- Carbene-based lewis pairs for hydrogen activation
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A series of Lewis acidbase pairs containing sterically demanding carbenes were investigated for hydrogen activation that could potentially be reversible for use in hydrogen storage applications. When electron-rich boranes are employed as electrophiles, the imidazolium cation is reduced to a 2H-imidazoline (aminal). The aminals were synthesized independently by reduction of imidazolium cations with strong reducing agents. Carbocations were also found to act as electrophiles for hydrogen activation. Preliminary results revealed that it is possible to reduce an alcohol to an alkane using hydrogen gas as a reducing agent in these systems. Finally, it was demonstrated that a transition metal can be used as an electrophile to activate hydrogen through heterolytic cleavage.
- Runyon, Jason W.,Steinhof, Oliver,Dias, H. V. Rasika,Calabrese, Joseph C.,Marshall, William J.,Arduengo, Anthony J.
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- Synthesis and structure of tritylium salts
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Several tritylium compounds [Ph3C][A] have been isolated by salt metathesis or halide abstraction reactions starting from Ph3C-X (X = halogen) and Lewis acids in good yields (A = BF4, BCl4, AlCl4, GaCl4, PF6, AsF6, SbF6, SbCl6, CHB11H5Cl6, CHB11Cl11, CHB11H5Br6, CF3COO, CF3SO3, N3). The structures of 15 tritylium salts bearing different types of weakly coordinating anions (A-) have been determined. The structures are discussed on the basis of ion pairing versus covalent bond formation and solid-state interactions in comparison with gas-phase data.
- Hinz, Alexander,Labbow, René,Rei?, Fabian,Schulz, Axel,Sievert, Katharina,Villinger, Alexander
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p. 1641 - 1650
(2015/10/28)
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- Optimized synthesis and detailed NMR spectroscopic characterization of the 1,8a-dihydroazulene-1,1-dicarbonitrile photoswitch
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An economical and effective protocol for large scale synthesis of the 2-phenyl-1,8adihydroazulene-1,1-dicarbonitrile (DHA) photoswitch has been developed. This compound is ring-opened by light to a vinylheptafulvene (VHF), which is thermally closed back to DHA. This compound serves as an important starting material for dihydroazulene photoswitches incorporating a substituent in the seven-membered ring and as a reference compound for comparison of properties. A detailed NMR spectroscopic characterization has allowed the assignment of all proton and carbon signals. In addition, the compound was characterized by Xray crystallography. A correlation between the rate constant for thermal ring-closure of VHF to DHA and empirical parameters of solvent polarity (ET (30)) was established. ARKAT-USA, Inc.
- Broman, Soren Lindbaek,Brand, Sophie Lehn,Parker, Christian Richard,Petersen, Michael Axman,Tortzen, Christian Gregers,Kadziola, Anders,Kilsa, Kristine,Nielsen, Mogens Brondsted
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experimental part
p. 51 - 67
(2011/06/19)
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- Synthesis and Isolation of Polytrityl Cations by Utilizing Hexaphenylbenzene and Tetraphenylmethane Scaffolds
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The successful isolation of stable (and soluble) hexa- and tetratrityl cations based on hexaphenyl-benzene and tetraphenylmethane scaffold has been accomplished by using readily available starting materials. These robust polytrityl cations can be isolated in crystalline form and stored indefinitely at 0 °C. Their structures have been established by 1H/ 13C NMR spectroscopy and by UV-vis spectroscopy. The structures of these polytrityl cations were further confirmed by quantitative transformations to the reduced (poly)triphenylmethyl derivatives by hydride transfer from triethylsilane, cycloheptatriene, or a borane-dimethyl sulfide complex.
- Rathore, Rajendra,Burns, Carrie L.,Guzei, Ilia A.
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p. 1524 - 1530
(2007/10/03)
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- Cyclisation reactions of 2-substituted biphenyl-2'-yldiazonium salts leading to O-alkyldibenzofuranium and S-alkyldibenzothiophenium salts: Modified Meerwein reagents
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The preparation of 2-amino-2'-methoxybiphenyl and 2-amino-2'-thiomethoxybiphenyl and analogues and their transformation into diazonium salts and hence into dibenzofuranium and dibenzothiophenium salts is described together with their use as alkylating agents.
- Downie,Heaney,Kemp,King,Wosley
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p. 4005 - 4016
(2007/10/02)
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