N,N,N‐trimethylchitosan (TMC) was prepared by reacting purified chitosan with iodomethane, in the presence of sodium hydroxide, water and sodium iodide, at room temperature. The reaction medium was N‐methyl‐2‐pyrrolidone. Different samples of TMC were obtained by adding to the reaction medium a fixed volume (5.5 mL) of aqueous NaOH solutions at different concentrations (15, 20, 30 and 40 wt.‐%) and carrying out the reactions for 9 or 24 h. The features observed in the 1H and 13C NMR spectra of these chitosan derivatives, in respect of the chemical shift, number and relative intensity of the signals, depended strongly on the excess of NaOH and H3CI added to the reaction medium, but when the lowest excess was employed, the characteristics of the derivative were not affected by the reaction time to the same extent. The average degree of quaternization of these N‐methylated derivatives of chitosan ranged from 10.5% to 44.8%, according to the reaction conditions. Increasing the excess of NaOH, in reactions carried out for 9 h, resulted in TMC samples with progressively higher content of trimethylated sites however, the reaction yields were correspondingly lower and O‐alkylation was favored in these cases.
1H NMR spectrum of sample [AX]24h dissolved in D2O (Cp = 10 g/L). 相似文献
Conversion of a cyclic carbonyl carbon into a quaternary carbon has been effected by a Wittig–Horner reaction with diethyl (N-benzyliden)aminomethylphosphonate and a subsequent alkylation with a protected vinyl ketone. The product was a substrate for spiroannulation after initial hydrolysis. The reaction sequence was carried out as a one-pot reaction. 相似文献
Methyl triflate is an efficient agent for the quaternization of nitropyridines containing an additional electron-withdrawing substituent. When triethyloxonium hexachloroantimonate is used as the quaternizing agent, -elimination occurs with formation of protic pyridinium salt and ethylene.M. V. Lomonosov Moscow State University, 119899 Moscow, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 53–54, January, 2000. 相似文献
The possibility has been studied of converting quaternary 3-anilino-1,5-dimethylpyrazolium salts into 3-anilino-1,5-dimethylpyrazole, the first representative of the 1-alkyl-3-arylaminopyrazoles. The dependence of the reaction direction on the nature of the substituent at position 2 has been clarified. The most effective result was obtained with a cyanoethyl substituent. On boiling the initial salt with aqueous ammonia the target product is isolated in quantitative yield. Syntheses of the initial salts are described. C-Sulfonation was detected on interacting 3-anilino-1-benzoyl-3-methylpyrazole and dimethyl sulfate, with the formation of p-(3-amino-1,2,5-trimethylpyrazolio)benzenesulfonate. 相似文献
New macromolecules such as dendrimers are increasingly needed to drive breakthroughs in diverse areas, for example, healthcare. Here, the authors report hybrid antimicrobial dendrimers synthesized by functionalizing organometallic dendrimers with quaternary ammonium groups or 2‐mercaptobenzothiazole. The functionalization tunes the glass transition temperature and antimicrobial activities of the dendrimers. Electron paramagnetic resonance spectroscopy reveals that the dendrimers form free radicals, which have significant implications for catalysis and biology. In vitro antimicrobial assays indicate that the dendrimers are potent antimicrobial agents with activity against multidrug‐resistant pathogens such as methicillin‐resistant Staphylococcus aureus and vancomycin‐resistant Enterococcus faecium as well as other microorganisms. The functionalization increases the activity, especially in the quaternary ammonium group‐functionalized dendrimers. Importantly, the activities are selective because human epidermal keratinocytes cells and BJ fibroblast cells exposed to the dendrimers are viable after 24 h.
The structure of 2-bromooreoselon, which was prepared by bromination of peucedanin or oreoselon with molecular bromine, was
established. The compositions and structures of the reaction products of this bromide with amines, such as pyridine, triethylamine,
and morpholine, as well as with sodium acetate and potassium hydroxide were studied. The reaction of peucedanin with m-chloroperoxybenzoic acid affords peuruthenicin isobutyrate.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 362—366, February, 2006. 相似文献