Modified tripyrrane-like intermediates have also been utilized in the synthesis of heterocarbaporphyrins and dicarbaporphyrinoid systems. For instance, azulitripyrranes 8 reacted with furan, thiophene, and selenophene dialdehydes to give oxa-, thia-, and selena-azuliporphyrins 9, [27,[31][32][33] while the reaction of 8 with indene dialdehyde 10 afforded the dicarbaporphyrinoid 11 (Scheme 3). [27] In addition, "2 + 2" MacDonald-type condensations have been used to prepare mono-and dicarbaporphyrinoids.…”