598-50-5Relevant articles and documents
Oxidation of 1,3,7-trimethylxanthine by hypochlorite ion
Kheidorov,Ershov,Chalyi,Titorovich
, p. 1358 - 1362 (2011)
The kinetics of the oxidative conversion of 1,3,7-trimethylxanthine upon treatment with hypochlorite ions (OCl-) in aqueous medium at 283-298 K and pH 8.2 was studied. The reaction order with respect to each component was determined and proved to be 1. It was established that the temperature dependence of the reaction rate follows the Arrhenius equation. The activation parameters of the reaction were measured: E a = 33.58 kJ/mol, ΔH ≠ = 31.12 kJ/mol, ΔS ≠ = -170.02 J/(K mol), ΔG ≠ = 81.45 kJ/mol. The stoichiometry of the reaction was studied, and the chemistry of the oxidative conversion of caffeine treated with OCl- is discussed.
The Absence of Nucleophilic Catalysis in the Nitrosation of Amides. Kinetics and Mechanism of the Nitrosation of Methylurea and the Reverse Reaction
Hallett, Geoffrey,Williams, D. Lyn H.
, p. 1372 - 1375 (1980)
Rate constants have been determined for the nitrosation of methylurea (MU) in acid solution and also for the reverse reaction, the denitrosation of N-methyl-N-nitrosourea (MNU).The nitrosation reaction is essentially irreversible at the low acidities (0.01-0.4M-H2SO4) chosen for the experiments whereas the denitrosation reaction was examined at higher acidities (0.5-2.7M-H2SO4) in the presence of excess of hydrazine sulphate (a trap for free nitrous acid) when it is irreversible.For nitrosation the rate law, rate = k+> was established and there was no catalysis by substantial concentrations of added potassium bromide or potassium thiocyanate.Similarly the rate law for denitrosation was found to be rate = khA (where hA is the acidity function used for the protonation of amides), and again there was no catalysis by added potassium bromide, potassium thiocyanate,or thiourea.Te absence of nucleophilic catalysis in the nitrosation of amides had previously been noted and is a puzzling feature when comparison is made with the well established catalysis for amines.This is explained, together with the other observed results, by a detailed consideration of the individual kinetic steps involved in both reactions, and in particular by application of a limiting condition to both forward and reverse reactions in which the actual rate constant for the denitrosation process in an amide is very large compared with the proton transfer to the solvent from the intermediate.
Oxyhalogen-sulfur chemistry: Bromate oxidation of 1-methyl-2-thiourea in acidic medium
Jonnalagadda, Sreekantha B.,Chinake, Cordelia R.,Simoyi, Reuben H.
, p. 13521 - 13530 (1996)
The reaction between bromate and 1-methyl-2-thiourea, CH3NH(NH2)C=S (MTU), has been studied in acidic medium. The stoichiometry of the reaction in excess MTU has been established as 4BrO3- + 3CH3NH-(NH2)C=S + 3H2O → 4Br- + 3SO42- + 3CH3NH(NH2)C=O + 6H+ (A); and in excess bromate the stoichiometry is: 8BrO3- + 5CH3NH(NH2)C=S + H2O → 4Br2 + 5SO42- + 5CH3NH(NH2)C=O + 2H+ (B). Stoichiometry B includes the oxidation of MTU (stoichiometry A) and the oxidation of Br- by the excess BrO3-: BrO3- + 5Br- + 6H+ → 3Br2 + 3H2O. In excess BrO3- the reaction is characterized by an induction period followed by formation of Br2. The reaction between Br2 and MTU is very fast with a bimolecular lower limit rate constant of 2.0 × 106 M-1 s-1 such that the formation of Br2 is an indicator for the complete consumption of MTU. The reaction could be followed by monitoring the depletion of MTU through its absorbance at λ = 239 nm or the formation of Br2 at λ = 390 nm. The rate of reaction was deduced as -d[BrO3-]/dt = k0[BrO3-][MTU][H+]2 with k0 = 14.7 ± 1.2 M-3 s-1. A proposed 17-step reaction mechanism gives good agreement between experimental data and computer simulations.
Regioselective Formal [3+2] Cycloadditions of Urea Substrates with Activated and Unactivated Olefins for Intermolecular Olefin Aminooxygenation
Wu, Fan,Alom, Nur-E,Ariyarathna, Jeewani P.,Na?, Johannes,Li, Wei
supporting information, p. 11676 - 11680 (2019/07/31)
A new class of intermolecular olefin aminooxygenation reaction is described. This reaction utilizes the classic halonium intermediate as a regio- and stereochemical template to accomplish the selective oxyamination of both activated and unactivated alkenes. Notably, urea chemical feedstock can be directly introduced as the N and O source and a simple iodide salt can be utilized as the catalyst. This formal [3+2] cycloaddition process provides a highly modular entry to a range of useful heterocyclic products with excellent selectivity and functional-group tolerance.
Noncanonical RNA Nucleosides as Molecular Fossils of an Early Earth—Generation by Prebiotic Methylations and Carbamoylations
Schneider, Christina,Becker, Sidney,Okamura, Hidenori,Crisp, Antony,Amatov, Tynchtyk,Stadlmeier, Michael,Carell, Thomas
supporting information, p. 5943 - 5946 (2018/04/30)
The RNA-world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth.
A practically simple, catalyst free and scalable synthesis of: N -substituted ureas in water
Tiwari, Lata,Kumar, Varun,Kumar, Bhuvesh,Mahajan, Dinesh
, p. 21585 - 21595 (2018/06/26)
A practically simple, mild and efficient method is developed for the synthesis of N-substituted ureas by nucleophilic addition of amines to potassium isocyanate in water without organic co-solvent. Using this methodology, a variety of N-substituted ureas (mono-, di- and cyclic-) were synthesized in good to excellent yields with high chemical purity by applying simple filtration or routine extraction procedures avoiding silica gel purification. The developed methodology was also found to be suitable for gram scale synthesis of molecules having commercial application in large volumes. The identified reaction conditions were found to promote a unique substrate selectivity from a mixture of two amines.
Activation of 1-methyl-5-nitro-2-pyrimidinone by dearomatization using a secondary amine
Asahara, Haruyasu,Yasuoka, Azusa,Nishiwaki, Nagatoshi
, p. 253 - 259 (2019/04/27)
Electron-deficient 1-methyl-5-nitro-2-pyrimidinone is easily attacked by methanol or pyrrolidine to afford the corresponding adducts, respectively, by which aromaticity of nitropyrimidinone is lost. Indeed, the amine-adduct exhibited higher reactivity than that of original structure to facilitate the reaction with 1,3-dicarbonyl compound leading to diazabicyclic compound at room temperature. The amine-adduct also underwent the ring opening reaction to furnish nitroenamines with (Z)-configuration.
N, O - dimethyl - N - nitro-isourea preparation method
-
Paragraph 0030, (2017/08/24)
The invention discloses a method for preparing N,O-dimethyl-N-nitroisourea by amination reaction, methylation reaction and nitration reaction. The equation is disclosed in the specification. The methyl urea obtained by the amination reaction and the monomethyl sulfate obtained by the methylation reaction can be directly used for the nitration reaction without purification. The cheap and accessible ammonia gas is used as the amination reagent in the amination reaction; in the nitration reaction, the sulfuric acid is used as a catalyst and a reaction solvent, thereby further lowering the raw material cost of the method; and the method has the advantages of mild technological conditions, wide raw material sources, lower production cost, high product quality and high content, and is easy to operate and suitable for industrial production.
Synthesis of 6-azapurines by transformation of toxoflavins and reumycins (7-azapteridines) and their cytotoxicities
Ma, Jun,Yoneda, Fumio,Nagamatsu, Tomohisa
, p. 203 - 210 (2015/02/19)
This paper describes a reliable and facile synthesis of 6-azapurines, 1,5-dimethyl-1H-imidazo[4,5-e][1,2,4]triazin-6(5H)-ones and 5-methyl-5H-imidazo[4,5-e][1,2,4]triazin-6(7H)-ones, by treatment of toxoflavins and reumycins with 10% aqueous or ethanolic sodium hydroxide at 5-70°C or reflux, followed by decarboxylation and oxidation by air along with a benzilic acid type rearrangement. Furthermore, heating the produced 6-azapurines in 10% ethanolic sodium hydroxide afforded the corresponding 1-methyl-5,6-dioxo-1,4,5,6-tetrahydro-1,2,4-triazines with 1-methylurea. The antitumour activities of the 6-azapurines against CCRF-HSB-2 (human T-cell acute lymphoblastoid leukemia) and KB (human oral epidermoid carcinoma) cell lines were also investigated in vitro and some of the compounds showed prospective antitumour activities.
An improved method for the preparation of alkyl/arylurea derivatives using chlorocarbonylsulfenyl chloride as carbonylating agent
Manidhar,K. Uma Maheswara Rao,C. Suresh Reddy,Ch. Syamasunder,Adeppa,Misra, Krishna
, p. 2479 - 2489 (2013/03/13)
A convenient procedure has been developed for preparation of aminesubstituted or monomethylamine-substituted alkyl/arylurea derivatives. The method comprises two steps-reaction of an alkyl/aryl amine with chlorocarbonylsulfenyl chloride in a non-polar solvent to produce an alkyl/arylcarbonylsulfenyl chloride, then reaction of this alkyl/ arylcarbonylsulfenyl chloride with ammonia or monomethylamine in a two-phase reaction with a phase-transfer catalyst, to produce the corresponding alkyl/aryl-substituted urea. Springer Science+Business Media B.V. 2012.
