- Formation of Aromatic O-Silylcarbamates from Aminosilanes and Their Subsequent Thermal Decomposition with Formation of Isocyanates
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A novel phosgene-free route to different isocyanates starts from CO2 and aminosilanes (cf. silylamines) to form so-called carbamoyloxysilanes (O-silylcarbamates), i. e., compounds with the general motif R1R2N?CO?O?SiR3R4R5 as potential precursors. We focused on the insertion reaction of CO2 into Si?N bonds of substrates with cyclic (mostly aromatic) amine substituents, i. e., PhNHSiMe3, (PhNH)2SiMe2, PhCH2NHSiMe3, p-(MeO)C6H4NHSiMe3, o-C6H4(NHSiMe3)2, 1,2-C6H10(NHSiMe3)2, o-C6H4(NHSiMe3)(CH2NHSiMe3) and 1,8-C10H6(NHSiMe3)2. Compared to previously investigated aminosilanes these reactions are hindered due to the reduced nucleophilicity/basicity of the N-atoms. Whereas slightly increased CO2 pressure (8 bar) and prolonged reaction times (24 h) were sufficient to overcome hindrance of the insertion into, e. g., PhNHSiMe3, intermolecular effects in some two-fold NHSiMe3 functionalized substrates led to partial mono-insertion (e. g., into o-C6H4(NHSiMe3)(CH2NHSiMe3)) or intra-molecular condensation of the intermediate insertion product in case of 1,8-C10H6(NHSiMe3)2 to form 1H-perimidin-2(3H)-one and other side products. Thermal treatment of mono-silylated O-silylcarbamates RHN?CO?O?SiR’3 resulted mainly in the formation of substituted ureas (RHN)2CO, whereas desired isocyanates could not be detected in these cases. Therefore, we continued our studies focussing on N,O-bissilylated precursors, which were obtained by an additional N-silylation of the O-silylated carbamates. This allowed the successful formation of isocyanates. As a sole byproduct hexamethyldisiloxane is formed. In all cases, known as well as yet unknown substances were characterised by 1H, 13C and 29Si NMR spectroscopy, along with X-ray diffraction analysis for crystallized solids.
- Gründler, Franziska,Herbig, Marcus,Kroke, Edwin,Scholz, Henrik,Schwarzer, Sandra,Wagler, J?rg
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supporting information
p. 2211 - 2224
(2021/06/11)
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- Insertion of phenyl isocyanate into monoand diaminosilanes
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The aminosilanes MenSi(NRR')4-n (n = 2,3) with NRR' = ethylamino (NHEt), n-propylamino (NHnPr), sec-butylamino (NHsBu), n-octylamino (NHnOct), n-dodecylamino (NHnDodec), allylamino (NHAll), tert-butylamino (NHtBu), diethylamino (NEt2), and anilino (NHPh) were synthesized and their reactions with phenyl isocyanate were studied. In all cases of these silanes Me3SiNRR' and Me2Si(NRR')2 formal insertion of the -NCO group into their Si-N bonds was observed, i.e. formation of products with Si-N (rather than Si-O) bonds was found. In some cases, the products could be crystallized and their molecular structures have been elucidated with single-crystal X-ray diffraction analyses.
- Kraushaar, Konstantin,Herbig, Marcus,Schmidt, Dana,Wagler, J?rg,B?hme, Uwe,Kroke, Edwin
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p. 909 - 921
(2018/01/19)
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- New diazasilaphosphetidines and their precursors
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A series of aminosilanes (R′HN)2SiR2 have been prepared. In case of bulky substituents R1 the aminolysis of Ph2SiCl2 stops at the (R′HN)ClSiPh2 stage. Replacement of the Cl atom is achieved with LiNHR′ which allows the synthesis of mixed bisaminosilanes (R′HN)(R″HN)SiPh2. The X-ray structures of three of these compounds have been determined. There are no intermolecular N-H...N hydrogen bonds in these compounds in the solid state. Several 1,3,2,4-diazaphosphetidines have been synthesized using bis(N-lithioamino)silanes and bis(N-lithioamino)phosphanes . Amongst these the heterocycle 18 possesses an almost planar four membered N2SiP ring system.
- Eichhorn, Bettina,Noeth, Heinrich
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p. 352 - 360
(2007/10/03)
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- Synthesis and application of some dianilinosilanes, bis (trimethylsilyl) phenylenediamines and dialkyl benzo-1,3,2-diazasilolines as antioxidants
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A number of dialkyl or diphenyl dianilinosilanes, bis (trimethylsilyl) phenylenediamines and dialkyl benzo-1,3,2-diazasilolines were synthesized and used as antioxidants for lubricating base oils. Thermal analysis methods (DSC, TG and DTG) and IR techniqu
- Ali, Hussein M.,El-Qurashi, Mohamed A. M.
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p. 521 - 529
(2007/10/03)
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- Indirect Nuclear Spin-Spin Coupling Constants of Nitrogen-15 to Silicon-29 in Silylamines
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The 15N-29Si spin-spin coupling constants in silylamines have been measured from 29Si satellites in their natural abundance 15N n.m.r. spectra in an INEPT sequence for accumulation of signals and interpreted in terms of Fermi-contact interaction; the sensitivity of 1J(15N-29Si) to d?-p? bonding was noted.
- Kupce, Eriks,Liepins, Edvards,Pudova, Olga,Lukevics, Edmunds
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p. 581 - 582
(2007/10/02)
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