759-73-9Relevant academic research and scientific papers
Metal-Free Ring-Expansion Reaction of Six-membered Sulfonylimines with Diazomethanes: An Approach toward Seven-Membered Enesulfonamides
Xia, An-Jie,Kang, Tai-Ran,He, Long,Chen, Lian-Mei,Li, Wen-Ting,Yang, Jin-Liang,Liu, Quan-Zhong
supporting information, p. 1441 - 1444 (2016/02/12)
A new metal-free, ring-expansion reaction of six-membered N-sulfonylimines with unstable diazomethanes, generated in situ from the N-tosylhydrazones, has been developed. This reaction delivers valuable seven-membered enesulfonamides by a Tiffeneau-Demjanov rearrangement and intramolecular proton transfer tautomerization process. Moreover, this ring-expansion reaction can be carried out in a one-pot fashion and scaled up to the gram scale by using aryl aldehydes, without the need to isolate the N-tosylhydrazone. A diazo thing: The title reaction between cyclic N-sulfonylimines and diazo compounds generated in situ from the N-tosylhydrazones is simple and functional-group tolerant. It thus delivers valuable seven-membered sulfonamides in up to 95 % yield. Moreover, this reaction can be carried out in one-pot starting from the aryl aldehydes, without the need to isolate the N-tosylhydrazone (right).
Synthetic approaches to the daucane sesquiterpene derivatives employing the intramolecular Buchner cyclisation of α-diazoketones
Foley, David A.,O'Leary, Patrick,Buckley, N. Rachael,Lawrence, Simon E.,Maguire, Anita R.
, p. 1778 - 1794 (2013/03/13)
The use of the intramolecular Buchner cyclisation of an α-diazoketone as an approach to the synthesis of daucane sesquiterpenes is described; in particular the synthesis of the cis-fused analogue of dihydro CAF-603. The key step in the synthesis is the intramolecular Buchner cyclisation, which provides the bicyclo[5.3.0]decane framework with the required stereochemistry at the quaternary centre generated in the cyclisation. A synthetic route enabling access to an asymmetric synthesis is also outlined.
Application of N-nitrosoureas in the synthesis of organophosphorus compounds
Afshar, Davood Aghaei,Islami, Mohammad Reza
scheme or table, p. 509 - 511 (2009/04/06)
N-nitrosoureas which are readily accessible from the reaction of urea derivatives with sodium nitrite and aqueous H2SO4 reacted with acetylenic esters in the presence of Ph3P in ethyl acetate at ambient pressure to give stable phosphorus ylides. This methodology is introduced as a simple and inexpensive procedure for the preparation of organophosphorus compounds in excellent yields.
Kinetic study of the nitrosation of N-alkylureas in dioxane-acetic acid mixtures
Alatorre,Zapiain,Quintana,Martinez
, p. 145 - 150 (2007/10/03)
The rate constants were determined for the nitrosation reactions of the following substrates: Methyl (MU), Ethyl (EU), Propyl (PU)Butyl (BU), and Allylurea (AU). The rate equation found at a constant pH was: v = k[HNO2] [Urea]. The reactions were carried out in predominantly organic media(dioxane-acetic acid-water) with differing polarities. The proposed reaction mechanism involves the proton transfer from the protonated N-alkyl-N-nitrosourea to the acetate anion. As the polarity of the medium decreased, an approximation of the rate constants of the nitrosation of the different substrates was observed. This approximation can be interpreted as a function of the impediment generated by the R alkyl radical in the rate controlling step. Accordingly, the substrate reactivity will be associated with the ease in which the protonated N-alkyl-N nitrosurea can transfer the proton to the acetate anion. The results achieved in this study are in accordance with there activities observed in the nitrosation of these substrates in aqueous media MU ? (EU ≈ PU ≈ BU) > AU.
The nitrosation of N-alkylureas: Evidence for a proton transfer mechanism
Casado, Iulio,Gonzalez-Alatorre, Guillermo,Izquierdo, Carmen,Brunner, Christian
, p. 307 - 313 (2007/10/03)
The kinetics of the nitrosation of methyl, ethyl, propyl, butyl, and allyl urea were studied by conventional and stopped-flow spectrophotometry in the presence or absence of acetate or mono-, di-, or trichloroacetate anions In the presence of a large excess of urea, the observed rate equation was chemical equations presented where Ka is the acidity constant of nitrous acid and KR that of the carboxylic acid The ureas exhibited the reactivity order methylurea ? (ethylurea ≈ propylurea ≈ butylureal ? allylurea. Experiments in D2O afforded values of kH2O/kD2O in general agreement with the values 4.1-5 5 predicted by a semiclassical transition state theory of kinetic isotope effects [i.e., kH2O/kD2O = exp(0.130hv/kT)]where v is the frequency of R3N - H stretching (2700-2250 cm-1) in the protonated urea. This result, the observed catalysis by carboxylate ions and the value of the Bronsted parameter β(0.45) show the rate-controlling step of these reactions to be the transfer of a proton from the protonated N-alkyl-N-nitrosourea to the solvent or to the organic anion. if present. The observed order of substrate reactivities is explicable in terms of the capacity of the protonated N-alkyl-N-nitrosourea for forming a hydrogen bond with the water molecule to which the proton will be transferred, and the degree to which the formation of such bonds is hindered by the hydrophobic alkyl chain of the nitrosourea.
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.
