- 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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Read Online
- Cyclisation of Stilbenes to Phenanthrenes by Flash Vacuum Pyrolysis
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Flash Vacuum Pyrolysis of the stilbene derivatives 3,4,6 and 7 gives the corresponding phenanthrenes in reasonable yields.
- Plater, M. John
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Read Online
- Synthesis of 1-(2-ethynyl-6-methylphenyl)- and 1-(2-ethynyl-6-methoxyphenyl)-naphthalene and their cyclization
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A Suzuki cross-coupling reaction of hindered 2-bromo-1-trimethylsilylethynylbenzenes with 1-naphthaleneboronic acid yielding (2-ethynylphenyl)naphthalenes has been achieved. Their subsequent cyclization was carried out, giving benzo[c]phenanthrenes, without the use of photochemical procedures.
- Storch, Jan,?ermák, Jan,Karban, Jind?ich
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Read Online
- Methylarene-based PAH synthesis via domino cyclization of 1, 1-difluoro-1-alkenes
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Polycyclic aromatic hydrocarbons (PAHs) containing 4-7 benzene rings were synthesized via a methylarene-based protocol. Trimethyl[2-(trifluoromethyl)allyl]silane was electrophilically benzylated with Ar1CH2Br (prepared from Ar1CH3) to afford 2-trifluoromethyl-1-alkenes that were in turn nucleophilically benzylated with Ar2CH2Li (prepared from Ar2CH3) through an SN2-type reaction to produce 1, 1-difluoroethylenes, which are cyclization precursors bearing two 2-arylethyl groups. Magic acid efficiently promoted the domino FriedelCrafts-type cyclization of these precursors, followed by dehydrogenation that enabled the connection among two aryl groups (Ar1 and Ar2) by forming two benzene rings between them, facilitating the synthesis of the desired higher-order PAHs. With the proposed protocol, the combination of even a limited number of methylarenes can yield a variety of PAHs in diverse configurations.
- Fuchibe, Kohei,Takao, Go,Takahashi, Hiroki,Ijima, Shiori,Ichikawa, Junji
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p. 2019 - 2029
(2019/12/23)
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- Water Docking Bias in [4]Helicene
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We report on the one- and two-water clusters of [4]helicene, the smallest polycyclic aromatic hydrocarbon with a helical sense, which were captured in the gas phase using high-resolution rotational spectroscopy. The structures of the complexes are unambiguously revealed using microwave spectra of isotopically enriched species. In the one-water cluster, the apparent splitting pattern is consistent with a tunneling motion that encompasses an exchange of strongly and weakly bonded water hydrogens. This motion is “locked” in the two-water cluster. The relevant intermolecular contacts, symmetry, and aromaticity effects are unveiled for the microsolvated chiral topologies. These observations entail the first glance at the structures and internal dynamics of the water binding motifs of a chiral polycyclic aromatic hydrocarbon.
- Domingos, Sérgio R.,Martin, Kévin,Avarvari, Narcis,Schnell, Melanie
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supporting information
p. 11257 - 11261
(2019/07/12)
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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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supporting information
p. 2960 - 2963
(2017/03/11)
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- Further insight into the photochemical behavior of 3-aryl-N-(arylsulfonyl)propiolamides: tunable synthetic route to phenanthrenes
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Reported herein is further insight into the photochemical behaviour of 3-aryl-N-(arylsulfonyl)-propiolamides, which provides a straightforward way to access meaningful phenanthrenes. Mechanistic investigation indicated that aryl migration, C-C coupling, 1,3-hydrogen shift, desulfonylation and elimination were involved in the process. Moreover, this protocol allowed for scale-up using a flow reactor.
- Chen, Ming,Zhao, Xinxin,Yang, Chao,Wang, Yanpei,Xia, Wujiong
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p. 12022 - 12026
(2017/03/01)
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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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- 1,7-Naphthodiyne: A new platform for the synthesis of novel, sterically congested PAHs
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The synthesis of an efficient precursor of the novel 1,7-naphthodiyne synthon is reported. Preliminary experiments demonstrate the usefulness of this platform for the synthesis of sterically congested polyarenes, such as helicenes and angularly fused acene derivatives. Furthermore, a novel intramolecular aryne trapping reaction is described.
- Pozo, Iago,Cobas, Agustín,Pe?a, Diego,Guitián, Enrique,Pérez, Dolores
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supporting information
p. 5534 - 5537
(2016/05/09)
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- Microwave flash pyrolysis: C9h8 interconversions and dimerisations
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The pyrolysis of 2-ethynyltoluene, indene, fluorene, and related compounds has been studied by sealed tube microwave flash pyrolysis (MFP), in concert with modelling of putative mechanistic pathways by density functional theory (DFT) computations. In the MFP technique, samples are admixed with graphite and subjected to intense microwave power (150-300 W) in a quartz reaction tube under a nitrogen atmosphere. The MFP reaction of 2-ethynyltoluene gave mostly indene, the product of a Roger Brown rearrangement (1,2-H shift to a vinylidene) followed by insertion. An additional product was chrysene, the likely result of hydrogen atom loss from indene followed by dimerisation. The intermediacy of dimeric bi-indene structures was supported by pyrolysis of bi-indene and by computational models. Benzo[a]anthracene and benzo[c]phenanthrene are minor products in these reactions. These are shown to arise from pyrolysis of chrysene under the same MFP conditions. MFP reaction of fluorene gave primarily bi-fluorene, bifluorenylidene, and dibenzochrysene, the latter derived from a known Stone-Wales rearrangement.
- Ajaz, Aida,Voukides, Alicia C.,Cahill, Katharine J.,Thamatam, Rajesh,Skraba-Joiner, Sarah L.,Johnson, Richard P.
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p. 1301 - 1308
(2014/11/07)
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- Bismuth-catalyzed synthesis of polycyclic aromatic hydrocarbons (PAHs) with a phenanthrene backbone via cyclization and aromatization of 2-(2-arylphenyl)vinyl ethers
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The reaction of 2-(2-arylphenyl)vinyl ethers in the presence of a catalytic amount of bismuth(III) triflate gave substituted phenanthrenes in excellent yields under mild reaction conditions. The reaction was also applied to the construction of other polycyclic aromatic hydrocarbons (PAHs), such as chrysene, helicene, and pyrene having a phenanthrene backbone, via regioselective cyclization. This method has the advantages of easy availability of the cyclization precursors, operational simplicity, and high reaction efficiency.
- Murai, Masahito,Hosokawa, Naoki,Roy, David,Takai, Kazuhiko
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supporting information
p. 4134 - 4137
(2014/09/30)
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- TETRACATIONIC CYCLOPHANES AND THEIR USE IN THE SEQUESTRATION OF POLYAROMATIC HYDROCARBONS BY WAY OF COMPLEXATION
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Novel tetracationic cyclophanes incorporating π-electron poor organic compounds into their ring structures, as well as methods of making the cyclophanes, are provided. The cyclophanes are able to form electron donor-acceptor complexes with a variety of polyaromatic hydrocarbons (PAHs) ranging in size, shape, and electron density. Also provided are methods of using the cyclophanes in the sequestration of PAHs in liquid or gaseous samples, the separation of PAHs from liquid or gaseous samples, the detection of PAHs in liquid samples, and the exfoliation of graphene via pseudopolyrotaxane formation.
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- Divergent reaction pathways for phenol arylation by arynes: Synthesis of helicenes and 2-arylphenols
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Two reactions of phenols with arynes have been developed. If LiTMP base is employed, arynes generated from aryl chlorides react with phenols to form helicenes. o-Arylation of phenols can be achieved by employing tBuONa base in the presence of AgOAc. Direc
- Truong, Thanh,Daugulis, Olafs
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p. 531 - 535
(2013/05/08)
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- ExBox: A polycyclic aromatic hydrocarbon scavenger
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A template-directed protocol, which capitalizes on donor-acceptor interactions, is employed to synthesize a semi-rigid cyclophane (ExBox 4+) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged ("extended") bipyridinium units (ExBIPY2+). ExBox4+ functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 A? in width and 11.2 A? in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with ExBox4+, with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes ExBox 4+?PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of ExBox4+ for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host-guest interactions in solution and determine the degree with which ExBox4+ binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, ExBox·4Cl, resulting in the isolation of different aromatic compounds after ExBox·4Cl was regenerated.
- Barnes, Jonathan C.,Jurí?ek, Michal,Strutt, Nathan L.,Frasconi, Marco,Sampath, Srinivasan,Giesener, Marc A.,McGrier, Psaras L.,Bruns, Carson J.,Stern, Charlotte L.,Sarjeant, Amy A.,Stoddart, J. Fraser
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supporting information
p. 183 - 192
(2013/02/23)
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- Synthesis of phenanthrenes by cationic chromium(III) porphyrin-catalyzed dehydration cycloaromatization
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Readily available biphenyl derivatives with ortho oxirane moiety react in the presence of cationic chromiun(III) porphyrin catalyst to afford phenanthrenes. The reaction is considered to be triggered by activation of the oxirane moiety through coordination to the Lewis acidic cationic chromium to give aldehyde via 1,2-hydride shift, which reacts with arene through intramolecular electrophilic aromatic substitution and subsequent dehydration. The reaction allows constructing a variety of polycyclic aromatic and heteroaromatic compounds.
- Wakabayashi, Ryota,Kurahashi, Takuya,Matsubara, Seijiro
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supporting information
p. 2297 - 2301
(2013/11/06)
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- Rhodium(II)-catalyzed cyclization of bis(N-tosylhydrazone)s: An efficient approach towards polycyclic aromatic compounds
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Ahead of the PAC: Polycyclic aromatic compounds (PACs) can be easily accessed by the combination of Suzuki-Miyaura cross-coupling and a [Rh 2(OAc)4]-catalyzed carbene reaction using easily available bis(N-tosylhydrazone)s as intermediates (see scheme; Ts=4-toluenesulfonyl). Copyright
- Xia, Ying,Liu, Zhenxing,Xiao, Qing,Qu, Peiyuan,Ge, Rui,Zhang, Yan,Wang, Jianbo
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p. 5714 - 5717
(2012/07/28)
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- Exploiting the π-acceptor properties of carbene-stabilized phosphorus centered trications [L3P] 3+: Applications in Pt(II) catalysis
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Reaction of tris(dimethylaminocyclopropenium) substituted phosphine 1 with K2PtCl4 afforded the bench stable complex 3 which upon treatment with Ag[CB11H6Cl6] turned out to be an excellent catalyst for the transformation of a variety of ortho-biaryl substituted alkynes into polycyclic homo- and heteroarenes of different size, shape, and curvature through a 6-endo-dig cyclization. This constitutes the first example ever reported of using a P1-centered trication as ligand in catalysis. The strong π-acceptor character of 1 that derives from its three positive charges substantially increases the intrinsic π-acidity of Pt in complex 1?PtCl2 and dramatically enhances its ability to activate π-systems toward nucleophilic attack. As a consequence, a remarkable acceleration of the model transformation is observed when compared with other classical π-acceptor ligands such as P(OPh)3 or P(C 6F5)3. Moreover, the employment of 1 as ligand also expands the scope of this reaction to previously inaccessible substitution patterns. Kinetic studies and deuterium labeling experiments as well as density functional theory (DFT) calculations were performed in order to explain these findings.
- Carreras, Javier,Patil, Mahendra,Thiel, Walter,Alcarazo, Manuel
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supporting information
p. 16753 - 16758,6
(2012/12/13)
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- Straightforward synthesis of phenanthrenes from styrenes and arenes
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Semi-one-pot synthesis of phenanthrenes from styrenes and arenes was developed through cross-dehydrogenative coupling. A sequence of Heck-type coupling and photo-cyclization were involved and a variety of functionalities were tolerated. This method provides an effective and practical protocol towards the synthesis of substituted phenanthrenes. The Royal Society of Chemistry 2012.
- Li, Hu,He, Ke-Han,Liu, Jia,Wang, Bi-Qin,Zhao, Ke-Qing,Hu, Ping,Shi, Zhang-Jie
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supporting information; experimental part
p. 7028 - 7030
(2012/08/07)
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- Expeditious synthesis of helicenes using an improved protocol of photocyclodehydrogenation of stilbenes
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An improved procedure has been developed for photodehydrocyclization of stilbenes for the synthesis of phenanthrenes and helicenes. This procedure involves the use of THF as a scavenger of hydriodic acid produced during iodine mediated photodehydrocyclization. The use of THF is advantageous due to its higher boiling point, lower cost and easy availability as compared to propylene oxide. The method is applied to synthesize a number of phenanthrenes and helicenes. ARKAT-USA, Inc.
- Talele, Harish R.,Chaudhary, Anju R.,Patel, Parthiv R.,Bedekar, Ashutosh V.
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experimental part
p. 15 - 37
(2011/06/19)
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- Domino Friedel-crafts-type cyclizations of difluoroalkenes promoted by the α-cation-stabilizing effect of fluorine: An efficient method for synthesizing angular PAHs
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In order to synthesize polycyclic aromatic hydrocarbons with nonlinear arrangements (angular PAHs), acid-promoted domino cyclizations of 1,1-difluoroalk-1-enes and 1,1-difluoroalka-1,3-dienes were studied. 1,1-Difluoroalkenes, each bearing two aryl substituents, were regioselectively protonated with FSO3H·SbF5 to generate fluorine-stabilized carbocations, which readily underwent domino Friedel-Crafts-type cyclizations to give carbocycles based on 6/n/m/6 ring systems (n,m=5-7) in good to high yields. Protonation of 1,1-difluoroalka-1,3- dienes took place at their electron-rich methylene (CH2) carbon atoms in the presence of milder acids such as camphorsulfonic acid and trifluoromethanesulfonic acid. Domino cyclizations of the resulting fluorine-stabilized allylic carbocations afford carbocycles based on 6/6/6/6 or 6/6/5/6 ring systems in high yields.
- Fuchibe, Kohei,Jyono, Hideharu,Fujiwara, Masaki,Kudo, Takao,Yokota, Misaki,Ichikawa, Junji
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experimental part
p. 12175 - 12185
(2011/12/01)
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- Palladium-catalyzed intramolecular C-H activation: A synthetic approach towards polycyclic aromatic hydrocarbons
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A simple and convenient synthetic protocol for the construction of polycyclic aromatic hydrocarbons has been developed. A variety of phenanthrene, benzo[c]phenanthrene and chrysene derivatives was synthesized via Pd-catalyzed intramolecular C-H activation followed by acid-catalyzed water elimination.
- Paul, Sunanda,Jana, Rathin,Ray, Jayanta K.
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experimental part
p. 1463 - 1468
(2010/08/20)
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- Highly efficient fluorine-promoted intramolecular condensation of benzo[c]phenanthrene: A new prospective on direct fullerene synthesis
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Various functional groups have been tested as alternative promoters of the intramolecular condensation of benzo-[c]phenanthrene under flash vacuum pyrolysis conditions. Methyl and fluorine functionalization were found to be promising approaches. Unexpectedly high selectivity was observed in the cyclization of fluorinated benzo[c]phenanthrenes. The mechanism for the condensation reaction and the advantages of fluorine as a promoter for the rational synthesis of fullerenes are discussed. Wiley-VCH Verlag GmbH & Co. KGaA.
- Amsharov, Konstantin Yu.,Kabdulov, Mikhail A.,Jansen, Martin
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p. 6328 - 6335
(2011/03/19)
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- Synthesis of derivatives of phenanthrene and helicene by improved procedures of photocyclization of stilbenes
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An improved method has been developed for photocyclization of stilbene to construct phenanthrenes and benzo[c]phenanthrenes. This reaction is promoted by iodine while tetrahydrofuran is used as an efficient and inexpensive scavenger of hydroiodic acid produced during the photocyclization sequence. In another process, cyclohexene is used as a reagent for dehydrogenation step in place of THFI2.
- Talele, Harish R.,Gohil, Monik J.,Bedekar, Ashutosh V.
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experimental part
p. 1182 - 1186
(2009/12/25)
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- Efficient helicene synthesis: Friedel-crafts-type cyclization of 1,1-difluoro-1-alkenes
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(Chemical Equation Presented) The unique properties of fluorine substituents, leaving groups that also stabilize an a carbocation, are exploited in a high-yielding synthesis of substituted [4]- to [6]helicenes in three or four steps from commercially available compounds: Two fused benzene rings are constructed in the title reaction of readily prepared 1,1-difluoro-1-alkenes containing two aryl groups followed by dehydrogenation (see scheme).
- Ichikawa, Junji,Yokota, Misaki,Kudo, Takao,Umezaki, Satoshi
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supporting information; experimental part
p. 4870 - 4873
(2009/02/08)
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- Emission factors and importance of PCDD/Fs, PCBs, PCNs, PAHs and PM 10 from the domestic burning of coal and wood in the U.K.
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This paper presents emission factors (EFs) derived for a range of persistent organic pollutants (POPs) when coal and wood were subject to controlled burning experiments, designed to simulate domestic burning for space heating. A wide range of POPs were emitted, with emissions from coal being higher than those from wood. Highest EFs were obtained for particulate matter, PM10, (~ 10 g/kg fuel) and polycyclic aromatic hydrocarbons (~ 100 mg/ kg fuel for ΣPAHs). For chlorinated compounds, EFs were highest for polychlorinated biphenyls (PCBs), with polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) being less abundant. EFs were on the order of 1000 ng/kg fuel for ΣPCBs, 100s ng/ kg fuel for ΣPCNs and 100 ng/kg fuel for ΣPCDD/Fs. The study confirmed that mono- to trichlorinated dibenzofurans, Cl1,2,3DFs, were strong indicators of low temperature combustion processes, such as the domestic burning of coal and wood. It is concluded that numerous PCB and PCN congeners are routinely formed during the combustion of solid fuels. However, their combined emissions from the domestic burning of coal and wood would contribute only a few percent to annual U.K. emission estimates. Emissions of PAHs and PM 10 were major contributors to U.K. national emission inventories. Major emissions were found from the domestic burning for Cl1,2,3DFs, while the contribution of PCDD/F-ΣTEQ to total U.K. emissions was minor.
- Lee, Robert G. M.,Coleman, Peter,Jones, Joanne L.,Jones, Kevin C.,Lohmann, Rainer
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p. 1436 - 1447
(2007/10/03)
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- Short and efficient synthesis of coronene derivatives via ruthenium-catalyzed benzannulation protocol
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TpRuPPh3(CH3CN)2PF6 (3 mol %) was very active in catalytic benzannulation of 1-phenyl-2-ethynylbenzenes in dichloroethane (60 °C, 36 h) to afford phenanthrene in 95% yield. This method is applicable to the synthesis of various polycyclic aromatic hydrocarbons via two- and four-fold benzannulations, including various substituted coronene derivatives (53-86% yields) using this catalyst at a moderate loading (10 mol %).
- Shen, Hung-Chin,Tang, Jhih-Meng,Chang, Hsu-Kai,Yang, Chia-Wei,Liu, Rai-Shung
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p. 10113 - 10116
(2007/10/03)
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- The synthesis of angularly fused polyaromatic compounds by using a light-assisted, base-mediated cyclization reaction
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The synthesis of substituted polyaromatic compounds that contain at least four benzene rings fused together in an angular fashion is described. Suzuki coupling of 1-bromo-3,4-dihydronaphthalene-2-carbaldehyde with a number of aromatic boronic acids affords products such as 1-(1,4-dimethoxy-3-methyl-2-naphthyl)-3,4-dihydronaphthalene-2-carbaldehyde. Exposure of these dihydronaphthalenes to potassium tert-butoxide and DMF at 80°C yields polyaromatic compounds such as 9,14-dimethoxynaphtho[1,2-a]anthracene.
- Pathak, Rakhi,Vandayar, Kantharuby,Van Otterlo, Willem A. L.,Michael, Joseph P.,Fernandes, Manuel A.,De Koning, Charles B.
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p. 3504 - 3509
(2007/10/03)
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- Elaboration of Diaryl Ketones into Naphthalenes Fused on Two or Four Sides: A Naphthoannulation Procedure
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Transition metal-catalyzed double ring closures of 1,1-diaryl-2,2- diethynylethylenes yield polycyclic aromatic hydrocarbons and heterocycles that contain a newly formed naphthalene ring system embedded in a larger polycyclic network. The diynes required for this procedure are readily synthesized from diaryl ketones by the Corey-Fuchs olefination and subsequent Sonogashira coupling with trimethylsilylacetylene followed by desilylation. This procedure provides easy access to new compounds such as 3,11-di-tert-butyl[4]helicene and 1,8,9-perinaphthothioxanthene. Double naphthoannulation of 9,10-anthraquinone by this procedure closes four new benzene rings in a single operation to give coronene, although the yield in this case is presently low.
- Donovan, Patrick M.,Scott, Lawrence T.
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p. 3108 - 3112
(2007/10/03)
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- Synthesis of phenanthrenes and polycyclic heteroarenes by transition-metal catalyzed cycloisomerization reactions
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Readily available biphenyl derivatives containing an alkyne unit at one of their ortho-positions are converted into substituted phenanthrenes on exposure to catalytic amounts of either PtCl2, AuCl, AuCl3, GaCl3 or InCl3 in toluene. This 6-endo-dig cyclization likely proceeds through initial π-complexation of the alkyne unit followed by interception of the resulting η2-metal species by the adjacent arene ring. The reaction is inherently modular, allowing for substantial structural variations and for the incorporation of substituents at any site of the phenanthrene product. Moreover, it is readily extended to the heterocyclic series as exemplified by the preparation of benzoindoles, benzocarbazoles, naphthothiophenes, as well as bridgehead nitrogen heterocycles such as pyrrolo[1,2-a]quinolines. Depending on the chosen catalyst, biaryls bearing halo-alkyne units can either be converted into the corresponding 10-halo-phenanthrenes or into the isomeric 9-halo-phenanthrenes; in the latter case, the concomitant 1,2-halide shift is best explained by assuming a metal vinylidene species as the reactive intermediate. The scope of this novel method for the preparation of polycyclic arenes is illustrated by the total synthesis of a series of polyoxygenated phenanthrenes that are close relatives of the anticancer agent combretastatin A-4, as well as by the total synthesis of the aporphine alkaloid O-methyl-dehydroisopiline and its naturally occurring symmetrical dimer.
- Mamane, Victor,Hannen, Peter,Fuerstner, Alois
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p. 4556 - 4575
(2007/10/03)
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- Semivolatile and volatile compounds in combustion of polyethylene
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The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- Flexible synthesis of phenanthrenes by a PtCl2-catalyzed cycloisomerization reaction
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Readily available biphenyl derivatives containing an alkyne unit at one of their ortho positions are converted into substituted phenanthrenes upon exposure to catalytic amounts of either PtCl2, AuCl3, GaCl3, or InCl3 in toluene. This 6-endo-dig cyclization likely proceeds through initial π-coordination of the alkyne unit followed by interception of the resulting η2-metal complex by the adjacent arene ring. The reaction is inherently modular, allowing for substantial structural variations and for the incorporation of substituents at any site of the phenanthrene product except C-9. Moreover, the reaction is readily applied to the heterocyclic series as exemplified by the preparation of benzoindoles, naphthothiophenes as well as bridgehead nitrogen hetero- cycles.
- Fuerstner, Alois,Mamane, Victor
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p. 6264 - 6267
(2007/10/03)
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- Flash vacuum pyrolysis of 1,6-diphenyl-1,5-hexadien-3-ynes: Tandem diaryldienyne cyclizations to form chrysene
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Flash vacuum pyrolysis of 1,6-diphenyl-1,5-hexadien-3-yne at 1000°C and its bromo derivative at 800°C yielded chrysene as the major product through tandem diaryldienyne cyclizations.
- Sonoda, Motohiro,Itahashi, Kayo,Tobe, Yoshito
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p. 5269 - 5272
(2007/10/03)
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- A convenient and general synthesis of cata- and peri-condensed polycyclic aromatic hydrocarbons with a Fjord-region
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Cata- and peri-condensed polycyclic aromatic hydrocarbons (PAHs) 10a-d and 11 have been conveniently synthesized by the application of Suzuki cross-coupling reaction. In three to four steps, these PAHs having fjord-region were obtained in an overall yield of 35-51% from commercially or easily accessible aryl boronic acids and aryl bromides.
- Kumar, Subodh
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p. 841 - 844
(2007/10/03)
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- Evolution of products in the combustion of scrap tires in a horizontal, laboratory scale reactor
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A horizontal laboratory reactor was used to study the evolution of byproducts from the combustion of scrap tires at five nominal temperatures (ranging from 650 to 1050 °C) and different oxygen:sample ratios A model was used to calculate the bulk air ratio (λ), and the oxygen consumption was discussed considering this ratio λ. More than 100 volatile and semivolatile compounds were identified and quantified by gas chromatography mass spectrometry, plotting their yields vs the bulk air ratio and temperature. Five different behaviors considering the bulk air ratio and the temperature were identified.
- Fullana,Font,Conesa,Blasco
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p. 2092 - 2099
(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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- 1,2-shifts of hydrogen atoms in aryl radicals
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An energy barrier on the order of 60 kcal/mol is predicted for the 1,2- shift of hydrogen atoms in aryl radicals. Such rearrangements are, therefore, not expected to occur under ordinary laboratory conditions, but they should be prevalent in the aryl radicals formed during combustion, flash vacuum pyrolysis, and other high-temperature gas-phase processes. As a demonstration of this rearrangement, the 2-benzo[c]phenanthryl radical (1) was generated by flash vacuum pyrolysis of the corresponding aryl bromide (9). A 1,2-shift of hydrogen out of the sterically congested cove region of 1, followed by cyclization and rearomatization of the resulting radical (Scheme 1), is proposed to explain the observation of benzo[ghi]fluoranthene (4) as the dominant monomeric product formed. Under the same conditions, [ 1,3,4,5- 2H4]-2-bromobenzo[c]phenanthrene (13) gives [ 1,2,3,4-2H4]- benzo[ghi]fluoranthene (15) as the dominant monomeric product (Scheme 6), in accord with the expectation of a deuterium atom 1,2-shift.
- Brooks, Michele A.,Scott, Lawrence T.
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p. 5444 - 5449
(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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- Fullerene tectonics. Part 2. Synthesis and pyrolysis of halogenated benzo[c]phenanthrenes
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Halogenated benzo[c]phenanthrenes with a halogen in the hindered fiord region are prepared by the photochemical cyclisation of appropriately substituted stilbenes. Pyrolysis gives the corresponding benzo[ghi]fluoranthrenes in moderate yields. At higher temperatures a competing rearrangement pathway to cyclopenta[cd]pyrene occurs.
- Plater, M. John
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p. 2903 - 2909
(2007/10/03)
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- Thermolysis of benzo[c]phenanthrene-5,6-dicarboxylic anhydride and 6H-benzo[cd]pyren-6-one. Entries to the combustion effluents benzo[ghi]fluoranthene and cyclopenta[cd]pyrene
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Thermolysis of the oxy-PAH benzo[c]phenanthrene 5,6-dicarboxylic anhydride (3) and 6H-benzo[cd]pyren-6-one (4) gave the abundant C18H10 CP-PAH combustion effluents benzo[gh]]fluoranthene (1) and cyclopenta[cd]pyrene (2).
- Sarobe, Martin,Jenneskens, Leonardus W.,Wiersum, Ulfert E.
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p. 4689 - 4692
(2007/10/03)
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- Rearrangements on Acid-Catalyzed Dehydration of Regioisomeric Thiol Adducts Formed from K-Region Arene Oxides
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K-Region 5,6-oxides of chrysene, benzanthracene, and benzophenanthrene undergo nucleophilic trans attack by tert-butylthiolate anion in aqueous dioxane to give mixtures of regioisomeric thiol adducts.These adducts have been separated by HPLC, and the positions of thiol addition have been assigned by NMR and/or CD spectroscopy.Adducts characterized were as follows: from chrysene 5,6-oxide, 5-hydroxy-6-(tert-butylthio) (minor) and 5-(tert-butylthio)-6-hydroxy (major); from benzanthracene 5,6-oxide, 5-(tert-butylthio)-6-hydroxy and 5-hydroxy-6-(tert-butylthio)(equal amounts); and from benzophenanthrene 5,6-oxide, 5-(tert-butylthio)-6-hydroxy (minor) and 5-hydroxy-6-(tert-butylthio) (major).Reaction of either one of a pair of regioisomeric adducts with boron trifluoride in ether gave the same mixture of aryl alkyl thioethers, as a result of sulfur migration, presumably via a common episulfonium ion intermediate.Under these acid conditions, both chrysene adducts gave exclusively 6-(tert-butylthio)chrysene, both benzanthracene adducts gave predominantly (87percent) 5-(tert-butylthio)benzanthracene, and both benzophenanthrene adducts gave predominantly (90percent) 5-(tert-butylthio)benzophenanthrene.We have observed for the first time that thiol adducts of K-region arene oxides also undergo a facile base-catalyzed elimination of water in the presence of sodium methoxide in THF.In contrast to the acid-catalyzed reactions, the reaction of each pure adduct under these basic conditions gave a single aryl alkyl thioether that resulted from dehydration without migration of the sulfur substituent.Because of the dissimilarity in mechanism between the acid and base reactions of the adducts, itis essential that a distinction be drawn between acid- and base-induced dehydrations of K-region thiol adducts, such that the stuctures of the original adducts can only be deduced from the aromatized products of the base-catalyzed dehydration.Reaction of several thiol adducts of benzophenanthrene 5,6-oxide in acid has been observed to yield benzophenanthrene.A proposed sulfenyl chloride intermediate from this reaction in hydrochloric acid has been trapped by its addition to cyclohexene.It is suggested that hydrocarbon formation occurs by attack of a nucleophile on the sulfur of a cationic intermediate.
- Balani, Suresh K.,Sayer, Jane M.,Jerina, Donald M.
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p. 3290 - 3295
(2007/10/02)
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- Synthesis of the K-Region Monofluoro- and Difluorobenzophenanthrenes
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Polycyclic aromatic hydrocarbons are metabolically activated by cytochromes P-450 an epoxide hydrolase to ultimate mutagens and carcinogens.Substitution by fluorine at specific positions has been used to elucidate metabolic activation and detoxication pathways of polycyclic aromatic hydrocarbons.Substitution by fluorine at the K-region C-6 position of the weak carcinogen benzophenanthrene (1) causes a >4-fold increase in its tumorigenicity.Out of the six possible monofluorobenzophenanthrenes, only 5-fluorobenzophenanthrene (8a) has not been evaluated as a carcinogen, presumably because a convenient synthetic method for the 5-fluoro derivative has not been available.Hence, a new method has been developed for the synthesis of 8a from readily available starting materials.The method consists of selective bromination of benzophenanthrene (1) to 5-bromobenzophenanthrene (3), substitution of bromine by an amino group, and a modified Schiemann reaction of 5-aminobenzophenanthrene (6a) to yield 5-fluorobenzophenanthrene (8a).An improved method for the synthesis of 6-fluorobenzophenanthrene (19) has also been developed which consist of bromofluorination of β-naphthylstyrene, followed by selective dehydrobromination and photocyclization of the fluorostyrene to the 6-fluoro derivative 19.The above methods, with minor modifications, also provided synthetic routes for the preparation of the difluoro derivatives 5,7-, 5,8-, and 6,7-difluorobenzophenanthrenes.
- Mirsadeghi, Seid,Prasad, Ganesh K. B.,Whittaker, Noel,Thakker, Dhiren R.
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p. 3091 - 3096
(2007/10/02)
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- The formation and reactions of 9,10-phenanthryne and related arynes by pyrolytic reactions in the vapor phase
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The formation of 9,10-phenanthryne (5), 4-methyl-9,10-phenanthryne (7) and 9,10-benz(c)phenanthryne (9) by the thermal degradation of appropriate arenedicarboxylic acid anhydrides has been investigated by a combination of VLPP and mass spectrometry and by a co-pyrolysis of the anhydrides with benzene, hexadeuterobenzene and 1,3-butadiene. Compounds 5,7 and especially 9 are formed easily by VLPP at 700-900° from the anhydrides. The results indicate that 7 and 9 are less reactive by H-addition to the aryne bond than 5, benzyne or naphthalyne, respectively. The results of the co-pyrolysis experiments show that 5 and 9 react with benzene and 1,3-butadiene by H-abstraction and addition reactions, similar to 1,2-benzyne and 2,3-naphthalyne. However, the reactivity of the aryne in the H-abstraction reaction decreases and the selectivity for the addition reaction increases in the series 1,2-benzyne, 2,3-naphthalyne, 9,10-phenanthryne and 9,10benz(c)phenanthryne.
- Gruetzmacher, Hans-Fr.,Strabtmans, Udo
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p. 807 - 813
(2007/10/02)
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