- Trinuclear tris(ansa-metallocene) complexes of zirconium and hafnium for olefin polymerization
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New platforms for trinuclear complexes, 1,3,5-tris(fluoren-2-yl-R)benzene (Ph{2-FluRH}3; R = H (2a), 6-tBu (2b), 7-tBu (2c), Tet (2d) (Tet = 2,2,5,5-tetramethyl-tetrahydrobenzofluorene), were synthesized via an acid-catalyzed cyclotrimerization of the corresponding substituted 2-acetylfluorenes. Subsequent nucleophilic addition of the [Ph{2-FluR}3]3? trianions onto 6,6,-dimethylfulvene afforded the corresponding isopropylidene-bridged pro-ligands Ph{Me2C(2-FluRH)(C5H5)}3 (3a-d). Discrete trinuclear tris(dichloro-ansa-zirconocene and hafnocene), Ph[{Me2C(2-FluR)(C5H4)}MX2]3 (X = Cl: 4b-d-Zr, 4c,d-Hf) were prepared by salt metathesis reactions. Some zirconium complexes were further alkylated towards the corresponding tris(dialkyls) (X = Me: 5c,d-Zr; X = CH2SiMe3: 6c-Zr). The structures of these metal complexes were determined by elemental analyses, and by 1D, inverse 2D heteronuclear correlation, and DOSY NMR spectroscopy, as well as by theoretical computations. Those studies revealed the existence of two isomers, of C3 and C1 symmetry respectively, originating from the mutual orientation of the three ansa-metallocene fragments. Preliminary studies on the catalytic performances of the dichloro complexes, upon activation with MAO, in ethylene and propylene homopolymerization and ethylene/1-hexene copolymerization were carried out and compared to those of the monometallic analogues under identical conditions.
- Jende, Lars N.,Vantomme, Aurelien,Welle, Alexandre,Brusson, Jean-Michel,Carpentier, Jean-Fran?ois,Kirillov, Evgueni
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- Palladium-catalyzed synthesis of fluorenes by intramolecular c(sp 2)-h activation at room temperature
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The synthesis of fluorenes by intramolecular Pd-catalyzed C(sp 2)-H activation of 2-arylbenzyl chlorides was conducted at room temperature by using commercially available triphenylphosphine and pivalic acid as ligands. The desired reactions proceeded efficiently at room temperature, and various substrates were converted into the corresponding fluorene derivatives in excellent yields.
- Fujihara, Tetsuaki,Tanji, Yutaka,Tsuji, Yasushi
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supporting information
p. 805 - 808
(2020/05/19)
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- Metal-Free and Redox-Neutral Conversion of Organotrifluoroborates into Radicals Enabled by Visible Light
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Converting organoboron compounds into the corresponding radicals has broad synthetic applications in organic chemistry. To achieve these transformations, various strong oxidants such as Mn(OAc)3, AgNO3/K2S2O8, and Cu(OAc)2, in stoichiometric amounts are required, proceeding by a single-electron transfer mechanism. Established herein is a distinct strategy for generating both aryl and alkyl radicals from organotrifluoroborates through an SH2 process. This strategy is enabled by using water as the solvent, visible light as the energy input, and diacetyl as the promoter in the absence of any metal catalyst or redox reagent, thereby eliminating metal waste. To demonstrate its synthetic utility, an efficient acetylation to prepare valuable aryl (alkyl) methyl ketones is described and applications to construct C?C, C?I, C?Br, and C?S bonds are also feasible. Experimental evidence suggests that triplet diacetyl serves as the key intermediate in this process.
- Liu, Wenbo,Liu, Peng,Lv, Leiyang,Li, Chao-Jun
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supporting information
p. 13499 - 13503
(2018/09/25)
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- Biocatalysis with the milk protein β-lactoglobulin: Promoting retroaldol cleavage of α,β-unsaturated aldehydes
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Enzymes with a hydrophobic binding site and an active site lysine have been suggested to be promiscuous in their catalytic activity. β-Lactoglobulin (BLG), the principle whey protein found in milk, possesses a central calyx that binds non-polar molecules. Here, we report that BLG can catalyze the retro-aldol cleavage of α,β-unsaturated aldehydes making it a naturally occurring protein capable of catalyzing retro-aldol reactions on hydrophobic substrates. Retroaldolase activity was seen to be most effective on substrates with phenyl or naphthyl side-chains. Use of a brominated substrate analogue inhibitor increases the product yield by a factor of three. BLG's catalytic activity and its ready availability make it a prime candidate for the development of commercial biocatalysts.
- Gowda, Vishruth,Foley, Brendan,Du, Jasmine,Esteb, Megan,Watanabe, Coran M. H.
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supporting information
p. 2210 - 2213
(2018/04/05)
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- Synthesis of Fluorenes Starting from 2-Iodobiphenyls and CH2Br2 through Palladium-Catalyzed Dual C-C Bond Formation
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A facile and efficient approach is developed for the synthesis of fluorene and its derivatives starting from 2-iodobiphenyls and CH2Br2. A range of fluorene derivatives can be synthesized under relatively mild conditions. The reaction proceeds via a tandem palladium-catalyzed dual C-C bond formation sequence through the key dibenzopalladacyclopentadiene intermediates, which are obtained from 2-iodobiphenyls through palladium-catalyzed C-H activation.
- Shi, Guangfa,Chen, Dushen,Jiang, Hang,Zhang, Yu,Zhang, Yanghui
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p. 2958 - 2961
(2016/07/06)
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- Direct catalytic cross-coupling of alkenyllithium compounds
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A catalytic method for the direct cross-coupling of alkenyllithium reagents with aryl and alkenyl halides is described. The use of a catalyst comprising Pd2(dba)3/XPhos allows for the stereoselective preparation of a wide variety of substituted alkenes in high yields under mild conditions. In addition (1-ethoxyvinyl)lithium can be efficiently converted into substituted vinyl ethers which, after hydrolysis, give readily access to the corresponding methyl ketones in a one pot procedure.
- Hornillos, Valentn,Giannerini, Massimo,Vila, Carlos,Faans-Mastral, Martn,Feringa, Ben L.
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p. 1394 - 1398
(2015/02/19)
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- Sterically expanded CGC catalysts: Substituent effects on ethylene and α-olefin polymerization
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Several analogues of the sterically expanded constrained geometry catalyst Me2Si(η1-C29H36) (η1-N-tBu)ZrCl2·OEt2 (2) were synthesized to assess the effect on branching and molecular weight for ethylene homopolymerization. Catalysts based on tetramethyltetrahydrobenzofluorene (TetH), ethylTetH, t-butylTetH, and octamethyloctahydrodibenzofluorenyl (OctH) bearing a diphenylsilyl bridge were prepared and characterized: Me 2Si(η5-C21H22) (η1-N-tBu)ZrCl2 (3); Me2Si(η 5-C23H26)(η1-N-tBu)ZrCl 2 (4); and Me2Si(η5-C25H 30)(η1-N-tBu)ZrCl2 (5); Me 2Si(η5-C21H22) (η1-N-tBu)ZrMe2 (6); and Ph2Si(η 5-C29H36)(η1-N-tBu)ZrCl 2 (7). Complexes 4, 5, 6, and 7 were characterized by X-ray crystallography and displayed η5 hapticity to the carbon ring in each case, in contrast to 2. In comparison to 2, complexes 3, 4, 5, and 7 (in combination with methylaluminoxane = MAO) showed diminished branching, higher molecular weight, and higher polydispersity indices for obtained ethylene homopolymers. While 4/MAO produced the greatest molecular weight polymers, no branching was observed. Reactivity ratios were determined for the copolymerization of ethylene and 1-decene with 2/MAO. A value of r ethylene = 14.9 and an exceedingly high value of r1-decene = 0.49 were found - in line with previous reports of this catalyst's unusual affinity for α-olefins.
- Chai, Jianfang,Abboud, Khalil A.,Miller, Stephen A.
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p. 9139 - 9147
(2013/07/27)
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- Molecular engineering of organic sensitizers with planar bridging units for efficient dye-sensitized solar cells
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Here comes the sun: Three highly efficient organic sensitizers with sterically hindered fluorenyl units and planar indenothiophene derivatives were designed and synthesized (see figure). Devices based on one of these compounds, JK-303, gave overall conversion efficiencies of 8.69, 9.04, 7.27, and 5.82 % using I-/I3-, CoII/CoIII, polymer gel, and solid-state electrolytes, respectively. These efficiencies are some of the highest reported for DSSCs based on organic sensitizers. Copyright
- Lim, Kimin,Ju, Myung Jong,Na, Jongbeom,Choi, Hyeju,Song, Min Young,Kim, Byeonggwan,Song, Kihyung,Yu, Jong-Sung,Kim, Eunkyoung,Ko, Jaejung
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supporting information
p. 9442 - 9446
(2013/07/26)
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- The synthesis, crystal structures and photophysical properties of a series of novel 4,6-diphenyl-1,9-anthrazolines
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The synthesis and properties of a series of nine new 4,6-diphenyl-1,9- anthrazolines molecules 1a-1i are reported. Compounds 1a-1i were synthesized by Friedl?nder condensation of 4,6-dibenzoyl-1,3-phenylenediamines and acetyl-functionalized compounds in the presence of polyphosphoric acid as catalyst, in yields ranging from 60% to 94%. The 4,6-diphenyl-1,9-anthrazolines are thermally robust with high decomposition temperatures (>371.0 °C) and high melt transitions (215.1-322.8 °C). Compounds 1a and 1f crystallized in the triclinic system with the space groups P-1. All of them show the lowest energy absorption bands (λmaxAbs: 397-454 nm), revealing low optical band gaps (2.55-3.00 eV). The compounds emit blue fluorescence with λmaxEm ranging from 432 to 493 nm in dilute toluene solution. 4,6-Diphenyl-1,9-anthrazolines 1a-1i have a formal reduction potential in the range -1.02 to -1.19 V (versus SCE) and estimated electron affinities (LUMO levels) of 3.21-3.38 eV. These results demonstrate that the new 4,6-diphenyl-1,9-anthrazolines are promising thermally stable n-type semiconductors for organic electronics.
- Zhang, Qin,Jiang, Peng,Wang, Kunyan,Song, Guangliang,Zhu, Hongjun
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experimental part
p. 89 - 97
(2012/01/06)
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- Synthesis and luminescent properties of branched oligophenylenefluorenes
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The spectrophotometric and luminescence studies on branched oligophenylenefluorenes have shown that the incorporation of n-octyl groups to the 9-position of the fluorene moiety does not interrupt the conjugation of internodal luminophore moieties, and there is also no aggregation or excimer emission both for functionalized and nonfunctionalized macromolecules in solution.
- Kovalev, Aleksei I.,Shapovalov, Aleksei V.,Sukhorukova, Evgeniya V.,Sergeev, Alexander M.,Peregudov, Alexander S.,Rusanov, Alexander L.,Khotina, Irina A.
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scheme or table
p. 9 - 11
(2012/04/10)
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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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- Synthesis and liquid crystal phase behaviour of 2-(4-cyanophenyl)-7-n-alkylfluorenes: Luminescent mesogens
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A new range of nematic liquid crystals containing the 2-phenylfluorene core has been prepared which may be considered as a model system for luminescent mesogens, which have potential interest as new display materials.
- Boardman, Frederick H.,Dunmur, David A.,Grossel, Martin C.,Luckhurst, Geoffrey R.
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- An N.M.R. Investigation of the Mills-Nixon Effect
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The 4J coupling constant, previously established as a probe of bond order, was used to examine the bond orders in a series of ortho-bridged compounds: benzocyclopropene, 1,2-dihydrobenzocyclobutene, indan and tetralin.No evidence for sterically induced bond fixation (i.e. the Mills-Nixon effect) was found, but some evidence for electronic distortion in the corresponding benzylic ketones was observed.The experimental results are in accord with SCF/MO calculations.
- Collins, Michael J.,Gready, Jill E.,Sternhell, Sever,Tansey, Charles W.
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p. 1547 - 1557
(2007/10/02)
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- 2-(Trifluoromethylsulfonyloxy)pyridine as a Reagent for the Ketone Synthesis from Carboxylic Acids and Aromatic Hydrocarbons
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A new reagent 2-(trifluoromethylsulfonyloxy)pyridine (TFOP) was prepared by the reaction of sodium salt of 2-pyridinol with trifluoromethylsulfonyl chloride in dioxane.The conpound TFOP in trifluoroacetic acid has been found to intermolecularly dehydrate from benzoic acid and aromatic hydrocarbons to give the corresponding benzophenones in high yield.It was further elucidated, in the reaction of fluorene, that a variety of carboxylic acids can be used as the acyl precursor for the aromatic ketone synthesis in conjunction with the TFOP/TFA system.This acylation procedure has been applied to the synthesis of 2-acylthiophenes, which are hard to prepare in a satisfactory yield by the classical Friedel-Crafts reaction using aluminum chloride as the catalyst.
- Keumi, Takashi,Yoshimura, Kiichiro,Shimada, Masakazu,Kitajima, Hidehiko
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p. 455 - 460
(2007/10/02)
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- Trifluoroacetic Acid-catalysed Transacylation of Arenes by Acylpentamethylbenzene
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Facile transacylation between acylpentamethylbenzene and activated arenes such as anisole was found to occur in boiling trifluoroacetic acid (TFA).The mechanism for the transacylation between acetylpentamethylbenzene (AcPMB) and anisole with TFA was elucidated by means of product isolation and kinetics.The reaction proceeds via reversible protodeacetylation of AcPMB involving an ipso-protonated intermediate B to give pentamethylbenzene and acetic trifluoroacetic anhydride followed by irreversible acetylation of anisole by the mixed anhydride.The mechanism resulting in an ipso-protonated intermediate B was deduced from the reaction of acetylmesitylene with TFA as well as from the rate of deacetylation of 3,5-dideuterioacetylmesitylene with TFA.The formation of such an intermediate was also independently confirmed by 13C n.m.r. spectroscopic syudies on AcPMB in superacid solutions under stable conditions.
- Keumi, Takashi,Morita, Toshio,Shimada, Takanobu,Teshima, Naomi,Kitajima, Hidehiko,Prakash, G. K. Surya
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p. 847 - 852
(2007/10/02)
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- Synthesis, molecular and electron transport properties of 2-alkyltrinitrofluoren-9-ones
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2-Alkyltrinitrofluoren-9-ones 2 were conveniently synthesized by controlled nitration of 2-alkylfluoren-9-ones 5 with a mixture of red fuming HNO3, and concentrated H2SO4 at 0-25 deg C.The precursors 5 were derived from the corresponding 2-acylfluorenes by appropriate reduction of the acyl function, followed by base-catalysed O2-oxidation at the C-9 position.The regiochemistry of nitration was interesting: with a sterically bulky substituent in 5, nitration occurred at C-4, -5, and -7 positions, affording 2-alkyl-4,5,7-trinitrofluoren-9-one in over 35percent yield; on the other hand, 5 with a primary alkyl function underwent nitration predominantly at C-3, -5, and 7- positions.By virtue of its alkyl function, 2-alkyltrinitrofluoren-9-one 2 displayed better solubility and polymer compatibility characteristics than its non-alkylated analog, TNF.However, the charge transfer interactions of 2 with electron donors were weaker than those of TNF, despite the fact that they both have the same electron affinity.Both 2 and TNF exhibited good electron transport properties in poly(N-vinylcarbazole) matrices.
- Ong, Beng S.,Keoshkerian, Barkev,Martin, Trevor I.,Hamer, Gordon K.
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p. 147 - 152
(2007/10/02)
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- N-Acylimidazoles-Trifluoroacetic Acid System as the Acylating Agent for Aromatic Hydrocarbons
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N-Benzoylimidazole in trifluoroacetic acid could benzoylate electron-rich aromatic compounds, such as durene, p-dimethoxybenzene, mesitylene, anisole, thiophene, and fluorene, to give the corresponding benzophenone derivatives in good yields.It was further elucidated, in the reaction of fluorene, that N-acylimidazoles composed of a variety of acyl groups also could be used for the ketone synthesis.Therein, the imidazolides of aliphatic carboxylic acids or substituted benzoic acid with an electron-donating group gave ketones in high yields.The above-mentioned aromaticcompounds were also acylated with N-trifluoroacetylimidazole and free carboxylic acids in trifluoroacetic acid.The mechanism for these reactions was assumed to proceed via a mixed anhydride between trifluoroacetic acid.
- Keumi, Takashi,Saga, Hiroshi,Kitajima, Hidehiko
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p. 1638 - 1641
(2007/10/02)
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- Equilibiria in Cyanohydrin Formation from, and the Kinetics of Reduction by Sodium Borohydride of, Substituted Acetylbiphenyls
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Equilibria in cyanohydrin formation from 4'-substituted-4-acetylbiphenyls in 80 percent v/v dioxan-water at 30 deg C and their rates of reduction by sodium borohydride in propan-2-ol at 30, 35, and 40 deg C have been studied.The Hammett equation is obeyed by both these reactions.The ρ values are found to be 0.52 and 0.66 at 30 deg C for cyanohydrin formation and for borohydride reduction, respectively.These results agree with the earlier conclusion that the transmission of electronic effects of substituents is less in the biphenyl than in the benzene system.
- Ananthakrishnanadar, P.,Kannan, N.
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p. 749 - 750
(2007/10/02)
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- Electron acceptor monomers and polymers
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Disclosed are electron acceptor monomers of the formula: STR1 wherein R is STR2 or --H; R' is hydrogen or methyl; X and Y are independently selected from the group consisting of --NO2, halogen, cyano and --CF3 ; Z is oxygen or dicyanomethylene; and A and b can range from 0 to 3; with the proviso that at least one of R is STR3 and polymers prepared therefrom. These monomers and polymers are suitable for use in electrophotographic devices and methods.
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- Medicinal preparation for treatment of viral-etiology diseases
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A medicinal preparation for treatment of viral-etiology diseases contains the bisulphite compound of 2-fluorenonyl-glyoxal in combination with a pharmaceutical vehicle or unctuous base. A method of producing the bisulphite compound of 2-fluorenonyl-glyoxal, viz, the active principle of said medicinal preparation, consists in that fluorene is acylated by dichloroacetyl chloride in the presence of aluminum chloride and phosphoryl chloride in an organic solvent, the resultant 2-ω-dichloroacetylfluorene is oxidized by the salts of chromic acid in an acetic-acid medium at 50°-90° C into 2-ω-dichloroacetylfluorenone which is made to interact with morpholine at 50°-98° C to form 2-ω-dimorpholinoacetylflourenone, or otherwise, fluorenone is acylated by acetic anhydride in an organic solvent in the presence of aluminum chloride, the resultant 2-acetylfluorene is oxidized by chromic acid or by the salts thereof in an acetic acid medium at 50°-90° C to obtain 2-acetylfluorenone which is brominated in an organic solvent at 60°-110° C, the resultant 2-ω-dibromoacetylfluorenone is reacted with morpholine at 50°-98° C to form 2-ω-dimorpholinoacetylfluorenone the latter is hydrolyzed by dilute mineral acids at 20°-100° C into 2-fluorenonyl-glyoxal hydrate which is then made to react with sodium bisulphite in an aqueous-alcohol medium at 60°-80° C to isolate the final product.
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- Fluorenone carboxyle acid esters
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Disclosed are monomers of the formula: STR1 WHEREIN R is STR2 R' is hydrogen or methyl; R" is alkyl of 1-10 carbon atoms; X and Y are independently selected from the group consisting of NO2, halogen, cyano and --CF3 ; Z is oxygen or dicyanomethylene; a and a' can range from 0-3; and n is 1-10. These monomers can be readily polymerized to polymers suitable for use in electrophotographic imaging members and methods.
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