Meso-tetraarylporphyrin

The thioglycosylated meso-tetraarylporphyrins 124(o,p) (A-C) photocytotoxicities were evaluated against K562 chronic leukaemia cell lines.81... 

Alternative approaches for substituted porphyrins have been devised in which pre-functionalized dipyrromethane derivatives 3 are condensed with similar diformyl dipyrromethanes 4 through a "2+2" condensation to form meso-tetraarylporphyrins 5 (Scheme 3). Such condensations are usually catalyzed by acids and the intermediate porphyrinogens are oxidized by air to obtain porphyrins. In a similar "3+1" synthetic approach, tripyrranes 6 are condensed with 2,5-diformylpyrroles to form etioporphyrin 5 (1996CEJ1197). 

Ionic meso-tetraarylporphyrins can be bound to a range of charged supports including cross-linked polystyrene based anions,78 cations,79 exchange resins, cross-linked and quaternized poly(4-vinylpyridine)80 and the oxides of silica, alumina and magnesia.81 Metalloporphyrins may be attached to supports by coordination of a ligand on the support to the metal centre. Such catalysts mimic... 

This multithreading process was realized in the construction of multiporphyrin assemblies from macrocycles with pendent zinc(II) or gold(III) meso-tetraarylporphyrins.59 These assemblies are shown in Figure 2.26,... 

Olefinic pyrazines like 108 were shown to react with QH in the superacid TfOH to give anti-Markovnikov addition products like 109 <050L2505>. The orientation observed is presumed to be due to the multiply charged heterocycle adjacent to the olefin. Pyrazine o-quinodimethanes underwent Diels-Alder condensation with meso-tetraarylporphyrins to give new jt-extended porphyrins <05TL2189>. A one-pot formation of polycyclic - and -lactones like 111 was developed using the reaction of pyridine and pyrazine (110) with bis(trimethylsilyl)ketene acetals. Many of them were characterized by X-ray <05EJO3724>. 

Most of the metalloporphyrin systems used as P450 models are variations on the theme of meso tetraarylporphyrins, with a variety of substituents in the meso-positions. These models manage to combine effective stereospecific oxidation of the products, protection of the iron porphyrin catalyst from... 

Ghosh, I. Halvorsen, H.J. Nilsen, E. Steene, T. Wondimagegen, R. Lie, E.V. Caemel-becke, N. Guo, Z. Ou, and K.M. Kadish (2001). Electrochemistry of nickel and copper 5-octahalogeno-meso-tetraarylporphyrins. Evidence for important role played by saddling-induced metal (dx2-y2)-porpliyrine( a2u ) orbital interactions. J. Phys. Chem. B 105, 8120-8124. 

The Diels-Alder reaction of meso-tetraarylporphyrins with the pyrazine o-quinodimethane mainly affords the oxidized 49a-c instead of the expected chlorin adducts. The bisaddition is site specific, occurring in opposite pyr-rolic rings and leads to 51 and 52. The novel polycyclic 50a-c, 52a, and 52b result from the coupling between the P-fused quinoxaline ring and one adjacent meso-aryl group. In contrast to compounds 49a and 51a, there... 

Electrochemistry and spectroscopy of the tt cation radical of meso-tetraalkylchlorin (tetra-methyl) and various porphyrins (tetramethyl, tetraethyl, and tetra-ra-propyl) indicate that these do not convert to Nim at low temperatures.280 Optical evidence reveals, however, that oxidation of the tt cation radical of [Ni(pEt2N)(TPP)] leads to a Ni111 cation radical which can be further oxidized to a Ni111 porphyrin dication. Similar studies have been carried out for various other derivatives of me.so-tetraarylporphyrins such as /V-oxides of TPP and 5,10,15,20-tetramesitylpro-phyrin (TMP). Addition of trifluoroacetic acid (TFA) to the /V-oxide of [NinTMP] at —25 °C in CH2C12 results in [Nim(TMP)]+ with a rhombic EPR spectrum, g = 2.40, 2.12, and 2.04.281... 

The functionalization of zinc porphyrin complexes has been studied with respect to the variation in properties. The structure and photophysics of octafluorotetraphenylporphyrin zinc complexes were studied.762 Octabromoporphyrin zinc complexes have been synthesized and the effects on the 11 NMR and redox potential of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraarylporphyrin were observed.763 The chiral nonplanar porphyrin zinc 3,7,8,12,13,17,18-heptabromo-2-(2-methoxyphenyl)-5,10,15,20-tetraphenylporphyrin was synthesized and characterized.764 X-ray structures for cation radical zinc 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin and the iodinated product that results from reaction with iodine and silver(I) have been reported.765 Molecular mechanics calculations, X-ray structures, and resonance Raman spectroscopy compared the distortion due to zinc and other metal incorporation into meso dialkyl-substituted porphyrins. Zinc disfavors ruffling over doming with the total amount of nonplanar distortion reduced relative to smaller metals.766 Resonance Raman spectroscopy has also been used to study the lowest-energy triplet state of zinc tetraphenylporphyrin.767... 

Starting from the Ni mrao-formyloctaethylporphyrin oxime complex, the meso-cyanooctaethylporphyrin N-oxide complex has been synthesized for the first time. The double addition of the nitrile oxide to 2,5-norbornadiene afford a porphyrin dimer, whose structure has been established by X-ray diffraction analysis (485). The 1,3-dipolar cycloaddition reaction of w< .so-tetraarylporphyrins with 2,6-dichlorobenzonitrile oxide yields isoxazoline-fused chlorins and stereoiso-metric bacteriochlorins. The crystal structure of one of bacteriochlorins has been characterized by X-ray diffraction (486, 487). 

A few other triads and more complex systems eonsisting of a porphyrin linked to two or more fullerene moieties have been reported [150, 159, 221]. The most complex to date is a tetraarylporphyrin linked to four fullerene moieties through double ester-containing bridges to the porphyrin meso aryl groups [151]. This molecule is rendered soluble in organie solvents via 16 twelve-carbon aliphatic chains. The porphyrin fluorescence is strongly quenehed by the attached Ceo moieties. 

Aqueous sodium hypochlorite is another low-priced oxidant. Very efficient oxidative systems were developed which contain a meso-tetraarylporphyrinato-Mn(III) complex salt as the metal catalyst and a QX as the carrier of hypochlorite from the water phase to the organic environment. These reactions are of interest also as cytochrome P-450 models. Early experiments were concerned with epoxidations of alkenes, oxidations of benzyl alcohol and benzyl ether to benzaldehyde, and chlorination of cyclohexane at room temperature or 0°C. A certain difficulty arose from the fact that the porphyrins were not really stable under the reaction conditions. Several research groups published extensively on optimization, factors governing catalytic efficiency, and stability of the catalysts. Most importantly, axial ligands on the Mn porphyrin (e.g., substituted imidazoles, 4-substituted pyridines and their N-oxides), 2 increases rates and selectivities. This can be demonstrated most impressively with pyridine ligands directly tethered to the porphyrin [72]. Secondly, 2,4- and 2,4,6-trihalo- or 3,5-di-tert-butyl-substituted tetraarylporphyrins are more... 

A good structural and functional model of the heme/nonheme di-iron center of the active site of the prototype NOR has been developed and characterized by Karlin and co-workers.The complexes consist of a binucleating ligand with a tetradentate tris(2-pyridylmethyl)amine moiety tethered to a synthetic tetraarylporphyrin (with three 2,6-difluorophenyl meso substituents see Figure 11). As discussed above, the resonance Raman spectra of the oxidized compound show features in common with NOR supporting the assignment of the active site as oxo-bridged in the oxidized enzyme. 

From these above-mentioned results, Pozzi and coworkers synthesized the new tetraarylporphyrin, 3, with eight perfluoroalkylponytails (fluorine content 65%) directly linked to die meso aryl groups((73). Compound 3 was obtained by condensation of the pyrrole derivative 4 (Scheme 1) in the presence of Zn(OAc)2 as... 

Reaction of 3,4-difluoropyrrole 391 with benzaldehydes 470 followed by oxidation with DDQ led to tetraarylporphyrins 471. On the base of that reaction sequence a convenient and common pathway towards p-octafluoroporphyrins 471, bearing meso-tetraaryl substituents, including perfluorinated tetraarylporphyrin was elaborated [153], In the case of AI2O3 catalysis the first step of above mentioned sequence afforded p-octafiuorocorroles 472 instead of porphyrins 471 [154],... 

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