2137-74-8Relevant academic research and scientific papers
Hydrogenation and dehydrogenation of pentaphenylcyclopentadienes and pentaphenylcyclopentenes
Kanthak, Matthias,Muth, Enrico,Dyker, Gerald
experimental part, p. 6084 - 6091 (2011/03/17)
Pentaaryl-substituted cyclopentadienes and cyclopentenes have been employed in catalytic hydrogenation and photochemical cyclodehydrogenation reactions, targeting strained bowl-shaped structures. Both types of reactions generally stop at the monohydrogena
The asymmetric aza-claisen rearrangement: development of widely applicable pentaphenylferrocenyl palladacycle catalysts
Fischer, Daniel F.,Barakat, Assem,Xin, Zhuo-Qun,Weiss, Matthias E.,Peters, Rene
supporting information; experimental part, p. 8722 - 8741 (2010/03/31)
Systematic studies have been performed to develop highly efficient catalysts for the asymmetric aza-Claisen rearrangement of trihaloacetimidates. Herein, we describe the stepwise development of these catalyst systems involving four different catalyst generations finally resulting in the development of a planar chiral pentaphenylferrocenyl oxazoline palladacycle. This complex is more reactive and has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza-Claisen rearrange-ments. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza-Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines, but also secondary and tertiary amines; al-lylic amines with N-substituted quaternary stereocenters are conveniently accessible as well. The reaction conditions tolerate many important functional groups, thus providing stereoselective access to valuable functionalized building blocks, for example, for the synthesis of unnatural amino acids. Our results suggest that face-selective olefin coordination is the enantioselectivitydetermining step, which is almost exclusively controlled by the element of planar chirality.
Combined ruthenium(II) and lipase catalysis for efficient dynamic kinetic resolution of secondary alcohols. Insight into the racemization mechanism
Martin-Matute, Belen,Edin, Michaela,Bogar, Krisztian,Kaynak, F. Betuel,Baeckvall, Jan-E.
, p. 8817 - 8825 (2007/10/03)
Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomerically pure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range of functionalized alcohols including heteroaromatic alcohols, and for many of the latter, enantiopure acetates were efficiently prepared for the first time via dynamic kinetic resolution (DKR). Different substituted cyclopentadienyl ruthenium complexes were prepared and studied as catalysts for racemization of alcohols. Pentaaryl-substituted cyclopentadienyl complexes were found to be highly efficient catalysts for the racemization. Substitution of one of the aryl groups by an alkyl group considerably slows down the racemization process. A study of the racemization of (S)-1-phenylethanol catalyzed by ruthenium hydride η5-Ph5CpRu(CO) 2H (8) indicates that the racemization takes place within the coordination sphere of the ruthenium catalyst. This conclusion was supported by the lack of ketone exchange in the racemization of (S)-1-phenylethanol performed in the presence of p-tolyl methyl ketone (1 equiv), which gave 1% of 1-(p-tolyl)ethanol. The structures of ruthenium chloride and iodide complexes 3a and 3c and of ruthenium hydride complex 8 were confirmed by X-ray analysis.
A convenient synthesis of bromopentaarylcyclopentadienes containing methyl or fluorine substituents
Thépot, Jean-Yves,Lapinte, Claude
, p. 179 - 188 (2007/10/03)
The ketones C5(3,5-C6H3Me2)4(O) (5b) and C5-2,5(3,5-C6H3Me2) 2(C6H5)2(O) (5c) were prepared and characterized. The pentaarylcyclopentadienols C5(C6H5)4(Ar′)(OH) (Ar′=3,5-C6H3Me2, 6a3; Ar′=2,4,6-C6H2Me3, 6a5; Ar′=3-C6H4F, 6a6; Ar′=3,5-C6H3F2, 6a7), C5(3,5-C6H3Me2) 4(Ar′)(OH) (Ar′=3-C5H4Me, 6b2; 3,5-C5H3Me2, 6b3; 3,6-C5H3Me2, 6b4; 2,4,6-C5H2Me3, 6b5; Ar′=3-C6H4F, 6a6; Ar′=3,5-C6H3F2, 6a7; Ar′=2,6-C6H3F2, 6a8) were obtained by reaction of the corresponding Ar′Li with the ketones C5(C6H5)4(O) (5a), or C5(3,5-C6H3Me2)4(O) (5b). The synthesis and characterization of the bromopentaarylcyclopentadienes C5(C6H5)4(Ar′)(Br) (Ar′=3,5-C6H3Me2, 7a3; Ar′=2,4,6-C6H2Me3, 7a5) and C5(3,5-C6H3Me2) 4(Ar′)(Br) (Ar′=3-C5H4Me, 7b2; 3,5-C5H3Me2, 7b3; 3,6-C5H3Me2, 7b4; 2,4,6-C5H2Me3, 7b5; Ar′=3-C6H4F, 7a6; Ar′=3,5-C6H3F2, 7a7; Ar′=2,6-C6H3F2, 7a8) containing methyl groups or fluorine atoms on the Ar′ rings are reported. The bromopentaarylcyclopentadienes are isolated as a 1:2:2 mixture of three isomers when Ar and Ar′ are different, except when the latter substituent bears two fluorine or two methyl groups in the ortho positions. In these cases the reaction is regiospecific and provides a unique isomer with the di-ortho-substituted arene located in the β-position with respect to the carbon bearing the bromine atom.
Titan(IV)-Verbindungen mit hochphenylierten ?-Cyclopentadienylliganden. Die Struktur von (?-C5H5)(?-C5Ph5)TiCl2
Thewalt, Ulf,Schmid, Guenter
, p. 343 - 352 (2007/10/02)
The reaction of (?-C5H5)TiCl3 with KC5Ph5 (4-Ph) in THF gives (?-C5H5)(?-C5Ph5)TiCl2 (5-Ph). (?-C5H5)(?-C5Ph4H)TiCl2 (5-H) can be prepared analogously.An X-ray diffraction study on 5-Ph has been undertaken.The Ti-C bond lengths for the C5Ph5 group are con
The Preparation and Characterization of Substituted Pentaphenylcyclopentadienyl Ligands, Their Precursors, and Complexes of Iron
Field, Leslie D.,Ho, Kathy M.,Lindall, Charles M.,Masters, Anthony F.,Webb, Alison G.
, p. 281 - 291 (2007/10/02)
The synthesis and characterisation by infrared, 1H and 13C n.m.r. and mass spectroscopy of the compounds C5Ph4(p-C6H4R)X (R=H, Me, But; X=OH, Br, H), C5Ph4-n(p-C6H4Me)nO (n=1, 2, 4), C5Ph5-n(p-C6H4Me)nX (n= 2, 3; X=OH, Br) and C5Ph4(p-C6H4R)Fe(
Decaphenylgermanocene, -stannocene, and -plumbocene and Pentaphenylstannocene: Synthesis, Properties and CMPAS-Metal-NMR Measurements
Janiak, Christoph,Schumann, Herbert,Stader, Carin,Wrackmeyer, Bernd,Zuckerman, Jerold J.
, p. 1745 - 1752 (2007/10/02)
An improved synthesis is described for pentaphenylcyclopentadienol (1), pentaphenylcyclopentadienyl bromide (2), pentaphenylcyclopentadiene (3), and pentaphenylcyclopentadienyllithium (4a).Decaphenylgermanocene (5), -stannocene (6), and -plumbocene (7) as well as pentaphenylstannocene (8) are prepared.Complete analytical data (IR, Raman, X-ray powder, NMR, mass, and 119mSn-Moessbauer spectra) are given. 119Sn- and 207Pb-CPMAS NMR measurements of various stannocenes and of the plumbocene 7 are reported for the first time.
Ring-Halogenated Carbonyl(η5-cyclopentadienyl)vanadium Complexes
Priebsch, Wolfgang,Hoch, Martin,Rehder, Dieter
, p. 1971 - 1976 (2007/10/02)
Hexacarbonylvanadium reacts with hexachloro- and hexabromocyclopentadiene to form the half-sandwich complexes (η5-C5X5)-V(CO)4 (X = Cl, 1; X = Br, 2).Complex 2 was characterized by X-ray structure analysis.With 1,2,3,4,5-pentachlorocyclopentadiene, (η5-C5HCl4)V(CO)4 (3) is formed along with 1.The reaction between 1,2,3,4-tetrachloro-6-phenylpentafulvene yields (η5-C5Cl4CH2Ph)V(CO)4 (4).Treatment of V(CO)6 with 1,1,3-trichloro- and -bromoindene results in the formation of 3,3'-dihaloindenyl-1-indenylidenes and small amounts of 5-(1,3-dichloroindenyl)>V(CO)4 (5). 1-bromo-1,2,3,4,5-penta phenylcyclopentadiene is debrominated to C5Ph5..
