Synthesis of Benziporphyrins and Heterobenziporphyrins and an Assessment of the Diatropic Characteristics of the Protonated Species

Abstract

Benzitripyrranes were prepared by reacting diphenyl-substituted benzenedicarbinols with excess pyrrole in the presence of BF3·Et2O. These dipyrrolic compounds underwent acid-catalyzed condensations with a pyrrole dialdehyde to afford good yields of diphenylbenziporphyrins, and further reaction with palladium(II) acetate gave stable organometallic derivatives. The X-ray crystal structure of a palladium(II) benziporphyrin showed that the system deviates significantly from planarity. Although the benzitripyrranes failed to give stable macrocyclic products with furan or thiophene dialdehydes, they afforded tetraphenyl heterobenziporphyrins upon reaction with diphenyl-substituted furan- or thiophenedicarbinols and BF3·Et2O. Benziporphyrins and their heteroanalogues showed no indication of a diamagnetic ring current by proton NMR spectroscopy, but addition of TFA gave rise to the formation of weakly diatropic dications.

An alternative synthesis of benziporphyrins starting from isophthaloyl chloride

“…This results in cross-conjugated structures that are devoid of macrocyclic aromatic properties [8]. However, electron-donating substituents such as methoxy groups introduce a degree of diatropic character [9] and protonated benziporphyrins also appear to possess significant diamagnetic ring currents [9][10][11][12][13][14][15]. Benziporphyrins act as dianionic organometallic ligands, forming stable derivatives with Ni(II), Pd(II), Pt(II), etc.…”

“…Benziporphyrins act as dianionic organometallic ligands, forming stable derivatives with Ni(II), Pd(II), Pt(II), etc. [13][14][15][16][17][18][19][20]. In addition, meso-tetraarylbenziporphyrins undergo selective oxidation reactions with silver(I) acetate [12,17], and rhodium(III) derivatives can undergo ring contraction reactions to afford metalated carbaporphyrins [21].…”

“…Alternatively, benzene dicarbinols 6 react with 3 equivalents of pyrrole and 2 equivalents of an aromatic dialdehyde in the presence of boron trifluoride etherate to give meso-tetraarylbenziporphyrins 7 (Scheme 1) [11,17]. These strategies have been adapted for the synthesis of heterobenziporphyrins [13,15], naphthiporphyrins [14] and fully aromatic oxybenzi porphyrins [10,14,24,25]. In order to further extend our inquiries into these types of porphyrinoid analogs, we have investigated the development of new synthetic routes to benziporphyrins and related systems.…”

Synthesis and Metalation of Dimethoxybenziporphyrins, Thiabenziporphyrins, and Dibenziporphyrins

“…20 Tripyrrane analogues 6 were prepared in good yields by reacting the known carbinols 7 6 with excess pyrrole in the presence of boron trifluoride etherate (Scheme 1). The tripyrranes reacted with pyrrole dialdehyde 8 in the presence of trifluoroacetic acid in dichloromethane, followed by oxidation with DDQ, to give the meso-diphenylbenziporphyrins 9.…”

Phenanthriporphyrin: An Antiaromatic Aceneporphyrinoid as a Ligand for a Hypervalent Organophosphorus(V) Moiety

“…Molecules comprising structural features of polycyclic aromatic hydrocarbons and polypyrrolic macrocycles in am anner which allows for electronic communication, for example aceneporphyrinoids, exemplify this approach. [1][2][3][4][5][6][7][8][9][10] Such compounds can demonstrate peculiar electronic and molecular structures and create au nique macrocyclic environment for coordination forcing atypical intermolecular reactivity.F or instance,acontraction of p-phenylene to cyclopentadiene is triggered by insertion of palladium(II) or gold(III) into p-benziporphyrin. [6,11,12] Herein, we report the synthesis and properties of an ew member of the aceneporphyrinoid class,n amely phenanthriporphyrin 4-H 3 (Scheme 1).…”