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51.
The 1,1‐ethylboration of alkyn‐1‐yl‐chloro(methyl)silanes, Me2Si(Cl)? C?C? R ( 1 ) and Me(H)Si(Cl)? C?C? R ( 2 ) [R = Bu ( 2a ), CH2NMe2 ( 2b )] requires harsh reaction conditions (up to 20 days in boiling triethylborane), and leads to alkenes in which the boryl and silyl groups occupy cis ((E)‐isomers: 3a , 3b , 5a , 5b ) or trans positions ((Z)‐isomers in smaller quantities: 4b and 6b ). The alkenes are destabilized in the presence of SiH(Cl) and CH2NMe2 units ( 5b , 6b ). NMR data indicate hyper‐coordinated silicon by intramolecular N? Si coordination in 3b and 5b , by which, at the same time, weak Si? Cl? B bridges are favoured. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
52.
Dr. M. Qadri E. Mubarak Dr. Hafiz Saqib Ali Jimei Zhou Prof. Chaoqun Li Prof. Jianliang Xiao Dr. Sam P. de Visser 《欧洲无机化学杂志》2023,26(5):e202200621
High-valent metal-oxo species are typical catalytic cycle intermediates in mono-oxygenases and dioxygenases and commonly react through oxygen atom transfer to substrates. In this work we study a biomimetic model complex with a 1,1’-bis((3,5-dimethylpyridin-2-yl)methyl)-2,2’-bipiperidine ligand system bound to a manganese(IV)-oxo(hydroxo) species and study its formation from manganese(II)-hydroxo and H2O2 as well as its reaction with (S)-1-phenylisochromane through dehydrogenative α-oxygenation. The work utilizes density functional theory methods to explore its catalytic cycle and its reactivity patterns. We show that the manganese(IV)-oxo(hydroxo) species is an active oxidant and preferentially the oxo group abstracts a hydrogen atom from substrate with barriers well lower in energy than those found for hydrogen atom abstraction by the hydroxo group. Interestingly, the rate-determining step is the OH rebound rather than the hydrogen atom abstraction, which would imply they would have limited kinetic isotope effect for the replacement of the transferring hydrogen atom by deuterium. 相似文献
53.
Wenyue Gao Muhammad Saqib Liming Qi Wei Zhang Guobao Xu 《Current Opinion in Electrochemistry》2017,4(1):4-10
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54.
The governing equations of shallow water magnetohydrodynamics describe the dynamics of a thin layer of nearly incompressible and electrically conducting fluids for which the evolution is nearly two-dimensional with magnetic equilibrium in the third direction. A high-resolution central-upwind scheme is applied to solve the model equations considering non-flat bottom topography. The suggested method is an upwind biased non-oscillatory finite volume scheme which doées not require a Riemann solver at each time step. To satisfy the divergence-free constraint, the projection method is used. Several case studies are carried out. For validation, a gas kinetic flux vector splitting scheme is also applied to the same model. 相似文献
55.
Razi MT Asad MH Khan T Chaudhary MZ Ansari MT Arshad MA Saqib QN 《Natural product research》2011,25(20):1902-1907
Plants have been extensively used as a remedy for the treatment of snake bites. The aim of this study was to determine the antivenom potentials of methanolic extract from the aerial parts (leaves and twigs) of Fagonia cretica L. on a haemorrhage induced by venom from Naja naja karachiensis. The haemorrhagic response of venom was dose dependent from 0.1 to 4.0?μg per 1.5?μL phosphate buffer saline (PBS) on vitelline veins of fertilised hens' eggs in their shells. The extract effectively eliminated and neutralised, in a dose-dependent manner, the haemorrhagic activity of snake venom. The minimum effective neutralising dose of F. cretica extract was found to be 15?μg per 1.5?μL PBS. The extract possesses potentials as haemorrhagic inhibitor against snake venom compared to the standard antiserum and various plants reported in the literature. This study also provides a scientific base for the use of F. cretica in traditional medicine for the treatment of snake bite. 相似文献
56.
Shaukat Shujah Niaz Muhammad Saqib Ali Nasir Khalid Muhammad Nawaz Tahir 《Journal of organometallic chemistry》2011,696(15-16):2772-2781
The paper describes the synthesis and structural characterization of six new diorganotin(IV) compounds 1–6, [R2SnL] and a monoorganotin(IV) derivative, C4H9SnClL (7). Here L = N′-(5-bromo-2-oxidobenzylidene)-N-(oxidomethylene)hydrazine ligand with ONO tridentate chelation capability and R = CH3 (1), C2H5 (2), n-C4H9 (3), C6H5 (4), C8H17 (5), tert-C4H9 (6), The packing diagram offers a supramolecular structure for 1 and a dimeric structure for 4 with distorted square-pyramidal and distorted trigonal geometry, respectively. The different geometry of 1 than 4 can be attributed to the presence of intermolecular non-covalent Sn---O and Sn---H interactions in the former. The antifungal, antibacterial, antiurease and antileishmanial activities of these complexes proved them to be active biologically and may be formulated as new metal-based drugs in future. 相似文献
57.
Maity PK Kainz QM Faisal S Rolfe A Samarakoon TB Basha FZ Reiser O Hanson PR 《Chemical communications (Cambridge, England)》2011,47(46):12524-12526
The utilization of a monomer-on-monomer (MoM) intramolecular Mitsunobu cyclization reaction employing norbornenyl-tagged (Nb-tagged) reagents is reported for the synthesis of benzofused thiadiazepine-dioxides. Facile purification was achieved via ring-opening metathesis (ROM) polymerization initiated by one of three metathesis catalyst methods: (i) free metathesis catalyst, (ii) surface-initiated catalyst-armed silica, or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles. 相似文献
58.
Zia‐ur‐Rehman Niaz Muhammad Afzal Shah Saqib Ali Ezzat Khan 《Heteroatom Chemistry》2012,23(6):560-567
Four triorganotin derivatives of general formula C10H10NS2SnR3,, where R = CH3 ( 1 ), C4H9 ( 2 ), C6H11 ( 3 ), and C6H5 ( 4 ), have been synthesized by the metathesis reaction of 1,2,3,4‐tetrahydroisoquinolnium salt of ligand with triorganotin(IV) chloride in the 1:1 ratio. These complexes were characterized by elemental analysis, Raman, IR, multinuclear NMR (1H, 13C, and 119Sn), and mass spectrometry. The crystal structure confirmed a supramolecular zig‐zag chain structure mediated by S–H (2.968 Å) for complex 4 with the central Sn atom exists in a distorted trigonal bipyramidal geometry. A subsequent antibacterial study indicates that the compounds are biologically active. 相似文献
59.
A series of new organotin(IV) derivatives; Me3SnL (1), Bu3SnL (2), Ph3SnL (3), Me2SnClL (4), Bu2SnClL (5), Ph2SnClL (6), Et2SnClL (7) and Et2SnL2 (8) where L = N-(2,3-dimethylphenyl)piperazine-1-carbodithioate have been synthesized and characterized by various analytical techniques. Among these techniques, 1H and 13C NMR were carried out to asses solution structures whereas the solid state structures were confirmed by FT-IR and X-ray single crystal analysis (3, 5 and 8). Crystal structure of complex (3) and (5) showed distorted trigonal bipyramidal geometry and square pyramidal geometry, respectively. The inclination of the structure 5 towards square-pyramidal may be due to the presence of the Sn-Cl?HN-piperazine hydrogen bonds between the adjacent molecules. A supramolecular structure is shown by compound (8), with central tin atom exists in a distorted octahedral geometry. The antibacterial results indicated the profound activity of the compounds against various strains of bacteria. In addition to this, the triorganotin(IV) derivatives were found more active than diorganotin(IV) compounds. 相似文献
60.
Farooq Ali Shah Saqib Ali Saira Shahzadi Corrado Rizzoli Sandra Ianelli 《Journal of chemical crystallography》2011,41(9):1249-1253