3066-65-7Relevant articles and documents
Visible-light photocatalyzed oxidative decarboxylation of oxamic acids: a green route to urethanes and ureas
Pawar, Govind Goroba,Robert, Frédéric,Grau, Etienne,Cramail, Henri,Landais, Yannick
supporting information, p. 9337 - 9340 (2018/08/31)
A sustainable metal-free route to urethanes and ureas based on a photocatalyzed oxidative decarboxylation of oxamic acids is described. The reaction includes in situ generation of an isocyanate from the oxamic acid, using an organic dye as a photocatalyst, a hypervalent iodine reagent as an oxidant and a light source, which trigger the free-radical decarboxylation. This protocol successfully avoids the isolation, purification and storage of carcinogenic isocyanates and allows elaboration of urethanes and ureas in a one-pot process from commercially available sources.
Immobilisation of iron tris(β-diketonates) on a two-dimensional flat amine functionalised silicon wafer: A catalytic study of the formation of urethane, from ethanol and a diisocyanate derivative
Conradie,Conradie,Erasmus
, p. 52 - 59 (2014/06/10)
A series of immobilised iron tris(β-diketonato) catalysts on a Si-wafer was prepared, by covalently anchoring the Fe(β-diketonato) 3 complexes [where β-diketonato = (RCOCHCOR′)-, with 1 = acac (R = CH3; R′ = CH3), 2 = dbm (R = C6H5; R′ = C6H5), 3 = tfaa (R = CH3; R′ = CF3), and 4 = hfaa (R = CF3; R′ = CF3)], onto an aminated functionalised Si-wafer. These new catalysts were characterised by X-ray photo-electron spectroscopy (XPS) and atomic force microscopy (AFM). XPS data revealed that ca. 27-91% of all the amine groups anchored the catalyst, Fe(β-diketonato)3. Different Gaussian peaks could be fitted into the F 1s peak, due to the fluorine either being positioned adjacent to the -C-O-Fe-, or to the -C-N-Fe-. The binding energy of the Fe 2p3/2 peak varied between ca. 710.4 and 711.0 eV, depending on the electron donating properties of the R-groups on the β-diketonato ligands, expressed as the sum of the Gordy group electronegativities of the R-groups in the β-diketonato ligands. The AFM photographs showed that the surface changed dramatically after each treatment: after amination (binding of the aminate silane onto the hydroxylate Si-wafer) the Si-wafer turned from flat with a few spikes, to a very wavy surface with smooth lumps. The surface topography again changed, after covalent anchoring of the iron tris(β-diketonato) complexes, to a nodular surface with poorly defined grain boundaries. These immobilised iron tris(β-diketonato) on Si-wafer catalysts, were evaluated for their catalytic activity, during the formation of hexamethylenediurethane from hexamethylenediisocyanate and ethanol. The TOF varied between 15 and 46 s-1, depending on the electron donating properties of the R-groups on the β-diketonato ligands. The more electron donating the R groups, the higher the TOF.
N-substituted carbamates syntheses with alkyl carbamates as carbonyl source over Ni-promoted Fe3O4 catalyst
Shang, Jianpeng,Guo, Xiaoguang,Shi, Feng,Ma, Yubo,Zhou, Feng,Deng, Youquan
scheme or table, p. 328 - 336 (2011/05/14)
A series of catalysts of magnetic iron oxide containing Ni with different nickel content were prepared with co-precipitation method and tested in the syntheses of N-substituted carbamates from various amines and alkyl carbamates. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 90-98% isolated yield. The catalyst could be recovered based on the magnetic property of the catalyst and reused for five runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption, and Moessbauer spectroscopy analyses. The results showed that the catalytic activity may be derived from the delicate synergy between Ni and Fe species resulted in specific basic sites. Quasi in situ FT-IR and isotopic tracer revealed that the formation of substituted urea was the key step and the N-substituted carbamate was formed via further alcoholysis of the substituted urea.
