- Studies of Collectors. IX. The Flotation of a Trace Amount of Uranium by Using 2-(Alkylamino)propionohydroxamic Acid and Cotelomer-Type Surfactants Bearing Hydroxyaminocarbonyl and Pyridyl Groups
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Chelating surfactants bearing hydroxyaminocarbonyl and amino groups (RnAHx) and cotelomer-type surfactants bearing hydroxyaminocarbonyl and pyridyl groups (Ls-VP-Q-Hx) were prepared and applied as flotation collectors for a trace amount of uranium.The uranium in an aqueous of pH 4-8 and in seawater was floated more effectively by ion flotation using RnAHx or by foam fractionation using Ls-VP-Q-Hx, compared with alkylhydroxamic acid (RnHx) and telomers bearing hydroxyaminocarbonyl groups (Lo-Hx).The effective floation was concluded to be due to the chelate effects between the two groups on the complex formation and to the HLB of the resulting complex.Furthermore, the uranium recoveries were examined by using a hydroxamic acid polymer (62Hx), a N-methylhydroxamic acid telomer (Ls5.6MHx), and its cotelomer (Ls3.2VP4.5MHx).
- Koide, Yoshifumi,Uchino, Masazumi,Yamada, Kimiho
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- Synthesis of benzothiadiazine-1-oxides by rhodium-catalyzed C-H amidation/cyclization
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A rhodium-catalyzed C-H amidation/cyclization sequence provides benzothiadiazine-1-oxides from sulfoximines and 1,4,2-dioxazol-5-ones in good yields. The reaction is characterized by a high functional group tolerance and, in contrast to most previous transformations of this type, is well-suited for S-alkyl-S-arylsubstituted sulfoximines.
- Bolm, Carsten,Kong, Deshen,Ma, Ding,Shi, Peng,Tu, Yongliang,Wang, Chenyang
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- Racemization free longer N-terminal peptide hydroxamate synthesis on solid support using ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate
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A facile, efficient, racemization-free, and environment friendly protocol for the synthesis of peptide hydroxamic acids directly from carboxylic/amino acids by ethyl 2-(tert-butoxycarbonyloxyimino)-2-cyanoacetate in the presence of DIPEA/DMAP at room temperature is described. The compatibility of this method with Fmoc based solid phase peptide synthesis (SPPS) is also demonstrated by synthesizing three relatively large N-terminal peptide hydroxamic acids on resin. Also, some biologically important hydroxamates are synthesized using this protocol.
- Manne, Srinivasa Rao,Thalluri, Kishore,Giri, Rajat Subhra,Paul, Ashim,Mandal, Bhubaneswar
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- The mechanism of dephosphorylation of bis(2,4-dinitrophenyl) phosphate in mixed micelles of cationic surfactants and lauryl hydroxamic acid
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(Figure Presented) Mixed micelles of cetyltrimethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the α-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl) phosphate (BDNPP) over the pH range 4-10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 104-fold faster than its spontaneous hydrolysis, and monoanionic LHA- is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, and (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate.
- Silva, Marcelo,Mello, Renata S.,Farrukh, M. Akhyar,Venturini, Janio,Bunton, Clifford A.,Milagre, Humberto M. S.,Eberlin, Marcos N.,Fiedler, Haidi D.,Nome, Faruk
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- Thioether-Directed NiH-Catalyzed Remote γ-C(sp3)-H Hydroamidation of Alkenes by 1,4,2-Dioxazol-5-ones
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A NiH-catalyzed thioether-directed cyclometalation strategy is developed to enable remote methylene C-H bond amidation of unactivated alkenes. Due to the preference for five-membered nickelacycle formation, the chain-walking isomerization initiated by the NiH insertion to an alkene can be terminated at the γ-methylene site remote from the alkene moiety. By employing 2,9-dibutyl-1,10-phenanthroline as the ligand and dioxazolones as the reagent, the amidation occurs at the γ-C(sp3)-H bonds to afford the amide products in up to 90% yield (>40 examples) with remarkable regioselectivity (up to 24:1 rr).
- Chen, Qishu,Du, Bingnan,Ouyang, Yuxin,Yu, Wing-Yiu
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supporting information
p. 14962 - 14968
(2021/09/29)
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- Method for synthesizing hydroximic acid compound
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The invention discloses a method for synthesizing a hydroximic acid compound. The method comprises the step of subjecting an organic carboxylic acid compound with a structure represented by a formula(I) shown in the description and a hydroxylamine compound with a structure represented by a formula (II) shown in the description to a grinding reaction in the presence of a coupling reagent, therebypreparing the hydroximic acid compound with a structure represented by a formula (III) shown in the description. According to the method, the technical problems that a large amount of organic solventis used, the reaction temperature is high, wastes are plenty, the aftertreatment is complicated, environmental protection is adverse and the like are solved, and the method has the advantages that thesource of the raw materials is wide, the cost is low, the operation is simple, the efficiency is high, the product is easy to separate, the yield is high, industrial production is easy to achieve andthe like.
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Paragraph 0089; 0090
(2019/06/13)
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- Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate-mediated lossen rearrangement: Single-pot racemization-free synthesis of hydroxamic acids and ureas from carboxylic acids
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Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.
- Thalluri, Kishore,Manne, Srinivasa Rao,Dev, Dharm,Mandal, Bhubaneswar
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p. 3765 - 3775
(2014/05/20)
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- Lossen rearrangements under heck reaction conditions
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The classical Lossen rearrangement converts activated hydroxamic acids to isocyanates that form numerous products upon their reaction with nucleophiles. We report a simple and highly efficient method of using Heck reaction conditions to initiate Lossen rearrangements of hydroxamic acids. In addition, Lossen rearrangements occur in the presence of palladium(II) acetate or triethylamine, components of the Heck reaction, alone. A potential mechanism is provided to explain this reactivity and these results show that Heck reactions and Lossen rearrangements occur under the same conditions and may provide new methods for facile initiation of Lossen rearrangements.
- AbdelHafez, El-Shimaa M.N.,Aly, Omar M.,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
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supporting information
p. 3456 - 3464
(2015/02/05)
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