39499-81-5Relevant articles and documents
The Use of Ureates as Activators for Samarium Diiodide
McDonald, Chriss E.,Ramsey, Jeremy D.,McAtee, Christopher C.,Mauck, Joseph R.,Hale, Erin M.,Cumens, Justin A.
, p. 5903 - 5914 (2016/07/23)
A novel mode of SmI2 activation has been developed using ureates as reaction promoters. Several ureates formed by treatment of the corresponding ureas with n-BuLi have been shown to activate SmI2 to a substantial extent toward the reduction of 1-chlorodecane. Complexes formed from SmI2 and various ureates have been shown to be useful for the reduction of a variety of organohalides, including substrates of low reactivity such as aryl fluorides. Because of ease of synthesis and low molecular weight, the conjugate base of triethylurea (TEU-) was of primary focus. Visible spectroscopy and reactivity data are consistent with the hypothesis that the same complex is being formed when SmI2 is combined with either 2 or 4 equiv of TEU-, in spite of the greater reactivity of SmI2/4 TEU- with some alkyl halides. We propose that the active reductant is an N,O chelate formed between SmI2 and 2 equiv of TEU-.
Preparation of mono-, di-, and trisubstituted ureas by carbonylation of aliphatic amines with S,S-dimethyl dithiocarbonate
Artuso, Emma,Degani, Iacopo,Fochi, Rita,Magistris, Claudio
, p. 3497 - 3506 (2008/09/19)
General procedures are reported to prepare N-alkylureas, N,N′-dialkylureas (both symmetrical and unsymmetrical), and N,N,N′-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60°C with a molar ratio of DMDTC:amine = 1:2, preferably under nitrogen. Unsymmetrical ureas were prepared in two steps via S-methyl N-alkyl-thiocarbamate intermediates, which are formed selectively in the first step at room temperature. These intermediates react in the second step with ammonia or various aliphatic amines, both primary and secondary, at temperatures varying between 50 and 70°C. All the target ureas were obtained in high yields (28 examples, average yield 94%) and with very high purity (generally >99.2%). Also to be noted is the recovery of a co-product of industrial interest, methanethiol, in an amount of two moles for each mole of DMDTC, with complete exploitation of the reagent. Georg Thieme Verlag Stuttgart.
Conformational Preferences in Alkylnitrosoureas
Snyder, John K.,Stock, Leon M.
, p. 886 - 891 (2007/10/02)
The spectroscopic properties of several N-alkyl-N-nitrosoureas, N,N'-dialkyl-N-nitrosoureas, and N,N',N'-trialkyl-N-nitrosoureas have been studied in carbon disulfide and chloroform solutions.The NH stretching frequencies in the IR spectra have been observed in both concentrated and dilute solution and in the presence of added dioxane.The results indicate that there is a strong intramolecular hydrogen bond in the mono- and dialkylnitrosoureas.The chemical shifts and line widths of the NMR spectra have also been studied in these solvents.The large chemical shift differences, about 1.3 ppm, for the NH protons in the monoalkylnitrosoureas and other spectroscopic features in the monoalkyl- and dialkylnitrosoureas also indicate that an intramolecular hydrogen bond contributes to a strong conformational preference.The temperature dependence of the NMR spectra of several N,N',N'-trialkyl-N-nitrosoureas establishes that the energy barrier for rotation about the carbon dialkylamide bond is about 13 kcal mol-1.Dipolar resonance interactions are primarily responsible for this barrier.This interaction is augmented by a strong, 8-10 kcal mol-1, hydrogen bond in the mono- and dialkylnitrosoureas.
