35103-35-6Relevant academic research and scientific papers
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.
A simple and efficient room temperature silylation of diverse functional groups with hexamethyldisilazane using CeO2 nanoparticles as solid catalysts
Anbu, Nagaraj,Vijayan, Chellappa,Dhakshinamoorthy, Amarajothi
, (2019/06/08)
In this study, a mild and efficient method is developed for the silylation of diverse functional groups using CeO2 nanoparticles (n-CeO2) as solid catalysts with hexamethyldisilazane (HMDS) as silylating agent at room temperature. Alcohols, phenols and acids are silylated to their respective silyl derivatives with faster reaction rate while amines and thiols required relatively longer reaction time. Moreover, the solid catalyst is easily be separated from the reaction mixture and recycled more than five times without any obvious decay in its activity. Powder X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis diffuse reflectance spectra (UV-DRS) and Raman analyses revealed identical structural integrity, particle size, absorption edge and valence state for the reused solid compared to the fresh solid catalyst.
Stoichiometric Reactions of CO2 and Indium-Silylamides and Catalytic Synthesis of Ureas
Xu, Maotong,Jupp, Andrew R.,Stephan, Douglas W.
supporting information, p. 14277 - 14281 (2017/10/31)
The indium compounds In(N(SiMe3)2)2Cl?THF (2) and In(N(SiMe3)2)Cl2?(THF)n (3) were shown to react with CO2 to give [(Me3Si)2N)InX(μ-OSiMe3)]2 (X=N(SiMe3)2 4, Cl 5). 0.05–2.0 mol % of the species 3 acts as a pre-catalyst for the conversion of aryl and alkyl silylamines under CO2 (2–3 atm) to give the corresponding ureas in 70–99 % yields. A proposed mechanism is supported by experimental and computational data.
Generation of Thionitrosoarenes (ArN=S) from N-(Arylaminothio)phthalimides and in situ Trapping with Alkenes and Conjugated Dienes
Bryce, Martin R.,Taylor, Paul C.
, p. 3225 - 3235 (2007/10/02)
A series of N-(arylaminothio)phthalimide derivatives (7a-h) has been prepared by reaction of phthalimidesulphenyl chloride with the trimethylsilyl derivative of the appropriate arylamine.On treatment with triethylamine at room temperature, compounds (7) fragment to yield transient thionitroso species (8).Derivatives (8a-h) have been trapped in good yield as their Diels-Alder adducts with the following conjugated dienes: butadiene, 2.3-dimethylbutadiene, 1.4-diphenylbutadiene, (E,E)- and (E,Z)-hexa-2,4-diene, 1,1'-bicyclopentenyl (25) and 1,1'-bicyclohexenyl (26).The stereochemistry of the diene is retained in the adducts (19)-(24).Thionitrosoarene derivatives (8) also afford sulphenamide derivatives, e.g. (11) and (12)-(16), by ene addition to dimethylbutadiene, isobutene, and α-methylstyrene.N-Aryliminosulphur dichlorides (34) react with 2,3-dimethylbutadiene to yield 1,2-thiazine and sulphenamide products, probably by way of thionitrosoarene intermediates.
