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Qiaoling Wei, Feng Zhang, Xiaofang Zhao, Chao Wang, Jianliang Xiao, Weijun Tang
A ruthenium pincer catalyst has been shown to be highly efficient for the hydrogenation of a wide range of α-ketimino esters derived from α-keto esters and chiral 2-methylpropyl-2-sulfinamide, affording chiral aryl glycine derivatives with high yields and diasteroselectivities (20 examples, dr values up to 99 : 1).
June 22, 2017: Organic & Biomolecular Chemistry
M Simon, F Breher
Silyl ligands are of great interest in transition metal coordination chemistry since they exhibit a strong trans-influence and create electron rich metals centres, which are in turn eligible to activate reagents. This review presents and discusses the use of multidentate Si-based ligand systems in transition metal coordination chemistry. These include tri- and tetradentate pincer and scorpionate-type ligands, which have been developed in recent years in order to tailor both steric and electronic properties for achieving a defined control over the reactivity of a transition metal complex...
June 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Bent Lund, Bjarne Mygind-Klavsen, Torsten Grønbech Nielsen, Niels Maagaard, Otto Kraemer, Per Hölmich, Søren Winge, Martin Lind
The Danish Hip Arthroscopy Registry (DHAR) was initiated in January 2012 as a web-based prospective registry. The purpose of this study was to evaluate and report the first registry based outcome data of a national population with radiological and clinical femoroacetabular impingement (FAI) undergoing hip arthroscopic treatment. Our primary hypothesis was that patients undergoing hip arthroscopy would improve significantly in pain, quality of life and sports related outcome measurements in Patient Related Outcome Measures (PROM)...
July 2017: Journal of Hip Preservation Surgery
Fernando M Comba, Pablo A Slullitel, Pedro Bronenberg, Gerardo Zanotti, Martin A Buttaro, Francisco Piccaluga
In order to access and resect the acetabular rim, arthroscopic acetabuloplasty was described with labral detachment. When the chondrolabral junction remains intact, acetabuloplasty and labral refixation can be performed maintaining an unharmed labrum. We aimed to evaluate the outcome of a group of patients treated with arthroscopic acetabuloplasty without labral detachment. During the study period, we retrospectively analysed 44 patients with pincer-type o combined impingement and an intact chondroblabral junction, with an average follow-up of 32 months (range: 27-38)...
July 2017: Journal of Hip Preservation Surgery
J W Thomas Byrd, Kay S Jones
Abductor lesions are increasingly recognized as a source of recalcitrant laterally based hip pain and dysfunction. There is a growing body of evidence that many of these may be amenable to endoscopic repair. To report the demographic data and outcomes of endoscopic hip abductor repair. Twelve patients underwent endoscopic abductor repair with 2-year follow-up. These patients were prospectively assessed with modified Harris hip and iHOT scores. The indications for surgery were clinical and MRI findings of symptomatic abductor tears that had failed conservative treatment...
January 2017: Journal of Hip Preservation Surgery
Matthias Mastalir, Ernst Pittenauer, Günter Allmaier, Karl Kirchner
This study represents the first example of a manganese-catalyzed environmentally benign, practical three-component aminomethylation of activated aromatic compounds including naphtols, phenols, pyridines, indoles, carbazoles, and thiophenes in combination with amines and MeOH as a C1 source. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps which give rise to selective C-C and C-N bond formations, thereby releasing hydrogen and water. A well-defined hydride Mn(I) PNP pincer complex, recently developed in our laboratory, catalyzes this process in a very efficient way, and a total of 28 different aminomethylated products were synthesized and isolated yields of up to 91%...
June 21, 2017: Journal of the American Chemical Society
Masaru Kondo, Masashi Omori, Tsubasa Hatanaka, Yasuhiro Funahashi, Shuichi Nakamura
The first highly enantioselective reaction of allenylnitriles with imines has been developed. Excellent yields and enantioselectivities were observed for the reaction with various imines using chiral Phebim-Pd(II) complexes. This process offers a simple and efficient synthetic route for various functionalized α-vinylidene-β-aminonitriles and their derivatives.
June 19, 2017: Angewandte Chemie
Michael Ho-Yeung Chan, Maggie Ng, Sammual Yu-Lut Leung, Wai Han Lam, Vivian Wing-Wah Yam
Dinuclear alkynylplatinum(II) metallofoldamers with an oligomeric m-phenyleneethynylene backbone have been designed with the incorporation of a sterically undemanding, π-conjugated, and hydrophobic 2,6-bis(N-dodecylbenzimidazol-2'-yl)pyridine pincer ligand. The complex with the optimal chain length has been found to exhibit gelation behavior via stabilization by noncovalent Pt···Pt and π-π stacking interactions in the hierarchical architecture constructed from the single-turn helix. The chain lengths of the complexes have been found to be a critical determinant for their gelation behavior, conformations, and morphologies...
June 16, 2017: Journal of the American Chemical Society
Sivashankar Chandrasekaran, Nader Darwish, Edwin O Chaharbakhshi, Carlos Suarez-Ahedo, Parth Lodhia, Benjamin G Domb
BACKGROUND: Advancements in instrumentation and techniques have extended the scope of hip arthroscopic surgery to treat complex osseous deformities that were previously best addressed with an open approach. Global pincer-type femoroacetabular impingement is an example of an abnormality requiring osseous correction with a technically challenging access point. PURPOSE: To report on the patterns of clinical presentation and intra-articular derangements, radiological associations, and minimum 2-year outcomes after hip arthroscopic surgery in patients with a lateral center edge angle (LCEA) >40° and profunda acetabulae in comparison with matched controls with normal acetabular coverage...
June 1, 2017: American Journal of Sports Medicine
Chanseok Rhee, Tina Le Francois, J W Thomas Byrd, Mark Glazebrook, Ivan Wong
BACKGROUND: Femoroacetabular impingement (FAI) is a well-recognized condition that causes hip pain and can lead to early osteoarthritis if not managed properly. With the increasing awareness and efficacy of operative treatments for pincer-type FAI, there is a need for consensus on the standardized radiographic diagnosis. PURPOSE: To perform a systematic review of the evidence regarding imaging modalities and radiographic signs for diagnosing pincer-type FAI. STUDY DESIGN: Systematic review; Level of evidence, 4...
May 2017: Orthopaedic Journal of Sports Medicine
Miles Wilklow-Marnell, Bo Li, Tian Zhou, Karsten Krogh-Jespersen, William W Brennessel, Thomas J Emge, Alan S Goldman, William D Jones
The pincer-iridium fragment ((iPr)PCP)Ir ((R)PCP = κ(3)-2,6-C6H3(CH2PR2)2) has been found to catalyze the dehydrogenative coupling of vinyl arenes to afford predominantly (E,E)-1,4-diaryl-1,3-butadienes. The eliminated hydrogen can undergo addition to another molecule of vinyl arene, resulting in an overall disproportionation reaction with 1 equiv of ethyl arene formed for each equivalent of diarylbutadiene produced. Alternatively, sacrificial hydrogen acceptors (e.g., tert-butylethylene) can be added to the solution for this purpose...
June 23, 2017: Journal of the American Chemical Society
Luís Fernando Saraiva Macedo Timmers, Antônio M S Neto, Rinaldo W Montalvão, Luiz A Basso, Diógenes S Santos, Osmar Norberto de Souza
Flexibility is involved in a wide range of biological processes, such as protein assembly and binding recognition. EPSP synthase is an enzyme that must undergo a large conformational change to accommodate its ligands into its binding cavity. However, although the structure of EPSP synthase has been determined, its plasticity has not been explored in depth. Therefore, in this work, we extensively examined the influence of the flexibility of Mycobacterium tuberculosis EPSP (MtEPSP) synthase on the function of this protein using classical and replica-exchange metadynamics simulations...
July 2017: Journal of Molecular Modeling
Nikolaus Gorgas, Luis G Alves, Berthold Stöger, Ana M Martins, Luis F Veiros, Karl Kirchner
The synthesis, characterization, and catalytic activity of nonclassical iron(II) polyhydride complexes containing tridentate PNP pincer-type ligands is described. These compounds of the general formula [Fe(PNP)(H)2(η(2)-H2)] exhibit remarkable reactivity toward terminal alkynes. They efficiently promote the catalytic dimerization of aryl acetylenes giving the corresponding conjugated 1,3-enynes in excellent yields with low catalyst loadings. When the reaction is carried out in the presence of pinacolborane, vinyl boronates are obtained...
June 21, 2017: Journal of the American Chemical Society
Elizabeth Suárez, Pablo Plou, Dmitry G Gusev, Marta Martín, Eduardo Sola
This work describes synthetic routes from the known precursor [IrClH{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (1) to new hydride and polyhydride derivatives. Substituting the chloride ligand with triflate leads to the five-coordinate complex [IrH{κO-O3S(CF3)}{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}] (2), which can undergo reversible coordination of water (H2O) or dihydrogen (H2) to generate respectively the cationic derivative [IrH{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}(OH2)2](CF3SO3) (3) or the neutral trans-hydride-dihydrogen [IrH{κO-O3S(CF3)}{κP,P,Si-Si(Me)(C6H4-2-PiPr2)2}(η(2)-H2)] (6) in equilibrium...
June 2, 2017: Inorganic Chemistry
Varadhan Krishnakumar, Basujit Chatterjee, Chidambaram Gunanathan
Activation of the N-H bond of amines by a ruthenium pincer complex operating via "amine-amide" metal-ligand cooperation is demonstrated. Catalytic formyl C-H activation of N,N-dimethylformamide (DMF) is observed in situ, which resulted in the formation of CO and dimethylamine. The scope of this new mode of bond activation is extended to the synthesis of urea derivatives from amines using DMF as a carbon monoxide (CO) surrogate. This catalytic protocol allows the synthesis of simple and functionalized urea derivatives with liberation of hydrogen, devoid of any stoichiometric activating reagents, and avoids the direct use of fatal CO...
May 30, 2017: Inorganic Chemistry
Changho Yoo, Yunho Lee
A T-shaped Ni(I) complex was synthesized using a rigid acridane-based pincer ligand to prepare a metalloradical center. Structural data displays a nickel ion is embedded in the plane of a PNP ligand. Having a sterically exposed half-filled dx2-y2 orbital, this three-coordinate Ni(I) species reveals unique open-shell reactivity including the homolytic cleavage of various σ-bonds, such as H-H, N-N, and C-C.
May 29, 2017: Angewandte Chemie
Sophie Jürgens, Fritz E Kühn, Angela Casini
BACKGROUND: The inherent problems accompanying chemotherapy necessitate the development of new anticancer approaches. The development of compounds that can disrupt cancerous cellular machinery by novel mechanisms, via interactions with proteins and non-canonical DNA structures (e.g. G-quadruplexes), as well as by alteration of the intracellular redox balance, is nowadays focus of intense research. In this context organometallic compounds of the noble metals Pt and Au have become prominent experimental therapeutic agents...
May 29, 2017: Current Medicinal Chemistry
Diane S Lye, Aaron E Cohen, Madeleine Z Wong, Marcus Weck
A direct and facile route toward semitelechelic polymers, end-functionalized with palladated sulfur-carbon-sulfur pincer (Pd(II) -pincer) complexes is reported that avoids any post-polymerization step. Key to our methodology is the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization with functionalized chain-transfer agents. This strategy yields Pd end-group-functionalized materials with monomodal molar mass dispersities (Đ) of 1.18-1.44. The RAFT polymerization is investigated using a Pd(II) -pincer chain-transfer agent for three classes of monomers: styrene, tert-butyl acrylate, and N-isopropylacrylamide...
May 22, 2017: Macromolecular Rapid Communications
Vladislav Vasilenko, Clemens K Blasius, Hubert Wadepohl, Lutz H Gade
A manganese alkyl complex containing a chiral bis(oxazolinyl-methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction under mild reaction conditions (TOF >450 h(-1) at -40 °C). The earth-abundant base-metal catalyst operates at very low catalyst loadings (as low as 0...
May 24, 2017: Angewandte Chemie
Anick Abourachid, Anne-Claire Fabre, Raphaël Cornette, Elizabeth Höfling
The feet are the only contact between the body and the substrate in limbed animals and as such they provide a crucial interface between the animal and its environment. This is especially true for bipedal and arboreal species living in a complex three-dimensional environment that likely induces strong selection on foot morphology. In birds, foot morphology is highly variable, with different orientations of the toes, making it a good model for the study of the role of functional, developmental, and phylogenetic constraints in the evolution of phenotypic diversity...
May 23, 2017: Journal of Anatomy
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