39804-96-1Relevant articles and documents
A nonpeptidic reverse-turn scaffold stabilized by urea-based dual intramolecular hydrogen bonding
Medda, Amiya K.,Park, Chul Min,Jeon, Aram,Kim, Hyunwoo,Sohn, Jeong-Hun,Lee, Hee-Seung
supporting information; experimental part, p. 3486 - 3489 (2011/09/12)
A novel nonpeptidic reverse-turn scaffold containing urea fragments that are connected by a conformationally constrained d-prolyl-cis-1,2- diaminocyclohexane (d-Pro-DACH) linker is reported. The scaffold adopts a well-defined reverse-turn conformation tha
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.
Electronic and Steric Effects of Alkyl Group on Denitrosation of 3-Alkyl-1-methyl-1-nitrosothioureas
Isobe, Masayoshi
, p. 2844 - 2848 (2007/10/02)
A series of 3-alkyl-1-methyl-1-nitrosothioureas with R=CH3, C2H5, cyclo-C6H11 (3), (CH3)2CH (4), C2H5(CH3)CH, and (CH3)3C were synthesized and their rates of acid catalyzes (pHH:kD is 1.25 for 4.Except 3, a linear plot of log kR/kMe for the denitrosation of RNHCSN(NO)CH3 vs. ?* provides ρ*=-0.98(r=-0.997).The significant factor affecting the rate determining step of the denitrosation of these N-nitrosothioureas at pH 4.6 is the electronic effect of the substituent at the N3 position.
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.
