- Urazole synthesis. Part 2: Facilitating N4 substitution
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The di-tert-butyl-di-p-nitrophenyl ester of hydrazinetetracarboxylic acid was prepared and shown to be useful in the preparation of urazoles (i.e., 1,2,4-triazolidine-3,5-diones), by reaction with a primary amine using either n-BuLi or pyridine as base, d
- Chai, Weirui,Nguyen, Emily,Doran, Jennifer,Han, Katie,Weatherbie, Alexander,Fernandez, Daniel,Karimi, Sarah,Mynam, Ritwick,Humphrey, Caroline,Rana, Sara,Buynak, John D.
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p. 2308 - 2310
(2013/06/26)
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- An efficient and general urazole synthesis
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A general two-step scheme for the synthesis of N4 substituted urazoles (i.e., 1,2,4-triazolin-3,5-diones) is described. The first step involves the reaction of a primary amine with 2.5 equiv of phenyl chloroformate to produce diphenyl (N-substituted)imidodicarbonates. The second step involves the reaction of these compounds with hydrazine to produce N4 substituted urazoles. The mild reaction conditions permit synthesis of N4 oxygenated urazoles, not available via existing methodology. Bicyclic urazoles can be prepared through the subsequent reaction of these N4-protected urazoles with 2.5 equiv of NaH in DMF together with either 1,3-dibromopropane or 2-(tert-butyldimethylsilyloxy)-1,3- dibromopropane in the presence of NaI. The resultant bicyclic urazoles are observed to display varying degrees of pyrimidalization at N1 and N2, depending on substituents.
- Chai, Weirui,Chang, Yuan,Buynak, John D.
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p. 3514 - 3517
(2012/08/14)
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- Synthetic studies on 4,5-dihydro-3H-1,2,4-triazole-3,5-diones bearing fluorogenic residues at N-4
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A number of fluorescent 4,5-dihydro-3H-1,2,4-triazole-3,5-diones have been made. Intra-inter-electrophilic substitution by the triazoledione moiety on the activated naphthalene ring of 4-[6-(5-dimethylamino-1-naphthylsulfonamido)hexyl]-4,5-dihydro-3H-1,2,4- triazole-3,5-dione 4a3 leads to rapid decomposition. The dienophilicity of the triazoledione moiety in 4-pyren-1-yl-4,5-dihydro-3H-1,2,4-triazole-3,5-dione 4d is dramatically lowered by steric shielding. Insertion of a three-carbon spacer unit into the latter compound, to give the 3-pyren-1-ylpropyl analogue 4e, affords a valuable fluorogenic reagent for the analysis of trace levels of 1,3-dienes. Powdered barium manganate is shown to be an excellent solid-phase oxidant for conversion of urazoles into 1,2,4-triazole-3,5-diones.
- Read, Gordon,Richardson, Nigel R.
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p. 167 - 174
(2007/10/03)
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