- Synthesis and thermal rearrangement of pentacyclo[6.5.0.04,12.05,10.09,13]trideca-2,6-diene
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Pentacyclo[6.5.0.04,12.05,10.09,13]trideca-2,6-diene (16) has been synthesized in five steps from 1-hydroxyhexacyclo[6.5.0.02,6.03,11.05,10.09,12]trideca n-7-one (10). Compound 16 undergoes thermal rearrangement to pentacyclo[7.4.0.02,6.03,11.05,10]trideca-7,12-diene (i.e. '[2.2.1]triblattadiene', 19). The intermediacy of cis,cisoid,cis-tricyclo[7.4.0.02,7[trideca-3,5,10,12-tetraene (18) in the thermal rearrangement of 16 was inferred via analysis of the 1H NMR spectrum of partially rearranged 16 and subsequently was further established via the results of a trapping experiment (i.e., fluorene was produced when thermal rearrangement of 16 was performed in the presence of 10% Pd/C).
- Marchand,Rajapaksa,Vidyasagar,Eckrich,Kumar
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- Hydrogenation of 9-pyridylmethylene- and 9-benzylidene(aza)fluorenes in the presence of rhenium heptasulfide
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Hydrogenation of 9-pyridylmethylene(aza)fluorenes and 9-benzylidene-4-azafluorene at 250°C and pH2 = 130 atm in the presence of Re2S7 as a catalyst occurs preferably at the exocyclic double bond of the fulvene fragment to yield pyridyl-9-(aza)fluorenylmethanes.
- Kolyadina,Soldatenkov,Ryashentseva,Prostakov
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- Laser-induced carbene-carbene rearrangement in solution: The diphenylcarbene-fluorene rearrangement
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Diphenylcarbene (DPC) generated by high-intensity laser photolysis of diphenyldiazomethane rearranges to fluorene (FL) by two distinct mechanisms as revealed by methyl-group labeling. Thus, excimer laser irradiation of p,p′-dimethyldiphenyldiazomethane generates 3,6-dimethylfluorene (3,6-DMF) and 2,7-dimethylfluorene (2,7-DMF), which were identified by fluorescence measurements as well as GC-MS and comparison with authentic materials. 3,6-DMF corresponds to direct bond formation between ortho positions in DPC, referred to as ortho,ortho′ coupling. 2,7-DMF corresponds to a carbene-carbene rearrangement, whereby DPC undergoes ring expansion to phenylcycloheptatetraene (PhCHT) followed by ring contraction to o-biphenylylcarbene (o-BPC), which then cyclizes to FL. The carbene-carbene rearrangement dominates over the ortho,ortho′ coupling under all conditions employed. The ortho,ortho′ coupling must take place in a higher excited state (most likely S2 or T1) of DPC, because it is not observed at all under thermolysis conditions, where only S1 and T0 are populated. The carbene-carbene rearrangement may take place either in a hot S1 state or more likely in a higher excited state (S2 or T1).
- Regimbald-Krnel, Michele J.,Wentrup, Curt
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- Fluorescence spectroscopy of aromatic species produced in rich premixed ethylene flames
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The fluorescence spectra of the condensed species (CS) collected in the soot inception region of a rich premixed laminar ethylene/oxygen flame have been measured by excitation in the UV at 266 and 355 nm excitation wavelength. The contribution of the most abundant polycyclic aromatic hydrocarbons (PAH) to the CS fluorescence has been evaluated in order to attribute the CS fluorescence at different emission wavelengths to specific aromatic structures. The fluorescence peaks detected in the UV region of the CS fluorescence spectrum was found to be mainly due to a typical PAH like fluorene, that is, the most fluorescent one among the PAH analyzed in the CS by chromatographic analysis, The CS exhibited the larger emission in the visible where the PAH contribution has been shown to be negligible and other fluorescing aromatic species, not identified by chromatographic analysis of the CS, have to be considered responsible for the visible fluorescence. Laser induced fluorescence (LIF) flame measurements excited at 266 nm and detected at two selected wavelengths (310 and 410 nm) have been performed along the flame axis and compared with the CS fluorescence intensity. The LIF and CS fluorescence signals show quite similar axial trends demonstrating that the LIF signals are related to CS fluorescence. In particular, the LIF fluorescence signals detected in the UV could be attributed to the PAH fluorescence whereas the unidentified species contained in the CS can be followed by LIF detection in the visible region.
- Ciajolo,Ragucci,Apicella,Barbella,De Joannon,Tregrossi
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- Palladium-Catalyzed Coupling of Biphenyl-2-yl Trifluoromethanesulfonates with Dibromomethane to Access Fluorenes
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A facile and efficient method has been developed for the synthesis of fluorenes by Pd-catalyzed C-H alkylation of biphenyl-2-yl trifluoromethanesulfonates. The trifluoromethanesulfonates are more readily available and more environmentally benign than biphenyl iodides, and are advantageous substrates for traceless directing-groupassisted C-H activation. The reaction generates C,C-palladacycles as the key intermediates that form two C(sp2)-C(sp3) bonds through reaction with CH2Br2. The reaction tolerates various functional groups, permitting easy access to a range of fluorene derivatives.
- Pan, Shulei,Zhang, Yanghui,Zhu, Qiongqiong
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- Pd-Catalyzed Assembly of Fluoren-9-ones by Merging of C-H Activation and Difluorocarbene Transfer
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We disclose a novel Pd-catalyzed assembly of fluoren-9-ones by merging of C-H activation and difluorocarbene transfer. ClCF2COONa served as a difluorocarbene precursor to be harnessed as a carbonyl source in this transformation. The current protocol enables us to afford fluoren-9-ones in high yields with excellent functional group compatibility, which also represents the first example of using difluorocarbene as a coupling partner in transition-metal-catalyzed C-H activation.
- Liu, Xiaobing,Sheng, Heyun,Zhou, Yao,Song, Qiuling
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supporting information
p. 2543 - 2547
(2021/05/05)
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- Method for reducing carbonyl reduction to methylene under illumination
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The invention belongs to the technical field of organic chemical synthesis. The method comprises the following steps: (1) mixing the carbonyl compound and the amine compound in a solvent, reacting 3 - 6 under the illumination of 380 - 456 nm, the reaction system is low in toxicity, high in atom utilization rate 12 - 24h. and production efficiency, safe and controllable in reaction process and capable of simplifying the operation in the preparation and production process. At the same time, the residue toxicity of the reaction is minimized, the pollution caused by the production process to the environment is reduced, and the steps and operations of removing residues after the reaction are simplified. In addition, the reactant feedstock is readily available. The reactant does not need additional modification before the reaction, can be directly used for preparing production, simplifies the operation steps, and shortens the reaction route. The production cost is obviously reduced.
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Paragraph 0033-0038
(2021/09/29)
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- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
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supporting information
p. 2095 - 2103
(2021/03/26)
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- Palladium-catalyzed intramolecular aromatic C-H acylation of 2-arylbenzoyl fluorides
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The catalytic intramolecular cyclization of acyl fluorides using a Pd(OAc)2/PCy3 system is described. A wide range of 2-arylbenzoyl fluoride derivatives can be used as fluorenone precursors and the reaction proceeds via an intramolecular coupling between aromatic C-H bonds with acyl C-F bonds. The reaction can be applied to the synthesis of indenofluorenedione derivatives and to the construction of other molecules with fivemembered rings.
- Hayakawa, Kazuki,Ikai, Kana,Ogiwara, Yohei,Sakai, Norio,Sakurai, Yuka
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p. 1882 - 1893
(2021/08/13)
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- Conversion of Aryl Aldehydes to Benzyl Iodides and Diarylmethanes by H3PO3/I2
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For the first time, H3PO3 was used as both the reducing reagent and the promotor in the reductive benzylation reactions with aryl aldehydes. By using a H3PO3/I2 combination, various aromatic aldehydes underwent iodination reactions and Friedel-Crafts type reactions with arenes via benzyl iodide intermediates, readily producing benzyl iodides and diarylmethanes in good yields. Intramolecular cyclization reactions also took place, giving the corresponding cyclic compounds. This new strategy features easy-handling, low-cost, and metal-free conditions.
- Lv, Fang,Xiao, Jing,Xiang, Junchun,Guo, Fengzhe,Tang, Zi-Long,Han, Li-Biao
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p. 3081 - 3088
(2021/02/01)
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- Heterogeneously Catalyzed Selective Decarbonylation of Aldehydes by CeO2-Supported Highly Dispersed Non-Electron-Rich Ni(0) Nanospecies
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Aldehyde decarbonylation has been extensively investigated, primarily using noble-metal catalysts; however, nonprecious-base-metal-catalyzed aldehyde decarbonylation has been hardly reported. We have established an efficient selective aldehyde decarbonylation reaction with a broad substrate scope and functional group tolerance utilizing a heterogeneous Ni(0) nanospecies catalyst supported on CeO2. The high catalytic performance is attributable to the highly dispersed and non-electron-rich Ni(0) nanospecies, which possibly suppress a side reaction producing esters and adsorbed CO-derived inhibition of the catalytic turnover, according to detailed catalyst characterization and kinetic evaluation.
- Matsuyama, Takehiro,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
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p. 13745 - 13751
(2021/11/17)
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- Solid-state construction of zigzag periphery: Via intramolecular C-H insertion induced by alumina-mediated C-F activation
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Caryl-F bond activation has become an important and quickly developing method for construction of carbon-based materials. We report that alumina-mediated C-F bond activation (AmCFA) enables construction of PAHs with zigzag periphery. This method includes
- Akhmetov, Vladimir,Amsharov, Konstantin,F?rtsch, Andreas,Feofanov, Mikhail
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supporting information
p. 12325 - 12328
(2021/11/30)
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- A denitrogenative palladium-catalyzed cascade for regioselective synthesis of fluorenes
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We herein report a denitrogenative palladium-catalyzed cascade for the modular and regioselective synthesis of polysubstituted fluorenes. Hydrazone facilitates the Pd(ii) to Pd(iv) oxidative addition in a Catellani pathway and is also the methylene synthon in the proposed reaction. Aryl iodides and 2-bromoarylaldehyde hydrazones undergo a norbornene-controlled tandem reaction sequence to give a broad scope of fluorenes in the presence of a palladium catalyst. The method described is scalable and adaptable to a three-component reaction with in situ generation of the hydrazone group. Preliminary mechanistic investigations have been conducted.
- Fu, Wai Chung,Kwong, Fuk Yee
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p. 1411 - 1417
(2020/02/18)
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- The Electronic Properties of Ni(PNN) Pincer Complexes Modulate Activity in Catalytic Hydrodehalogenation Reactions
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Three chloronickel(II) complexes of PNN- pincer ligands with pyrazolyl and diphenylphosphino donors appended to different arms of diarylamido anchors were prepared and fully characterized. The three derivatives (1-OMe, 1-Me, 1-CF3) differ only by the identity of the para-aryl substituent on the pyrazolyl arm with 1-OMe being 310 mV easier to oxidize than 1-CF3. All three complexes are competent catalysts for hydrodehalogenation reactions of 1-bromooctane and a variety of aryl halides in dimethylacetamide using NaBH4 as both base and hydride source. Comparative studies using diverse substrates showed that catalytic activity correlates with electron donor properties; 1-OMe was superior to the other two. Deuterium labeling studies verified NaBD4 as the deuteride source and excluded solvent-assisted radical pathways.
- Wang, Denan,Gardinier, James R.
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p. 4425 - 4434
(2020/10/19)
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- Palladium-catalyzed synthesis of fluorenes by intramolecular c(sp 2)-h activation at room temperature
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The synthesis of fluorenes by intramolecular Pd-catalyzed C(sp 2)-H activation of 2-arylbenzyl chlorides was conducted at room temperature by using commercially available triphenylphosphine and pivalic acid as ligands. The desired reactions proceeded efficiently at room temperature, and various substrates were converted into the corresponding fluorene derivatives in excellent yields.
- Fujihara, Tetsuaki,Tanji, Yutaka,Tsuji, Yasushi
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supporting information
p. 805 - 808
(2020/05/19)
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Hydrodehalogenation of Aryl Halides through Direct Electrolysis
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A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu3N/Et3N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale.
- Ke, Jie,Wang, Hongling,Zhou, Liejin,Mou, Chengli,Zhang, Jingjie,Pan, Lutai,Chi, Yonggui Robin
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supporting information
p. 6911 - 6914
(2019/05/10)
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- Nickel-catalyzed synthesis of 9-monoalkylated fluorenes from 9-fluorenone hydrazone and alcohols
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A practical protocol was disclosed for the nickel-catalyzed C-alkylation of 9-fluorenone hydrazone with alcohols using t-BuOK as the base, and 9-monoalkylated fluorene derivatives were obtained in good yields under the benign conditions.
- Fan, Jiang-Tao,Fan, Xin-Heng,Chen, Yong-Jie,Gao, Cai-Yan,Yang, Lian-Ming
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p. 2895 - 2902
(2019/08/12)
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- Scalable and safe synthetic organic electroreduction inspired by Li-ion battery chemistry
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Reductive electrosynthesis has faced long-standing challenges in applications to complex organic substrates at scale. Here, we show how decades of research in lithium-ion battery materials, electrolytes, and additives can serve as an inspiration for achieving practically scalable reductive electrosynthetic conditions for the Birch reduction. Specifically, we demonstrate that using a sacrificial anode material (magnesium or aluminum), combined with a cheap, nontoxic, and water-soluble proton source (dimethylurea), and an overcharge protectant inspired by battery technology [tris(pyrrolidino)phosphoramide] can allow for multigram-scale synthesis of pharmaceutically relevant building blocks. We show how these conditions have a very high level of functional-group tolerance relative to classical electrochemical and chemical dissolving-metal reductions. Finally, we demonstrate that the same electrochemical conditions can be applied to other dissolving metal-type reductive transformations, including McMurry couplings, reductive ketone deoxygenations, and epoxide openings.
- Peters, Byron K.,Rodriguez, Kevin X.,Reisberg, Solomon H.,Beil, Sebastian B.,Kawamata, Yu,Baran, Phil S.,Hickey, David P.,Klunder, Kevin,Gorey, Timothy J.,Anderson, Scott L.,Minteer, Shelley D.,Collins, Michael,Starr, Jeremy,Chen, Longrui,Udyavara, Sagar,Neurock, Matthew
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p. 838 - 845
(2019/04/30)
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- RING CLOSURE REACTION
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The present invention relates to a ring closure reaction useful in synthesizing fused aromatic or heteroaromatic ring systems, which may, for example, be used as organic semiconductor materials.
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Page/Page column 22
(2019/02/02)
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- Photochemical generation of 9-Fluorenyl radicals
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A series of 9H-fluorenols and 9H, 9′H-bifluorenyls were irradiated in less polar solvents giving photoproducts derived from their corresponding 9H-fluorenyl radicals. These transient species were directly observed by laser flash photolysis and their UV/visible spectra compared with those of their corresponding cations. Theoretical calculations (density functional theory [DFT]) of these intermediates indicate their destabilizing nature in similar fashion to the antiaromatic character of the corresponding cations.
- Duffy, Ian R.,Leigh, William J.,Afifi, Hanan,Ebead, Abdelaziz,Fournier, René,Lee-Ruff, Edward
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- Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
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A novel metal-free process allowing the reductive desulfurization of various benzylic dithioketals to afford diarylmethane and benzylester derivatives with good to excellent yields is reported. At room temperature, this mild reduction process requires only the use of TMSCl and NaI in CH2Cl2 and tolerates a large variety of functional groups. (Figure presented.).
- Zhao, Guangkuan,Yuan, Ling-Zhi,Alami, Mouad,Provot, Olivier
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p. 2522 - 2536
(2018/05/14)
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- Hydrodebromination of allylic and benzylic bromides with water catalyzed by a rhodium porphyrin complex
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Hydrodebromination of allylic and benzylic bromides was successfully achieved by a rhodium porphyrin complex catalyst using water as the hydrogen source without a sacrificial reductant. Mechanistic investigations suggest that bromine atom abstraction via a rhodium porphyrin metalloradical operates to give the rhodium porphyrin alkyl species and the subsequent hydrolysis of the rhodium porphyrin alkyl species to a hydrocarbon product is a key step to harness the hydrogen from water.
- Yang, Wu,Chen, Chen,Chan, Kin Shing
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p. 12879 - 12883
(2018/10/02)
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- Air-Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo-Reductant
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Strong photo-reductants have applications in photo-redox organic synthesis involving reductive activation of C?X(halide) and C=O bonds. We report herein air-stable PtII complexes supported by tetradentate bis(phenolate-NHC) ligands having peripheral electron-donating N-carbazolyl groups. Photo-physical, electrochemical, and computational studies reveal that the presence of N-carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo-reductant with E([Pt]+/*) over ?2.6 V vs. Cp2Fe+/0. The one-electron reduced [Pt]? species are stronger reductants with EPC([Pt]0/?) up to ?3.1 V vs. Cp2Fe+/0. By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light-driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.
- Li, Kai,Wan, Qingyun,Yang, Chen,Chang, Xiao-Yong,Low, Kam-Hung,Che, Chi-Ming
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supporting information
p. 14129 - 14133
(2018/10/15)
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- Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent-free reductive-deoxygenation of ketones with NaBH3CN
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NaBH3CN as a modified hydroborate agent and due to a strong withdrawing CN group does not show any reducing ability to reduce functional groups in the absence of acidic media (pH ~ 3–4). In this study, the immobilized sulfonic acid on silica, SiO2@SO3H, was prepared and applied as a new solid acid catalyst for extremely enhancing the reducing ability of NaBH3CN. The influence of SiO2@SO3H was highlighted by performing the quick and green reduction of structurally diverse carbonyl compounds involving aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones, and acyloins to the corresponding alcohols or alkanes with NaBH3CN. By the NaBH3CN/SiO2@SO3H system, aldehydes were reduced to the corresponding alcohols and ketonic compounds to alkanes as reductive-deoxygenation products. All reduction reactions were carried out within 3 min at room temperature and under solvent-free conditions to afford the products in high to excellent yields (90–98%).
- Zeynizadeh, Behzad,Kouhkan, Mehri
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p. 1521 - 1528
(2018/11/23)
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- Intermolecular Dehydrative Coupling and Intramolecular Cyclization of Ruthenium Vinylidene Complexes Formed from Aromatic Propynes Containing Carbonyl Functionalities
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A remarkable intermolecular dehydrative coupling reaction with the formation of a C?C bond was found for the vinylidene complex 2 a, yielding the dinuclear bisvinylidene complex 4 a. Complex 2 a containing 1-hydroxyindan moiety was first formed from the reaction of o-propynyl benzaldehyde 1 a with [Ru]–Cl ([Ru]=Cp(PPh3)2Ru) by a cyclization process. For analogous aldehyde 1 b containing an additional 1,3-dioxolane group on the aryl ring, similar intermolecular coupling yields the dinuclear bisvinylidene complex 4 b. However, the fluoro group on the aryl ring in aldehyde 1 c inhibits the coupling reaction, giving only the vinylidene complex 2 c. For the reactions of [Ru]–Cl in MeOH with compounds 1 f, 1 g and 1 h, each with a ketone functionality, cyclization gives vinylidene complexes 2 f, 2 g and 2 h, respectively. However, no similar intermolecular coupling was observed, instead, the intramolecular dehydration yields 8 f, 8 g and 8 h, respectively. In CDCl3, catalytic cyclization is observed for the o-propynylphenyl ketone 1 h with [Ru]–Cl at 50 °C giving the isochromene products 14 h. Furthermore, treatment of the o-propynylaryl α,β-unsaturated ketones 1 k–m and 1 n with [Ru]–Cl in MeOH affords the corresponding vinylidene complexes 10 k–m and 11 n each with 1-benzosuberone moiety in the presence of NH4PF6. These intramolecular cyclization products were formed by the addition of Cβ onto the terminal carbon of the alkene moiety. All these reaction products were characterized by spectroscopic methods. In addition, structures of complexes 4 a, and 10 l were confirmed by single crystal X-ray diffraction analysis.
- Chia, Pi-Yeh,Kuo, Cheng-Chen,Huang, Shou-Ling,Liu, Yi-Hong,Liu, Ling-Kang,Lin, Ying-Chih
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p. 3885 - 3894
(2018/11/10)
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- Activation of Molecular Hydrogen by Arylcarbenes
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The hydrogenation reactions of diphenylcarbene 1, fluorenylidene 2, and dibenzocycloheptadienylidene 3 were investigated in solid H2 and D2 matrices and in H2- and D2-doped argon matrices at cryogenic temperatures. The reactivity of the carbenes towards H2 increases in the order 12, 2 and 3 react fast under the same conditions via quantum chemical tunneling. In D2 both 1 and 3 are stable, whereas 2 slowly reacts. The different reactivity of the three carbenes is rationalized in terms of differing carbene stabilization energies.
- Mendez-Vega, Enrique,Maehara, Mika,Raut, Akshay Hemant,Mieres-Perez, Joel,Tsuge, Masashi,Lee, Yuan-Pern,Sander, Wolfram
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p. 18801 - 18808
(2018/11/27)
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- Palladium-Catalysed Cross-Coupling of Benzylammonium Salts with Boronic Acids under Mild Conditions
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Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C-H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.
- Türtscher, Paul L.,Davis, Holly J.,Phipps, Robert J.
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p. 793 - 803
(2017/10/07)
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- Dimerization of the Benzyl Radical in a High-Temperature Pyrolysis Reactor Investigated by IR/UV Ion Dip Spectroscopy
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We investigate the self-reaction of benzyl, C7H7, in a high-temperature pyrolysis reactor. The work is motivated by the observation that resonance-stabilized benzyl radicals can accumulate in reactive environments and contribute to the formation of polycyclic aromatic hydrocarbons (PAHs) and soot. Reaction products are detected by IR/UV ion dip spectroscopy, using infrared radiation from the free electron laser FELIX, and are identified by comparison with computed spectra. Among the reaction products identified by their IR absorption are several PAHs linked to toluene combustion such as bibenzyl, phenanthrene, diphenylmethane, and fluorene. The identification of 9,10-dihydrophenanthrene provides evidence for a mechanism of phenanthrene formation from bibenzyl that proceeds by initial cyclization rather than an initial hydrogen loss to stilbene.
- Hirsch, Florian,Constantinidis, Philipp,Fischer, Ingo,Bakels, Sjors,Rijs, Anouk M.
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p. 7647 - 7652
(2018/05/03)
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- Recovery processing method of 2,7-dichlorofluorene reaction mother solution
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The invention relates to a recovery processing method of a 2,7-dichlorofluorene reaction mother solution, in particular to a method for reusing waste liquid after treatment. Reductive dechlorination is carried out on the 2,7-dichlorofluorene reaction mother solution through zinc powder to obtain a mixed liquid mainly composed of 2-chlorofluorene and fluorine, the mixed liquid is filtered to removethe zinc powder and zinc acetate, and directed chloridized or chloridized with the raw material fluorine to prepare 2,7-dichlorofluorene. The recovery processing method of the 2,7-dichlorofluorene reaction mother solution is applied to the recycling of the 2,7-dichlorofluorene reaction mother solution, and has the advantages of simple operation, cheap treatment and the like.
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Paragraph 0027-0030
(2018/10/19)
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- Au-catalyzed biaryl coupling to generate 5- to 9-membered rings: Turnover-limiting reductive elimination versus π-complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes-substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to π-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the π-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Corrie, Tom J. A.,Ball, Liam T.,Russell, Christopher A.,Lloyd-Jones, Guy C.
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p. 245 - 254
(2017/05/29)
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- Au-Catalyzed Biaryl Coupling to Generate 5- To 9-Membered Rings: Turnover-Limiting Reductive Elimination versus ?-Complexation
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The intramolecular gold-catalyzed arylation of arenes by aryl-trimethylsilanes has been investigated from both mechanistic and preparative aspects. The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 include a heteroatom (N, O). Tethering of the arene to the arylsilane provides not only a tool to probe the impact of the conformational flexibility of Ar-Au-Ar intermediates, via systematic modulation of the length of aryl-aryl linkage, but also the ability to arylate neutral and electron-poor arenes - substrates that do not react at all in the intermolecular process. Rendering the arylation intramolecular also results in phenomenologically simpler reaction kinetics, and overall these features have facilitated a detailed study of linear free energy relationships, kinetic isotope effects, and the first quantitative experimental data on the effects of aryl electron demand and conformational freedom on the rate of reductive elimination from diaryl-gold(III) species. The turnover-limiting step for the formation of a series of fluorene derivatives is sensitive to the reactivity of the arene and changes from reductive elimination to ?-complexation for arenes bearing strongly electron-withdrawing substituents (σ > 0.43). Reductive elimination is accelerated by electron-donating substituents (ρ = -2.0) on one or both rings, with the individual σ-values being additive in nature. Longer and more flexible tethers between the two aryl rings result in faster reductive elimination from Ar-Au(X)-Ar and lead to the ?-complexation of the arene by Ar-AuX2 becoming the turnover-limiting step.
- Ball, Liam T.,Corrie, Tom J. A.,Lloyd-Jones, Guy C.,Russell, Christopher A.
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p. 245 - 254
(2021/09/04)
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- Transfer Hydro-dehalogenation of Organic Halides Catalyzed by Ruthenium(II) Complex
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A simple and efficient Ru(II)-catalyzed transfer hydro-dehalogenation of organic halides using 2-propanol solvent as the hydride source was reported. This methodology is applicable for hydro-dehalogenation of a variety of aromatic halides and α-haloesters and amides without additional ligand, and quantitative yields were achieved in many cases. The potential synthetic application of this method was demonstrated by efficient gram-scale transformation with catalyst loading as low as 0.5 mol %.
- You, Tingjie,Wang, Zhenrong,Chen, Jiajia,Xia, Yuanzhi
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p. 1340 - 1346
(2017/02/10)
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- Reductive dehalogenation method of organic halide
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The invention discloses a reductive dehalogenation method of an organic halide. In the inert gas atmosphere, the organic halide shown as the formula I or the formula II is subjected to reductive dehalogenation to generate an organic compound shown as the formula III or the formula IV (the formulas are shown as the description) in the presence of a catalyst, alkali and a solvent, wherein the reaction temperature is controlled to 90-100 DEG C. The reductive dehalogenation method has the advantages that the range of substrates is widened; the solvent in use does not need extra phosphorous ligands, the price is relatively cheap, and the consumption can be greatly reduced to 0.1 mol%; the solvent in use serves as a hydrogen source and reacts, the operation is simple, a lot reactions can reach quantitative yields, and when the reactions are scaled up to gram level reactions, almost quantitative yields can still be achieved.
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Paragraph 0069; 0070; 0071; 0072; 0073; 0074
(2017/08/28)
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- Dual Gold Catalysis: Synthesis of Fluorene Derivatives from Diynes
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1,5-Diyne systems bearing one terminal and one benzyl- or allyl-substituted alkyne attached to an aromatic backbone were converted in the presence of a gold catalyst. In a dual gold-catalyzed process, gold vinylidenes are formed that selectively undergo formal CH insertion into the C(sp2)–H bond of the offered unsaturated systems. If H atoms are present in the propargylic position, a subsequent isomerization to the aromatic system takes place leading to 9H-fluorene and 11H-benzo[b]fluorene derivatives as final products. In the case of a quaternary carbon in the propargylic position no further aromatization is observed and 10H-benzo[b]fluorene derivatives are obtained in high yield. (Figure presented.).
- Bucher, Janina,Wurm, Thomas,Taschinski, Svenja,Sachs, Eleni,Ascough, David,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 225 - 233
(2017/02/05)
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- Palladium-Catalyzed Formal [4 + 1] Annulation via Metal Carbene Migratory Insertion and C(sp2)-H Bond Functionalization
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A highly efficient and operationally simple palladium-catalyzed formal [4 + 1] annulation reaction has been developed. The reaction is featured by the formation of two different C-C bonds on a carbenic center. It represents a concise method for the synthesis of a wide range of polycyclic aromatic hydrocarbons (PAHs) and 1H-indenes with easily available (trimethylsilyl)diazomethane as the carbene source. Metal carbene migratory insertion and C(sp2)-H bond activation are proposed as the key steps in this transformation. The reaction further demonstrates the versatility of the carbene-based coupling in combination with various transition-metal-catalyzed transformations.
- Xu, Shuai,Chen, Ri,Fu, Zihao,Zhou, Qi,Zhang, Yan,Wang, Jianbo
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p. 1993 - 1997
(2017/08/14)
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- Ring-closure reaction of 2-benzoylbenzenediazonium salts in 1-butyl-3- methylimidazolium ionic liquids
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A ring-closure reaction by thermal dediazoniation of 2-substituted benzenediazonium tetrafluoroborates in imidazolium-based ionic liquids was investigated. Dediazoniation of 2-(4-R-benzoyl)benzenediazonium tetrafluoroborates (R = H, Me, OMe, Cl) in ionic liquid [BMIM][TfO] gave 3-R-9-fluorenones as ring-closure products and 2-(4-R-benzoyl)phenyl trifluoromethanesulfonates as substitution products. Dediazoniation in [BMIM][Tf2N] afforded 3-R-9-fluorenones and R-C6H4-CO-C6H4-OSO(CF3)(NSO2CF3). Yields of the ring-closure products were higher in [BMIM][Tf2N] than in [BMIM][TfO]. 2-Benzylbenzenediazonium and 2-phenoxybenzenediazonium tetrafluoroborates exclusively produced substitution products in both ionic liquids. DFT calculations suggest that electron transfer from the anion to render homolytic process should be induced more readily in [BMIM][Tf2N] than in [BMIM][TfO]. This ability may be responsible for the higher yields of the ring-closure products via homolytic pathway and the smaller yields of the substitution products via heterolytic pathway in [BMIM][Tf2N].
- Okazaki, Takao,Yamamoto, Hiroyuki,Kitagawa, Toshikazu
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- Efficient palladium-catalyzed C(sp2)-H activation towards the synthesis of fluorenes
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A facile protocol for the synthesis of fluorene derivatives has been developed through palladium-catalyzed cyclization of 2′-halo-diarylmethanes via activation of arylic C-H bonds. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates to convert into their corresponding fluorenes in good to excellent yields. Studies revealed that this Pd-catalyzed cyclization was also available for the substrates of 2′-chloro-diarylmethanes and no catalyst poisoning occurred for 2′-iodo-diphenylmethane.
- Song, Juan,Li, Yali,Sun, Wei,Yi, Chenglong,Wu, Hao,Wang, Haotian,Ding, Keran,Xiao, Kang,Liu, Chao
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supporting information
p. 9030 - 9033
(2016/11/11)
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- Synthesis of Fluorenes Starting from 2-Iodobiphenyls and CH2Br2 through Palladium-Catalyzed Dual C-C Bond Formation
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A facile and efficient approach is developed for the synthesis of fluorene and its derivatives starting from 2-iodobiphenyls and CH2Br2. A range of fluorene derivatives can be synthesized under relatively mild conditions. The reaction proceeds via a tandem palladium-catalyzed dual C-C bond formation sequence through the key dibenzopalladacyclopentadiene intermediates, which are obtained from 2-iodobiphenyls through palladium-catalyzed C-H activation.
- Shi, Guangfa,Chen, Dushen,Jiang, Hang,Zhang, Yu,Zhang, Yanghui
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p. 2958 - 2961
(2016/07/06)
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- C-OH bond cleavage initiated by electron transfer: Electroreduction of 9-fluorenol
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Cyclic voltammetry, chronoamperometry, coulometry, electrolysis, digital simulation, quantum chemical calculations of 9-fluorenol as an example, were used to show that the electroreduction of aryl derivatives of methanol in 0.1 M Bu4NClO4/DMF proceeds via the ECE mechanism (including the stages of radical anion formation and the C-OH bond cleavage in the radical anion) complicated by the reactions of the depolarizer with the anionic products. Among these reactions are the deprotonation of 9-fluorenol and its monoanions by hydroxide anion and fluorenyl anion. The thermodynamic parameters of the reactions have been estimated both theoretically and experimentally. It was found that the equilibrium constants of the fluorenyl anions deprotonation are close (C-anion) or higher (O-anion) than that of fluorenol. As a result the total equilibrium is shifted towards the side of the dianion of 9-fluorenone. The unusual ratio of the equilibrium constants was explained by lower basicity of π?-dianion compare with other anions.
- Mendkovich, Andrey S.,Syroeshkin, Mikhail A.,Nasybullina, Darya V.,Mikhailov, Mikhail N.,Gultyai, Vadim P.,Elinson, Mikhail N.,Rusakov, Alexander I.
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p. 962 - 973
(2016/02/05)
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- Halogen-Adjusted Chemoselective Synthesis of Fluorene Derivatives with Position-Controlled Substituents
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Fluorenes have been synthesized through an efficient novel Pd-catalyzed tandem cross-coupling reaction; these substrates are fascinating building blocks found in organic photoelectric materials. The position of the substituent on fluorenes could be conveniently tuned by changing the halogen in the ortho-halobenzyl bromide substrates when coupled with various arylboronic acids. This newly developed synthetic approach could achieve the potential diversity in fluorene-based molecular architectures.
- Song, Juan,Sun, Wei,Li, Yali,Wei, Fuliang,Liu, Chao,Qian, Yan,Chen, Shufen
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supporting information
p. 211 - 215
(2016/03/01)
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- Efficient One-Pot Synthesis of Mono- and Bis[di(2-pyridyl)phosphine Oxides] from Tris(2-pyridyl)phosphine
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An efficient one-pot access to di(2-pyridyl)phosphine oxides Py2P(R)=O and bis[di(2-pyridyl)phosphine oxides] Py2P(O)-Z-P(O)Py has been developed based on the reaction of available tris(2-pyridyl)phosphine with various organic halides, followed by treatment of the resulting phosphonium salts with alkali in situ. The isolated yields of the phosphine oxides were in the range 40-96%.
- Malysheva, Svetlana F.,Gusarova, Nina K.,Belogorlova, Nataliya A.,Sutyrina, Anastasiya O.,Litvintsev, Yuriy I.,Albanov, Alexander I.,Sterkhova, Irina V.,Artem'ev, Alexander V.
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supporting information
p. 2451 - 2454
(2016/10/24)
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- One-Pot Defunctionalization of Lignin-Derived Compounds by Dual-Functional Pd50Ag50/Fe3O4/N-rGO Catalyst
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Generation of hydrogen from renewable sources and its safe utilization for efficient one-pot upgrading of renewable biofuels are a challenge. Bimetallic PdAg catalyst supported on Fe3O4/nitrogen-doped reduced graphene oxide (N-rGO) were synthesized for hydrogen generation from formic acid with high TOF (497 h-1 at 50 °C), and the hydrogen was subsequently utilized in situ for selective defunctionalization of lignin-derived chemicals with preserved aromatic nature at ambient pressure. Hydrodeoxygenation of aromatic aldehydes and ketones gave excellent yields (99% at 130 °C) with no use of additives. Furthermore, hydrogenolysis of β-O-4 and α-O-4 C-O model compounds produced only two products with high selectivity at 120 °C, which is an efficient and versatile one-pot platform for valorization of lignin biomass.
- Singh, Ajay K.,Jang, Seungwook,Kim, Jae Yul,Sharma, Siddharth,Basavaraju,Kim, Min-Gyu,Kim, Kyung-Rok,Lee, Jae Sung,Lee, Hong H.,Kim, Dong-Pyo
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p. 6964 - 6972
(2015/11/18)
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- Dehalogenation of functionalized alkyl halides in water at room temperature
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Alkyl bromides and chlorides can be reduced to the corresponding hydrocarbons utilizing zinc in the presence of an amine additive. The process takes place in water at ambient temperatures, enabled by a commercially available designer surfactant. The reaction medium can be readily recycled, and the amount of organic solvent invested for product isolation is minimal, leading to very low E Factors. This journal is
- Isley, Nicholas A.,Hageman, Matt S.,Lipshutz, Bruce H.
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supporting information
p. 893 - 897
(2015/03/04)
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- Transition-metal-free intramolecular carbene aromatic substitution/Büchner reaction: Synthesis of fluorenes and [6,5,7]benzo-fused rings
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Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by RhII catalysts with a-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.
- Liu, Zhenxing,Tan, Haocheng,Wang, Long,Fu, Tianren,Xia, Ying,Zhang, Yan,Wang, Jianbo
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p. 3056 - 3060
(2015/03/30)
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- Novel imidazolium and imidazolinium salts containing the 9-nickelafluorenyl anion - Synthesis, structures and reactivity
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Investigation of the properties of carbene complexes is one of the most important fields of modern coordination chemistry. In this paper, we propose the convenient synthesis of NHC-nickel compounds. The 9-nickelafluorenyllithium complex reacts with imidazolium or imidazolinium salts to afford 9-nickelafluorenyl-NHC salts via ionic metathesis with very good yields (66-92%). These compounds can be isomerised at elevated temperatures to give Ni-NHC complexes with excellent yields (88-91%), probably via nickel mediated hydrogen transfer to the biphenyl moiety. In this reaction, the nickelacyclic ring itself serves as a base in the deprotonation of the carbene precursor. DFT calculations show the thermodynamic instability of the synthesized salts, with Gibbs free energy differences for 1 of -84 kJ mol-1 at 298 K and -167 kJ mol-1 at 374 K. The obtained salts and carbene complexes are relatively air and moisture stable in the solid state.
- Buchalski, Piotr,Pacholski, Roman,Chodkiewicz, Krzysztof,Buchowicz, W?odzimierz,Suwińska, Kinga,Shkurenko, Aleksander
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p. 7169 - 7176
(2015/04/27)
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- Solid-supported hydrazone of 4-(4′-Formyl-3′-methoxyphenoxy)butyric acid as a new traceless linker for solid-phase synthesis
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The use of a hydrazine derived from a backbone amide linker as a new hydrazone-based traceless linker for solid-phase organic synthesis is described. The stability of the linker was tested under various conditions, including treatment with acids, bases, and borohydrides. Final compounds can be released by selective cleavage using trimethylsilanolate. To demonstrate the versatility of the linker, the synthesis of a model compound under various reaction conditions was performed with good results.
- Okorochenkov, Sergei,Burglova, Kristyna,Popa, Igor,Hlavac, Jan
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supporting information
p. 180 - 183
(2015/01/30)
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- Pd(0)-Catalyzed Cross-Coupling of 1,1-Diboronates with 2,2′-Dibromobiphenyls: Synthesis of 9H-Fluorenes
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An efficient and mild synthesis of 9H-fluorene derivatives through a Pd(0)-catalyzed cross-coupling reaction of 1,1-diboronates with 2,2′-dibromobiphenyls has been developed. This reaction features high yields, operational simplicity, and mild reaction conditions, thus providing an excellent alternative to published methods for 9H-fluorene synthesis.
- Xu, Shuai,Shangguan, Xianghang,Li, Huan,Zhang, Yan,Wang, Jianbo
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p. 7779 - 7784
(2015/08/18)
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- Gold-Catalyzed Proto- and Deuterodeboronation
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A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.
- Barker, Graeme,Webster, Stacey,Johnson, David G.,Curley, Rachel,Andrews, Matthew,Young, Paul C.,MacGregor, Stuart A.,Lee, Ai-Lan
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p. 9807 - 9816
(2015/11/03)
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- Palladium-Catalyzed Reaction of Haloarenes with Diarylethynes: Synthesis, Structural Analysis, and Properties of Methylene-Bridged Arenes
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Fluorenes and methylene-bridged polyarenes were easily and efficiently synthesized from haloarenes (or aryl triflates) and diarylethynes by a one-pot, two-step procedure. This protocol involves the palladium-catalyzed cycloisomerization and a subsequent base-mediated retro-aldol condensation. A major advantage is that the starting materials need not have ortho functional groups to complete the annulation. The backbone of the designed products was enlarged using dihaloarenes, highly π-conjugated haloarenes, or diarylalkynes. The mechanism of the formation of benzo[a]fluorene was investigated. The bowl-shaped structure of methylene-bridged indenocorannulene was verified by X-ray crystallography. The photophysical and electrochemical properties of the products thus prepared were investigated.
- Lee, Che-Wei,Liu, En-Chih,Wu, Yao-Ting
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p. 10446 - 10456
(2015/11/18)
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- Photochemical generation of 9h-fluorenyl radicals
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A series of 9-substituted fluorenols and 9,9′-disubstituted-9, 9′-bifluorenyls were irradiated to give products derived from fluorenyl radicals. Product distribution was solvent dependent. A TEMPO adduct was isolated from the photoexcitation of 9-fluorenol. An unusual unsymmetrical 3,9′-bifluorenyl was observed from the photolysis of 9- trifluoromethylfluorenol and 9,9′-di(trifluoromethyl)-9,9′- bifluorenyl in more polar or hydrogen-bonding solvents. The electronic nature of 9-substituted fluorenyl radicals was probed using theoretical calculations showing the dipolar character of species with electron-deficient groups. These constitute the first examples of "doubly destabilized" radicals. Substituted 9-fluorenols and 9,9′-bifluorenyls undergo photolysis to give products derived from 9-fluorenyl radicals. These intermediates decay by hydrogen abstraction giving 9H-fluorenes, or coupling to 9,9′bifluorenyls. The 9-trifluoromethyl-9-fluorenyl radical undergoes an unusual coupling to the unsymmetrical 9,3′-bifluorenyl.
- Dyblenko, Tatiana,Chtchemelinine, Andrei,Reiter, Ryan,Chowdhury, Ruhul Q.,Enaya, Alexander,Afifi, Hanan,Fournier, Rene,Mladenova, Gabriela,Lever, Alfred Barry P.,Lee-Ruff, Edward
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p. 470 - 475
(2014/04/03)
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- Br?nsted acid-mediated intramolecular cyclization of biaryl triazenes for the synthesis of fluorenes and 9,10-dihydro-phenanthrenes
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The efficient synthesis of fluorenes from biaryl triazenes is successfully developed. Up to 27 examples of biaryl triazenes are converted into their corresponding fluorene derivatives in the presence of CF3COOH (4.0 equiv). Mechanism research i
- Xu, Lijun,Yang, Weijun,Zhang, Lili,Miao, Maozhong,Yang, Zhigen,Xu, Xin,Ren, Hongjun
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p. 9206 - 9221
(2015/01/08)
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- Direct access to fluorene by successive C-O/C-H bond activations of 2-phenylbenzyl ester
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Catalytic formation of fluorene has been achieved from 2-phenylbenzyl trifluoroacetate via successive C-O and C-H bond cleavage reactions by Pd(OAc)2/PPh3 in 97% yield. This reaction involves the oxidative addition of ester to give (carboxylato)(2-phenylbenzyl)palladium(II) species and deprotonation from the 2-phenylbenzyl group by the cleaved carboxylato group via an internal electrophilic substitution mechanism.
- Hirano, Masafumi,Kawazu, Sosuke,Komine, Nobuyuki
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p. 1921 - 1924
(2014/05/20)
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- Gold(I) carbenes by retro-buchner reaction: Generation and fate
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The fate of the aryl gold(I) carbenes generated by retro-Buchner reaction of ortho-substituted 7-aryl-1,3,5-cycloheptatrienes is dependent on the constitution of the ortho substituent. Indenes and fluorenes are obtained by intramolecular reaction of highly electrophilic gold(I) carbenes with alkenes and arenes. According to density functional theory calculations, the gold-catalyzed retro-Buchner process occurs stepwise, although the two carbon-carbon cleavages occur on a rather flat potential energy surface.
- Wang, Yahui,McGonigal, Paul R.,Herle, Bart,Besora, Maria,Echavarren, Antonio M.
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p. 801 - 809
(2014/02/14)
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