- Photochemistry of supramolecular complex formed by trans-stilbene and the metal-organic coordination polymer
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Supramolecular adduct consisting from the metal-organic framework (MOF) [Zn4(dmf)(ur)2(ndc)4] (ndc2- is 2,6-naphtalenedicarboxylate, ur is urotropin, and dmf is N,N'-dimethylformamide) and trans-stilbene was synthesized and its photochemistry was studied. The quantum yield of trans-cis photoisomerization of stilbene in adduct (0.2) was found to be an order of magnitude higher than for crystalline trans-stilbene and comparable with that in organic solvents. The results demonstrate that the creation of MOFs adducts with organic photochroms is a prospective approach for the creation of new hybrid photochromic materials.
- Semionova, Veronica V.,Glebov, Evgeni M.,Korolev, Valeri V.,Sapchenko, Sergey A.,Samsonenko, Denis G.,Fedin, Vladimir P.
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- Standard enthalpies of formation of phenanthrene and naphthacene
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Standard enthalpies of combustion of phenanthrene and naphthacene were determined to be -(7048.7 ± 0.9) kJ·mol-1 and -(9005.1 ± 1.8) kJ·mol-1, respectively, by means of high-precision micro-combustion calorimetry. The former result a
- Nagano, Yatsuhisa
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- Polycyclic arene episulfides. Attempted synthesis, molecular orbital calculations and comparison with arene oxides
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In pursuit of the elusive polycyclic arene episulfides, the synthesis of phenanthrene-9,10-episulfide (5b) was attempted. However, the reactions of phenanthrene-9,10-oxide and of phenanthrene with sulfur transfer agents and of 5,7-dihydrodibenzo[c,e]thiepine (9) with butyllithium did not afford 5b, although its intermediacy could be detected by NMR and inferred from the products isolated. Quantum-mechanical ab initio and density functional methods were used to calculate the thermodynamic stability of representative arene episulfides and arene oxides. The arene episulfides were found to be thermodynamically significantly less stable than the corresponding oxides, towards elimination of sulfur and oxygen respectively. K-region arene episulfides are found to be thermodynamically more stable towards sulfur extrusion than their bay-region isomers. The thermodynamic stabilities of analogous arene oxides and arene episulfides parallel each other, and the relative thermodynamic stabilities of arene oxides and episulfides can be deduced from the degree of the aromatic character of the rings which do not carry the heteroatom.
- Zoller, Uri,Shakkour, Elias,Pastersky, Irine,Sklenak, Stepan,Apeloig, Yitzhak
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- Synthesis of new furan polycycles via photochemical reaction in neutral and acidic medium
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New furan derivatives of o-divinylbenzenes were synthesized and their photochemical reactivity has been investigated in neutral and acidic medium. Depending of the structure of the starting materials and pH value, the new cyclization (11, 16, 20), cycloaddiotion (12, 13, endo-17, exo-18), electrocyclization (21, 22) and dimeric (15, 19) products were isolated. While photochemical investigation in neutral medium showed that the main intramolecular process is cycloaddition, in the case of acidic photochemistry, due to the protonation of the starting molecule, electrocyclization process comes to expression and formation of dihydronaphtalene products 21 and 22.
- Kuzmi?, ?eljka,?kori?,Marini?, ?eljko,Vuk, Dragana
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- Synthesis of Difluoroalkyl Unsaturated β-Amino Acid Derivatives Exclusively through Alkyne Difunctionalization
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Alkynes difunctionalization is a powerful strategy in organic synthesis that provides a convenient synthetic entry for internal alkenes. The main challenge in this field was considered to be the geometry control of the newly formed double bond (thermodynamically controlled or kinetically controlled). Herein, we report a novel procedure (through the cyclic compounds broken) to completely control the regioselectivity of olefins. The products, difluoroalkyl unsaturated β-amino acid derivatives, have potential applications in some important pharmaceuticals on account of the special nature of fluorine atoms.
- Wang, Qiang,Jin, Jia-Ni,Chen, Xi,Wang, Xin-Gang,Zhang, Bo-Sheng,Ma, Jun-Wei,Liang, Yong-Min
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- Bicyclo[2.2.1]heptan-1-ylcarbene can ring expand
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Generation of bicyclo[2.2.1]heptan-1-ylcarbene from a hydrocarbon precursor avoids the problems that attend generation from nitrogenous molecules and allows the determination that such carbenes can ring expand to bridgehead alkenes.
- Ruck, Rebecca T.,Jones Jr., Maitland
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- An amine template strategy to construct successive C-C bonds: Synthesis of benzo[: H] quinolines by a deaminative ring contraction cascade
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We developed a convergent strategy to build, cyclize and excise nitrogen from tertiary amines for the synthesis of polyheterocyclic aromatics. Biaryl-linked azepine intermediates can undergo a deaminative ring contraction cascade reaction, excising nitrogen with the formation of an aromatic core. This strategy and deaminative ring contraction reaction are useful for the synthesis of benzo[h]quinolines. This journal is
- McFadden, Timothy Patrick,Nwachukwu, Chideraa Iheanyi,Roberts, Andrew George
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supporting information
p. 1379 - 1385
(2022/03/01)
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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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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- A Bottleable Imidazole-Based Radical as a Single Electron Transfer Reagent
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Reduction of 1,3-bis(2,6-diisopropylphenyl)-2,4-diphenyl-1H-imidazol-3-ium chloride (1) resulted in the formation of the first structurally characterized imidazole-based radical 2. 2 was established as a single electron transfer reagent by treating it with an acceptor molecule tetracyanoethylene. Moreover, radical 2 was utilized as an organic electron donor in a number of organic transformations such as in activation of an aryl-halide bond, alkene hydrosilylation, and in catalytic reduction of CO2 to methoxyborane, all under ambient temperature and pressure.
- Das, Arpan,Ahmed, Jasimuddin,Rajendran,Adhikari, Debashis,Mandal, Swadhin K.
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p. 1246 - 1252
(2020/12/21)
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- Reduced Phenalenyl in Catalytic Dehalogenative Deuteration and Hydrodehalogenation of Aryl Halides
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Dehalogenative deuteration reactions are generally performed through metal-mediated processes. This report demonstrates a mild protocol for hydrodehalogenation and dehalogenative deuteration of aryl/heteroaryl halides (39 examples) using a reduced odd alternant hydrocarbon phenalenyl under transition metal-free conditions and has been employed successfully for the incorporation of deuterium in various biologically active compounds. The combined approach of experimental and theoretical studies revealed a single electron transfer-based mechanism.
- Singh, Bhagat,Ahmed, Jasimuddin,Biswas, Amit,Paira, Rupankar,Mandal, Swadhin K.
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p. 7242 - 7255
(2021/05/29)
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- Br?nsted Acid-Catalyzed Carbonyl-Olefin Metathesis: Synthesis of Phenanthrenes via Phosphomolybdic Acid as a Catalyst
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Compared with the impressive achievements of catalytic carbonyl-olefin metathesis (CCOM) mediated by Lewis acid catalysts, exploration of the CCOM through Br?nsted acid-catalyzed approaches remains quite challenging. Herein, we disclose a synthetic protocol for the construction of a valuable polycycle scaffold through the CCOM with the inexpensive, nontoxic phosphomolybdic acid as a catalyst. The current annulations could realize carbonyl-olefin, carbonyl-alcohol, and acetal-alcohol in situ CCOM reactions and feature mild reaction conditions, simple manipulation, and scalability, making this strategy a promising alternative to the Lewis acid-catalyzed COM reaction.
- Chen, Yi,Jin, Yuan,Lin, Zhihua,Liu, Di,Shu, Mao,Tan, Jingyao,Tian, Lingfeng,Wang, Rui,Xu, Li,Zhang, Xiaoke
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- Intermolecular C?H Activation at the Allylic/Benzylic and Homoallylic/Homobenzylic Positions of Cyclic Hydrocarbons by a Stable Divalent Silicon Species
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Direct activation of inert C(sp3)?H bonds by main group element species is yet a formidable challenge. Herein, the dehydrogenation of cyclohexene and 1,2,3,4-tetrahydronaphthalene through the allylic/benzylic and homoallylic/homobenzylic C?H bond activation by cyclic (alkyl)(amino)silylene 1 in neat conditions is reported to yield the corresponding aromatic compounds. As for the reaction of cyclohexene, allylsilane 3 and 7-silanorbornene 4 were also observed, which could be interpreted as a direct dehydrogenative silylation reaction of monoalkenes at the allylic positions. Experimental and computational studies suggest that the dehydrogenation of cyclohexene at the homoallylic position was accomplished by a combination of silylene 1 and radical intermediates such as hydrosilyl radical INT1 or cyclohexenyl radical H, which are generated in the initial step of the reaction.
- Koike, Taichi,Kosai, Tomoyuki,Iwamoto, Takeaki
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p. 724 - 734
(2020/12/11)
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- Coumarin (5,6-Benzo-2-pyrone) Trapping of an HDDA-Benzyne
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Although the parent 2-pyrone is known to react with simple o-benzynes to produce naphthalene derivatives, there appear to be no examples of the successful reaction of coumarin, a benzo-annulated 2-pyrone analogue, with an aryne. We report such a process here using benzynes generated by the hexadehydro-Diels-Alder reaction to produce phenanthrene derivatives (i.e., benzo-annulated naphthalenes). Density functional theory computations were used to help understand the difference in reactivity between 2-pyrone and the slower trapping agent, coumarin. Finally, the reaction of o-benzyne itself [from o-(trimethylsilyl)phenyl triflate and CsF] with coumarin was shown to be viable, although slow.
- Chinta, Bhavani Shankar,Lee, Daniel,Hoye, Thomas R.
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supporting information
p. 2189 - 2193
(2021/04/05)
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- Catalytic Reductions Without External Hydrogen Gas: Broad Scope Hydrogenations with Tetrahydroxydiboron and a Tertiary Amine
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Facile reduction of aryl halides with a combination of 5% Pd/C, B2(OH)4, and 4-methylmorpholine is reported. Aryl bromides, iodides, and chlorides were efficiently reduced. Aryl dihalides containing two different halogen atoms underwent selective reduction: I over Br and Cl, and Br over Cl. Beyond these, aryl triflates were efficiently reduced. This combination was broadly general, effectuating reductions of benzylic halides and ethers, alkenes, alkynes, aldehydes, and azides, as well as for N-Cbz deprotection. A cyano group was unaffected, but a nitro group and a ketone underwent reduction to a low extent. When B2(OD)4 was used for aryl halide reduction, a significant amount of deuteriation occurred. However, H atom incorporation competed and increased in slower reactions. 4-Methylmorpholine was identified as a possible source of H atoms in this, but a combination of only 4-methylmorpholine and Pd/C did not result in reduction. Hydrogen gas has been observed to form with this reagent combination. Experiments aimed at understanding the chemistry led to the proposal of a plausible mechanism and to the identification of N,N-bis(methyl-d3)pyridin-4-amine (DMAP-d6) and B2(OD)4 as an effective combination for full aromatic deuteriation. (Figure presented.).
- Korvinson, Kirill A.,Akula, Hari K.,Malinchak, Casina T.,Sebastian, Dellamol,Wei, Wei,Khandaker, Tashrique A.,Andrzejewska, Magdalena R.,Zajc, Barbara,Lakshman, Mahesh K.
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supporting information
p. 166 - 176
(2020/01/02)
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- Exploiting the radical reactivity of diazaphosphinanes in hydrodehalogenations and cascade cyclizations
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The remarkable reducibility of diazaphosphinanes has been extensively applied in various hydrogenations, based on and yet limited by their well-known hydridic reactivity. Here we exploited their unprecedented radical reactivity to implement hydrodehalogenations and cascade cyclizations originally inaccessible by hydride transfer. These reactions feature a broad substrate scope, high efficiency and simplicity of manipulation. Mechanistic studies suggested a radical chain process in which a phosphinyl radical is generated in a catalytic cycle via hydrogen-atom transfer from diazaphosphinanes. The radical reactivity of diazaphosphinanes disclosed here differs from their well-established hydridic reactivity, and hence, opens a new avenue for diazaphosphinane applications in organic syntheses.
- Cheng, Jin-Pei,Yang, Jin-Dong,Zhang, Jingjing
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p. 4786 - 4790
(2020/06/18)
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- Hydrodebromination of Aromatic Bromides Catalyzed by Unsupported Nanoporous Gold: Heterolytic Cleavage of Hydrogen Molecule
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Unsupported nanoporous gold (AuNPore) is a highly efficient, practically applicable, and recyclable catalyst for hydrodebromination of aromatic bromides. The AuNPore-catalyzed hydrodebromination of aromatic bromides proceeded smoothly at relatively low hydrogen pressure and temperature to achieve good to excellent yields of the corresponding non-bromine variants. The selective hydrodebromination reaction occurred exclusively in the coexistence of chlorine atom. For the first time, a mechanistic study revealed that the H?H bond splits in a heterolysis manner on the surface of AuNPore to generate Au?H hydride species.
- Bao, Ming,Feng, Xiujuan,Yamamoto, Yoshinori,Zhang, Sheng,Zhao, Yuhui
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p. 4951 - 4957
(2020/09/09)
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- Visible-Light-Induced, Base-Promoted Transition-Metal-Free Dehalogenation of Aryl Fluorides, Chlorides, Bromides, and Iodides
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We report a simple and efficient visible-light-induced transition-metal-free hydrogenation of aryl halides. The combined visible light and base system is used to initiate the desired radical-mediated hydrogenation. A variety of aryl fluorides, chlorides, bromides, and iodides could be reduced to the corresponding (hetero)arenes with excellent yields under mild conditions. Various functional groups and other heterocyclic compounds are tolerated.
- Ding, Ting-Hui,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 3084 - 3088
(2020/04/10)
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- Transition-Metal-Free and Visible-Light-Mediated Desulfonylation and Dehalogenation Reactions: Hantzsch Ester Anion as Electron and Hydrogen Atom Donor
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Novel approaches for N- and O-desulfonylation under room temperature (rt) and transition-metal-free conditions have been developed. The first methodology involves the transformation of a variety of N-sulfonyl heterocycles and phenyl benzenesulfonates to the corresponding desulfonylated products in good to excellent yields using only KOtBu in dimethyl sulfoxide (DMSO) at rt. Alternately, a visible light method has been used for deprotection of N-methyl-N-arylsulfonamides with Hantzsch ester (HE) anion serving as the visible-light-absorbing reagent and electron and hydrogen atom donor to promote the desulfonylation reaction. The HE anion can be easily prepared in situ by reaction of the corresponding HE with KOtBu in DMSO at rt. Both protocols were further explored in terms of synthetic scope as well as mechanistic aspects to rationalize key features of desulfonylation processes. Furthermore, the HE anion induces reductive dehalogenation reaction of aryl halides under visible light irradiation.
- Heredia, Micaela D.,Guerra, Walter D.,Barolo, Silvia M.,Fornasier, Santiago J.,Rossi, Roberto A.,Budén, Mariá E.
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p. 13481 - 13494
(2020/12/15)
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- Catalytic Dehydrogenative Cyclization of o-Teraryls under pH-Neutral and Oxidant-Free Conditions
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A cobaloxime-catalyzed acceptorless dehydrogenative cyclization of o-teraryls was developed. In stark contrast to the established methods such as the Scholl or Mallory reactions, this method does not require any strong acids or oxidants, and shows high atom economy and a broad substrate scope. It operates at near room temperature with light as the source of energy. Acid- or oxidant-sensitive functional groups, such as 4-methoxyphenyl, unprotected benzyl alcohol, silyl ether, and thiophene groups are tolerated. Remarkably, aryls with electron-withdrawing groups, and electron-poor heteroarenes, such as pyridine and pyrimidine, can also react. Preliminary mechanistic study reveals that hydrogen gas is released during the reaction, and both light and the cobalt catalyst are important for the dehydrogenation step.
- Dong, Guangbin,Tsukamoto, Tatsuhiro
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supporting information
p. 15249 - 15253
(2020/06/30)
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- Palladium-catalyzed denitrative Sonogashira-type cross-coupling of nitrobenzenes with terminal alkynes
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Described herein is a palladium-catalyzed cross-coupling reaction between nitroarenes and terminal alkynes, offering a facile method for C(sp2)-C(sp) bond formation. The utility of this protocol has been proven by the construction of polycyclic aromatic hydrocarbons (PAHs) and orthogonal cross-coupling.
- Feng, Boya,Yang, Yudong,You, Jingsong
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p. 790 - 793
(2020/01/29)
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- Syntheses of diarylethenes by perylene-catalyzed photodesulfonylation from ethenyl sulfones
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Diarylethenes were obtained from the corresponding ethenyl sulfones by photocatalyzed desulfonylation using UV or blue LEDs. When perylene and i-Pr2NEt were used as a photocatalyst and a sacrificing reagent, respectively, this desulfonylation proceeded smoothly to afford the desired ethenes with the functional groups such as chloro, alkoxy and heteroaromatic rings remaining untouched. The use of a flow photoreactor enabled this desulfonylation to proceed more rapidly to finish in an hour of residence time.
- Adachi, Kazumasa,Dakegata, Aki,Fukuyama, Takahide,Okuda, Yasuhiro,Orita, Akihiro,Ryu, Ilhyong,Takemoto, Mai,Wakamatsu, Kan,Watanabe, Hikaru
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supporting information
p. 409 - 412
(2020/04/27)
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- Direct Exploitation of the Ethynyl Moiety in Calcium Carbide Through Sealed Ball Milling
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Ball milling of calcium carbide (CaC2) enables the reaction of its ethynyl moiety with organic electrophiles. This was realized simply by co-milling CaC2 with organic substrates in a sealed jar without the need for an additive or a catalyst. Various ketones including those bearing α-hydrogens were ethynylated in good yields at short reaction times. Aryl halides are also amenable substrates for this protocol as they furnish aryl ethynes through a benzyne intermediate. This method offers a practical and cheap alternative to the established procedures for introducing ethynyl functionalities.
- Hosseini, Abolfazl,Schreiner, Peter R.
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p. 4339 - 4346
(2020/07/04)
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- Photochemical Unmasking of Polyyne Rotaxanes
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Bulky photolabile masked alkyne equivalents (MAEs) are needed for the synthesis of polyyne polyrotaxanes, as insulated molecular wires and as stabilized forms of the linear polymeric allotrope of carbon, carbyne. We have synthesized a novel MAE based on phenanthrene and compared it with an indane-based MAE. Photochemical unmasking of model compounds was studied at different wavelengths (250 and 350 nm), and key products were identified by NMR spectroscopy and X-ray crystallography. UV irradiation at 250 nm leads to unmasking of both MAEs. Irradiation of the phenanthrene system at 350 nm results in quantitative dimerization via [2 + 2] cycloaddition to form a [3]-ladderane; irradiation of this ladderane at 250 nm generates a dihydrotriphenylene, which can be oxidized easily to a triphenylene. Irradiation of the indane-based MAE at 350 nm in the presence of traces of oxygen forms an endoperoxide and a bisepoxide. Both MAEs have been incorporated into rotaxanes via copper-mediated active metal template Glaser or Cadiot-Chodkiewicz coupling. The identity of the rotaxanes was confirmed by NMR spectroscopy and mass spectrometry. The phenanthrene rotaxane decomposes during attempted photochemical unmasking, whereas photolysis of the indane rotaxane results in unmasking of the polyyne thread to form a rotaxane with a chain of 16 sp-hybridized carbon atoms. This approach opens avenues toward the synthesis of encapsulated carbon allotropes.
- Woltering, Steffen L.,Gawel, Przemyslaw,Christensen, Kirsten E.,Thompson, Amber L.,Anderson, Harry L.
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supporting information
p. 13523 - 13532
(2020/09/02)
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- Sequential Cross-Coupling/Annulation of ortho-Vinyl Bromobenzenes with Aromatic Bromides for the Synthesis of Polycyclic Aromatic Compounds
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A sequential cross-coupling/annulation of ortho-vinyl bromobenzenes with aromatic bromides was realized, providing a direct and modular approach to access polycyclic aromatic compounds. A vinyl-coordinated palladacycle was proposed as the key intermediate for this sequential process. Excellent chemoselectivity and regioselectivity were observed in this transformation. The practicability of this method is highlighted by its broad substrate scope, excellent functional group tolerance, and rich transformations associated with the obtained products.
- Wei, Dong,Li, Meng-Yao,Zhu, Bin-Bin,Yang, Xiao-Di,Zhang, Fang,Feng, Chen-Guo,Lin, Guo-Qiang
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supporting information
p. 16543 - 16547
(2019/11/03)
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- Regioselective arene homologation through rhenium-catalyzed deoxygenative aromatization of 7-oxabicyclo[2.2.1]hepta-2,5-dienes
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Combined use of oxorhenium catalysts with triphenyl phosphite as an oxygen acceptor allowed efficient deoxygenative aromatization of oxabicyclic dienes. The reaction proceeded under neutral conditions and was compatible with various functional groups. Combining this deoxygenation with regioselective bromination and trapping of the generated aryne with furan resulted in benzannulative π-extension at the periphery of the PAHs. This enabled direct use of unfunctionalized PAHs for extension of π-conjugation. Iteration of the transformations increased the number of fused-benzene rings one at a time, which has the potential to alter the properties of PAHs by fine-tuning the degree of π-conjugation, shape, and edge topology.
- Murai, Masahito,Ogita, Takuya,Takai, Kazuhiko
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supporting information
p. 2332 - 2335
(2019/02/27)
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- Method for synthesizing phenanthrene compound by using nitroolefin
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The invention provides a method for synthesizing a phenanthrene compound. According to the synthesizing method, a 2-phenyl nitroolefin compound as shown in a formula (I) or a 2-thienyl nitroolefin asshown in the formula (II) is used as an initiator for carrying out a reaction at a temperature of 60-100 DEG C for 4-12 hours under the action of an alkaline substance, a silver catalyst, an oxidizingagent and a solvent, and then the corresponding phenanthrene compound as shown in a formula (III) or a formula (IV) is prepared through separation and purification of a reaction liquid. The synthesizing method disclosed by the invention has the characteristics of small harm to the environment, mild reaction conditions, simple and convenient operation, and the like.
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Paragraph 0034-0037; 0038-0041; 0042-0045; 0093-0095
(2019/03/26)
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- Method for synthesizing phenanthrene and derivatives thereof
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The present invention provides a method for synthesizing phenanthrene and derivatives thereof represented by a formula (III) or (IV). The method is characterized in that a substituted 2-phenylcinnamaldehyde compound represented by a formula (I) or 2-thiophenylcinnamaldehyde represented by a formula (II) is taken as an initial substance, under the effect of a silver catalyst, an oxidant, a basic substance and a solvent, a reaction is carried out at 60 DEG C-100 DEG C for 12-36 hours, the reaction solution is separated and purification is carried out, so that corresponding phenanthrene and derivatives thereof represented by the formula (III) or (IV) are obtained. The synthesis method of the invention has the characteristics of small environmental hazard, mild reaction conditions, simple operation and the like.
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Paragraph 0032-0047
(2019/03/26)
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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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- Mechanisms of Heptane Degradation and Product Formation in Microwave Discharge
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Abstract: A mechanism for the degradation of n-heptane and the formation of the products of its plasma-chemical transformation by microwave discharge treatment has been proposed. Chemical reactions resulting in reactive species, namely free radicals that form lower hydrocarbons and polyaromatic structures are presented. The product composition of the gas, liquid, and solid phases has been studied using gas chromatography–mass spectrometry analysis of the precipitate obtained by evaporation of the liquid phase after the treatment of n-heptane.
- Bobkova,Stokolos,Garifullin
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p. 336 - 340
(2019/08/15)
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- Construction of Phenanthrenes and Chrysenes from β-Bromovinylarenes via Aryne Diels-Alder Reaction/Aromatization
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A highly efficient transition-metal-free general method for the synthesis of polycyclic aromatic hydrocarbons like phenanthrenes and chrysenes (and tetraphene) from β-bromovinylarenes and arynes has been developed. The reactions proceed via an aryne Diels-Alder (ADA) reaction, followed by a facile aromatization. This is the first report on direct construction of chrysenes (and tetraphene) using the ADA approach. Unlike the literature method which is limited to only 9/10-substituted derivatives, this method gives access to a wide variety of functionalized phenanthrenes.
- Singh, Vikram,Verma, Ram Subhawan,Khatana, Anil K.,Tiwari, Bhoopendra
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p. 14161 - 14167
(2019/10/28)
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- Generation and Rearrangement of (1-Hydroxycyclopropyl)- A nd (1-Hydroxycyclobutyl)carbene
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Photolysis of exo-1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and exo-1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclobutan-1-ol in benzene-d6 produces (1-hydroxycyclopropyl)- A nd (1-hydroxycyclobutyl)carbene respectively. It was observed that (1-hydroxycyclopropyl)carbene rearranges to cyclobutanone whereas (1-hydroxycyclobutyl)carbene forms cyclopentanone. Formation of both ketones is attributed to tautomerization of the corresponding enols that arise from ring expansion of the carbenes. Products assignable to intramolecular C-H insertions were not detected in the photolysates.
- Deangelo, Joseph D.,Hatano, Sayaka,Thamattoor, Dasan M.
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p. 890 - 893
(2019/10/22)
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- Vicinal Dichlorination of o -Vinylbiphenyls and the Synthesis of 9-(Arylmethyl)fluorenes via Tandem Friedel-Crafts Alkylations
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Reacting ortho -vinylbiphenyls with (dichloroiodo)benzene (PhICl 2) gives vicinal dichlorides, rapidly, and in excellent yield at room temperature. Treating the vic -dichlorides with 50 molpercent AlCl 3 in the presence of arene nucleophiles results in sequential intramolecular and intermolecular Friedel-Crafts alkylations to generate 9-(arylmethyl)fluorene derivatives. The dichlorination and alkylation reactions are operationally simple and tolerant of a variety of functional groups and substitution patterns, and give the products in moderate to excellent yield.
- Jameel, Islam,Murphy, Graham K.,Zhao, Zhensheng
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p. 2648 - 2659
(2019/06/20)
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- Earth-Abundant Mixed-Metal Catalysts for Hydrocarbon Oxygenation
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The oxygenation of aliphatic and aromatic hydrocarbons using earth-abundant Fe and Cu catalysts and "green" oxidants such as hydrogen peroxide is becoming increasingly important to atom-economical chemical processing. In light of this, we describe that dinuclear CuII complexes of pyrrolic Schiff-base macrocycles, in combination with ferric chloride (FeCl3), catalyze the oxygenation of π-activated benzylic substrates with hydroperoxide oxidants at room temperature and low loadings, representing a novel design in oxidation catalysis. Mass spectrometry and extended X-ray absorption fine structure analysis indicate that a cooperative action between CuII and FeIII occurs, most likely because of the interaction of FeCl3 or FeCl4- with the dinuclear CuII macrocycle. Voltammetric measurements highlight a modulation of both CuII and FeIII redox potentials in this adduct, but electron paramagnetic resonance spectroscopy indicates that any Cu-Fe intermetallic interaction is weak. High ketone/alcohol product ratios, a small reaction constant (Hammett analysis), and small kinetic isotope effect for H-atom abstraction point toward a free-radical reaction. However, the lack of reactivity with cyclohexane, oxidation of 9,10-dihydroanthracene, oxygenation by the hydroperoxide MPPH (radical mechanistic probe), and oxygenation in dinitrogen-purge experiments indicate a metal-based reaction. Through detailed reaction monitoring and associated kinetic modeling, a network of oxidation pathways is proposed that includes "well-disguised" radical chemistry via the formation of metal-associated radical intermediates.
- Pankhurst, James R.,Curcio, Massimiliano,Sproules, Stephen,Lloyd-Jones, Guy C.,Love, Jason B.
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supporting information
p. 5915 - 5928
(2018/05/28)
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- Oxidative, Iodoarene-Catalyzed Intramolecular Alkene Arylation for the Synthesis of Polycyclic Aromatic Hydrocarbons
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A catalytic, metal-free and chemoselective oxidative intramolecular coupling of arene and alkene C?H bonds is reported. The active hypervalent iodine (HVI) reagent, generated catalytically in situ from iodotoluene and meta-chloroperoxybenzoic acid (m-CPBA), reacts with o-vinylbiphenyls to generate polyaromatic hydrocarbons in up to 95 % yield. Experimental evidence suggests the reactions proceed though vinyliodonium and, possibly, vinylenephenonium intermediates.
- Zhao, Zhensheng,Britt, Liam H.,Murphy, Graham K.
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p. 17002 - 17005
(2018/11/01)
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- Efficient and selective hydrogenation of C-O bonds with a simple sodium formate catalyzed by nickel
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A Ni-catalyzed hydrogenation of C-O compounds with sodium formate is developed. Various esters, i.e. aryl, alkenyl, benzyl pivalates, and even the aryl ethers, were efficiently reduced with a loading of nickel catalysts down to 0.5 mol%. Reactive functional groups such as C-C double bonds, carbonyl, CN, MeS and halogen groups are tolerable. This reaction can be used for the modification of complex molecules and carried out at a large scale.
- Xi, Xiaoxiang,Chen, Tieqiao,Zhang, Ji-Shu,Han, Li-Biao
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p. 1521 - 1524
(2018/02/19)
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- Br?nsted Acid-Catalyzed Carbonyl-Olefin Metathesis inside a Self-Assembled Supramolecular Host
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Carbonyl–olefin metathesis represents a powerful yet underdeveloped method for the formation of carbon–carbon bonds. So far, no Br?nsted acid based method for the catalytic carbonyl–olefin metathesis has been described. Herein, a cocatalytic system based on a simple Br?nsted acid (HCl) and a self-assembled supramolecular host is presented. The developed system compares well with the current benchmark catalyst for carbonyl–olefin metathesis in terms of substrate scope and yield of isolated product. Control experiments provide strong evidence that the reaction proceeds inside the cavity of the supramolecular host. A mechanistic probe indicates that a stepwise reaction mechanism is likely.
- Catti, Lorenzo,Tiefenbacher, Konrad
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p. 14589 - 14592
(2018/01/27)
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- Carbonyl–Olefin Cross-Metathesis Through a Visible-Light-Induced 1,3-Diol Formation and Fragmentation Sequence
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A visible-light-mediated approach to carbonyl–olefin cross-metathesis is described. Photoinduced hole catalysis was used to promote the formation of 1,3-diols from aldehydes and styrenes, which were then readily fragmented under acidic conditions to form the cross-metathesis products. The use of 1,3-diols as intermediates, rather than the energetically more demanding oxetanes, provides a new, orthogonal mechanistic strategy for carbonyl–olefin cross-metathesis. Furthermore, this approach does not require any metals, ligands, or additives, and provides the products with high levels of E selectivity. A mechanistic rationale is provided and supported by both theoretical calculations and experiments. Additionally, a practical synthesis of a new acridinium-based photocatalyst, including full characterization, is presented.
- Pitzer, Lena,Sandfort, Frederik,Strieth-Kalthoff, Felix,Glorius, Frank
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p. 16219 - 16223
(2018/11/23)
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- Base-Free Generation of Organic Electron Donors from Air-Stable Precursors
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Organic electron donors (OEDs) are powerful reducing agents recognized for their potential in the reduction of challenging substrates and in original applications. Nonetheless, their low stability in atmospheric oxygen or over time complicates their manipulation and storage. To overcome these constraints and enhance OED practicality, new air- and moisture-stable aminopyridinium carboxylate and carbonate precursors were synthesized and thermally activated to generate the potent electron donor in situ. Carboxylate adducts proved to be excellent latent OED systems, enabling the facile and efficient reduction of challenging substrates. Their reduction properties were correlated to their structural characteristics by thermogravimetric and spectroscopic analysis.
- Tintori, Guillaume,Nabokoff, Pierre,Buhaibeh, Ruqaya,Bergé-Lefranc, David,Redon, Sébastien,Broggi, Julie,Vanelle, Patrice
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supporting information
p. 3148 - 3153
(2018/03/13)
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- Catalysis of Radical Cyclizations from Alkyl Iodides under H2: Evidence for Electron Transfer from [CpV(CO)3H]-
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Radical cyclizations are most often achieved with Bu3SnH in the presence of a radical initiator, but environmental considerations demand that alternative reagents be developed - ones that can serve as a synthetic equivalent to the hydrogen atom. We have revisited [CpV(CO)3H]-, a known replacement for Bu3SnH, and found that it can be used catalytically under H2 in the presence of a base. We have carried out tin-free catalytic radical cyclizations of alkyl iodide substrates. The reactions are atom-efficient, and the conditions are mild, with broad tolerance for functional groups. We have, for example, achieved the first 5-exo radical cyclization involving attack onto a vinyl chloride. We suggest that the radicals are generated by an initial electron transfer.
- Kuo, Jonathan L.,Lorenc, Chris,Abuyuan, Janine M.,Norton, Jack R.
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supporting information
p. 4512 - 4516
(2018/04/10)
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- Radical Alkyne peri-Annulation Reactions for the Synthesis of Functionalized Phenalenes, Benzanthrenes, and Olympicene
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Radical cyclization reactions at a peri position were used for the synthesis of polyaromatic compounds. Depending on the choice of reaction conditions and substrate, this flexible approach led to Bu3Sn-substituted phenalene, benzanthrene, and olympicene derivatives. Subsequent reactions with electrophiles provided synthetic access to previously inaccessible functionalized polyaromatic compounds.
- Tsvetkov, Nikolay P.,Gonzalez-Rodriguez, Edgar,Hughes, Audrey,dos Passos Gomes, Gabriel,White, Frankie D.,Kuriakose, Febin,Alabugin, Igor V.
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supporting information
p. 3651 - 3655
(2018/03/06)
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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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- Ni-Catalyzed Cross-Coupling of Dimethyl Aryl Amines with Arylboronic Esters under Reductive Conditions
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Herein, we reported a successful Suzuki-Miyaura coupling of dimethyl aryl amines to forge biaryl skeleton via Ni catalysis in the absence of directing groups and preactivation. This transformation proceeded with high efficiency in the presence of magnesium. Preliminary mechanism studies demonstrated dual roles of magnesium: (i) a reductant that reduced Ni(II) species to active Ni(I) catalyst; (ii) a unique promoter that facilitated the Ni(I)/Ni(III) catalytic cycle.
- Cao, Zhi-Chao,Xie, Si-Jun,Fang, Huayi,Shi, Zhang-Jie
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supporting information
p. 13575 - 13579
(2018/10/24)
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- Stannylated Vinylic addition polynorbornene: Probing a reagent for friendly tin-mediated radical processes
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Vinylic addition polynorbornenes (VA-PNB) with stannyl functional groups have been prepared and used in tinmediated radical dehalogenation reactions. The aliphatic and robust scaffold of VA-PNB is well suited for a support in radical processes. VA-PNB-(CH2)nSnHBu2 can be used as a stoichiometric reagent and VA-PNB-(CH2)nSnBu2Cl as a catalyst in the presence of a hydride donor for the reduction of RBr. The mixture KF (aq.)/polymethylhydrosiloxane (PMHS) is the most convenient hydride source to generate VA-PNB-(CH2)nSnHBu2 in situ. Al-though quite popular in this context, boron hydrides, being a source of radicals themselves, are not adequate to correctly evaluate the performance of the anchored organotin group. VAPNB-(CH2)4SnBu2Cl can be recycled and, even if it loses activity upon reuse, it is still useful after ten cycles. The stannylated VAPNB can be separated from the products by simple filtration, and it leads to very low tin contamination (at least 250 times lower than that with use of conventional separation methods).
- García-Loma, Rodrigo,Alb é Niz, Ana C.
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supporting information
p. 4247 - 4254
(2018/08/24)
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- Radical Hydrodehalogenation of Aryl Bromides and Chlorides with Sodium Hydride and 1,4-Dioxane
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A practical method for radical chain reduction of various aryl bromides and chlorides is introduced. The thermal process uses NaH and 1,4-dioxane as reagents and 1,10-phenanthroline as an initiator. Hydrodehalogenation can be combined with typical cyclization reactions, proving the nature of the radical mechanism. These chain reactions proceed by electron catalysis. DFT calculations and mechanistic studies support the suggested mechanism.
- Hokamp, Tobias,Dewanji, Abhishek,Lübbesmeyer, Maximilian,Mück-Lichtenfeld, Christian,Würthwein, Ernst-Ulrich,Studer, Armido
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supporting information
p. 13275 - 13278
(2017/10/09)
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- Transition-metal-free hydrogenation of aryl halides: From alcohol to aldehyde
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A transition-metal-and catalyst-free hydrogenation of aryl halides, promoted by bases with either aldehydes or alcohols, is described. One equivalent of benzaldehyde affords an equal yield as that of 0.5 equiv of benzyl alcohol. The kinetic study reveals that the initial rate of PhCHO is much faster than that of BnOH, in the ratio of nearly 4:1. The radical trapping experiments indicate the radical nature of this reaction. Based on the kinetic study, trapping and KIE experiments, and control experiments, a tentative mechanism is proposed. As a consequence, a wide range of (hetero)aryl iodides and bromides were efficiently reduced to their corresponding (hetero)arenes. Thus, for the first time, aldehydes are directly used as hydrogen source instead of other well-established alcohol-hydrogen sources.
- Zheng, Hong-Xing,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 5114 - 5117
(2017/11/07)
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- Base-Selective Five- versus Six-Membered Ring Annulation in Palladium-Catalyzed C–C Coupling Cascade Reactions: New Access to Electron-Poor Polycyclic Aromatic Dicarboximides
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Palladium-catalyzed base-selective annulation of dibromonaphthalimide to different aryl boronate esters by combined Suzuki–Miyaura cross-coupling and direct C?H arylation afforded a series of new five- and six-membered ring annulated electron-poor polycyclic aromatic hydrocarbons. Cesium carbonate (Cs2CO3) as auxiliary base in these C?C coupling cascade reactions led exclusively to six-membered ring annulation, while the use of organic base diazabicycloundecene (DBU) afforded the corresponding five-membered ring annulated products. This base-dependent selective mode of annulation is attributed to different mechanistic pathways directed by the applied base. The selective annulation was revealed by single crystal X-ray analysis of the respective five- and six-membered ring annulated products. The optical and redox properties of the new polycyclic aromatic dicarboximides were characterized by UV/Vis absorption and fluorescence spectroscopy and cyclic voltammetry.
- Seifert, Sabine,Schmidt, David,Shoyama, Kazutaka,Würthner, Frank
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p. 7595 - 7600
(2017/06/13)
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- Initiation in Photoredox C-H Functionalization Reactions. Is Dimsyl Anion a Key Ingredient?
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Previous studies have reported the arylation of unactivated arenes with ArX, base (KOtBu or NaOtBu), and an organic additive at high temperatures. Recently, we showed that this reaction proceeds in the absence of additives at rt but employs UV-vis light. However, details of mechanisms that can use a photoinduced base-promoted homolytic aromatic substitution reaction (photo-BHAS) have remained elusive until now. This work examines different mechanistic routes of the essential electron-transfer step (ET) of this reaction in order to identify a possible path for the formation of 1-adamantyl radicals from 1-haloadamantanes (initiation step). On the basis of photochemical and photophysical experiments and computational studies, we propose an unprecedented initiation step that could also be applied to other ET reactions performed in DMSO. For the first time, it is reported that dimsyl anion, formed from a strong base and DMSO (solvent), is responsible for inducing the initiation by a photo-BHAS process on alkyl halides.
- Budén, María E.,Bardagí, Javier I.,Puiatti, Marcelo,Rossi, Roberto A.
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supporting information
p. 8325 - 8333
(2017/08/23)
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- Facile Synthesis of Polycyclic Aromatic Hydrocarbons: Br?nsted Acid Catalyzed Dehydrative Cycloaromatization of Carbonyl Compounds in 1,1,1,3,3,3-Hexafluoropropan-2-ol
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The cycloaromatization of aromatic aldehydes and ketones was readily achieved by using a Br?nsted acid catalyst in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP). In the presence of a catalytic amount of trifluoromethanesulfonic acid, biaryl-2-ylacetaldehydes and 2-benzylbenzaldehydes underwent sequential intramolecular cationic cyclization and dehydration to afford phenacenes and acenes, respectively. Furthermore, biaryl-2-ylacetaldehydes bearing a cyclopentene moiety at the α-position underwent unprecedented cycloaromatization including ring expansion to afford triphenylenes. HFIP effectively promoted the cyclizations by suppressing side reactions presumably as a result of stabilization of the cationic intermediates.
- Fujita, Takeshi,Takahashi, Ikko,Hayashi, Masaki,Wang, Jingchen,Fuchibe, Kohei,Ichikawa, Junji
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supporting information
p. 262 - 265
(2017/01/24)
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- Synthesis and characterization of phenanthrene derivatives with anticancer property against human colon and epithelial cancer cell lines
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A variety of polycyclic aromatic hydrocarbons have been synthesized and structurally characterized in our laboratory. Phenanthrene derivatives were efficiently prepared in excellent yields and high purity via a two-step sequence. Heck coupling yielded the corresponding diarylethenes, followed by classical oxidative photocyclization to achieve the expected phenanthrenes. First, we envisioned to synthesize a variety of substituted phenanthrenequinones. Second, we investigated the possibility of a dibenz[a,c]phenazine formation by addition of o-phenylenediamine after completion of the oxidation process. Moreover, because phenanthrenequinones are available so simply, it is likely that other uses will be found for these compounds. For example, 9,10-phenanthrenequinone can be sequentially reduced, alkylated, acetylated, and sulfonated. All the synthesized derivatives were evaluated for cytotoxic activity in vitro against the human epidermoid carcinoma epithelial cells Hep-2 and human colon carcinoma cells Caco-2 using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. From the structure–activity point of view, position and nature of the electron donating and electron withdrawing functional groups attached to the phenanthrene skeleton may contribute to the anticancer action. Interestingly, the analysis of the IC50 values suggests that most compounds exerted cytotoxic effects with selectivity against both cancer cells. Among them, methyl 8-methyl-9,10-phenanthrenequinone-3-carboxylate 11d showed the highest potency with IC50 values of 2.81 and 0.97 μg/mL.
- Guédouar, Habiba,Aloui, Faouzi,Beltifa, Asma,Ben Mansour, Hedi,Ben Hassine, Béchir
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p. 841 - 849
(2017/06/20)
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- Acid-Catalyzed Skeletal Rearrangements in Arenes: Aryl versus Alkyl Ring Pirouettes in Anthracene and Phenanthrene
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In 1 M triflic acid/dichloroethane, anthracene is protonated at C9, and the resulting 9-anthracenium ion is easily observed by NMR at ambient temperature. When heated as a dilute solution in triflic acid/dichloroethane, anthracene undergoes conversion to phenanthrene as the major volatile product. Minor dihydro and tetrahydro products are also observed. MALDI analysis supports the simultaneous formation of oligomers, which represent 10-60% of the product. Phenanthrene is nearly inert to the same superacid conditions. DFT and CCSD(T)//DFT computational models were constructed for isomerization and automerization mechanisms. These reactions are believed to occur by cationic ring pirouettes which pass through spirocyclic intermediates. The direct aryl pirouette mechanism for anthracene has a predicted DFT barrier of 33.6 kcal/mol; this is too high to be consistent with experiment. The ensemble of experimental and computational models supports a multistep isomerization process, which proceeds by reduction to 1,2,3,4-tetrahydroanthracene, acid-catalyzed isomerization to 1,2,3,4-tetrahydrophenanthrene with a predicted DFT barrier of 19.7 kcal/mol, and then reoxidation to phenanthrene. By contrast, DFT computations support a direct pirouette mechanism for automerization of outer ring carbons in phenanthrene, a reaction demonstrated previously by Balaban through isotopic labeling.
- Skraba-Joiner, Sarah L.,Brulet, Jeffrey W.,Song, Min K.,Johnson, Richard P.
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p. 13076 - 13083
(2017/12/26)
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- Polycyclic Aromatic Hydrocarbons via Iron(III)-Catalyzed Carbonyl-Olefin Metathesis
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Polycyclic aromatic hydrocarbons are important structural motifs in organic chemistry, pharmaceutical chemistry, and materials science. The development of a new synthetic strategy toward these compounds is described based on the design principle of iron(III)-catalyzed carbonyl-olefin metathesis reactions. This approach is characterized by its operational simplicity, high functional group compatibility, and regioselectivity while relying on FeCl3 as an environmentally benign, earth-abundant metal catalyst. Experimental evidence for oxetanes as reactive intermediates in the catalytic carbonyl-olefin ring-closing metathesis has been obtained.
- McAtee, Christopher C.,Riehl, Paul S.,Schindler, Corinna S.
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p. 2960 - 2963
(2017/03/11)
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- LOW TEMPERATURE RADICAL INITIATOR SYSTEM AND PROCESSES MAKING USE THEREOF
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The present invention refers to a process making use of a radical initiator system comprising peroxy compounds, in particular peroxyketals, in the presence of an acid catalyst to initiate radical processes at low temperature, such as room temperature and below.
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