- Solvent-Free Condensation Reactions to Synthesize Five-Membered Heterocycles Containing the Sulfamide Fragment
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We report a study of the solvent-free condensation reaction of 1,2-dicarbonyl compounds with sulfamide catalyzed by a Keggin-type acid (H3PMo12O40·nH2O, MPA) to obtain 3,4-disubstituted 1,2,5-thiadiazole 1,1-dioxide derivatives. Some reactions were also performed in solution or using nano-sized silica-supported MPA catalyst in order to compare the results under different experimental conditions. Effects of the temperature used for the thermal pretreatment of the catalyst, the reaction temperature, the molar ratios sulfamide/1,2-dicarbonyl compound and MPA/1,2-dicarbonyl compound, and alternative experimental procedures on the yield of the reaction product were investigated. Under suitable experimental conditions eight compounds were obtained in good yields. The catalyst was recycled and reused, but with some loss of its catalytic activity. The presented synthetic method is a simple, clean, and environmentally friendly alternative for synthesizing different 1,2,5-thiadiazole 1,1-dioxide derivatives.
- Arroyo, Nelson Rodríguez,Rozas, María F.,Vázquez, Patricia,Romanelli, Gustavo P.,Mirífico, María V.
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p. 1344 - 1352
(2016/05/02)
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- Enantioselective synthesis of 3,4-disubstituted cis- and trans-1,2,5-thiadiazolidine-1,1-dioxides as precursors for chiral 1,2-diamines
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Both, cis- and trans-3,4-disubstituted thiadiazolidines 5 and 6 can enantioselectively be obtained from thiadiazoles 2 which, in turn, are efficiently prepared from the respective 1,2-diketone by an improved protocol. An asymmetric ruthenium-catalyzed transfer hydrogenation followed by a diastereoselective hydride addition furnishes exclusively the cis-isomers 5 which, under acidic conditions, undergo a novel isomerization into the trans-isomers 6. These cyclic sulfamides can be transformed into 1,2-diamines as well as 2,3-diamino acids.
- Schüttler, Christian,Li-B?hmer, Zhen,Harms, Klaus,Von Zezschwitz, Paultheo
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p. 800 - 803
(2013/04/24)
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- Electrochemical and spectroscopic study of the addition of several nucleophiles to 1,2,5-thiadiazole 1,1-dioxide derivatives
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The nucleophilic addition reactions of several alcohols and 1-propanethiol to a C=N double bond of 3,4-disubstituted derivatives of 1,2,5-thiadiazole 1,1-dioxide were studied in acetonitrile solution. The substrates used were 3,4-diphenyl (1a), 3-methyl-4-phenyl (1b), phenanthro[9,10-c] (1c) and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide (1d), 3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2a) and 4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2b). Spectroscopically (UV-VIS) and electrochemically (cyclic voltammetry) measured equilibrium constants at 25.0°C are presented and discussed for the reaction of 1a and 1b with alcohols (methanol, n-propanol, n-butanol, isobutanol, 2-propanol, sec-butanol, tert-butanol, ethylene glycol, allyl alcohol and 2-phenylethanol). A reaction of 1-propanethiol with 1c was observed, but the alcohols did not react with 1c, 1d or the thiadiazolines (2a, 2b). The effect of the solvent on the equilibrium constant of the 1a-ethanol system was measured using, besides acetonitrile, propylene carbonate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and tert-butanol. The results were correlated with an empirical H-bond acceptor solvent parameter. Previously unreported spectroscopic (UV-VIS, IR, 1H and 13C NMR) data for some of the compounds studied are also provided. Copyright
- Aimone, Silvia Lucia,Caram, Jose Alberto,Mirifico, Maria Virginia,Vasini, Enrique Julio
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p. 272 - 282
(2007/10/03)
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- 3,4-Disubstituted derivatives of 1,2,5-thiadiazole 1,1-dioxide. Ethanol addition reactions and electroreduction of 3-methyl-4-phenyl and 3,4-dimethyl derivatives in acetonitrile and ethanol solvents
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3-Methyl-4-phenyl-1,2,5-thiadiazole 1,1-dioxide (TMP), as well as 3,4-dimethyl-1,2,5-thiadiazole 1,1-dioxide (TMM), react with ethanol (EtOH), which adds to one of their C=N double bonds. The equilibrium constants for the addition reaction are measured in mixed acetonitrile (ACN) - EtOH solvents by means of UV spectroscopy in the case of TMP, and by 13C NMR spectroscopy in the case of TMM, since TMM presents only terminal UV absorption. Both equilibrium constants are also estimated through cyclic voltammetry (CV) experiments. In the case of TMP, the ethanol molecule adds to the C=N bond located on the methyl-substituted side of the substrate, according to 13C NMR spectroscopy and CV results. The electroreduction characteristics of the substrates and their ethanol addition products are studied using CV techniques in ACN, EtOH, and ACN-EtOH solvent mixtures. The radical anion formed by the first electron transfer to TMM is unstable and decomposes rapidly while that corresponding to TMP undergoes a relatively slow homogeneous second-order reaction with the substrate (k = 3 × 102 M-1 s-1). The equilibrium constant for EtOH addition and the voltammetric properties of the substrates are compared with those of the previously studied 3,4-diphenyl derivative (TPP).
- Caram, Jose Alberto,Mirifico, Maria Virginia,Aimone, Silvia Lucia,Vasini, Enrique Julio
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p. 1564 - 1571
(2007/10/03)
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