- Dinitrogen tetroxide-impregnated charcoal (N2O 4/charcoal): Selective nitrosation of amines, amides, ureas, and thiols
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Efficient N-nitrosation of amines, amides, and ureas, and also S-nitrosation of thiols were performed with dinitrogen tetroxide impregnated on activated charcoal (N2O4/charcoal) in CH 2Cl2 at room temperature. High selectivity was observed for N-nitrosation of dialkyl amines, N-alkylamides and N-alkylureas. Dealkylation and N-nitrosation of trialkylamines were also performed by this reagent. Copyright Taylor & Francis, Inc.
- Iranpoor, Nasser,Firouzabadi, Habib,Pourali, Ali Reza
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p. 1517 - 1526
(2007/10/03)
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- Selective N-nitrosation of amines, N-alkylamides and N-alkylureas by N2O4 supported on cross-linked polyvinylpyrrolidone (PVP-N2O4)
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N2O4 was supported on the cross-linked polyvinylpyrrolidone (PVP) to afford a solid, stable and recyclable nitrosating agent. This reagent shows excellent selectivity for N-nitrosation of dialkyl amines in the presence of diaryl-, arylalkyl-, trialkylamines and also for secondary amides in dichloromethane at room temperature under mild and heterogeneous conditions. Also N-nitroso-N-alkyl amides can be selectively prepared in the presence of primary amides and N-phenylamides under similar reaction conditions. Selective N-nitrosation or dealkylation and N-nitrosation of tertiary amines can also be performed by this reagent.
- Iranpoor, Nasser,Firouzabadi, Habib,Pourali, Ali-Reza
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p. 1591 - 1597
(2007/10/03)
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- Hydrogen bonding of 2-tetrazenes, 2. Synthesis and structural studies of hydroxyalkyl-substituted 2-tetrazenes
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Five hydroxyethyl-2-tetrazenes (1 - 5) and their methyl ethers (6 - 10) have been synthesized and hydrogen bonding in these compounds has been investigated by theoretical and spectroscopic (IR, 1H NMR, 15N NMR) methods. The structure of 1,1,4,4-tetrakis(2-hydroxyethyl)-2-tetrazene (4) was determined by X-ray diffraction analysis. Several conformations with intramolecular hydrogen bonds were investigated by ab initio B3LYP as well as semiempirical SCF calculations. In all cases, conformers with OH---N hydrogen bonds with azo nitrogen atoms as acceptors (conformers A, B, C) are found as most stable. In compounds with small or flexible N1- and N4- substituents R besides the hydroxyethyl group (3, 4), hydrogen bonds forming six-membered rings, with the R groups taking syn positions at the N1-N2 and N3-N4 bonds (conformer A), are preferred over those with seven-membered rings and R taking anti positions (conformer B). Steric interaction in the other compounds (1, 2, 5) leads to destabilization of conformers A and conformers B become more stable. A special case is presented by compound 4 which has only hydroxyethyl substituents on the 2-tetrazene unit. In the most stable conformer (4C) there are two OH---O and one OH---N hydrogen bonds. By IR solution measurements intra- and intermolecular hydrogen bonds could be distinguished. Association shifts Δδ measured by 1H NMR spectroscopy, indicate that the investigated compounds exhibit comparable association properties with intermolecular association clearly prevailing. 15N NMR spectra of compounds 1 - 10 in two solvents have been measured if solubility was sufficient. The data indicate that all nitrogen atoms of 1 - 5 participate in H bonding. In the crystalline state, molecules 4 adopt a conformation without intramolecular H bonds (4D) and are associated by intermolecular OH---O hydrogen bonds that form a three-dimensional network. An untypical decomposition pattern was discovered for benzyl derivatives 5 and 10.
- Porath, Bernd,Rademacher, Paul,Boese, Roland,Bl?ser, Dieter
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p. 365 - 376
(2007/10/03)
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