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1.
Katherine K. Lara 《Tetrahedron》2005,61(9):2529-2539
Osmium tetraoxide-mediated dihydroxylation of meso-tetraaryl-21,23-dithiaporphyrins generates the corresponding meso-tetraaryl-7,8-dihydroxy-21,23-dithiachlorins and meso-tetraaryl-7,8,17,18-tetrahydroxy-21,23-dithiabacteriochlorins. Oxidative diol cleavage reactions of the meso-tetraaryldithia-7,8-dihydroxychlorin generate, depending on the conditions chosen, the corresponding meso-tetraaryldithia-7-oxa-8-oxo-21,23-dithiaporphyrin (dithiaporpholactone) or meso-tetraaryl-7,8-ethoxy-7a-oxa-7a-homo-21,23-dithiaporphyrin (morpholinodithiachlorin), respectively. The UV-vis spectra of the heterochlorins and pyrrole-modified dithiaporphyrins are compared to those of the corresponding all-aza homologues. In general, the trends which distinguish the spectra of dithiaporphyrins from those of all-azaporphyrins are preserved. Thus, the spectra of the dioldithiachlorins tetraoldithiabacteriochlorins are chlorin- and bacteriochlorin-like and bathochromically shifted as compared to the all-azaanalogues, respectively. Also, the dithiaporpholactone spectrum is porphyrin-like. However, the UV-vis spectrum of the morpholinodithiachlorin is uncharacteristic for a morpholinochlorin spectrum. The derivatives described are the first examples of heterochlorins and pyrrole-modified dithiaporphyrins.  相似文献   

2.
DDQ Oxidation of meso-tetraphenyl-cis-2,3-dihydroxychlorins leads to an efficient synthesis of the corresponding 2,3-dioxochlorins. This alternative synthesis of these known chromophores is simple and likely to be more general as compared to established syntheses. A single crystal structure of [meso-tetraphenyl-cis-2,3-dihydroxychlorinato]Ni(II) proves the ruffled structure of the chromophore. The reduction of the free base dioxochlorin allows the preparation of the meso-tetraphenyl-trans-2,3-dihydroxychlorin.  相似文献   

3.
7,8‐Dehydropurpurin has attracted much attention owing to the dual 18π‐ and 20π‐electron circuits in its macrocyclic conjugation. The two‐fold Pd‐catalyzed [3+2] annulation of meso‐bromoporphyrin with 1,4‐diphenylbutadiyne furnished 7,8‐dehydropurpurin dimers. The 8a,8a‐linked dimer displays a red‐shifted and enhanced absorption band in the NIR region and a small electrochemical HOMO–LUMO band gap as a consequence of efficient conjugation between the two coplanar 7,8‐dehydropurpurin units. Treatment of this dimer with N‐bromosuccinimide in chloroform and ethanol gave β‐to‐β vinylene‐bridged porphyrin dimers. Owing to the highly constrained conformations, these dimers exhibit perturbed absorption spectra, small Stokes shifts, and high fluorescence quantum yields.  相似文献   

4.
A series of meso-furyl porphyrins with four different porphyrin cores (N4, N3S, N2S2 and N3O) were synthesized and characterized. The comparison of NMR, optical and fluorescence properties of meso-furyl porphyrins with porphyrins with six-membered aryl groups indicates that electronic properties of porphyrins were changed drastically on the introduction of furyl groups at meso positions. The maximum shifts in spectral bands were observed for meso-furyl porphyrins with N2S2 core. On protonation, the absorption bands of meso-furyl porphyrins were further red shifted. All these changes were ascribed to the possibility of more planarity of the meso-furyl porphyrins due to the small size of the furyl groups which results in extending the π-delocalisation of the porphyrin ring in to the furyl groups.  相似文献   

5.
A series of meso-dithiole and tetrathiafulvalene (TTF) dipyrromethanes have been prepared via the reaction of the appropriate aldehyde with either pyrrole or 3-ethyl-2,4-dimethyl-pyrrole under acid catalysis. Oxidation to the corresponding meso-dithiole dipyrrins is reported together with the formation of the metal chelate complexes (M=Zn, Cu, Ni) as well as the meso-dithiole boron-dipyrromethene (BODIPY). The molecular structures of these metal (Cu, Ni) and boron complexes are presented and discussed. According to a similar strategy the meso-TTF BODIPY is prepared and its photophysical properties are presented and compared with those of the meso-dithiole BODIPY.  相似文献   

6.
The absorption and fluorescence properties of a series of meso-thienylporphyrins with different porphyrin cores (N4, N3O, N3S and N2S2 cores) were studied and compared with the corresponding meso-tetraarylporphyrins. The replacement of six-membered phenyl groups with five-membered thienyl groups at meso-positions resulted in red shifts and broadening of absorption and emission bands, low quantum yields and decreased S1 state lifetimes and the maximum effects were observed for meso-tetrathienylporphyrin with N2S2 porphyrin core. Similar observations were noted for the dications of meso-thienylporphyrins compared to the dications of the corresponding meso-tetraarylporphyrins. These results suggest that the replacement of six-membered aryl group with five-membered thienyl groups at meso-positions, the electronic properties of the porphyrin were altered significantly.  相似文献   

7.
B. Evans  K.M. Smith 《Tetrahedron》1977,33(6):629-633
Treatment of meso-substituted metalloporphyrins [meso -substituent = OCOCF3, OCOCH3, OMe, CHO, CN, Cl; metal = Zn(II) or Cd(II)] with thallium(III) trifluoroacetate, followed by an acidic work-up, gives the corresponding β-substituted α-oxophlorins which were either characterised as such or else further derivatised. In all cases the major (or only) disubstitution product has the αβ orientation at the meso positions, indicating that the existing meso substituent directs the incoming one (trifluoroacetate) into the flanking, rather than opposite, meso position of the intermediate π-cation radical or π-dication. In contradistinction, meso substituted zinc(II) porphyrins which are able to lose protons (e.g. α-oxophlorins or α-aminoporphyrins) react with thallium(III) trifluoroacetate, and after a work-up with HCl the corresponding γ-chloro-α-oxophlorin or γ-chloro-α-aminoporphyrin is obtained.  相似文献   

8.
《Tetrahedron: Asymmetry》2006,17(6):1017-1021
The stereoselective enzymatic acylation of meso-6,7-diazabicyclo[3.2.1]oct-6-ene-2,4-diol 4 and meso-4,6-diazidocyclohexane-1,3-diol 5 in organic media gave the corresponding monoesters in high enantiomeric excess. The hydrolysis of the corresponding diacetate derivatives in the presence of a different set of enzymes provided the same monoesters. The products are precursors of dideoxystreptamine, an aminocyclitol found in synthetic aminoglycoside antibiotics.  相似文献   

9.
Chlorins have been synthesized through the reduction of the corresponding porphyrins although theoretically they can be obtained from reduced macrocycle forms as porphyrinogens. A new method for the oxidation of meso-tetraarylporphyrinogens was developed generating a substantial amount of chlorin relatively to porphyrin. The structure of the porphyrinogen, particularly the presence of substituents on the meso-phenyl groups, is decisive for the final yield of chlorin. In the case of meso-tetrakis(2,6-dichlorophenyl)porphyrinogen, 92% of the corresponding chlorin is obtained.  相似文献   

10.
Despite significant interest, the chiroptical properties of subporphyrins have rarely been investigated because chiral subporphyrins are elusive. Here, inherently chiral subporphyrins are elaborated by forming a fused pyran ring at the periphery of an A2B-type meso-aryl-substituted subporphyrin. Their circular dichroism (CD) properties are largely affected by the peripheral substituents and the dihedral angles between the meso-aryl substituents and the subporphyrin core: the β-perbromo subporphyrin with an orthogonal arrangement of the meso-phenyl substituents to the subporphyrin core exhibits weak CD signals corresponding to the Q bands, whereas the unsubstituted species with smaller dihedral angles shows relatively intense CD signals. A detailed structure–property relationship of these chiral subporphyrins was elucidated by time-dependent (TD) DFT calculations. This study reveals that the CD properties of chiral subporphyrins can be controlled by peripheral substitution and meso-aryl substituents.  相似文献   

11.
BF2- and PO2-smaragdyrins containing one five membered heterocycle such as pyrrole, thiophene and furan at one of the meso-position of corresponding 25-oxasmaragdyrins were synthesized by treating the appropriate mono meso-heterocycle substituted 25-oxasmaragdyrin with BF3.OEt2 and POCl3 respectively in CH2Cl2 under mild reaction conditions. All macrocycles were thoroughly characterized by HR-MS and 1D and 2D NMR spectroscopy. The presence of a five membered heterocycle in place of a six membered aryl group significantly alters the electronic properties of the smaragdyrin macrocycle as reflected in their spectral and electrochemical properties. The meso-pyrrole BF2-smaragdyrin was subjected to a Vilsmeier-Haack reaction to prepare meso-(α-formyl pyrrolyl) BF2-smaragdyrin which was subsequently used to prepare meso-(α-dipyrromethanyl pyrrolyl) BF2-smaragdyrin. The further use of meso-heterocycle substituted BF2- and PO2-oxasmaragdyrins was demonstrated by treating meso-pyrrolyl BF2-smaragdyrin with pentafluorobenzaldehyde in CHCl3 under mild acid catalysed conditions to afford an unusual dipyrromethanyl bridged BF2-smaragdyrin dyad which exhibits excellent photophysical properties.  相似文献   

12.
《Tetrahedron: Asymmetry》1998,9(16):2827-2831
The stereoselective acetylation of meso-2,3-bis(3,4-dimethoxybenzyl)butanediol by vinyl acetate in the presence of Candida antarctica lipase in benzene gave the corresponding (+)-(2S,3R) monoester (ee ≥98%). Transesterification of meso-2,3-bis(3,4-dimethoxybenzyl)butyl diacetate, in the presence of the same enzyme, by ethanol in benzene/isopropyl ether gave the corresponding (−)-(2R,3S) monoester (ee ≥98%). Both enantiomers of the known cis-2,3-bis(3,4-dimethoxybenzyl)butyrolactone were synthesized from these monoesters.  相似文献   

13.
The reactions of 4-phenyl-and 4-phenoxyphthalimide with benzoic acid in the presence of zinc(II) oxide gave zinc complexes of meso-tetraphenyltetra(4-phenylbenzo)porphyrin and meso-tetraphenyltetra(4-phenoxybenzo)porphyrin, respectively, and the latter were treated with hydrochloric acid to isolate the corresponding metal-free prophyrins. Spectral properties of the complexes and ligands were studied.  相似文献   

14.
Further examples of the broad applicability of horse liver alcohol dehydrogenase-catalyzed oxidations of meso-diols as a route to chiral lactones of asymmetric synthetic value are described. The acyclic meso substrates, cis-2,3-dimethyl- and -diethylbutane-l,4-diols, and cis-2,4-dimethylpentane-l,5diol, are stereospecifically oxidized in good yields to the corresponding enantiomerically pure γ- and δ-lactones. The oxidation of cis-3,4-bis(hydroxymethyl)thiacyclopentane is similarly stereospecific. For each meso-diol the oxidation takes place with a net stereospecificity for the hydroxymethyl groups attached to the S-enters, with the initially formed hydroxyaldehydes undergoing further enzymecatalyzed oxidations via their hemiacetal forms to produce lactone products directly.  相似文献   

15.
The direct organocatalytic desymmetrization of cyclic meso-anhydrides was achieved by alcoholysis with nitroallylic alcohols. The reaction between primary nitroallylic alcohols and cyclic meso-anhydrides catalyzed by cinchonidine derived thiourea organocatalyst II (10 mol %) proceeded smoothly. The corresponding hemiesters were obtained in high chemical yields with high to excellent levels of stereoselectivity (up to 90% yield and 99% ee). On the other hand, the reversal of enantioselectivity was observed when an amino cinchonidine derivative (III) was used as the organocatalyst under the similar reaction conditions. This demonstrated an example of activation of the nucelophilic component in the desymmetrization of cyclic meso-anhydrides.  相似文献   

16.
An efficient one-pot protocol for the direct conversion of free base 5,15-disubstituted porphyrins into the corresponding meso activated alkenyl-substituted meso-formylporphyrins has been developed using a sequential SNAr reaction with PyMe2SiCH2Li, conjugate addition to enones or alkenoates in the presence of TMSCl, and oxidation with DDQ.  相似文献   

17.
The desymmetrization of meso compounds is one of the most effective strategies for asymmetric synthesis. This digest focuses on recent progress in the desymmetrization of meso-diols and their derivatives. The topics discussed here include methods for the enzymatic acylation of meso-diols and the hydrolysis of meso-diesters, acylation, related reactions of meso-diols with organocatalysts and metal catalysts, the oxidation of meso-diols by enzymes, organocatalysts, and metal catalysts, and the desymmetrization of meso-dicarbamates with metal catalysts. The desymmetrization of meso-diols using tandem reactions is also discussed.  相似文献   

18.
Fluorination of quadruply bicyclo[2.2.2]octadiene-fused porphyrin (CP) with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) occurred at the meso positions to give a mixture of various meso-fluorinated CPs, which were separated and then quantitatively transformed to the corresponding meso-fluorinated tetrafluorobenzoporphyrins (BPs) at 240 °C for 30 min. X-ray analysis of the mono-fluoro BPs revealed that the BP skeleton remained flat, which is crucial for retaining aggregation behavior similar to that of the parent BP, thus producing highly crystalline BP derivatives.  相似文献   

19.
Alkyl-substituted bis(cyclopentadienyl)dimethylsilanes react with Me2Sn(NEt2)2 and with (Me2N)4Sn to yield correspondingly substituted, meso-configurated RS-8-sila-4-stanna-s-tetrahydroindacene and axially symmetric RR,SS-4-spiro-bis(8-sila-4-stanna-s-tetrahydroindacene) compounds, respectively, which are stereoselectively converted by reaction with ZrCl4 to the corresponding meso- and rac-configurated ansa-zirconocene complexes.  相似文献   

20.
Synthetic strategies for using the meso-β-linkage as a structural motif in electron transfer mimics have been tested. Exploratory syntheses of directly meso-β-linked bis- and trisporphyrins and the first representative X-ray structure of a meso-β-linked bisporphyrins are reported. The structure reveals a unique form of intramolecular π-π stabilization between one porphyrin and a meso-aryl substituent in a second porphyrin unit that accounts for the stability of different atropisomers in trimers. Using β-formyl porphyrins, dipyrromethanes, and suitable quinone precursor aldehydes, mixed condensations gave convenient access to porphyrin-porphyrin-quinone (P-P-Q) donor-acceptor systems consisting of a meso-β-linked bisporphyrin, a spacer, and a quinone acceptor.  相似文献   

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