- One-pot radiosynthesis of [13N]urea and [13N] carbamate using no-carrier-added [13N]NH3
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The aim of this study was to develop a practical labeling method of [ 13N]ligands using no-carrier-added [13N]NH3 with high specific activity. [13N]urea analogues [13N]1a and [13N]2a or [13N]carbamate [13N]3a were synthesized by reacting isocyanate 5a, carbamoyl chloride 6a or chloroformate 7a with [13N]NH3. The precursors 5a-7a were prepared by treating amines 8a and 9a and alcohol 10a with triphosgene in situ. These reaction mixtures were not purified and were used directly for [ 13N]ammonolysis, respectively. Using the one-pot method, we synthesized [13N]carbamazepine ([13N]4), a putative positron emission tomography ligand for brain imaging. Copyright
- Kumata, Katsushi,Takei, Makoto,Ogawa, Masanao,Kato, Koichi,Suzuki, Kazutoshi,Zhang, Ming-Rong
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experimental part
p. 166 - 172
(2010/07/02)
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- KINETICS AND MECHANISM OF METHANOLYSIS OF BENZOYL DERIVATIVES OF SUBSTITUTED PHENYLUREAS AND PHENYLTHIOUREAS
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The methanolysis rate constants and dissociation constants have been measured of benzoyl derivatives of substituted phenylureas and phenylthioureas.The dissociation constants of the thio derivatives are higher by 1 order of magnitude and the rate constants are higher by 2 orders of magnitude than the respective values of the oxygen analogues.Logarithms of the rate and dissociation constants have been correlated with Hammett ? constant; the ρ constant of the methanolysis of the oxygen derivatives is almost 2 * higher than that of the thio derivatives, which is explained by a change in the rate-limiting step.Methylation of the phenyl nitrogen atom increases the acidity by almost 2 orders of magnitude.This effect is due obviously to steric hindrance to the conjugation with the adjacent carbonyl or thiocarbonyl group.
- Kavalek, Jaromir,El Bahaie, Said,Sterba, Vojeslav
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p. 2103 - 2110
(2007/10/02)
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- An efficient synthesis of 1,1-disubstituted hydrazines
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1,1-disubstituted hydrazines were prepared from the corresponding 1,1-disubstituted ureas by means of the Hofmann rearrangement reaction. The yields were fairly good, except from the ureas susceptible to oxidation, and thus the present method represents an additional and efficient procedure for the synthesis of 1,1-disubstituted hydrazines.
- Murakami,Yokoyama,Sasakura,Tamagawa
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p. 423 - 428
(2007/10/02)
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- Some Extensions of von Braun (BrCN) Reaction on Organic Bases: Part II
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Extensions of von Braun Cyanogen bromide reaction on Ephedra alkaloids and simpler bases have resulted in synthesis of substituted oxazolidines and a whole series of nitrogen analogues of ephedrine, desoxy ephedrine and simpler amines.The general applicability and limitations of such extension of the reaction are also discussed. - Key words: von Braun Cyanogen Bromide Reaction
- Malik, Abdul,Afza, Nighat,Siddiqui, Salimuzzaman
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p. 512 - 518
(2007/10/02)
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- Method for preparing acylated products
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Acylation of nitrogen containing compounds utilizing esters as acylation agents in the presence of salts of substituted pyridine compounds.
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