- THE ROLE OF INTERSYSTEM CROSSING STEPS IN SINGLET OXYGEN CHEMISTRY AND PHOTO-OXIDATIONS
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Singlet oxygen chemistry and photo-oxidation reactions, in general, often require one or more critical reaction steps that involve an intersystem crossing from a singlet state to a triplet state or vice versa.This paper considers two important intersystem crossing mechanisms, electron spin-electron orbit (spin-orbit) coupling and electron spin-nuclear spin (spin-spin) coupling, and how they may be involved: (1) in the deactivation of 1O2 to 3O2; (2) in the thermal catalytic conversion of 3O2 to 1O2; and (3) in the fragmentation of aromatic endoperoxides to yield O2 and an aromatic substrate.
- Turro, Nicholas J.
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- NHC Hg(II) and Pd(II) complexes based on 1,8-dihydroxy-9,10-anthraquinone: synthesis, structure and catalysis
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Three bis-azolium salts, 1,8-bis[3′-(N-R-azoliumyl)propoxy]-9,10-anthraquinone hexafluorophosphate L1H2(PF6)2-L2H2(PF6)2 (R = ethyl or picolyl, azoliumyl = imidazoliumyl or benzimidazoliumyl) and 1,3-bis[8′-(3′′-(N-ethyl-imidazoliumyl)propoxy)anthraquinon-l-yloxy]propane hexafluorophosphate (L3H2(PF6)2), as well as their three macrometallocycle N-heterocyclic carbene mercury(ii) complexes [L1′HgBr2] (1), [L2Hg](PF6)2 (3) and [L3Hg](PF6)2 (3) were prepared and characterized by 1H NMR and 13C NMR spectroscopy and X-ray crystallography. In complexes 1-3, each macrometallocycle (18-membered macrometallocycle for 1, one 18-membered and two 6-membered macrometallocycles for 2, and 28-membered macrometallocycle for 3) was formed by one biscarbene ligand (L1′ for 1, L2 for 2, and L3 for 3) and one Hg(ii) ion. Interestingly, the carbonyl group on the 9-position in complex 1 reacted with two acetonitrile molecules in the presence of the strong base KOtBu through losing one molecule of H2O to form L1′. As a result, two-CH2CN units were introduced to anthraquinone, in which the two-CH2CN units lie on two flanks of the anthraquinone plane. In the crystal packings of 1-3, 2D supramolecular layers and 3D supramolecular frameworks are formed via hydrogen bonds and ππ interactions. Additionally, the catalytic activity of the L1-Pd(ii) complex in situ in the Suzuki-Miyaura reaction was studied. The results show that this catalyst is efficient in the Suzuki-Miyaura reaction.
- Zhao, Zhi-Xiang,Hu, Ze-Liang,Yu, Shao-Cong,Liu, Qing-Xiang
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- Selective recognition of Cr (VI) ion as Cr2O72? in aqueous medium using CTAB-capped anthracene-based nanosensor: Application to real water sample analysis
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Surfactant-capped nanoparticles of 9, 10-diphenyl anthracene prepared by reprecipitation method found highly fluorescent due to aggregation-induced enhanced emission (AIEE). Cetyltrimethyl ammonium bromide (CTAB) surfactant not only generated positive zeta potential on the surface of nanoparticles to attract anions of interest but also stabilized nanoparticles into brick-shape morphology. The fluorescence of nanoparticles is quenched by Cr2O72- ion very significantly in comparison with other diverse ions, namely, MnO4-, S2O82-, HCO3-, and Cr2O42-. Though S2- and IO3- showed increase in the fluorescence of nanoparticles, the interference found is negligible in the Cr (VI) analysis. The selectivity and sensitivity of nanoparticles for recognition of Cr2O72? were explored by systematic fluorescence titration. The fluorescence quenching data fits into the usual Stern-Volmer equation. A calibration curve constructed by plotting quenching of fluorescence (?F) against concentration of Cr (VI) exhibiting a linear fit in the equation, ?F?=?3070x, is used for the estimation of chromium concentration (x). The correlation coefficient value R2?=?0.998 obtained from curve is nearly equal to 1 indicates linear fit between quenching data and concentration of Cr (VI). The estimated values of limit of detection (LOD) in the method 0.01392?μg.mL?1 is far below the permissible value of Cr (VI) 0.05?μg.mL?1 in drinking water approved by world health organization (WHO) and United State Environmental Protection Agency (USEPA). The proposed method of Cr (VI) detection is applied for real sample collected from hard chrome deposition industry from nearby region. The amount of Cr (VI) estimated by present method is comparable with AAS determination for the same samples.
- Suryawanshi, Sonali B.,Mahajan, Prasad G.,Kolekar, Govind B.,Bodake, Anita J.,Patil, Shivajirao R.
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- Remote substituent effects on the reactivity of 9-aryl- and 9,10-diarylanthracene radical cations with anions and amines
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Radical cations of 9-aryl- and 9,10-diarylanthracenes with substituents on the 4 position of the aryl rings (PA-X?+ and DPA-X?+, respectively) have been generated by photoionization in acetonitrile. Their reactivity with n-butylamine (n-BuNH2) and 1,4-diazabicyclo[2.2.2]octane (DABCO) and a number of anions (CH3CO2-, Br-, CN-, N3-) has been studied using nanosecond laser flash photolysis. Reactions proceed by electron transfer and/or nucleophilic addition. Using PA-X and DPA-X as chemical probes, simple criteria are established that allow one mechanistic pathway to be distinguished from another. When electron transfer is thermodynamically feasible, this pathway dominates (e.g., DABCO and azide). For endothermic electron transfer, addition is not necessarily the preferred ultimate reaction pathway and an inner sphere process (addition/ homolysis) can compete. In these cases other, criteria including steric factors and the strength of the incipient bond become important. Simple kinetic criteria and an approach to estimate the thermochemistry of the addition process are developed. It is clear from these studies that reactivity trends in the radical cation chemistry cannot be generalized as easily as those in carbocation chemistry. This has some implications concerning the development and utility of "clock" reactions in radical cation chemistry.
- Workentin, Mark S.,Parker, Vernon D.,Morkin, Tracy L.,Wayner, Danial D. M.
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- Synthesis of Pyridylanthracenes and Their Reversible Reaction with Singlet Oxygen to Endoperoxides
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The ortho, meta, and para isomers of 9,10-dipyridylanthracene 1 have been synthesized and converted into their endoperoxides 1-O2 upon oxidation with singlet oxygen. The kinetics of this reaction can be controlled by the substitution pattern an
- Fudickar, Werner,Linker, Torsten
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- SINTHESIS OF THE COVALENT BENZENE-CARBON MONOXIDE CYCLOADDUCT, NORBORNA-2,5-DIEN-7-ONE CORRELATION OF KINETIC AND THERMODINAMIC STABILITIES IN CYCLOREVERSION REACTIONS
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endo-Tricyclo2,5>non-7-ene-3,4,9-trione (14) is prepared from the 5,5-diethoxy-cyclopentadiene-diethyl maleate Diels-Alder adduct.Photolysis of the trione in CD2Cl2 solution at 192 K forms norborna-2,5-dien-7-one (2).The latter substance is thermally unstable and decomposes to benzene and CO with ΔG= 15 kcal mol-1.This appears to be the lowest activation energy for a cycloreversion yet measured.A correlation is found for the kinetic and thermodynamic stabilities in a series of 18 orbital symmetry allowed cycloreversions by plotting ΔG vs ΔHr.
- Birney, David M.,Berson, Jerome A.
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- Kinetic and equilibrium parameters of [4+2] cycloaddition reaction of 2,6-dimethylnaphthalene with 4-phenyl-1,2,4-triazoline-3,5-dione
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Kinetic parameters of forward and retro Diels-Alder reactions between 2,6-dimethylnaphthalene and 4-phenyl-1,2,4-triazolinedione were determined, as well as the equilibrium parameters of the reaction in 1,2-dichloroethane.
- Kiselev,Kashaeva,Potapova,Kornilov,Konovalov
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- Gel-entrapped bases: A smart window for the ligand-free Suzuki-Miyaura cross-coupling reaction
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A gel-entrapped base has been fabricated by using agarose (biopolymer), and tested in the Suzuki-Miyaura cross-coupling reaction in 95% ethanol. The developed environmentally benign polymer-supported base has low leaching and high stability for the Suzuki-Miyaura cross-coupling reaction to give high yield with green credit.
- Jadhav, Sanjay,Kumbhar, Arjun,Kamble, Santosh,More, Pallavi,Salunkhe, Rajashri
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- Palladium supported hybrid cellulose-aluminum oxide composite for Suzuki-Miyaura cross coupling reaction
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A cellulose-aluminum oxide composite was prepared and modified with organo-functional groups by reacting with the coupling reagent (CH 3O)3Si(CH2)3NH2 through Al-O-Si bonds. The amino groups confined in the composite were found to be efficient for palladium entrapment, leading to a highly active and reusable heterogeneous catalyst (Pd@Al2O3-CELL) for Suzuki-Miyaura cross coupling reaction in water and H2O/DMF (8:2) mixture at 80 °C. Copyright
- Kumbhar, Arjun,Jadhav, Sanjay,Kamble, Santosh,Rashinkar, Gajanan,Salunkhe, Rajashri
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- Synthesis of 9,10-diarylanthracene derivatives via bis Suzuki-Miyaura crosscoupling reaction
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A convenient and one-step synthesis of 9,10-diarylanthracenes is described via a bis Suzuki-Miyaura (SM) cross-coupling reaction. In this regard, 9,10-dibromoanthracene was reacted with various aryl boronic acids in presence of palladium(O) catalyst to give 9,10-diarylanthracenes in good yield.
- Kotha, Sambasivarao,Ghosh, Arun Kumar
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- Radical cations of twisted acenes: Chiroptical properties and spin delocalization
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We introduce the first series of enantiopure twistacene radical cations, which form reversibly upon chemical or electrochemical oxidation. Their vis-NIR chiroptical properties (Cotton effect and anisotropy factor) increase systematically with the backbone twist. The hyperfine constants observed by EPR demonstrate significant spin delocalization even for large backbone twist angles.
- Bedi, Anjan,Carmieli, Raanan,Gidron, Ori
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- Low temperature Kumada-Corriu cross-coupling of polychlorinated acene derivatives and a synthesis of sterically demanding acenes
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Conditions for low-temperature Kumada-Corriu cross-coupling of polychlorinated acenes with Grignard reagents are reported. Our work was motivated by a search for cross-coupling reactions effective in the synthesis of functionalized linear acenes for organic materials applications. Treatment of polychlorinated acenes with the PEPPSI-IPr catalyst and MeMgBr undergo 6-8 concurrent coupling reactions to yield products such as octamethylnaphthalene, which is distorted out of planarity due to the steric interaction between the methyl groups. More sterically demanding Grignard reagents such as PhMgBr coupled cleanly with 9,10-dichloroanthracene to provide products such as 9,10-diphenylanthracene, a blue OLED component, in excellent yield.
- Yagodkin, Elisey,Douglas, Christopher J.
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- State-Selective Photochemistry of Singlet Oxygen Precursors: Kinetics and Wavelength Dependence of the Photodissociation of Anthracene Endoperoxides
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The photochemical behavior of the two isomeric endoperoxides (9,10-PMO2 and 1,4-PMO2) of 1,4-dimethyl-9,10-diphenylanthracene was found to differ in their kinetics and reaction efficiencies.Consistent with the work of Rigaudy et al. and Brauer et al. on a related endoperoxide we find that the generation of 1O2 is wavelength dependent, occuring from upper excited singlet states of the endoperoxide, whereas bond cleavage of the O-O endoperoxide bond occurs principally from the lowest excited singlet and triplet states.Results of picosecond kinetics and absolute quantum yield measurements are discussed in terms of various concerted and nonconcerted mechanisms for the formation of 1O2 and the anthracene fragment.
- Eisenthal, K. B.,Turro, N. J.,Dupuy, C. G.,Hrovat, D. A.,Langan, J.,et al.
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- The improvement of π-conjugation by the lateral benzene of anthracene and naphthalene
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The 1,4-diarylnaphthalenes, 1,4-diarylanthracenes, and 9,10-diarylanthracenes containing the different side arenes, including phenyl, 2-thienyl, and 2-furyl groups, were synthesized to study the influence of structures on π-conjugation. According to photophysics and computation, the smaller dihedral angles and the lateral benzene of anthracene would increase the π-conjugation in some cases. Compared to 1,4-diarylnaphthalenes, 1,4-di(thien-2-yl)anthracene, 1,4-di(fur-2-yl)anthracene, and 9,10-di(fur-2-yl)anthracene displayed better π-conjugation in both of the ground and fluorescing excited states, but 9,10-di(thien-2-yl)anthracene only showed better π-conjugation in the fluorescing excited state.
- Ho, Jinn-Hsuan,Chen, Yu-Hsien,Chou, Li-Ting,Lai, Po-Wei,Chen, Pin-Sian
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- Photochemistry of 1,1,3-triphenyl-2-indanone. Spontaneous and photochemical decay of ortho-xylylenes
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The photochemistry of the title compound leads to the formation of a long lived ortho-xylylene which decays by two competing cyclization pathways leading to benzocyclobutene and dihydroanthracene ring systems. The ratio of products V and VI is different for one and two-photon processes, thus providing another example where the products can be controlled by the type of photoexcitation used.
- Netto-Ferreira,Wintgens,Scaiano
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- Synthesis of symmetrical and unsymmetrical 9,10-diarylanthracene derivatives via bis-Suzuki-Miyaura cross-coupling reaction
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Synthesis of various 9,10-diarylanthracene derivatives via bis-Suzuki-Miyaura cross-coupling reaction as a key step is described. Availability of the 9,10-dithienylanthracenes derivatives where the thiophene unit is present in the molecule (e. g. 11, 12, 14) may provide an easy access to novel polymer and/or dendrimer preparation. In addition, we have synthesized unsymmetrical 9,10-diarylanthracene derivatives 20-25 by the Suzuki-Miyaura cross-coupling reaction, which are difficult to prepare by other transition metal-catalyzed cross-coupling reactions.
- Kotha, Sambasivarao,Ghosh, Arun Kumar,Deodhar, Kodand Dinkar
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- Covalent organic framework-supported Pd nanoparticles: An efficient and reusable heterogeneous catalyst for Suzuki–Miyaura coupling reactions
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A Schiff base hollow covalent organic framework (COF) was used for anchoring Pd(II) to synthesize the Pd@COF-TB nanocatalyst. Then, the as-synthesized Pd@COF-TB catalyst has been meticulously characterized using several methods. Thereafter, the catalytic performance of the Pd@COF-TB species regarding Suzuki–Miyaura coupling reactions was examined, and the corresponding products were obtained with good to excellent yields. Besides, the Pd@COF-TB catalyst could be recovered conveniently and reused at least eight times without obvious decrease in activity and selectivity. More importantly, the leaching of Pd during the reaction process could be negligible, which is crucially important when preparing bioactive species.
- Ge, Xin,Jin, Hao,Liu, Pingwei,Zhang, Chi,Zhou, Shaodong
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- Synthesis of N-Heterocyclic Carbine Silver(I) and Palladium(II) Complexes with Acylated Piperazine Linker and Catalytic Activity in Three Types of C—C Coupling Reactions
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Two bis-imidazolium salts LH2·Cl2 and LH2·(PF6)2 with acylated piperazine linker and two N-heterocyclic carbene (NHC) silver(I) and palladium(II) complexes [L2Ag2](PF6)2 (1) and [L2Pd2Cl4] (2) were prepared. The crystal structures of LH2·Cl2 and 1 were confirmed by X-ray analysis. In 1, one 26-membered macrometallocycle was generated through two silver(I) ions and two bidentate ligands L. The catalytic activity of 2 was investigated in Sonogashira, Heck-Mizoroki and Suzuki-Miyaura reactions. The results displayed that these C—C coupling reactions can be smoothly carried out under the catalysis of 2.
- Liu, Qingxiang,Zhang, Xiantao,Zhao, Zhixiang,Li, Xinying,Zhang, Wei
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supporting information
p. 605 - 613
(2021/02/01)
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- Method for synthesizing anthracene OLED intermediate
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The invention relates to a method for synthesizing anthracene OLED (organic light emission diode) intermediates. According to the method, the anthracene OLED intermediates are prepared from an aryl Grignard reagent and aryl halide through a Kumada cross-coupling reaction at the temperature of 25-35 DEG C under the protection of inert atmosphere and in the presence of a catalyst. The method has thebeneficial effects as follows: the NiCl2(dppp) catalyst is cheap and easily available, and a prepared product is high in yield and high in purity; the reaction condition is the room temperature, energy is saved, and the reaction condition is milder.
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Paragraph 0024; 0043-0047
(2020/11/23)
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- Modular synthesis of unsymmetrical doubly-ring-fused benzene derivatives based on a sequential ring construction strategy using oxadiazinones as a platform molecule
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An efficient benzene ring construction method using oxadiazinones as a platform molecule has been developed. Sequential reactions of oxadiazinones with cycloalkynes and arynes afforded partially reduced polyaromatics. This method enables facile preparation of various unsymmetrical doubly-ring-fused benzene derivatives including multisubstituted tetrahydroanthracenes and anthracenes.
- Meguro, Tomohiro,Chen, Shengnan,Kanemoto, Kazuya,Yoshida, Suguru,Hosoya, Takamitsu
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supporting information
p. 582 - 585
(2019/06/11)
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- Chromium- and Cobalt-Catalyzed, Regiocontrolled Hydrogenation of Polycyclic Aromatic Hydrocarbons: A Combined Experimental and Theoretical Study
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Polycyclic aromatic hydrocarbons are difficult substrates for hydrogenation because of the thermodynamic stability caused by aromaticity. We report here the first chromium- and cobalt-catalyzed, regiocontrolled hydrogenation of polycyclic aromatic hydrocarbons at ambient temperature. These reactions were promoted by low-cost chromium or cobalt salts combined with diimino/carbene ligand and methylmagnesium bromide and are characterized by high regioselectivity and expanded substrate scope that includes tetracene, tetraphene, pentacene, and perylene, which have rarely been reduced. The approach provides a cost-effective catalytic protocol for hydrogenation, is scalable, and can be utilized in the synthesis of tetrabromo- and carboxyl-substituted motifs through functionalization of the hydrogenation product. The systematic theoretical mechanistic modelings suggest that low-valent Cr and Co monohydride species, most likely from zerovalent transition metals, are capable of mediating these hydrogenations of fused PAHs.
- Han, Bo,Ma, Pengchen,Cong, Xuefeng,Chen, Hui,Zeng, Xiaoming
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supporting information
p. 9018 - 9026
(2019/06/13)
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- Immobilization of an Aminobisphosphine–PdII Complex over Graphene Oxide: An Efficient and Reusable Catalyst for Suzuki–Miyaura, Ullmann Coupling and Cyanation Reactions
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The grafting of an aminobis(phosphine)–PdII complex (PNP–PdII) [PdCl2{(Ph2P)2N(CH2)3Si(OMe)3}] (2) on graphene oxide (GO) has been carried out by a condensation reaction between methoxysilane groups of 2 and hydroxyl groups of GO. The composite material was characterized by FTIR spectroscopy, solid-state 31P NMR spectroscopy, SEM, TEM, XPS and ICP-AES techniques. All these tools support the clean immobilization of compound 2 on GO. The composite material showed high catalytic activity in Suzuki–Miyaura, Ullmann coupling and cyanation reactions. The heterogeneity of the composite was confirmed by a hot filtration test. The immobilized PNP–PdII shows comparable activity to its homogeneous analogue 2. The recycling ability of the catalyst was examined for five consecutive runs, which showed little or no reduction in its catalytic efficiency.
- Sengupta, Debasish,Pandey, Madhusudan K.,Mondal, Dipanjan,Radhakrishna, Latchupatula,Balakrishna, Maravanji S.
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p. 3374 - 3383
(2018/05/08)
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- Benzyloxycalix[8]arene: A new valuable support for NHC palladium complexes in C-C Suzuki-Miyaura couplings
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Benzyloxycalix[8]arene supported catalysts bearing N-heterocyclic carbene palladium complexes on each subunit were readily synthesized. Intermediates and catalysts were fully characterized, allowing for a fine control of their structure. X-ray diffraction analysis confirmed the formation of a calix[8]arene bearing eight well-defined NHC palladium complexes. The macrocyclic structure of calix[8]arenes allowed for a scalable and chromatography-free catalyst synthesis under homogeneous conditions, while the catalytic reaction proceeded under heterogeneous conditions, just by changing the nature of the solvent. Indeed, when used as a suspension in ethanol, a high TON and TOF were obtained through a large panel of functionalized brominated substrates in C-C Suzuki-Miyaura couplings, with low metal contamination after simple filtration.
- Abdellah, Ibrahim,Kasongo, Pauline,Labattut, Axel,Guillot, Régis,Schulz, Emmanuelle,Martini, Cyril,Huc, Vincent
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supporting information
p. 13843 - 13848
(2018/10/20)
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- Catalytic activities of NHC-PdCl2 species based on functionalized tetradentate imidazolium salt in three types of C-C coupling reactions
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A functionalized tetradentate imidazolium salt 9,10-bis{di[2′-(N-ethylimidazolium-1-yl)ethyl]aminomethyl}anthracene tetrakis(hexafluorophosphate) (1) has been synthesized and characterized. The catalytic activity of the NHC-PdCl2 species formed by compound 1 and PdCl2 was tested in Suzuki-Miyaura, Heck-Mizoroki and Sonogashira reactions. The results showed that this catalytic system was effective for above three types of C-C coupling reactions.
- Liu, Qing-Xiang,Zhao, Dong-Xue,Wu, Hao,Zhao, Zhi-Xiang,Lv, Shi-Zhen
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- Effect of thiophene substitution on the intersystem crossing of arene photosensitizers
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The effect of thienyl substitution on the intersystem crossing (ISC) of a few arenes was studied using steady state and time-resolved transient absorption and emission spectroscopies, as well as DFT/TDDFT computations. We found that the phenyl and thienyl substituents generally induce red-shifted absorptions for the chromophores, and the DFT/TDDFT computations show that the red-shifted absorption and emission are due to the increased HOMO and the reduced LUMO energy levels. Nanosecond transient absorption spectra indicate the formation of a triplet state, the triplet state lifetime is up to 282 μs, and the singlet oxygen quantum yields (ΦΔ) are up to 60%. DFT/TDDFT computations indicate that introducing the thienyl substituent alters the relative singlet/triplet excited state energy levels, and the energy level-matched S1/T2 states are responsible for the enhanced ISC of the thienyl compounds. This information is useful for the design of heavy atom-free triplet photosensitizers and for the study of the fundamental photochemistry of organic compounds.
- Sadiq, Farhan,Zhao, Jianzhang,Hussain, Mushraf,Wang, Zhijia
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p. 1794 - 1803
(2018/11/23)
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- N-heterocyclic carbene palladium complex and preparation method and purpose thereof
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The invention discloses a N-heterocyclic carbene palladium complex and a preparation method thereof, and the N-heterocyclic carbene palladium complex takes 1,8-dis[3-(N-ethyl imidazolyl)propanolato] anthraquinone hexafluorophosphate as a precursor, and the synthesized N-heterocyclic carbene palladium complex is used as a catalyst for catalyzing a carbon-carbon bond cross-coupling reaction. The preparation method comprises the following steps: under nitrogen protection, 1,8-dis[3-(N-ethyl imidazolyl)propanolato] anthraquinone hexafluorophosphate and a palladium compound are added in a reactionvessel according to a mol ratio being 2:1, an organic solvent is added, a reaction is carried out for 12-24 hours at the temperature of 0-100 DEG C, and filtering and ether diffusion are carried to obtain the N-heterocyclic carbene palladium complex. The prepared N-heterocyclic carbene palladium complex t is used for the technical field of the catalyst.
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Paragraph 0018; 0025
(2018/10/11)
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- Synthesis of 9,10-Diarylanthracenes via Mg(TMP) 2 ·2LiCl-Mediated Benzyne Generation/[4+2] Cycloaddition and Deoxygenation of 9,10-Epoxyanthracene Intermediates
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A new synthetic route to functionalized 9,10-diarylanthracenes has been developed. 9,10-Epoxyanthracene intermediates were prepared by [4+2] cycloaddition of 1,3-diarylisobenzofuran with a variety of functionalized benzyne intermediates, which were obtained by Mg(TMP) 2 ·2LiCl-mediated benzyne generation. For the cleavage of the resultant 9,10-epoxyanthracene intermediates, we developed mild deoxygenation conditions using a combination of trifluoroacetic acid and Et 3 SiH. The utility of this sequence was demonstrated by application to the synthesis of 5,7,12,14-tetraphenylpentacene.
- Miyamoto, Naoya,Nakazawa, Yuki,Nakamura, Takanori,Okano, Kentaro,Sato, Sota,Sun, Zhe,Isobe, Hiroyuki,Tokuyama, Hidetoshi
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supporting information
p. 513 - 518
(2017/12/08)
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- Suzuki-Miyaura Micellar Cross-Coupling in Water, at Room Temperature, and under Aerobic Atmosphere
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Recently, oxygen-equilibrated water solutions of Kolliphor EL, a well-known surfactant, have been seen to form nanomicelles with oxygen-free cores. This has prompted the successful testing of the core environment as a green medium for palladium-catalyzed Suzuki-Miyaura cross couplings. The versatility of these conditions is endorsed by several examples, including the synthesis of relevant molecular semiconductors. The reaction medium can also be recycled, opening the way for an extremely easy and green chemistry compliant methodology.
- Mattiello, Sara,Rooney, Myles,Sanzone, Alessandro,Brazzo, Paolo,Sassi, Mauro,Beverina, Luca
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supporting information
p. 654 - 657
(2017/02/10)
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- Polyaniline coated on celite, a heterogeneous support for palladium: Applications in catalytic Suzuki and one-pot Suzuki-aldol reactions
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Particles of celite were coated with polyaniline, characterized and used as a support for heterogenization of palladium metal ions. The prepared heterogeneous palladium catalysts were screened for Suzuki-Miyaura and one-pot Suzuki-aldol reactions with high conversions. The process of heterogenization on celite reduces the PANI consumption ten-fold when anchoring palladium ions onto the support. The recyclable catalyst was also used for the sunlight mediated Suzuki-Miyaura reaction with good conversion.
- Patel, Heta A.,Patel, Arun L.,Bedekar, Ashutosh V.
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p. 8935 - 8945
(2016/10/13)
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- Synthesis, structure and catalysis of a NHC-Pd(II) complex based on a tetradentate mixed ligand
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Bis-benzimidazolium salt (S)-2,2′-bis[2′′-(N-picolyl-benzimidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [(S)-LH2]·(PF6)2 and its NHC palladium(ii) complex [(S)-LPd](PF6)2 (1) have been prepared and characterized. Complex 1 is formed by one tetradentate mixed ligand (S)-L and one Pd(ii) ion, in which one 15-membered ring and two 6-membered rings are present. In this complex, intramolecular π-π interactions between naphthalene rings and benzimidazole rings are observed. Additionally, the catalytic activity of complex 1 in three types of C-C coupling reactions (Suzuki-Miyaura, Heck-Mizoroki and Sonogashira reactions) was investigated. The results show that complex 1 is an effective catalyst in these coupling reactions.
- Liu, Qing-Xiang,Cai, Kang-Qing,Zhao, Zhi-Xiang
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p. 85568 - 85578
(2015/11/03)
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- Palladium supported on silica-chitosan hybrid material (Pd-CS@SiO2) for Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions
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Palladium supported on silica-chitosan hybrid material was prepared and characterized using thermogravimetric and differential thermogravimetric analyses, scanning electron microscopy, and Fourier transform infrared, energy-dispersive X-ray and X-ray photoelectron spectroscopies. The prepared Pd-CS@SiO2 catalyst (1 mol%) was used for the Suzuki-Miyaura cross-coupling reaction of various aryl halides and arylboronic acids in 95% ethanol at 80 °C and the Mizoroki-Heck reaction in dimethylformamide at 110 °C using K2CO3 as a base. The developed catalyst is well suitable for the 3R approach (recoverable, robust, recyclable) for cross-coupling reactions without appreciable loss of its activity.
- Jadhav, Sanjay,Kumbhar, Arjun,Salunkhe, Rajashri
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p. 339 - 345
(2015/06/02)
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- Triple aryne-tetrazine reaction enabling rapid access to a new class of polyaromatic heterocycles
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One of the most challenging goals of modern synthetic chemistry is to develop multi-step reactions for rapid and efficient access to complex molecules. We report a triple aryne-tetrazine reaction that enables rapid access to a new class of polyaromatic heterocycles. This new reaction, which couples diverse reactivity modes between simple aryne and tetrazine starting materials, proceeds in a single operation and takes less than 5 minutes in air with no metal catalyst.
- Suh, Sung-Eun,Barros, Stephanie A.,Chenoweth, David M.
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p. 5128 - 5132
(2015/08/24)
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- Direct C-H arylations of unactivated arenes catalyzed by amido-functionalized imidazolium salts
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The synthesis of biaryls from unactivated arenes and a broad range of aryl bromides and chlorides via the direct C-H functionalization can be efficiently performed with the aid of amido-functionalized imidazolium salts as organocatalysts. This method avoids the use of toxic transition metal catalysts and organometallic reagents.
- Ghosh, Debalina,Lee, Jhen-Yi,Liu, Chian-Yu,Chiang, Yen-Hsin,Lee, Hon Man
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supporting information
p. 406 - 410
(2014/05/20)
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- Features of the Diels-Alder reaction between 9,10-diphenylanthracene and 4-phenyl-1,2,4-triazoline-3,5-dione
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The Diels-Alder reaction between substituted anthracenes 1a-1j and 4-phenyl-1,2,4-triazoline-3,5 (2) is studied. In all cases except one, the reaction proceeds on the most active 9,10-atoms of substituted anthracenes. The orthogonality of the two phenyl groups at the 9,10-position of diene 1a is found to shield 9,10-reactive centers. No dienophiles with C=C bonds are shown to participate in the Diels-Alder reaction with 1a; however, the reaction 1a + 2 proceeds with the very active dienophile 2,4-phenyl-1,2,4-triazoline-3,5-dione. It is shown that attachment occurs on the less active but sterically accessible 1,4-reactive center of diene 1a. The structure of adduct 3a is proved by 1H and 13C NMR spectroscopy and X-ray diffraction analysis. The following parameters are obtained for reaction 1a + 2 ? 3a in toluene at 25°C: Keq = 2120 M-1, ΔHf≠ = 58.6 kJ/mol, ΔSf≠ = -97 J/(mol K), ΔVf≠ = -17.2 cm3/mol, ΔHb ≠ = 108.8 kJ/mol, ΔSb≠ = 7.3 J/(mol K), ΔVb≠ = -0.8 cm3/mol, ΔHr-n = -50.2 kJ/mol, ΔSr-n = -104.3 J/(mol K), ΔVr-n = -15.6 cm3/mol. It is concluded that the values of equilibrium constants of the reactions 1a-1j + 2 ? 3a-3j vary within 4 × 101-1011 M-1.
- Kiselev,Kornilov,Kashaeva,Potapova,Krivolapov,Litvinov,Konovalov
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p. 2073 - 2080
(2015/02/19)
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- Synthesis of diarylated aromatic hydrocarbons by dehydroxylation of diols using the titanium(IV) chloride and triethylamine reagent system
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1,2-Diarylacenaphthylene, 9,10-diarylphenanthrene and 9,10-diarylanthracene derivatives were obtained in good yields (61-92%) in short reaction times (5-30 min) from the corresponding diols with the titanium(III) reagent prepared in situ using the TiCl4/Et3N reagent system in dichloromethane at 25 °C. Georg Thieme Verlag Stuttgart ? New York.
- Periasamy, Mariappan,Beesu, Mallesh,Shanmugaraja, Masilamani
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p. 2913 - 2918
(2013/10/22)
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- Silica tethered Pd-DABCO complex: An efficient and reusable catalyst for suzuki-miyaura reaction
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A palladium-based catalyst supported on DABCO-functionalized silica was successfully prepared by a facile procedure. The prepared heterogeneous catalyst showed a high activity for the Suzuki-Miyaura reaction of aryl bromides, affording excellent yield in all the cases investigated. Interestingly, the catalyst could be quantitatively recovered from the reaction mixture and recycled for five times without any significant loss in activity. Furthermore, this protocol could be extended to the palladium catalyzed synthesis of annulated pyrazines. Springer Science+Business Media, LLC 2012.
- Kumbhar, Arjun,Kamble, Santosh,Jadhav, Sanjay,Rashinkar, Gajanan,Salunkhe, Rajashri
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p. 1388 - 1396
(2013/01/15)
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- Dynamic Covalent chemistry: A facile room-temperature, reversible, diels-alder reaction between anthracene derivatives and n-phenyltriazolinedione
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A series of readily accessible, dynamic Diels-Alder reactions that are reversible at room temperature have been developed between anthracene derivatives as dienes and N-phenyl-1,2,4-triazoline-3,5-dione as the dienophile. The adducts formed undergo reversible component exchange to form dynamic libraries of equilibrating cycloadducts. Furthermore, reversible adduct formation allows temperature-dependent modulation of the fluorescent properties of anthracene components; a feature of potential interest for the design of optodynamic polymeric materials by careful selection and manipulation of these simple dienes and dienophiles. Copyright
- Roy, Nabarun,Lehn, Jean-Marie
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p. 2419 - 2425
(2012/07/03)
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- Protolytic defluorination of trifluoromethyl-substituted arenes
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A series of trifluoromethyl-substituted arenes were studied in their reactions with Bronsted superacids. The products from these reactions suggest the formation of reactive electrophiles, such as carbocations, acylium cations or equivalent electrophilic species. As such, Friedel-Crafts-type reactions occur between these species and arene nucleophiles. NMR studies were done, and the results suggest the formation of an acyl group from the trifluoromethyl groups in the superacid.
- Kethe, Anila,Tracy, Adam F.,Klumpp, Douglas A.
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experimental part
p. 4545 - 4549
(2011/07/29)
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- Dichloro-bis(aminophosphine) complexes of palladium: Highly convenient, reliable and extremely active suzuki-miyaura catalysts with excellent functional group tolerance
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Dichloro-bis(aminophosphine) complexes are stable depot forms of palladium nanoparticles and have proved to be excellent SuzukiMiyaura catalysts. Simple modifications of the ligand (and/or the addition of water to the reaction mixture) have allowed their formation to be controlled. Dichlorobis[1- (dicyclohexylphosphany1)piperidine]palladium (3), the most active catalyst of the investigated systems, is a highly convenient, reliable, and extremely active Suzuki catalyst with excellent functional group tolerance that enables the quantitative coupling of a wide variety of activated, nonactivated, and deactivated and/or sterically hindered functionalized and heterocyclic aryl and benzyl bromides with only a slight excess (1.1-1.2 equiv) of arylboronic acid at 80°C in the presence of 0.2 mol % of the catalyst in technical grade toluene in flasks open to the air. Conversions of >95% were generally achieved within only a few minutes. The reaction protocol presented herein is universally applicable. Side-products have only rarely been detected. The catalytic activities of the aminophosphine-based systems were found to be dramatically improved compared with their phosphine analogue as a result of significantly faster palladium nanoparticle formation. The decomposition products of the catalysts are dicyclohexylphosphinate, cyclohexylphosphonate, and phosphate, which can easily be separated from the coupling products, a great advantage when compared with non-water-soluble phosphine-based systems.
- Bolliger, Jeanne L.,Frech, Christian M.
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supporting information; experimental part
p. 4075 - 4081
(2010/08/05)
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- The 1,3-diaminobenzene-derived aminophosphine palladium pincer complex {C6H3[NHP(piperidinyl)2]2Pd(Cl)} - A highly active Suzuki-Miyaura catalyst with excellent functional group tolerance
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The rapidly prepared 1,3-diaminobenzenederived aminophosphine pincer complex {C6H3 [NHP(piperidinyl)2] 2Pd(Cl)} (1) is an effective Suzuki catalyst with excellent functional group tolerance. Side-product formations, such as homocoupling, debromation or protodeboration have only rarely been detected and if so, were in all cases below the 5% level. The presented reaction protocol is universally applicable. Experimental observations indicate that palladium nanoparticles are the catalytically active form of 1.
- Bolliger, Jeanne L.,Frech, Christian M.
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experimental part
p. 1075 - 1080
(2010/06/17)
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- Palladium supported on a polyionic resin as an efficient, ligand-free, and recyclable catalyst for Heck, Suzuki-Miyaura, and Sonogashira reactions
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Polyionic Amberlite resin formate (ARF), derived from commercially available Amberlite resin chloride by simple rinsing with aqueous formic acid, could be soaked with palladium(0) from palladium salts, the formate counteranion being the reducing source. The resulting Amberlite resin formate supported with palladium(0), ARF-Pd, showed excellent catalytic activity in Heck, Suzuki-Miyaura, and Sonogashira couplings with a range of substrates. The catalyst may be recovered easily and quantitatively without leaching and recycled; it was tested for five runs without any significant loss of activity. Georg Thieme Verlag Stuttgart.
- Basu, Deb,Das, Sajal,Das, Pralay,Mandal, Bablee,Banerjee, Dipanjan,Almqvist, Fredrik
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experimental part
p. 1137 - 1146
(2009/12/01)
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- BF3-H2O catalyzed hydroxyalkylation of aromatics with aromatic aldehydes and dicarboxaldehydes: Efficient synthesis of triarylmethanes, diarylmethylbenzaldehydes, and anthracene derivatives
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(Figure Presented) BF3-monohydrate is found to be an efficient and strong acid catalyst as well as an effective protosolvating medium suitable for the hydroxyalkylation of arenes with aromatic aldehydes. This reaction has been extended to aromatic dialdehydes, such as terephthalic dicarboxaldehyde and isoterephthalic dicarboxaldehyde, for the efficient synthesis of diarylmethylbenzaldehydes, which are useful synthons for various organic transformations. Further, successful one step convergent synthesis of various synthetically useful anthracene derivatives from phthalaldehyde was also achieved. BF3-H2O is less expensive and acts as an efficient substitute for nonoxidizing strong protic acids/superacids.
- Prakash, G. K. Surya,Panja, Chiradeep,Shakhmin, Anton,Shah, Eric,Mathew, Thomas,Olah, George A.
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supporting information; experimental part
p. 8659 - 8668
(2009/12/30)
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- Tris(4-methylpiperazin-1-yl)phosphane, P(NC4H 8NMe)3: Synthesis, structural studies, group 10 and 11 metal complexes and catalytic investigations
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Group 10 and 11 metal complexes of a multidentate phosphorus-nitrogen donor ligand tris(4-methylpiperazin-1-yl)-phosphane, P(NC4H 8NMe)3 (1) are reported. The reactions of 1 with an equimolar amount of CuX (X = Cl, Br and I) afford tetranuclear cubane-like complexes [(CuX)-{P(NC4H8NMe)3}]4 (2, X = Cl; 3, X = Br and 4, X = I) in excellent yield. Treatment of 1 with AuCl(SMe2) produces a mononuclear complex, [(AuCl){P(NC 4H8NMe)3}] (5). Reaction of 1 with AgCN produces a 2D AgI polymeric sheet, [(AgCN)2-{P(NC4H 8NMe)3}]n (6) in moderate yield. The similar 1:1 reactions of 1 with AgX (X = Cl and Br) furnish dinuclear complexes, [(AgX){P(NC4H8NMe)3}]2 (7, X = Cl and 8, X = Br). The 2:1 reactions of 1 with [M(COD)Cl2] (M = Pd or Pt) afford [{P(NC4H8NMe)3}2MCl 2] (9, M = Pd and 10, M = Pt) in quantitative yield. The molecular structures of complexes 1-3 and 6 are established through single-crystal X-ray diffraction studies. The catalytic activity of the PdII complex 9 has been investigated in Suzuki cross coupling reactions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Ganesamoorthy, Chelladurai,Mague, Joel T.,Balakrishna, Maravanji S.
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p. 596 - 604
(2008/12/22)
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- Remote substituent effects on the photooxygenation of 9,10- diarylanthracenes: Strong evidence for polar intermediates
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Two different reaction pathways in the photooxygenation of 9,10-diarylanthracenes are identified, with strong evidence for polar (forward, singlet oxygen addition) and radical (backward, thermolysis) intermediates. The Royal Society of Chemistry.
- Fudickar, Werner,Linker, Torsten
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p. 1771 - 1773
(2008/12/22)
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- Luminescent assays for ketones and aldehydes employing catalytic signal amplification
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Herein we report the first use of transition metal catalytic signal enhancement for the analysis of small organic analytes. Two assays using Sonogashira and Suzuki cross-couplings have been used in the detection of ketones and aldehydes produce highly luminescent markers. The latter analysis utilizing the Suzuki coupling demonstrates the first use of peroxyoxalate initiated chemiluminescence in a sensing application. Chemiluminescent measurement revealed much higher sensitivity than fluorescence. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Houk, Ronald J. T.,Anslyn, Eric V.
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p. 729 - 735
(2008/02/12)
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- Process for producing 9,10-diphenylanthracene
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9,10-Diphenylanthracene, which can be produced applicably for industrial use in one or two process steps by subjecting a 9,10-dihalogenoanthracene and a metal or half-metal phenyl compound to a cross-coupling reaction.
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- Synthesis of t-butylated diphenylanthracene derivatives as blue host materials for OLED applications
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This paper describes the cost-effective synthesis and the photoluminescence of diphenylanthracene derivatives, which are found to be potential blue host materials for organic light emitting diode (OLED) technology.
- Balaganesan, Banumathy,Shen, Wen-Jian,Chen, Chin H.
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p. 5747 - 5750
(2007/10/03)
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- Microwave-assisted Suzuki coupling on a KF-alumina surface: Synthesis of polyaryls
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A range of conjugated polyaryls has been synthesized through one-pot microwave assisted palladium-catalyzed consecutive Suzuki coupling reactions on a KF-alumina surface with notable features including rapid reaction times, solvent-free conditions, high yields, atom economic and air-insensitive reactions.
- Basu, Basudeb,Das, Pralay,Bhuiyan, Md. Mosharef H.,Jha, Satadru
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p. 3817 - 3820
(2007/10/03)
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- Method for producing biaryl compound
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There is disclosed a method for producing a biaryl compound of formula (I): wherein R1 is the same or different and independently denotes a substituted or unsubstituted hydrocarbon group or the like, A and B denote an aromatic hydrocarbon ring having from 6 to 14 carbon atoms or the like, k and m independently denote an integer of from 0 to 5, and 1 denotes an integer of 1 or 2, which method is characterized by reacting an aromatic compound of formula (II): wherein R1, k and l denote the same as defined above, and X1 denotes a leaving group, with a Grignard reagent of formula (III): (R2). 9MgX2 (IIIg) wherein R2, B, and m denote the same as defined above and X2 denotes chlorine or the like, in the presence of a cyclic ether, or an acyclic ether having two or more ether oxygens in the molecule and a nickel catalyst.
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- Preparation of benzocyclobutenols by low temperature reaction of ketone enolates with benzynes
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The reaction of benzynes, generated from halobenzenes with lithium tetramethylpipiperide (LTMP) at -40 to -78°C, with ketone enolates affords benzocyclobutenols in fair to good yields.
- Tripathy, Sasmita,Reddy, Ranga,Durst, Tony
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p. 997 - 1002
(2007/10/03)
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- Electro-organic reactions. Part 54: Quinodimethane chemistry; Part 2 - Electrogeneration and reactivity of o-quinodimethanes
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The electrochemical generation and characterisation of a variety of o-quinodimethanes (o-QDMs) are described together with the outcome of preparative experiments in which they are key intermediates. The quinodimethanes are conveniently formed, in DMF, by both direct and redox-catalysed electroreduction of 1,2-bis(halomethyl)arenes. Their predominant reaction is polymerisation to poly(o-xylylene) (o-PX) polymers. In the presence of dienophiles the electrogenerated o-QDMs may undergo efficient cycloaddition reaction and distinctions between the possible mechanisms have been attempted on the basis of voltammetric, preparative and stereochemical experiments. Contrary to the precedent of the corresponding methyl ester, diphenyl maleate radical-anion isomerises only slowly to the fumarate radical-anion, yet co-electrolysis of 2,3-bis(bromomethyl)-1,4-dimethoxybenzene and diphenyl maleate or diphenyl fumarate gives exclusively the corresponding trans-adduct. Co-electrolysis of dimethyl maleate with either 1,2-bis(bromomethyl)benzene (more easily reduced) or 2,3-bis(bromomethyl)-1,4-dimethoxybenzene (less easily reduced) gave only o-PX polymer. The results are rationalised in terms of a double nucleophilic substitution mechanism where electron transfer between dienophile radical-anion and dihalide is relatively slow. Where electron transfer from maleate or fumarate radical-anions is likely to be fast o-quinodimethanes are formed by redox-catalysis and they polymerise rather than undergo Diels-Alder reaction. Dimerisation of the dienophile radical-anions, with k2 = 104 to 105 M-1 s-1, does not apparently compete with nucleophilic substitution or, where relevant, electron transfer.
- Utley, James H.P.,Ramesh, Shalini,Salvatella, Xavier,Szunerits, Sabine,Motevalli, Majid,Nielsen, Merete F.
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p. 153 - 163
(2007/10/03)
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- Reaction kinetics of electrogenerated 9,10-bis(4-substituted-phenyl)anthracene cation radicals with methanol: A change in mechanism brought about by remote substituents
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The reactions of 9,10-bis(4-nitrophenyl)- and 9,10-bis(4-methoxyphenyl)anthracene cation radicals (DNA+ and DAA+) with methanol (MeOH) in acetonitrile were analyzed using a pulse electrolysis stopped-flow method. The reaction of DNA+ was found to proceed via the same rate law as the 9,10-diphenylanthracene cation radical (DPA+), i.e. -d[DNA-]/dt = k[DNA+][MeOH]2, with a reaction rate 6 times faster. In contrast, the rate law governing the reaction of DAA+ with MeOH was different from that of DPA+, and was found to be -d[DAA+]/dt = k[DAA+]2[MeOH]. Reflecting this difference in the rate laws, an acceleration of the reaction was observed in the decay of DAA+ relative to DPA+, though methoxy groups usually stabilize aromatic cation radicals. This unusual remote substituent effect, which involves a change in the reaction mechanism, is discussed in terms of stabilization of intermediates in the proposed reaction mechanisms.
- Oyama, Munetaka,Yamanuki, Mikito,Sasaki, Teruo,Okazaki, Satoshi
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p. 1745 - 1748
(2007/10/03)
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- Kinetics of the reduction of dialkyl peroxides. New insights into the dynamics of dissociative electron transfer
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The concerted dissociative reduction of di-tert-butyl peroxide (DTBP), dicumyl peroxide (DCP), and di-n-butyl peroxide (DNBP) is evaluated by both heterogeneous and homogeneous electron transfer using electrochemical methods. Electrochemical and thermochemical determination of the O-O bond energies and the standard potentials of the alkoxyl radicals allow the standard potentials for dissociative reduction of the three peroxides in N,N-dimethylformamide and acetonitrile to be evaluated. These values allowed the kinetics of homogeneous ET reduction of DTBP and DCP by a variety of radical anion donors to be evaluated as a function of overall driving force. Comparison of the heterogeneous ET kinetics of DTBP and DNBP as a function of driving force for ET allowed the distance dependence on the reduction kinetics of the former to be estimated. Results indicate that the kinetics of ET to DTBP is some 0.8 order of magnitude slower in reactivity than DNBP because of a steric effect imposed by the bulky tert-butyl groups. Experimental activation parameters were measured for the homogeneous reduction of DTBP with five mediators, covering a range of 0.4 eV in driving force over the temperature range -30 to 50°C in DMF. The temperature dependence of the kinetics leads to unusually low preexponential factors for this series. The low preexponential factor is interpreted in terms of a nonadiabatic effect resulting from weak electronic coupling between the reactant and product surfaces. Finally, the data are discussed in the context of recent advances of dissociative electron transfer reported by Saveant and by German and Kuznestov. In total the results suggest that these peroxides undergo a nonadiabatic dissociative electron transfer and represent the first reported class of compounds where this effect is reported.
- Donkers, Robert L.,Maran, Flavio,Wayner, Danial D. M.,Workentin, Mark S.
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p. 7239 - 7248
(2007/10/03)
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- Thermal rearrangements of di- and triphenyl-substituted benzocyclobutenes and corresponding o-quinodimethanes
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7,8-Dimethoxy-7,8-diphenyl- (1c), 7,8-dimethyl-7,8-diphenyl- (1d), 7- methoxy-7,8,8-triphenyl- (1e), 7-methyl-7,8,8-triphenyl- (1f), 7-isocyano- 7,8,8-triphenyl- (1g), and 7,7,8-triphenylbenzocyclobutene (1h) are amenable to a variety of thermal rearrangements following initial electrocyclic ring- opening to the corresponding 7,8-diphenyl- (2c,d) and 7,8,8-triphenyl-o- quinodimethanes (2e-h). meso-1c was found to undergo a facile meso/rac isomerization at room temperature, indicating that other processes such as a symmetry-forbidden disrotatory ring-opening or a stepwise reaction compete with the symmetry-allowed conrotatory process. An estimate of the energy profile of the 1c/2c reaction system was made by kinetic simulation in combination with oxygen trapping of the intermediate o-quinodimethanes (2c) and semiempirical PM3 calculations, and revealed that the barrier for the symmetry-forbidden pathway is merely about 4 kJ · mol-1 higher than that for the symmetry-allowed one. o-Quinodimethanes 2c, 2g, 2e, and 2h underwent further electrocyclic hexatriene-cyclohexadiene ring-closure to give 4a,10- dihydroanthracene derivatives at temperatures between 20 and 80 °C. The 4a,10-dihydroanthracenes were further transformed to 9,10-disubstituted anthracenes by elimination of methanol or HCN, as well as to 9,10-substituted 9,10-dihydroanthracene derivatives. ESR and ENDOR spectroscopic detection of related 9-anthryl radicals lends support to the view that 9,10- dihydroanthracene products are formed by a homolytic hydrogen-transfer reaction (retrodisproportionation). By way of contrast, the aforementioned transformations play only a minor role in the case of methyl-substituted benzocyclobutenes 1d, 1f as here they are overruled by faster 1,5-H shift reactions of the corresponding o-quinodimethanes 2d, 2f, leading to styrene derivatives.
- Paul, Thomas,Boese, Roland,Steller, Ingo,Bandmann, Heinz,Gescheidt, Georg,Korth, Hans-Gert,Sustmann, Reiner
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p. 551 - 563
(2007/10/03)
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- Development of a dual-electrolysis stopped-flow method for the observation of electrogenerated chemiluminescence in energy-sufficient systems
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New methodology for the measurement of electrogenerated chemiluminescence (ECL) has been developed by using a dual-electrolysis stopped-flow system. Using this method, the ECL from 'energy-sufficient' systems composed of different kinds of ion radicals can be easily observed by mixing both the electrolyzed solutions directly. The apparatus and method have been described in detail as well as the ECL observations for various energy-sufficient systems. In particular, in the reaction between the thianthrene (TH) cation radical and the pyrene (PY) anion radical, it was found that the emission spectra changed with the addition of the precursors, reflecting both complex electron- and energy-transfer processes in solution. The present results indicate that the electron- and energy-transfer reactions changed significantly, depending on the type of molecules. The ECL observation with the addition of the third molecule was also informative to compare the ease of the formation of the excited states. It was clarified that the excited states of 9,10-diphenylanthracene and rubrene are easily formed compared with those of TH and PY.
- Oyama, Munetaka,Okazaki, Satoshi
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p. 5079 - 5084
(2007/10/03)
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