30882-95-2Relevant articles and documents
Formation of Aromatic O-Silylcarbamates from Aminosilanes and Their Subsequent Thermal Decomposition with Formation of Isocyanates
Gründler, Franziska,Herbig, Marcus,Kroke, Edwin,Scholz, Henrik,Schwarzer, Sandra,Wagler, J?rg
, p. 2211 - 2224 (2021/06/11)
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.
Chemical transformations of diazoles in the reactions of carboxylation, N-siloxycarbonylation, and transsilylation
Belova,Pletnev,Kirilin
, p. 1365 - 1368 (2013/09/23)
The behavior of 3,5-dimethylpyrazole, 3(5)-methylpyrazole, imidazole and their trimethyl-silyl derivatives in carboxylation, N-siloxycarbonylation, and transsilylation reactions was studied. A new Nsiloxycarbonylation reagent, diazole trimethylsilyl derivative-carbon dioxide, was found. This reagent makes it possible to obtain easily O-silylurethanes starting from primary, secondary amines and hydrazine derivatives, as well as to develop a convenient one pot synthesis method for trimethylsiloxycarbonyldiazoles.
Solvolysis of trimethylsilyl-N-aryl carbamates
Boecskei, Zsolt,Knausz, Dezsoe,Gal, Miklos,Szakacs, Laszlo,Csakvari Bela
, p. 159 - 166 (2007/10/02)
The kinetics of the solvolysis reaction of various trimethylsilyl esters of N-aryl carbamic acid with isopropanol was studied.UV spectrophotometry was used to monitor the reaction and the pseudo first order rate constants were determined.The experiments w
Homogeneous Catalytic Formation of Carbon-Nitrogen Bonds. 2. Catalytic Activation of the Silicon-Nitrogen Bond
Zoeckler, M. T.,Laine, R. M.
, p. 2539 - 2543 (2007/10/02)
The catalytic formation of new carbon-nitrogen single bonds can be promoted via catalytic activation of silicon-nitrogen bonds.Silazanes, compounds containing Si-N bonds, will react, in the presence of a catalyst, with compounds containing carbon-oxygen double bonds to form new C-N and Si-O bonds concurrently.Thus, CO2 and phenyl isocyanate can be reacted with a number of silazane compounds to give urethane and urea derivatives in 60-90percent yields.In the absence of catalysts, the identical reactions either do not proceed or go to less than 20percent conversion.Aldehydes and ketones also react in a similar manner to give imines and enamines, respectively.A variety of group 8 metals have been found to activate the Si-N bond in the catalytic formation of PhCH=NPh from PhNHSiM3 and PhCHO.Iron and rhodium catalysts were found to be the most active for this reaction.The catalytic activation of Si-N bonds was also found useful in the ring-opening oligomerization of in the presence of (Me3Si)2NH.
