- Palladium Catalyzed Regioselective Cyclization of Arylcarboxylic Acids via Radical Intermediates with Diaryliodonium Salts
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Palladium-catalyzed C2-arylation/intramolecular acylation with arylcarboxylic acids was developed by using diaryliodonium salts. The protocol has the advantage of good step-economy by two chemical bonds formation in one pot.
- An, Guoqiang,Wang, Limin,Han, Jianwei
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supporting information
p. 8688 - 8693
(2021/11/24)
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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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- 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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- 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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supporting information
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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supporting information
p. 245 - 254
(2021/09/04)
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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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- Rhodium- and iridium-catalyzed dehydrogenative cyclization through double C-H bond cleavages to produce fluorene derivatives
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The rhodium-catalyzed cyclization of a series of 2,2-diarylalkanoic acids in the presence of copper acetate as an oxidant smoothly proceeded through double C-H bond cleavages and subsequent decarboxylation to produce the corresponding fluorene derivatives. The direct cyclization of triarylmethanols also took place efficiently by using an iridium catalyst in place of the rhodium, while the hydroxy function was still intact.
- Itoh, Masaki,Hirano, Koji,Satoh, Tetsuya,Shibata, Yu,Tanaka, Ken,Miura, Masahiro
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p. 1365 - 1370
(2013/03/28)
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- Aromatic hydrocarbon growth from indene
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Aromatic hydrocarbon growth from indene (C9H8), which contains the five-membered ring cyclopentadienyl moiety, was investigated experimentally in a 4 s flow reactor over a temperature range 650-850°C. Major products observed were three C18H12 isomers (chrysene, benz[a]anthracene and benzo[c]phenanthrene), two C17H12 isomers (benzo[a]fluorene and benzo[b]fluorene), and two C10H8 isomers (naphthalene and benzofulvene). Reaction pathways to these products are proposed. Indenyl radical addition to indene produces a resonance-stabilized radical intermediate which further reacts by one of two routes. Rearrangement by intramolecular addition produces a bridged structure that leads to the formation of C17H12 and C10H8 products. Alternatively, β scission produces biindenyl, which leads to the formation of C18H12 products by a ring condensation mechanism analogous to that proposed for cyclopentadiene-to-naphthalene conversion. Temperature dependencies of both the partitioning between these two routes and the product isomer distributions are consistent with thermochemical modeling using semi-empirical molecular orbital methods. The results further illustrate the role of resonance-stabilized radical rearrangement in aromatic growth and condensation of systems with cyclopentadienyl moieties.
- Lu, Mingming,Mulholland, James A.
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p. 625 - 633
(2007/10/03)
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- Characterization of the combustion products of polyethylene
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Polyethylene (PE) was burned in a tube-type furnace with an air flow at a temperature of 600~900°C. Combustion products were collected with glass wool, glass fiber filter, and XAD-2 adsorbent. The analysis of the products was performed with GC-FID and GC-MSD. At low temperature, hydrocarbons were the major components, while at higher temperature the products were composed of polycyclic aromatic hydrocarbons. With the high performance of the Hewlett-Packard 6890GC-5973MSD, more compounds were identified in comparison with previous studies.
- Piao, Mingjun,Chu, Shaogang,Zheng, Minghui,Xu, Xiaobai
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p. 1497 - 1512
(2007/10/03)
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- Characterization of polycyclic aromatic hydrocarbon particulate and gaseous emissions from polystyrene combustion
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The partitioning of polycyclic aromatic hydrocarbons (PAHs) between the particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres (100-300 μm) at different combustion temperatures (800- 1200 °C) to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments (differential mobility particle sizer and/or optical particle counter) to determine the particle size distribution. For chemical composition analyses, the particles were either collected on Teflon filters or split into eight size fractions using a cascade impactor with filter media substrates, while the gaseous products were collected on XAD-2 adsorbent. Gas chromatography/mass spectroscopy (GC/MS) was used to identify and quantify the specific PAH species, their partitioning between the gas and particulate phases, and their distribution as a function of emission particle size. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes. The experimental results have been analyzed to elucidate the formation mechanisms of PAHs and particles during polystyrene combustion. The implications of these results are also discussed with respect to the control of PAH emissions from municipal waste-to-energy incineration systems. The partitioning of polycyclic aromatic hydrocarbons (PAHs) between particulate and gaseous phases resulting from the combustion of polystyrene was studied. A vertical tubular flow furnace was used to incinerate polystyrene spheres to determine the effect of temperature and polystyrene feed size on the particulate and gaseous emissions and their chemical composition. The furnace reactor exhaust was sampled using real-time instruments to determine the particle size distribution. The total mass and number of PAH species in both the particulate and gas phases were found to decrease with increasing incineration temperature and decreasing polystyrene feed size, while the mean diameter of the particles increases with increasing incineration temperature and decreasing feed size. In addition, the PAH species in the particulate phase were found to be concentrated in the smaller aerosol sizes.
- Durlak, Susan K.,Biswas, Pratim,Shi, Jichun,Bernhard, Mary Jo
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p. 2301 - 2307
(2007/10/03)
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- Flash-vacuum pyrolysis (FVP) on zeolites. II: Pyrolysis of 5β-(acetoxyethyl)-5H-dibenzo[a,d]cycloheptene; 11-acetoxy-9,10-dihydro-9,10-propanoanthracene and 11-hydroxy-9,10-dihydro-9,10-propanoanthracene
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Flash-vacuum pyrolyses (FVP) of the title compounds 8, 7 and 6, performed at 0.65 mbar in argon atmosphere at 350°C in the presence of different acidic zeolites, afforded product distributions similar to FVP of 5β-(hydroxyethyl)-5H-dibenzo[a,d]cycloheptene (1) indicating 7H-benzo[c]fluorene (2); 6,11b-dihydro-7H-benzo[c]fluorene (3) and benzo[a]fluorene (13) as main reaction products. The reaction seems to involve only the outer surface of catalysts. The cationic reaction mechanism is supported by identification of two hydrocarbon intermediates which afford the same FVP products as 6-8 as well as by comparison with the results of the FVP of 6-8 over acidic alumina at different temperatures.
- Banciu, Mircea D.,Cira, Ovidiu,Petride, Aurica,Banciu, Anca
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p. 1093 - 1098
(2007/10/03)
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- Equilibrium acidities of some sulfones and sulfoxides in tetrahydrofuran
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Ion pair acidities are reported in tetrahydrofuran (THF) solution for the lithium and cesium salts of several sulfones and one sulfoxide. These salts are shown to be monomeric in the THF solutions studied. Thermodynamic constants are reported for several salts. The results and some conductivity studies show that both the lithium and cesium salts are contact ion pairs in THF. Because of ion association the relative pKs are slightly lower for cesium salts and much lower for lithium salts than for the free ions in DMSO solution.
- Streitwieser, Andrew,Wang, George Peng,Bors, Daniel A.
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p. 10103 - 10112
(2007/10/03)
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- Flow-vacuum pyrolysis of polycyclic compounds. 101: Pyrolysis of cyclopropa[r]-9,10-ethano-9,10-dihydroanthracene
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The title hydrocarbon (11) reacts thermally by two competitive routes: (a) a retrodiene reaction affording anthracene and (b) a sequence of isomerizations generating 9,10-dihydro-9,10-propenoanthracene (1), 1,1a,6,10b-tetrahydro-1,6-methanodibenzo[a,e] cyclopropa[c]cycloheptene (2), 11,11a-dihydro-6aH-benzo[a]fluorene (4), 6,11-dihydro-5H-benzo[a]fluorene (5) and finally through dehydrogenation 11H-benzo[a]fluorene (6).
- Banciu, Mircea D.,Hada, Catalina,Parvulescu, Luminitza,Petride, Aurica,Chanon, Michel
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p. 661 - 666
(2007/10/03)
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- Equilibrium acidities of some α,ω-diphenylpolyenes
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Cesium ion pair acidities were measured in THF for a series of diphenylmethane vinylogues that form α,ω-diphenylpolyenyl anions with linearly conjugated chains of 3-9 carbon atoms. The dissociation constants of the diphenylpolyenyls in THF were determined by UV-vis spectroscopy and are rationalized with an electrostatic model. Acidity and dissociation data were combined with measurements of stereoisomer equilibria to estimate the differences in delocalization energy among the diphenylpolyenyl ions. The experimental differences in acidity correlate well with AMI and molecular mechanics (MMPI) calculations.
- Thiele, Georg,Streitwieser, Andrew
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p. 446 - 454
(2007/10/02)
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- BENZOANNELATED VALENCE ISOMERS OF HOMOANNULENES. 2. THERMAL BEHAVIOUR OF DIBENZOBICYCLONONA-2,4,6-TRIENE
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The flow-vacuum pyrolysis of the title dibenzo(C9H10) hydrocarbon 3 was investigated between 400-650 deg C and 1 Torr.The main reaction product, 11,11a-dihydro-6aH-benzofluorene (5) was isolated and characterized.At elevated temperatures 5 is converted into a mixture of 6,11-dihydro-5H-benzofluorene (6) and 11H-benzofluorene (7).A reaction mechanism for pyrolysis is suggested and a comparison between the thermal behaviour of 3 and of some related hydrocarbons is made.
- Banciu, Anca,Petride, Aurica,Draghici, Constantin,Banciu, Mircea D.
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p. 1205 - 1213
(2007/10/02)
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- Benzoannelated valence isomers of homoannulenes. I. Thermal behaviour of some dibenzo(C9H10)hydrocarbons
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The flow-vacuum pyrolyses of 9,10-dihydro-9,10-propenoanthracene 1 and 1,1a,6,10b-tetrahydro-1,6-methanodibenzocyclopropacycloheptene 2 (two isomeric dibenzo(C9H10)hydrocarbons occuring in the acetolysis of 5-(β-tosyloxyethyl)-5H-dibenzocycloheptene 4a) were examined at 1.33 mbar and various temperatures between 300 deg C and 700 deg C.The thermal interconversion of 1 and 2 was proved as well as the formation of a new unstable dibenzo(C9H10) valence isomer, 3, which is converted further at higher temperatures into stable benzofluorene derivatives 6 and 7.Radical mechanisms are proposed and the possibility of formation of another transient dibenzo(C9H10)hydrocarbon 30 is supposed.The essential role of the CH2 moiety in pyrolyses of the investigated hydrocarbons is underlined and a comparsion of pyrolysis mechanisms in C9H10-, benzo(C9H10)- and dibenzo(C9H10)-series is made. Key words: valence isomers of homoannulenes / dibenzo(C9H10)hydrocarbons / flow-vacuum pyrolysis
- Banciu, M. D.,Stanescu, M. D.,Florea, C.,Petride, A.,Draghici, C.,Cioranescu, E.
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p. 919 - 925
(2007/10/02)
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- A New General Synthesis of Polycyclic Aromatic Compounds Based on Enamine Chemistry
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Alkylation of enamines and enamine salts by benzylic and (β-haloethyl)aryl halides, respectively, followed by acidic cyclodehydration and dehydrogenation provides an efficient synthetic approach to a wide range of polycyclic aromatic compounds of diverse structural types.Specific polycyclic hydrocarbons synthesized by this route include benzo- and benzofluorene, 7H-dibenzo-, 13H-dibenzo-, and 13H-dibenzofluorene, 15H-tribenzofluorene, dibenzochrysene, benzopentaphene, indenofluorene, fluorenofluorene, octahydrodibenzanthracene, dibenzanthracene, octahydrodibenzanthracene, dibenzanthracene, picene, benzopicene, 1H-benzaceanthrylene, and 4H-cyclopentachrysene.This method with appropriate modifications appears to be potentially broader in scope than established traditional methods of polycyclic hydrocarbon synthesis.
- Harvey, Ronald G.,Pataki, John,Cortez, Cecilia,Raddo, Pasquale Di,Yang, ChengXi
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p. 1210 - 1217
(2007/10/02)
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- Scope of Tandem Cycloaddition/Radical Cyclization Methodology
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Tandem cycloaddition/radical cyclization is an effective strategy for the rapid assembly of a wide variety of ring systems.To set up the reagents for this sequence, it is necessary to include a potential radical site in one of the two cycloaddition partners, located at an appropriate distance from a new double bond that will be formed in the cycloaddition step.Examples in which the cycloaddition step is or and in which the radical cyclization creates 5-, 6-, or 7-membered rings are described.Examples of the tandem methodology carried out in a completely intramolecular mode are also described.
- Ghosh, Tirthankar,Hart, Harold
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p. 5073 - 5085
(2007/10/02)
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- Tandem Cycloaddition/Radical Cyclization, a Widely Applicable Strategy for the Rapid Assembly of Polycyclic Systems
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By treating a diene (or 1,3-dipole) that contains an appropriately located potential radical site successively with a dienophile (or dipolarophile) and a radical source one can construct a variety of polycyclic systems in two steps.
- Ghosh, Tirthankar,Hart, Harold
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p. 2396 - 2398
(2007/10/02)
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- Synthesis of the Major Metabolic Dihydrodiols of Benzofluoranthene
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Syntheses are described for the major dihydrodiol metabolites of benzofluoranthene. trans-4,5-Dihydro-4,5-dihydroxybenzofluoranthene was prepared via 9-methoxy-11H-benzofluorene.Two of the intermediates in this synthetic sequence, 4-hydroxybenzofluoranthene and benzofluoranthene-4,5-dione, are also suspect metabolites of the parent hydrocarbon.An improved synthesis for trans-9,10-dihydro-9,10-dihydroxybenzo-fluoranthene is described.The key steps in this preparation are the Wittig reaction of acenaphthenequinone with (3-methoxyphenethyl)triphenylphosphonium bromide and the cyclization-dehydration of the intermediate, forming 10-methoxybenzofluoranthene exclusively.The synthesis of trans-2,3-dihydro-2,3-dihydroxybenzo-fluoranthene was accomplished through the intermediacy of 1,12c-dihydrobenzofluoranthen-3(2H)-one.This ketone was converted to its α-phenylseleno derivative which underwent selenoxide elimination in basic hydrogen peroxide, forming benzofluoranthene-2,3-dione directly.In each synthesis reduction of the appropriate quinone with potassium borohydride afforded the desired dihydrodiol.
- Rice, Joseph E.,Shih, Hsien-Cheng,Hussain, Nalband,LaVoie, Edmond J.
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p. 849 - 855
(2007/10/02)
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- An Efficient Synthesis of Benzofluorenes Via α-Alkoxycarbonyldiarylmethyl Cations
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Rearrangement of α-alkoxycarbonyldiarylmethyl cations lead to 9-fluorenecarboxylic esters.Decarboxylation of these esters generates the fluorene derivatives 9a-f.The precursors to the cations are the α-hydroxyesters 6a-g.This conversion constitutes a facile synthesis of benzofluorenes.
- Hopkinson, A. C.,Lee-Ruff, E.,Maleki, M.
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p. 366 - 371
(2007/10/02)
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- Condensed Cyclic and Bridged-ring systems. Part 13. Synthesis of the Insect Attractant Hydrocarbon, 9a-Carbamorphinan, and X-Ray Structural Analyses of 9a-Carbamorphinan-10-one and 9a-Carba-14α-morphinan-10-one
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The insect attractant bridged hydrocarbon, (+/-)-9a-carbamorphinan (1) and its inactive epimer, (+/-)-9a-carba-14α-morphinan (2), have been synthesized through (+/-)-9a-carbamorphinan-10-one (3), and (+/-)-9a-carba-14α-morphinan-10-one (4), prepared by polyphosphoric acid-catalysed cyclization of the double-bond isomeric benzyloctalins (7), derived from Huang-Minlon reduction of 1-benzyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one (6), followed by the benzylic oxidation with chromic acid.The reduction of the easily accessible (+/-)-9a-carbamorphinan-16-one (10), the orthophosphoric acid-induced cyclization product of (6), provides an efficient alternative route to (1).The structures of the epimeric ketones (3) and (4) have been established by X-ray analysis.
- Chakraborti, Asit K.,Alam, Shaikh Khairul,Chakraborti, Prabir C.,Dasgupta, Rupak,Chakravarty, Jyotirmoy,et al.
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p. 1243 - 1248
(2007/10/02)
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- HOMO- AND SPIROCONJUGATIVE EFFECTS IN THE SIGMATROPIC REARRANGEMENT OF 1,1'-SPIROBIINDENES
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Due to homoconjugative interactions 2,3-dihydro-1,1'-spirobiindene and 1,1'-spirobiindene yield isomeric benzofluorenes in thermal, photochemical, and electron transfer induced rearrangement.
- Kiesele, Herbert
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p. 1097 - 1100
(2007/10/02)
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