Showing papers on "Benzophenone published in 2005"
TL;DR: Results suggest that a 4-hydroxyl group on the phenyl ring of benzophenone derivatives is essential for high hormonal activities, and the presence of other hydroxyl groups markedly alters these activities.
312 citations
TL;DR: An innovative development allows the incorporation of a site-specific photo-cross-linker into virtually any protein that can be expressed in Escherichia coli, thereby promoting in vivo or in vitro cross-linking of proteins.
Abstract: A major challenge in understanding the networks of interactions that control cell and organism function is the definition of protein interactions1–4. Solid-phase peptide synthesis has allowed the photo-crosslinkable amino acid p-benzoyl-L-phenylalanine (pBpa; Fig. 1a) to be site-specifically incorporated into peptide chains, to facilitate the definition of peptide-ligand complexes5,6. This method, however, is limited to the in vitro study of peptides and small proteins. An innovative development allows the incorporation of a site-specific photo-cross-linker into virtually any protein that can be expressed in Escherichia coli, thereby promoting in vivo or in vitro cross-linking of proteins7–9. The method relies on an orthogonal aminoacyl tRNA synthetase–tRNACUA pair that incorporates pBpa at the position encoded by the amber codon (UAG) in any gene transformed into E. coli7 (Fig. 1b). The system described in this protocol uses two plasmids: a p15A-based plasmid to express the orthogonal tRNA and synthetase pair (pDULE) and a second plasmid containing an amber mutant of the gene of interest. To produce the photocross-linker–containing protein, cultures of E. coli carrying both plasmids are grown in the presence of the unnatural amino acid. To photo-cross-link the protein to its binding partner in vivo or in vitro, cells or purified proteins, respectively, are exposed to UV light (Fig. 2).
163 citations
TL;DR: Two types of copper( II) and nickel(II) complexes derived from benzophenone anthranoylhydrazone and bidentate heterocyclic base with general stoichiometry [ML2] and [ML(phen)]Cl have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements.
118 citations
TL;DR: Observations in the photoreaction of benzophenones with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI) are consistent with the hypothesis that DMPBI*+ donates a proton at the C2 position to the benzophenone ketyl radicals while o-HPDMBI+Donates a phenol proton.
Abstract: In the photoreaction of benzophenones with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), benzhydrols were major products. Addition of H2O accelerated the reaction with no change in the product distribution, while AcOH, PhOH, and metal salts such as LiClO4 and Mg(ClO4)2 were effective additives to produce benzpinacols. In contrast, benzpinacols were exclusively formed regardless of the solvent and the additive in the reactions with 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (o-HPDMBI). These observations are consistent with the hypothesis that DMPBI•+ donates a proton at the C2 position to the benzophenone ketyl radicals while o-HPDMBI•+ donates a phenol proton.
78 citations
TL;DR: In this paper, three kinds of polymeric photoinitiators, PBPB, PBPE and PBPP, were synthesized and the photopolymerization of two monomers was studied.
Abstract: Through introducing of benzophenone and different coinitiator amines, three kinds of polymeric photoinitiator, PBPB, PBPE and PBPP, were synthesized. The UV–vis spectra of these polymeric photoinitiators are similar to the parent benzophenone. The photopolymerization of two monomers, methyl methacrylate (MMA) and poly(propylene glycol) diacrylate (PPGDA), initiated by these three types of polymeric photoinitiators was studied by dilatometer and photo-DSC. The results show that the structure of coinitiator amine has important influence on photopolymerization and different photoinitiators exhibit different behavior towards different monomers: PBPP is the most efficient for MMA, and PBPE is the most efficient for PPGDA.
75 citations
TL;DR: In this paper, the effects of solvent, support and its acidity on the course of benzophenone transformations were studied, using acid zeolite or active carbon as supports were found very effective in hydrodeoxygenation reaction.
Abstract: Catalytic hydrogenation and hydrogenolysis of benzophenone in a liquid phase at the reaction temperature of 130 °C and pressure 6 MPa on supported palladium catalysts were investigated. A number of different supports including active carbon, alumina, Beta and ZSM-5 zeolites with different Si/Al ratios and MCM-41 was tested. The effects of solvent, support and its acidity on the course of benzophenone transformations were studied. Catalysts using acid zeolite or active carbon as supports were found very effective in hydrodeoxygenation reaction. Based on the kinetic model applied, possibilities of conversion of benzophenone to diphenylmethane were discussed. The model confirmed that both the possible mechanisms (the hydrogenation–hydrogenolytic and the direct hydrogenolysis of the C O bond of benzophenone) took place in a significant manner.
67 citations
TL;DR: In this paper, a very efficient concept to increase the photoinitiator activity by the covalent binding of phenylglycine to benzophenone using a methylene spacer is presented.
Abstract: Summary: Bimolecular type-II photoinitiators for radical photopolymerization suffer from a diffusion-controlled limitation of reactivity and from deactivation by back electron transfer Here, a very efficient concept to increase the photoinitiator activity by the covalent binding of phenylglycine to benzophenone using a methylene spacer is presented Photo-DSC experiments proved that the rate of polymerization can be tripled in comparison to a physical mixture of the components or an industrially applied system with triethanolamine as coinitiator
Structure of the new photoinitiator synthesized here
64 citations
TL;DR: The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form.
Abstract: There has been a recent upsurge of activity in the study of alkali metal zincate reagents due to their often special reactivity/selectivity in, for example, deprotonative metalation and nucleophilic addition reactions. Heteroleptic dialkylamidozincates, [M+Zn(R)2(NR‘2)-], usually transfer selectivity of the amide ligand to electrophiles. Here, in contrast, it is reported that the sodium zincate [TMEDA·Na(μ-tBu)(μ-TMP)Zn(tBu)] reacts as an alkylating agent toward the diaryl ketone benzophenone (Ph2CO), selectively adding one of its tBu ligands to the para-C atom of one of the Ph rings. The reaction can be carried out at room temperature, which is a decided advantage over lithium reagents as these are generally utilized at subambient temperatures. The stabilizing effect of the bimetallic (Na, Zn) cationic residue of the starting zincate reagent in coordinating to the dearomatized enolate anion of the 1,6-addition adduct allows the adduct to be isolated in a pure crystalline form. An X-ray crystallographic s...
63 citations
TL;DR: Photocatalytic oxygenation of tetraphenylethylene (TPE) with oxygen occurs efficiently via electron-transfer reactions of TPE and oxygen with a photogenerated electron transfer state of 9-mesityl-10-methylacridniium ion to produce 1,2-dioxetane selectively.
60 citations
TL;DR: Observations suggest that an intramolecular triplet energy transfer occurs in Gn-NBD molecules, and it is proposed to proceed mainly via a through-space mechanism involving the closest donor (folding back conformation) and acceptor groups.
Abstract: A series of benzophenone (BP) and norbornadiene (NBD)-labeled poly(aryl ether) dendrimers (Gn-NBD), generations 1−4, were synthesized, and their photophysical and photochemical properties were examined. The phosphorescence of the peripheral BP (donor) chromophore was efficiently quenched by the NBD (acceptor) group attached to the focal point. Time-resolved spectroscopic measurements indicated that the lifetime of the triplet state of the BP chromophore was shortened due to the proximity of the NBD group. Selective excitation of the BP chromophore resulted in isomerization of the NBD group to quadricyclane (QC). All of these observations suggest that an intramolecular triplet energy transfer occurs in Gn-NBD molecules. The light-harvesting ability of these molecules increases with generation due to an increase in the number of peripheral chromophores. The energy transfer efficiencies are ca. 0.97, 0.54, 0.45, and 0.37 for generations 1−4, respectively, and the rate constant of the triplet−triplet energy t...
57 citations
TL;DR: Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions, and quenching is fastest for Ag+, whereas Cu2+ and Aucl4- exhibit similar rate constants.
Abstract: Illumination of air-free aqueous solutions containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol) with 350 nm light results in benzophenone ketyl radicals of the polyketone. The polymer radicals form with a quantum yield 0.02 and decay with a second-order rate constant 6 orders of magnitude lower than that of typical α-hydroxy radicals. Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions. Decreases in the reduction rates with increasing AgI, CuII, and AuIII concentrations are explained using a kinetic model in which the metal ions quench the excited state of the polymeric benzophenone groups, which forms the macromolecular radicals. Quenching is fastest for Ag+, whereas Cu2+ and AuCl4- exhibit similar rate constants. Particle formation becomes more complex as the number of equivalents needed to reduce the metal ions increases; the AuIII system is an extreme case where the radical reactions operate in p...
TL;DR: The selective activation of different photosensitizers has been carried out under comparable conditions and their efficiency towards di-n-butylsulfide oxidation in oxygenated acetonitrile compared from the product distribution after 150 minutes of irradiation is compared.
Abstract: The selective activation of different photosensitizers has been carried out under comparable conditions and their efficiency towards di-n-butylsulfide oxidation in oxygenated acetonitrile compared from the product distribution after 150 minutes of irradiation. As expected, the best selectivity towards sulfoxide is obtained with a conventional energy transfer sensitizer such as Rose Bengal (RB), but also with a quinone with a low-lying triplet state, 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil or CHLO) and with 9,10-dicyanoanthracene (DCA). More significant yields in sulfonic and sulfuric acids are obtained under sensitization with 9,10-anthraquinone (ANT) or a derivative of benzophenone, 4-benzoyl benzoic acid (4-BB), with which additional experiments were carried out in order to discuss the involvement of either singlet oxygen or superoxide radical anion. Triphenyl pyrylium tetrafluoroborate (TPT+) is inefficient under the selected conditions and sulfide photo-oxidation can only be achieved with higher TPT+ concentrations with simultaneous total TPT+ bleaching. With TPT+, 1,2,4,5-tetracyanobenzene (TCNB) and TiO2, the product distribution and the low selectivity as well as the formation of numerous common by-products are indicative of radical mechanisms. All these results are discussed according to the possible formation of activated oxygen species, such as singlet oxygen, superoxide radical anion or alkylperoxy radicals.
TL;DR: A new methodology for a lifetime distribution analysis of the decay curve of probes onto heterogeneous surfaces is presented, which allows for asymmetric distributions and uses Voigt profiles (Gaussian and Lorenzian mixture) instead of pure Gaussian or Lorentzian distributions.
Abstract: A detailed study of the luminescence decay curves of pyrene included within p-tert-butylcalix[4]arene cavities and benzophenone into silicalite channels is reported. A new methodology for a lifetime distribution analysis of the decay curve of probes onto heterogeneous surfaces is presented, which allows for asymmetric distributions and uses Voigt profiles (Gaussian and Lorentzian mixture) instead of pure Gaussian or Lorentzian distributions. Our approach uses a very simple and widely available tool for fitting, the Microsoft Excel Solver. In the case of the pyrene/tert-butylcalix[4]arene sample, the room temperature luminescence detected in the microsecond time scale was not only the phosphorescence of pyrene but also monomer delayed fluorescence, crystal phosphorescence, and excimer delayed fluorescence. In the benzophenone/silicalite case, three emissive forms of benzophenone could be assigned, one of benzophenone included into the silicalite circular zigzag channels, another for emplacement into the el...
TL;DR: In this article, a photoinitiator-monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacryls, and both rate of polymerization and percentage conversion increased with increase in initiator concentration.
Abstract: A new class of multifunctional photoinitiating system based on 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM), N,N,N′-trimethylethylenediamine (TMED) and 3-benzoylbenzoyl chloride present in the same molecule has been synthesized and characterized by 1H and 13C NMR spectroscopy. This self-contained photoinitiator-monomer (photoinimer) was used to efficiently initiate polymerization of acrylates and methacrylates. Both rate of polymerization and percentage conversion increased with increase in initiator concentration. An increment in rate of polymerization observed when the benzophenone moiety was directly attached to the parent molecule (obtained from the Michael addition reaction between AHM and TMED) appears to be due to proximity effect: chemical bonding provides a high local concentration of both components of the photo-activated system involving benzophenone and a hydrogen atom source from an electron-rich tertiary amine. For the three initiating systems investigated, lowering the initiator concentration plays an important role; i.e., the polymerization rate for the chemically linked system was about two times faster than the mixed initiating system. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5661–5670, 2005
TL;DR: Efficient photorelease of carboxylic acids is achieved with a covalently linked mediator (benzophenone) protecting group (N-alkyl-4-picolinium ester) molecule through initial photoreduction of the mediator, followed by rapid electron transfer to the protecting group.
TL;DR: Time-resolved measurements using nanosecond laser flash photolysis have revealed significant enantiodifferentiation in the interaction between ketoprofen and two relevant nucleosides, namely, thymidine and 2'-deoxyguanosine.
Abstract: Time-resolved measurements using nanosecond laser flash photolysis have revealed significant enantiodifferentiation in the interaction between ketoprofen (a chiral benzophenone derivative) and two relevant nucleosides, namely, thymidine and 2‘-deoxyguanosine. In both cases, the highest quenching rate constants have been observed for (R)-ketoprofen, the enantiomer with lower pharmacological activity. Photoproduct studies performed in the case of thymidine suggest that the enantiodifferentiating process corresponds to a Paterno−Buchi reaction, leading to the formation of oxetanes. With 2‘-deoxyguanosine, the quenching is associated with an electron-transfer process monitored through the generation of a ketyl radical.
TL;DR: Arylhydrazones have been successfully synthesized via a highly efficient palladium-catalyzed cross-coupling reaction between aryl halides and benzophenone hydrazone as mentioned in this paper.
Abstract: Various arylhydrazones have been successfully synthesized via a highly efficient palladium-catalyzed cross-coupling reaction between aryl halides and benzophenone hydrazone. All the reaction parameters have been studied and coupling products were obtained with excellent yields from the corresponding bromides or chlorides.
TL;DR: Computer studies reveal the conformational equilibrium structures of the triplet 1,4-diradicals, energy barriers between the conformers, and the conjectural equilibrium constants from relative potential energies of the stable conformers.
Abstract: [reaction: see text] The [2 + 2] photochemical additions of 1,3-dimethylthymine (DMT) with benzophenone and its 4,4'-substituted derivatives (BPs), difluoro, di-tert-butyl, and dimethoxy benzophenones, have been investigated at a temperature range from -40 to 70 degrees C. The photochemical reactions, which are cycloaddition of the 5-6 double bond of DMT with the carbonyl group of BPs, the so-called the Paterno-Buchi (PB) reaction, reveal largely temperature-dependent regioselectivity. The chemical yields of one series of regioisomers, 2, decrease with the increase of the reaction temperature, but those of another regioisomer series, 3, increase, and thus the ratio of 2/3 is strongly dependent on the temperature (2/3 = ca. 70:30 to 30:70). The temperature dependence of the regioselectivity yields two linear functions in the corresponding Eyring diagrams. The Eyring plot with changed slopes is clearly indicative of the change for the selectivity-determining step in the PB reaction, in which the triplet 1,4-diradicals play a crucial role. Computational studies reveal the conformational equilibrium structures of the triplet 1,4-diradicals, energy barriers between the conformers, and the conjectural equilibrium constants from relative potential energies of the stable conformers. A proposed mechanism can reasonably explain the temperature-dependent regioselectivity and chemical yields of two regioisomers varying with the reaction temperature.
TL;DR: Evidence suggests that the highly efficient (Phi approximately 0.6) reaction involves a unimolecular mechanism and an overall formal intramolecular photoredox process, which requires electronic communication between the 1,3-positions of the benzene ring, an unprecedented example of the photochemical meta effect.
TL;DR: Laser photolysis studies revealed that enhanced access of sulfide to the (3)BZP core inside the apolar microenvironment accelerates the TET to sulfide, whereas prompt migration of polar sulfoxide to the polar outer shell of the dendrimer suppresses a competitive Tet to sulfoxide, thus resulting in effective ( 3)sulfide formation.
Abstract: Photosensitized oxygenation of sulfides within amphiphilic dendrimers, Gn [n(generation) = 1-3], consisting of a benzophenone (BZP) sensitizing core, apolar interior based on n-undecane spacer, and polar dendron exterior based on 2,2-bis(hydroxymethyl)propionic acid, has been investigated in 02-saturated methanol. Sulfoxide formation occurring via reaction of 02 with triplet excited-state sulfide ( 3 sulfide*), which is formed by a triplet energy transfer (TET) from photoformed 3 BZP* to sulfide, was accelerated by the dendric sensitizers, where G2 showed the highest yields of alkylaryl and dialkyl sulfoxides. Laser photolysis studies revealed that enhanced access of sulfide to the 3 BZP* core inside the apolar microenvironment accelerates the TET to sulfide, whereas prompt migration of polar sulfoxide to the polar outer shell of the dendrimer suppresses a competitive TET to sulfoxide, thus resulting in effective 3 sulfide* formation. Another notable feature of the dendric sensitizer appears in oxygenation of diaryl sulfide, which is promoted by a persulfoxide intermediate formed by photooxygenation of dialkyl sulfide; photoirradiation of a mixture of diethyl sulfide (la) and diphenyl sulfide (4a) with G2 gave 17-fold higher diphenyl sulfoxide (4b) yield than that obtained with unmodified BZP. The apolar microenvironment within the dendric sensitizer encapsulates a large quantity of 4a, which is oxidized effectively by the persulfoxide of la, thus resulting in high 4b yield. The BZP core within the dendric sensitizer is stable even by photoexcitation in protic solvent, suggesting potential utilities of this dendric system for effective and selective photosensitized oxygenation of sulfides.
TL;DR: In this paper, the photo-initiator of polystyrene−ethylene−butylene sulfonate copolymer membranes (PSEBS) was decomposed by first-order kinetics.
Abstract: Polystyrene−ethylene−butylene sulfonate copolymer membranes (PSEBS) were photochemically cross-linked using benzophenone as the photo-initiator. Benzophenone decomposed by first-order kinetics duri...
TL;DR: The development of three novel sulfhydryl-reactive benzophenone photoprobes of short "arm" length, each with a substitution of either amino, iodo, or nitro at the para-position, rendering the Benzophenone moiety directly radioiodinatable.
TL;DR: The ratio benzhydrol/benzopinacol reaches a maximum, decreases, and then levels off as the proton donor concentration is further increased, while the momentary concentration of the intermediate radicals governs the product distribution.
TL;DR: In this article, a high selective formation of benzophenone (99.1%) from diphenylmethane was reported using H2O2 (30%) as an oxidant and Co/MCM-41 as the catalyst.
Abstract: Highly selective formation of benzophenone (99.1%) from diphenylmethane is reported for the first time using H2O2 (30%) as an oxidant and Co/MCM-41 as the catalyst.
Patent•
28 Dec 2005
TL;DR: In this paper, the authors provided a fluorochemical composition comprising a mixture of a fluorine selected from the formula (I): wherein RF is a fluorinated group having the formula: Rf-W-, wherein Rf is a perfluoroalkyl or perfluoropolyether group and W is a divalent linking group.
Abstract: In one aspect, the invention provides a fluorochemical composition comprising a mixture of: a fluorochemical selected from the formula (I): wherein RF is a fluorinated group having the formula: Rf- W-, wherein Rf is a perfluoroalkyl or perfluoropolyether group and W is a divalent linking group; PI is a monovalent pendant organic moiety comprising benzophenone, substituted benzophenone, acetophenone, or substituted acetophenone groups; R is H, CH3, or F; Rh is lower alkyl selected from the group consisting of linear or branched alkyl groups having from 1 to about 8 carbon atoms, cycloalkyl-containing alkyl groups having from 4 to about 8 carbon atoms, and cycloalkyl groups having from 3 to about 8 carbon atoms, all optionally containing catenated O or N atoms; m is at least 2; n is at least 1; q is zero or greater; and a hydrofluoroether.
TL;DR: The photochemistry of benzophenone adsorbed on a channel-type solid support MCM-41 was studied by the use of diffuse reflectance and chromatographic techniques as discussed by the authors.
TL;DR: The vibrational spectra of 3,4-diamino benzophenone (DABP) have been computed using B3LYP methodology and 6-31G* and 6 -31G** basis sets and were found to be well comparable.
TL;DR: It is found that the C-O bond cleavage and production of free radicals, such as BPCH2*, C6H5O*, and CH3O*, can be performed by a stepwise two-photon excitation.
Abstract: The C−O bond cleavage from benzophenone substituted with 4-CH2OR (p-BPCH2OR, 1−3), such as p-phenoxymethylbenzophenone (1, R= C6H5) and p-methoxymethylbenzophenone (2, R= CH3), occurred by a stepwise two-photon excitation during two-color, two-laser flash photolysis. On the other hand, no C−O bond cleavage occurred from p-hydroxymethylbenzophenone (3, R = H). The first 355-nm laser excitation of 1−3 generates p-BPCH2OR in the lowest triplet excited state (T1) which has an absorption at 532 nm. When p-BPCH2OR(T1) is excited with the second 532-nm laser to p-BPCH2OR in the higher triplet excited state (Tn), the C−O bond cleavage occurred within the laser flash duration of 5 ns. The quantum yields of the C−O bond cleavage during the second 532-nm laser irradiation were found to be 0.015 ± 0.007 and 0.007 ± 0.003 for 1 and 2, respectively. Although these values are low, the diminishing 1(T1) or 2(T1) was found to convert, in almost 100% yield, to phenoxyl (C6H5O•) and p-benzoylbenzyl (BPCH2•) radicals or meth...
TL;DR: In this article, an axis-selective photo-excitation of TPS and the polarization-preserved energy transfer to the photoreactive mesogenic groups dominated the photoinduced optical anisotropy as well as the thermal enhancement of the molecular reorientation.
Abstract: An axis-selective photosensitized reaction of a photo-cross-linkable liquid crystalline polymer film doped with a triplet photosensitizer (TPS) based on axis-selective triplet energy transfer achieved a thermally enhanced molecular reorientation of the film using linearly polarized (LP) 405 nm light. Four types of TPS4,4‘-(N,N‘-bis(diethylamino))benzophenone (DBP), 4-(N-diethylamino)benzophenone (BP), 5-nitroacenaphthene (AN), and p-nitroaniline (pNA)were used to compare the efficiency of the axis selection of the energy transfer. In all cases, the photoreactivity of a film was generated when doping with less than 9 wt % of TPS. The quenching sphere played a role in the photoreactivity, while the photoinduced optical anisotropy depended on the type of TPS. The axis-selective photoexcitation of TPS and the polarization-preserved energy transfer to the photoreactive mesogenic groups dominated the photoinduced optical anisotropy as well as the thermal enhancement of the molecular reorientation.
TL;DR: Two polyisoprenylated benzophenones along with the known compound 28,29-Epoxyplukenetione A were isolated from the hexane extract of Clusia obdeltifolia after extensive chromatographic procedures as discussed by the authors.