MTO/H 2 O 2 /Pyrazole-Mediated N-Oxidation of meso -Tetraarylporphyrins and -chlorins, and S-Oxidation of a meso -Tetraaryldithiaporphyrin and -chlorin (original) (raw)
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The Journal of Organic Chemistry, 2010
The OsO 4 -mediated dihydroxylation of meso-tetraphenylporphyrin N-oxide yields two regioisomeric chlorin N-oxides. These chlorin N-oxides can be manipulated to provide pairs of regioisomers of pyrrole-modified porphyrin N-oxides. The UV-vis absorption and fluorescence emission spectra of the neutral and protonated regioisomers are distinct from each other, and generally different from the parent chromophore. The outcome of diol oxidation reactions of some N-oxide diolchlorins varies from the corresponding reactions of the parent diolchlorins. The crystal structure of a free base porpholactone N-oxide carrying the N-oxide on the oxazolone moiety is reported.
European Journal of Organic Chemistry, 2016
Application of a variant of our “porphyrin breaking and mending strategy” to free base and NiII complexes of meso‐tetraarylporphyrin – dihydroxylation, oxidative diol cleavage and reaction of the resulting seco‐chlorin bis(aldehyde) with ammonia – generates pyrazinoporphyrins. Thus, a nitrogen atom was inserted between the two former β‐carbon atoms, overall formally replacing a pyrrolic building block by a pyrazine moiety. Treatment of the initially formed pyrazine hemiaminals with alcohols converts them into the corresponding hemiaminal ethers. This stabilizes the chromophores significantly, but the free‐base pyrazinoporphyrins still remain sensitive toward (acid‐induced) degradation reactions. Free‐base pyrazinoporphyrins possess slightly redshifted porphyrin‐type UV/Vis spectra, while the spectra of the pyrazinoporphyrin NiII complexes resemble more those of metallochlorins.
Journal of Porphyrins and Phthalocyanines, 2012
trans-Diolchlorin was prepared by nucleophilic addition of methyl-Grignard bromide to meso-tetraphenyl-2,3-dioxoporphyrin, as its free base or Ni(II) complex. The trans-configuration of the vic-diol functionality was shown by single crystal X-ray diffractometry. The nickel complex of the trans-dimethyldiol proved susceptible to Pb(IV) acetate-induced, oxidative diol cleavage, generating a meso-tetraphenylsecochlorin bismethylketone Ni(II) complex, the first example of this chromophore class. Under Brønsted-basic conditions, this bisketone cyclized via an intramolecular aldol condensation to provide a meso-tetra phenyloxypyriporphyrin. Reduction of this porphyrin analog saturated the double bond in the pyridinone moiety, generating an oxypyrichlorin. Reaction of the meso-tetraphenylsecochlorin bismethylketone Ni(II) complex with Lawesson's reagent induced the formation of a thiomorpholinochlorin substituted with two methylene groups, the first example of any porphyrin analog containing a thiomorpholine moiety. MESO-TETRAPHENYLPORPHYRIN-DERIVED OXYPYRIPORPHYRIN 577 N OH OH O 5, M = 2H 5Ni, M = Ni(II) M M M 6, M = 2H 6Ni, M = Ni(II) 7, M = 2H 7Ni, M = Ni(II) Scheme 1. Synthesis of octaalkyloxypyriporphyrin by oxidation and subsequent aldol condensation of a diolchlorin
European Journal of Organic Chemistry, 2016
Application of a variant of our "porphyrin breaking and mending strategy" to free base and Ni II complexes of mesotetraarylporphyrin-dihydroxylation, oxidative diol cleavage and reaction of the resulting seco-chlorin bis(aldehyde) with ammonia-generates pyrazinoporphyrins. Thus, a nitrogen atom was inserted between the two former-carbon atoms, overall formally replacing a pyrrolic building block by a pyrazine moiety. Treatment of the initially formed pyrazine hemiaminals
Synthesis, Reactivity, and Spectroscopic Properties of meso-Triaryl-5-oxaporphyrins
Journal of Organic Chemistry, 2012
Triaryl-21,23-didehydro-23H-5-oxaporphyrinato](trifluoroacetato)zinc(II) was prepared by the reaction of meso-triarylbilindione with acetic anhydride and zinc acetate, and it was isolated as a trifluoroacetate salt. The X-ray crystallographic study demonstrated that the trifluoroacetate anion was coordinated to the zinc ion. [21,23-Didehydro-10,15,20-tris(4-methoxycarbonylphenyl)-23H-5oxaporphyrinato](trifluoroacetato)zinc(II) 3a was dissolved in various organic solvents such as toluene, chloroform, diethyl ether, ethyl acetate, acetone, acetonitrile, methanol, DMSO, and DMF, although it readily reacted with alcohols and DMF to yield linear tetrapyrroles. The solubility of 3a in toluene was 4.2 ± 0.1 g dm −3 at room temperature. 3a showed characteristic UV−vis absorption at 649 nm and fluorescence emission at 657 nm in chloroform. The fluorescence quantum yields of 3a, [21,23-didehydro-10,15,20-triphenyl-23H-5-oxaporphyrinato]-(trifluoroacetato)zinc(II) (3c), and [21,23-didehydro-10,15,20-tris(4-methoxyphenyl)-23H-5-oxaporphyrinato]-(trifluoroacetato)zinc(II) (3b) were 0.071, 0.071, and 0.050, respectively. Reaction of 3a with EtOH afforded the zinc complex of 19-ethoxybilinone, and it proceeded 2 orders of magnitude faster than that of [β-octaalkyl-21,23-didehydro-23H-5oxaporphyrinato]zinc(II). The reaction with alcohols was sensitive to steric bulk of the alcohols; the rate of reaction with i-PrOH was 2700 times faster than that of t-BuOH at 303 K. The reaction of [meso-triaryl-21,23-didehydro-23H-5-oxaporphyrinato]zinc(II) with water proceeded 3 orders of magnitude slower than that with EtOH.
European Journal of Inorganic Chemistry, 2017
In continuing our studies on the photosensitizing ability of the 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) molecular complex of meso-tetraphenylporphyrin H2TPP, in the present study the photocatalytic activity of tetra-cyanoethylene (TCNE) molecular complexes of a series of para or ortho substituted mesotetraarylporphyrins (aryl = phenyl, 2-methylphenyl, 4-methylphenyl and 4-methoxylphenyl) for the areobic oxidation of olefins has been studied and compared with that of the DDQ counterparts and the free base porphyrins. Significantly higher catalytic performances were observed for the TCNE molecular complexes in a much shorter reaction time. This observation is in accord with the remarkably greater singlet oxygen quantum yield of the TCNE complexes (φΔ = 0.57-0.98) relative to that of the DDQ complexes (φΔ = 0.03-0.57) and the free base porphyrins (0.32-0.63). Also, the photocatalytic activity of the molecular complexes was found to be greatly influenced by the meso substituents. The involvement of a singlet oxygen mechanism in the oxidation reactions was confirmed by using 1,3-diphenylisobenzofuran and 1,4-benzoquinone as the singlet oxygen quencher and superoxide anion radical scavenger, respectively.
Synthesis of meso-tetraarylporphyrins using SeO2 as oxidant
Tetrahedron Letters, 2011
The oxidative step of the two-step, one-flask synthesis of meso-tetraarylporphyrins is herein conducted with heterogeneous oxidant SeO 2 instead of the usual quinones DDQ or p-chloranil. Evaluation of BF 3 O(Et) 2 or I 2 amount for the condensation of the first step combined with the excess of SeO 2 defined porphyrin synthesis conditions employing benzaldehydes and pyrrole (or 5-phenyldipyrromethane) as starting materials. The simplicity of the workup, allied with reaction mild conditions, makes this method a good option for the synthesis of this kind of compound.
International Journal of Photoenergy, 2009
This paper deals with a series of new unsymmetrically substituted mesoporphyrins: 5-(2-hydroxyphenyl)-10,15,20-trisphenyl-21,23-H-porphyrin (TPPOH O ), 5-(3-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOH M ), 5-(4-hydroxyphenyl)-10,15,20-tris-phenyl-21,23-H-porphyrin (TPPOH P ), 5-(2-hydroxyphenyl)-10,15,20-tris-butyl-21,23-H-porphyrin (TBPOH O ), and their parent nonsubstituted compounds, respectively, 5,10,15,20-tetrakis-phenyl-21,23-H-porphyrin (TPP) and 5,10,15,20-tetrakis-butyl-21,23-H-porphyrin (TBP). Several photophysical studies were carried out to access the influence of the unsymmetrical substitution at the porphyrinic macrocycle on porthyrin's photophysical properties, especially porthyrin's efficiency as singlet oxygen sensitizers. The quantum yields of singlet oxygen generation were determined in benzene (Φ Δ (TPP) = 0.66 ± 0.05; Φ Δ (TPPOH O ) = 0.69 ± 0.04; Φ Δ (TPPOH M ) = 0.62 ± 0.04; Φ Δ (TPPOH P ) = 0.73 ± 0.03; Φ Δ (TBP) = 0.76 ± 0.03; Φ Δ (TBPOH O ) = 0.73 ± 0.02) using the 5,10,15,20-tetraphenyl-21,23-H-porphine (Φ Δ (TPP) = 0.66) and Phenazine (Φ Δ (Phz) = 0.83) as reference compounds. Their fluorescence quantum yields were found to be (Φ f (TPPOH O ) = 0.10 ± 0.04; Φ f (TPPOH M ) = 0.09 ± 0.03; Φ f (TPPOH P ) = 0.13 ± 0.02; Φ f (TBP) = 0.08 ± 0.03 and Φ f (TBPOH O ) = 0.08 ± 0.02 using 5,10,15,20-tetraphenyl-21,23-H-porphine as reference Φ f (TPP) = 0.13). Singlet state lifetimes were also determined in the same solvent. All the porphyrins presented very similar fluorescence lifetimes (mean values of τ S (with O 2 , air equilibrated) = 9.6 ± 0.3 nanoseconds and (without O 2 , argon purged) = 10.1 ± 0.6 nanoseconds, resp.). The phosphorescence emission was found to be negligible for this series of unsymmetrically substituted mesoporphyrins, but an E-type, thermally activated, delayed fluorescence process was proved to occur at room temperature.
First synthesis of meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins
Beilstein Journal of Organic Chemistry, 2014
A synthetic protocol for the construction of new meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins is described starting from 5-(4-amino-3-nitrophenyl)-10,15,20-triphenylporphyrin. The reaction of this porphyrin with 2,5-dimethoxytetrahydrofuran, followed by the reduction of the nitro group in the presence of NiCl2/NaBH4 afforded 5-(3-amino-4-(pyrrol-1-yl)phenyl)-10,15,20-triphenylporphyrin. This triphenylporphyrin underwent a Pictet–Spengler cyclization after the reaction with various aromatic aldehydes followed by in situ KMnO4 oxidation to form target porphyrin analogues in good yields. The structures of all synthesized products were established on the basis of spectral data and elemental analyses.