- Rearrangement of 1,1'-Spirobiindene and Thermochemical Evidence for Its Spiroconjugative Destabilization
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Thermal rearrangement of 1,1'-spirobiindene (1) in a flow system at temperatures above 300 deg C leads exclusively to 3,4-benzofluorene, the product of vinyl migration.The same product is formed by direct irradiation at 254 nm or by treatment with potassium in refluxing THF.Determination of the heats of hydrogenation of 1 (-61.0 kcal/mol) and indene (-23.63 kcal/mol) reveals a destabilization in 1 of 13.7 kcal/mol relative to indene, in agreement with literature calculations that spiroconjugated systems like 1 possess high strain energies attributable to unfavorable ?-orbital interactions.
- Hill, Richard K.,Morton, Gerald H.,Rogers, Donald W.,Choi, Ling S.
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Read Online
- 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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- 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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- Gold(I) carbenes by retro-buchner reaction: Generation and fate
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The fate of the aryl gold(I) carbenes generated by retro-Buchner reaction of ortho-substituted 7-aryl-1,3,5-cycloheptatrienes is dependent on the constitution of the ortho substituent. Indenes and fluorenes are obtained by intramolecular reaction of highly electrophilic gold(I) carbenes with alkenes and arenes. According to density functional theory calculations, the gold-catalyzed retro-Buchner process occurs stepwise, although the two carbon-carbon cleavages occur on a rather flat potential energy surface.
- Wang, Yahui,McGonigal, Paul R.,Herle, Bart,Besora, Maria,Echavarren, Antonio M.
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supporting information
p. 801 - 809
(2014/02/14)
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- Synthesis of methylene-bridge polyarenes through palladium-catalyzed activation of benzylic carbon-hydrogen bond
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In the presence of palladium(II) acetate [Pd(OAc)2] and an N-heterocyclic carbene (NHC) ligand, fluorene derivatives can be generated in good to excellent yields from 2-halo-2′-methylbiaryls through the benzylic C-H bond activation (14 examples; 81-97% yields). The scope and limitations of this protocol have been examined. A wide range of functional groups, such as alkyl, alkoxy, ester, nitrile, and others, is able to tolerate the reaction conditions herein. The cyclization of an isotope-labelled biphenyl gave the corresponding product with a primary kinetic isotope effect (k H/kD=4.8:1), which indicates that the rate-determining step of this reaction is the activation of the benzylic C-H bond. Moreover, indenofluorenes were also accessed in excellent results from terphenyls (3 examples; 91-92% yields). The cascade reaction of 2,6-dichloro-2′- methylbiphenyl with diphenylacetylene produced 8,9-diphenyl-4H-cyclopenta[def] phenanthrene in 60% yield through the activation of an aryl and a benzylic C-H bond. Copyright
- Hsiao, Chien-Chi,Lin, Yi-Kuan,Liu, Chia-Ju,Wu, Tsun-Cheng,Wu, Yao-Ting
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experimental part
p. 3267 - 3274
(2011/02/23)
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- Highly efficient and versatile synthesis of polyarylfluorenes via Pd-catalyzed C-H bond activation
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A facile protocol for the Pd-catalyzed preparative synthesis of fluorene derivatives has been developed. While a wide range of fluorenes were easily obtained with high efficiency and selectivity under mild conditions, excellent functional group tolerance
- Hwang, Seung Jun,Kim, Hyun Jin,Chang, Sukbok
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supporting information; experimental part
p. 4588 - 4591
(2009/12/09)
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- BENZOFLUORENE COMPOUND AND USE THEREOF
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A novel material having high hole-transporting ability and a high glass transition temperature and having long-lasting durability is obtained. A benzofluorene compound represented by formula (1) is used. (In the formula, M is a substituted or unsubstituted aryl group having 6-40 carbon atoms or a substituted or unsubstituted heteroaryl group having 5-40 carbon atoms; Ar1 to Ar4 each independently is a substituted or unsubstituted aryl group having 6-40 carbon atoms or a substituted or unsubstituted heteroaryl group having 5-40 carbon atoms, provided that at least one of Ar1 to Ar4 is a substituent represented by any of the following formulae (2) to (5); and p is an integer of 0-2.) (In the formulae, R1 to R4 each independently is a hydrogen atom, a halogen atom, a substituted or unsubstituted amino group, a linear, branched, or cyclic alkyl group, a linear, branched, or cyclic alkoxy group, a substituted or unsubstituted aryl group having 6-40 carbon atoms, or a substituted or unsubstituted aryloxy group having 6-40 carbon atoms, provided that R1 and R2 may be bonded to each other to form a ring.)
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Page/Page column 26-27
(2009/01/24)
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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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- Basicity of a stable carbene, 1,3-di-tert-butylimidazol-2-ylidene, in THF
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The basicity of 1,3-di-tert-butylimidazol-2-ylidene (1) was measured in THF against three hydrocarbon indicators. Both ion pairs and free ions were found and the corresponding equilibrium constants were measured. Homoconjugation was not found in either THF or DMSO. The carbene is effectively more basic in DMSO by several pK units, probably because of hydrogen bonding of 1-H+ to DMSO. Model ab initio computations are consistent with these results.
- Kim, Yeong-Joon,Streitwieser, Andrew
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p. 5757 - 5761
(2007/10/03)
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- Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 10. Generation of 2-methylstyrylalkynes and their thermal cyclisation to 2-alkenylnaphthalenes
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A series of nine 2-methylcinnamoyl phosphorus ylides 7 have been prepared and are found upon FVP at 500°C to undergo loss of Ph3PO to afford the corresponding styrylalkynes 8 whose fully assigned 13C NMR spectra are presented. FVP of the ylides at 900°C leads to cyclisation to give substituted naphthalenes 9-18; the mechanism of these reactions may proceed either by initial hydrogen atom loss or an initial [1,7]hydrogen shift, but an alternative route involving an initial [1,3]hydrogen shift has been ruled out by examination of a deuterium labelled analogue. For the α-phenyl ylides 7d and 7i a further cyclisation leads to benzo[c]fluorene derivatives and this process has been extended to a thiophene analogue to give fluoreno[3,4-b]thiophene. The formation of 2-ethylnaphthalene as the main product from the α-methoxycarbonyl ylide 7e is due to a secondary thermal reaction of methyl 2-naphthylacetate which may involve a radical chain reaction featuring, as the propagation step, an unusual homolytic substitution at a methoxy carbon by a 2-naphthylmethyl radical.
- Aitken, R. Alan,Boeters, Christine,Morrison, John J.
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p. 2625 - 2631
(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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- Syndiospezifische polymerisation von propylen: 3-, 4-, 3,4-und 4,5-substituierte zirkonocenkomplexe des typs (C13H8-nRnCR′2C5H4)ZrCl2 (n = 1, 2; R = alkyl, aryl; R′ = Me, Ph)
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Substituents in the positions 3, 4, 5 and 6 of the fluorenylidene fragment clearly influence the polymerization behaviour of the syndiospecific catalyst systems (C13H8-nRnCR′2C5H4)ZrCl2/MAO (n = 1, 2; R = alkyl, aryl; R′ = Me, Ph). We report seven new catalyst precursors of this type, including first polymerization results. An X-ray study of the 4,5-dimethyl derivative 10b explains the reduced activity and stereospecifity of this catalyst.
- Alt, Helmut G.,Zenk, Roland,Milius, Wolfgang
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p. 257 - 270
(2007/10/03)
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- Organometallic fluorenyl compounds, preparation, and use
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Benzofluorenyl-containing metallocenes are disclosed along with methods for making the metallocenes. Also disclosed are methods for using the metallocenes as polymerization catalysts. In addition, polymers resulting from such polymerizations are disclosed.
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- Novel Thermal Cyclisation of o-Methylstyrylalkynes to give 2-Alkenylnaphthalenes
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Formation of o-methylstyrylalkynes by flash vacuum pyrolysis of the corresponding stabilised phosphorus ylides at 900 deg C is accompanied by unexpected cyclisation to give 2-alkenylnaphthalenes and deuterium labelling has been used to elucidate the mechanisms involved.
- Aitken, R. Alan,Boeters, Christine,Morrison, John J.
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p. 1303 - 1306
(2007/10/02)
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- BENZOANNELATED VALENCE ISOMERS OF HOMOANNULENES. III. SYNTHESIS AND THERMAL BEHAVIOR OF 5,7,7a,11b-TETRAHYDROBENZO-CYCLOPROPABIPHENYLENE
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The title compound 7, a new dibenzo-(C9H10)hydrocarbon, was synthesized from Cava's angular dimer of benzocyclobutadiene through dibromocarbene addition followed by LiAlH4-reduction.Flow-vacuum pyrolysis of 7 afforded: 1a,9a-dihydro-9H-benzofluorene (10) (new compound), 1,2-dihydro-9H-benzofluorene (11) and 9H-benzofluorene (12).The new compounds were characterized by IR-, UV-, and 1H-NMR data.A reaction mechanism involving radical- and concerted steps is suggested for pyrolysis of 7.
- Bangh, Mircea D.,Hada, Catalina,Draghici, Constantin,Petride, Aurica,Banciu, Anca
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p. 645 - 652
(2007/10/02)
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- Functionalized Enantiomerically Pure -, -, -, and Triblattanes
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The methylene (2, 7, 10) and spirocyclopropane derivatives (8, 11, 12) are made accessible from rac-trishomocubane(mono-, di-, tri-)ones and optically pure unsaturated and benzoannulated - (19, 48), - (30, 53), and D3-symmetrical triblattanes (3, 4) from the enantiomers of these ketones by expeditious (one pot) ring enlargement and olefination procedures.In the case of the central trienes (+)-3/(-)-3, novel members of the (CH)14 family, optical resolution is advantageously postponed to the stage of the intermediate triones (35, 41) and effected via their (R,R)-2,3-butanediol acetals.In the α-diketone series only the dione (70) is sufficiently stable to allow isolation; tetrone 73 and hexone 5 are indirectly identified as quinoxalines 74 and 76; respectively.Tribenzotriblattane (-)-4 is established as the M-helical enantiomer by X-ray crystallography.Generally the thermal stabilization pathway of unsaturated and benzoannulated triblattanes is a cycloreversion with the primary cycloreversion products 2,7>tetradeca-3,5,9,11,13-pentane (78) from rac-3> being unstable under the drastic reaction conditions required.The stereochemical course of the perepoxidation of rac-3 is investigated. - Key Words: Trishomocubanes/ Spirocyclopropanes/ -, -, -, Triblattanes
- Mueller-Boetticher, Hermann,Fessner, Wolf-Dieter,Melder, Johann-Peter,Prinzbach, Horst,Gries, Stefan,Irngartinger, Hermann
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p. 2275 - 2298
(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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- 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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- 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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