Showing papers on "Xanthene published in 2006"

Amberlyst-15: An efficient reusable heterogeneous catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines

Abstract: Amberlyst-15 has been found to be an efficient catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines in excellent yields. The former have been synthesized from aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione while the latter from this mixture along with amines. The method is an easy access to functionalized xanthene and acridine derivatives. The catalyst can be reused.

An organic white light-emitting fluorophore.

Abstract: The synthesis of new benzo[a]- and [b]xanthene dye frameworks is described. A unique benzo[a]xanthene, seminaphtho[a]fluorone (SNAFR-1), is studied in a variety of media. The optimization of solution parameters and excitation wavelengths allows SNAFR-1 to display red, green, and blue emission bands of approximately equal intensities and also to produce white light. Ratiometric red (anion) and green (neutral) emissions are observed upon varying solution pH. A pH-independent violet-blue emission band is due to the addition of nucleophiles to the benzylic carbon of SNAFR-1.

An Efficient Catalyst System for the Asymmetric Transfer Hydrogenation of Ketones: Remarkably Broad Substrate Scope

Abstract: A BINOL-derived diphosphonite having a xanthene backbone is an excellent bidentate ligand in Ru-catalyzed 2-propanol-based transfer hydrogenation of aryl/alkyl and alkyl/alkyl ketones (ee = 76−99%). Even notoriously difficult ketones such as isopropyl methyl ketone are reduced with extraordinarily high enantioselectivity (ee = 99%).

The Phototoxicity of Xanthene Derivatives Against Escherichia coli, Staphylococcus aureus , and Saccharomyces cerevisiae

Abstract: We assessed the phototoxicity of a series of xanthene derivatives against E. coli, S. aureus, and S. cerevisiae, measured the physicochemical properties of the photosensitizers, and found the relationship between them. Without illumination, the dyes tested showed almost the same level of inherent toxicity to the same organism, which showed the inherent toxicity of dyes was primarily dependent on the structure of parent molecule. Upon illumination, the photosensitizers showed obvious phototoxicity to all organisms. The dyes showed stronger phototoxicity to Gram-positive bacteria. With the increasing number of halogen substituents, the singlet oxygen yields increased and the phototoxic activity increased too. There was no obvious correlation between relative lipophilicity and activity in the current study. Our results showed xanthenes had the potential to act as alternatives to conventional antimicrobial compounds and also could be used for the decontamination of microbially polluted waters.

Complex Formation between Rhodamine B and Poly(sodium 4-styrenesulfonate) Studied by 1H-NMR

Abstract: A 1H NMR study is presented for the binding of rhodamine B (RB) to the polyanion containing aromatic groups poly(sodium 4-styrenesulfonate) (PSS), which is also evidenced by diafiltration. 1H NMR spectra showed an accentuated upfield shift of proton H6‘ of the benzoic ring of RB at pH 7, indicating the stacking of RB onto PSS. The corresponding structure is proposed which is in accordance to Hunter and Sanders rules. At pH 2, an upfield shift of the xanthene protons of RB would indicate a highly condensed state for this molecule.

Hangman salen platforms containing two xanthene scaffolds.

Abstract: A synthetic strategy for the construction of chiral salen ligands bearing two rigid xanthene spacers functionalized with carboxylic acid and ester groups is presented. Suzuki cross-coupling methodology is used to furnish the appropriately functionalized xanthene spacers to a salicyladehyde, which is subsequently condensed with (1R,2R)-(−)-1,2-diaminocyclohexane to produce salen ligands featuring an expandable molecular cleft capable of multiple hydrogen-bonding interactions in addition to metallosalen oxidation chemistry. The ability of these “Hangman” platforms to support multielectron chemistry mediated by proton-coupled electron transfer (PCET) is established by their proclivity to promote the catalytic disproportionation of hydrogen peroxide to oxygen and water via a high-valent metal oxo. Within this functionalized Hangman framework, the stereochemistry of the cyclohexyl backbone of the salen platform is revealed in the epoxidation of 1,2-dihydronaphthalene by the metal oxo.

Xanthene-Based Ligand with Two Adjacent β-Diiminato Binding Sites

Abstract: A novel potential ligand has been designed where two β-dialdimine units are linked by a xanthene backbone (H2Xanthdim). The synthesis proceeds via a double vinamidinium salt and the products of its...

Facile and selective aerobic oxidation of arylalkanes to aryl ketones using cesium carbonate

Abstract: Various arylalkanes such as fluorenes, xanthene, anthrone, 9,10-dihydroanthracene, and diphenylmethane are effectively transformed into the corresponding aryl ketones, while amino and aldehyde functionalities remain intact, under air in the presence of cesium carbonate.

Microwave irradiation for accelerating the synthesis of acridine and xanthene derivatives from dimedone

Abstract: Microwave (MW) irradiation activated the reaction of dimedone with aniline or p-chloroaniline in formic acid to give the acridine derivatives 2a and 2 b, respectively, which can be derivatized as the bisoximes 3 and bisphenylhydrazone 4. However, under the same reaction conditions 2- aminopyridine gave the xanthene derivative 6 and not the expected acridine derivative 2c. When 2-aminopyridine was allowed to react under MW irradiation with dimedone in presence of benzaldehyde in ethanol it gave the bis(dimedonyl)methane derivative 10. Cyclization of 10 has been enhanced under MW irradiation to give the xanthene derivative 9 in improved yield and in less time than the conventional heating. The structures of products were confirmed from the analysis of their IR, 1 H-NMR and mass spectra. The antimicrobial activity has been investigated for compounds 3, 4, 6 and 10.

Inhibition Mechanism of UDP-Glucuronosyltransferase 1A6 by Xanthene Food Dyes

Abstract: We have reported that erythrosine (ET), a xanthene dye, inhibited uridine 5-diphosphate (UDP)glucuronosyltransferase 1A6 (UGT1A6). In order to clarify the structure-inhibition relationships of these xanthene dyes, the inhibitory effect of xanthene dye on human UGT1A6 activity was investigated, such as acid red (AR), ET, phloxine (PL), and rose bengal (RB). ET, PL, and RB strongly inhibited human UGT1A6 activity, with IC50 values = 0.05, 0.04, and 0.015 mM, respectively. Meanwhile, AR had almost no effect (IC50 value = 1.7 mM). ET, PL and RB have four halogen atoms on their xanthene backbone, unlike AR. Meanwhile, some contrast media with high halogens on those aromatic compounds, such as ioxaglic acid, iodixanol, meglumine iotalamate, and diatriazole sodium, did not inhibit human UGT1A6 activity. These results suggest that halogens enhance the inhibitory effect of xanthene dyes. In this study, it was proved that xanthene dyes had an inhibitory effect on human UGT1A6 activity by the combination of xanthene structure and halogens on its. Part of this inhibition by xanthene dyes depends the reaction of 1 O2 originated on xanthene dyes by light irradiation, because the inhibition was prevented by 1 O2 quenchers, such as NaN3 and histidine, and in the dark.

Protolytic equilibria of fluorescein halo derivatives in aqueous-organic systems

Abstract: The dissociation constants of fluorescein halo derivatives containing substituents in the xanthene ring and/or in the phthalic acid moiety were determined in 91.4 wt % aqueous ethanol. The tautomerism of the dyes was inferred from the electronic absorption spectra of ions and molecules in this solvent and of the dichloromethane and chloroform extracts of associates of the anions with tetra-n-butylammonium cations. The equilibria in two-phase systems were considered.

Optical compensation sheet, polarizing plate, and liquid crystal display device

Abstract: An optical compensation sheet having, on a transparent support, an optically anisotropic layer comprising a liquid crystalline compound fixed by using a photo-polymerization initiator system, wherein the photo-polymerization initiator system comprises at least one acylphosphine compound and at least one aromatic ketone compound selected from the group consisting of xanthene compounds, xanthone compounds, thioxanthone compounds and acridone compounds, which has less coloring and can be produced with less-power UV light, is provided.

Xanthene-based compound and coloring liquid

Abstract: PROBLEM TO BE SOLVED: To provide a new xanthene-based compound useful as a coloring agent, etc., and coloring liquid containing the same and the xanthene-based compound having high light fastness of its color. SOLUTION: This xanthene-based compound is characterized by being expressed by general formula (I) [wherein, R 1 is a 1-4C straight chain alkyl; R 2 , R 3 are each independently H or a 1-4C straight chain or branched chain alkyl or a 1-4C straight chain or branched chain alkoxy; and M is H, an alkali metal or NH 4 ]. COPYRIGHT: (C)2006,JPO&NCIPI

14-(4-Fluorophenyl)-14H-dibenzo(a,j)xanthene

Abstract: In the title compound, C27H17FO, the mean plane of the xanthene core is almost perpendicular to that of the the 4-fluoro­phenyl substituent, the dihedral angle being 87.69 (6)°. The xanthene core has a boat conformation, the folding angle between the naphthyl units being 22.54 (4)°.

Crystal Structure of o-Sulfophenylfluorone as a Bioquantification Probe

Abstract: The crystal structure of o-sulfophenylfluorone (SPF) was determined by X-ray diffraction. This compound crystallizes in monoclinic, space P21/c with a = 10.5722(6), b = 15.6153(9), c = 17.216(1)A, β = 91.420(1)°, V = 2841.2(3)A3, Z = 4. The final R value is 0.046 for 5242 reflections (I > 2σ(I)). The structure takes a dihedral formation consisting of xanthene and benzene sulfonic rings and tautomers exist with a zwitterionic character.

4a-Hydr­oxy-9-(3-nitrophen­yl)-3,4,4a,5,6,7,9,9a-octa­hydro-2H-xanthene-1,8-dione

Abstract: The title compound, C19H19NO6, has been synthesized by the reaction of 3-nitro­benzaldehyde with 1,3-cyclo­hexa­nedione in glycol under microwave irradiation. The compound is an inter­mediate of the target product 9-(3-nitro­phen­yl)-3,4,6,7-tetra­hydro-2H-xanthene-1,8(5H,9H)-dione. X-ray crystal-structure analysis reveals that the central hydro­pyran ring adopts a half-chair conformation.

9‐(2‐Carboxy­phen­yl)‐3,6‐bis­(diethyl­amino)xanthylium bis­(2‐thioxo‐1,3‐dithiole‐4,5‐dithiol­ato)nickelate(III)

Abstract: In the title compound, (C28H31N2O3)[Ni(C3S5)2], the two symmetry-independent anions are located on inversion centres and adopt planar conformations with an approximate D2h symmetry. The Ni atoms both show a square-planar coordination geometry. The xanthene system is planar, with the attached benzene ring twisted by 75.8 (11)° from the xanthene plane. One of the four ethyl groups of the cation is disordered. The xanthylium cation and one of the symmetry-independent 2-thioxo-1,3-dithiole-4,5-dithiol­ate anions are arranged into columns, with the anion sandwiched between hydrogen-bonded dimers of the cation. The second symmetry-independent anion is enclosed between these columns.

An Efficient Catalyst System for the Asymmetric Transfer Hydrogenation of Ketones: Remarkably Broad Substrate Scope.

Abstract: A BINOL-derived diphosphonite having a xanthene backbone is an excellent bidentate ligand in Ru-catalyzed 2-propanol-based transfer hydrogenation of aryl/alkyl and alkyl/alkyl ketones (ee = 76−99%). Even notoriously difficult ketones such as isopropyl methyl ketone are reduced with extraordinarily high enantioselectivity (ee = 99%).

The photo-Fries rearrangement of 9-trimethylsilyl substituted xanthenes

Abstract: In this paper, the absorption and fluorescence spectra of xanthene, 9-trimethylsilyl xanthene (1) and 9-methyl-9-trimethylsilyl xanthene (2) are presented and discussed with the help of CNDO/S and ab initio calculations Introduction of the trimethylsilyl group at the 9-position of the xanthene molecule considerably shifts the short-wavelength band (246 nm) to the red and reduces the fluorescence quantum yields (Φfl = 003 for xanthene, 0008 for 1 and Si bond rupture Using ps-laser flash photolysis (266 nm laser, MeCN) we observed a broad absorption spectrum peaking up at 960 nm and decaying monoexponentially with a lifetime of 130 ps, close to the measured fluorescence lifetime We assigned therefore this transient to the singlet excited state of 1 (S1 → Sn absorption) We assume the S1 state as the origin of the photo-Fries rearrangement, giving via C Si bond dissociation a singlet geminal radical pair (9-xanthyl radical + SiMe3) In the next step, the radical pair undergoes predominantly in-cage recombination to the persistent photo-Fries intermediates with high quantum yields (Φ1CHT = 070 and Φ2CHT = 050), while to a lesser extent it escapes the solvent cage (Φ = 030 for 1) and undergoes typical free radical reactions (eg, scavenging with O2) The estimation of the above quantum yields was possible only after determination of the absorption coefficients (ɛ) of the photo-Fries intermediates [ɛ1CHT(410 nm) = 16,800 M−1 cm−1 and ɛ2CHT(403 nm) = 15,900 M−1 cm−1] using three independent methods; this represents the first example in the literature

9H-Xanthene-9-carboxylic Acid [1,2,4]Oxadiazol-3-yl- and (2H-Tetrazol-5-yl)-amides as Potent, Orally Available mGlu1 Receptor Enhancers.

Abstract: Small molecule mGluR1 enhancers based on the lead compound (9H-xanthene-9-carbonyl)-carbamic acid butyl ester derived from random-screening hit diphenylacetyl-carbamic acid ethyl ester were designed and synthesized as useful pharmacological tools for the study of the physiological roles mediated by mGlu1 receptors. The synthesis and the structure-activity relationship of this new class of positive allosteric modulators of mGlu1 receptors will be discussed in detail.

Xanthene Derivatives and ortho‐Substituted Phenols — Products from Dehydrogenation of Acyclic 1,5‐Diketones.

Abstract: Xanthene derivatives and ortho-substituted phenols were obtained during the dehydrogenation of 1,5-diketones and their ketol forms at a Pt/C catalyst at 280–320°C.

Photo-Induced Aromatic Assembly of Benzocycloalka[1,2-b]furan and Spiro[furan-2(3H),1′-benzocycloalkane] Derivatives.

Abstract: The photo-induced benzannulation of benzocycloalka[1,2- b ]furans produced hydrohelicene-type compounds in good yields. A similar photoreaction of the spiro[furan-2(3 H ),1′-benzocycloalkane]s afforded dihydrophenalene derivatives in moderate yields. Benzo[ kl ]xanthene was also formed by a similar photoreaction of spiro[furan-2(3 H ),9′-xanthene]. The reaction pathway was elucidated by the 1 H NMR spectrum of the reaction mixture and the alternative synthesis of the intermediate.