781-73-7Relevant articles and documents
Trinuclear tris(ansa-metallocene) complexes of zirconium and hafnium for olefin polymerization
Jende, Lars N.,Vantomme, Aurelien,Welle, Alexandre,Brusson, Jean-Michel,Carpentier, Jean-Fran?ois,Kirillov, Evgueni
, p. 19 - 29 (2018)
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.
Palladium-catalyzed synthesis of fluorenes by intramolecular c(sp 2)-h activation at room temperature
Fujihara, Tetsuaki,Tanji, Yutaka,Tsuji, Yasushi
, p. 805 - 808 (2020/05/19)
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.
Metal-Free and Redox-Neutral Conversion of Organotrifluoroborates into Radicals Enabled by Visible Light
Liu, Wenbo,Liu, Peng,Lv, Leiyang,Li, Chao-Jun
supporting information, p. 13499 - 13503 (2018/09/25)
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.
Biocatalysis with the milk protein β-lactoglobulin: Promoting retroaldol cleavage of α,β-unsaturated aldehydes
Gowda, Vishruth,Foley, Brendan,Du, Jasmine,Esteb, Megan,Watanabe, Coran M. H.
supporting information, p. 2210 - 2213 (2018/04/05)
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.
Synthesis of Fluorenes Starting from 2-Iodobiphenyls and CH2Br2 through Palladium-Catalyzed Dual C-C Bond Formation
Shi, Guangfa,Chen, Dushen,Jiang, Hang,Zhang, Yu,Zhang, Yanghui
, p. 2958 - 2961 (2016/07/06)
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.
Direct catalytic cross-coupling of alkenyllithium compounds
Hornillos, Valentn,Giannerini, Massimo,Vila, Carlos,Faans-Mastral, Martn,Feringa, Ben L.
, p. 1394 - 1398 (2015/02/19)
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.
Molecular engineering of organic sensitizers with planar bridging units for efficient dye-sensitized solar cells
Lim, Kimin,Ju, Myung Jong,Na, Jongbeom,Choi, Hyeju,Song, Min Young,Kim, Byeonggwan,Song, Kihyung,Yu, Jong-Sung,Kim, Eunkyoung,Ko, Jaejung
supporting information, p. 9442 - 9446 (2013/07/26)
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
Sterically expanded CGC catalysts: Substituent effects on ethylene and α-olefin polymerization
Chai, Jianfang,Abboud, Khalil A.,Miller, Stephen A.
, p. 9139 - 9147 (2013/07/27)
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.
Synthesis and luminescent properties of branched oligophenylenefluorenes
Kovalev, Aleksei I.,Shapovalov, Aleksei V.,Sukhorukova, Evgeniya V.,Sergeev, Alexander M.,Peregudov, Alexander S.,Rusanov, Alexander L.,Khotina, Irina A.
scheme or table, p. 9 - 11 (2012/04/10)
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.
The synthesis, crystal structures and photophysical properties of a series of novel 4,6-diphenyl-1,9-anthrazolines
Zhang, Qin,Jiang, Peng,Wang, Kunyan,Song, Guangliang,Zhu, Hongjun
experimental part, p. 89 - 97 (2012/01/06)
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.
