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Search Results: 1 - 10 of 385924 matches for " Guillermo E. Negrón-Silva "
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Multicomponent Click Synthesis of New 1,2,3-Triazole Derivatives of Pyrimidine Nucleobases: Promising Acidic Corrosion Inhibitors for Steel
Rodrigo González-Olvera,Araceli Espinoza-Vázquez,Guillermo E. Negrón-Silva,Manuel E. Palomar-Pardavé,Mario A. Romero-Romo,Rosa Santillan
Molecules , 2013, DOI: 10.3390/molecules181215064
Abstract: A series of new mono-1,2,3-triazole derivatives of pyrimidine nucleobases were synthesized by one-pot copper(I)-catalyzed 1,3-dipolar cycloaddition reactions between N-1-propargyluracil and thymine, sodium azide and several benzyl halides. The desired heterocyclic compounds were obtained in good yields and characterized by NMR, IR, and high resolution mass spectrometry. These compounds were investigated as corrosion inhibitors for steel in 1 M HCl solution, using electrochemical impedance spectroscopy (EIS) technique. The results indicate that these heterocyclic compounds are promising acidic corrosion inhibitors for steel.
Sulphated Zirconia as an Eco-Friendly Catalyst in Acylal Preparation under Solvent-Free Conditions, Acylal Deprotection Assisted by Microwaves, and the Synthesis of Anhydro-Dimers of o-Hydroxybenzaldehydes
Laura Nadxieli Palacios-Grijalva,Deysi Y. Cruz-González,Leticia Lomas-Romero,Eduardo González-Zamora,Gerardo Ulibarri,Guillermo E. Negrón-Silva
Molecules , 2009, DOI: 10.3390/molecules14104065
Abstract: A solvent-free approach is described for the regioselective synthesis of acylals (1,1-diacetates) in shorter reaction times and higher yields, compared to conventional methodology using solvents. In the protection reaction of the o-hydroxybenzaldehyde the formation of acetyl compounds and anhydro-dimers was observed. The deprotection reaction involves microwave (MW) exposure of diluted reactants in the presence of solid sulphated zirconia (SZ) catalyst that can be easily recovered and reused. The sulphated zirconia was recycled several times without any loss of activity.
Synthesis of New 1,2,3-Triazole Derivatives of Uracil and Thymine with Potential Inhibitory Activity against Acidic Corrosion of Steels
Guillermo E. Negrón-Silva,Rodrigo González-Olvera,Deyanira Angeles-Beltrán,Nidia Maldonado-Carmona,Araceli Espinoza-Vázquez,Manuel E. Palomar-Pardavé,Mario A. Romero-Romo,Rosa Santillan
Molecules , 2013, DOI: 10.3390/molecules18044613
Abstract: Ten 1,4-disubstituted 1,2,3-triazoles were synthesized from one of 1-(azido-methyl)benzene, 1-(azidomethyl)-4-fluorobenzene, 1-(azidomethyl)-4-chlorobenzene, 1-(azidomethyl)-4-bromobenzene or 1-(azidomethyl)-4-iodobenzene, generated in situ from sodium azide and the corresponding benzyl halide, and dipropargyl uracil or dipropargyl thymine. Optimal experimental conditions were established for the conventional click chemistry. The corrosion inhibiting properties of some of these compounds, which were determined by means of an electrochemical technique, are also presented.
Synthesis of Azanucleosides through Regioselective Ring-Opening of Epoxides Catalyzed by Sulphated Zirconia under Microwave and Solvent-Free Conditions
Celia Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora,Rubén Gavi?o,Jorge Cárdenas,José Antonio Morales-Serna,Guillermo E. Negrón-Silva
Molecules , 2012, DOI: 10.3390/molecules17033359
Abstract: New azanucleosides were obtained using sulphated zirconia (ZS) as catalyst in the nucleophilic oxirane ring opening reaction of 1-allyl-3-(oxiran-2-ylmethyl) pyrimidine-2,4(1H,3H)-dione and 1-allyl-5-methyl-3-(oxiran-2-ylmethyl)-pyrimidine-2,4(1H,3H)-dione, with (S)-prolinol. The new templates were obtained with good yields following a route which exploits the reactivity of epoxides in the presence of sulphated zirconia as catalyst. The key step was carried out using microwave and solvent-free conditions and proceeds with high selectivity.
Synthesis of New Pentacyclo[,6.03,10.05,9]undecane-8,11-dione (PCU) Cyanosilylated Derivatives Using Sulphated Zirconia and Hydrotalcite as Catalysts in Microwave-Assisted Reactions under Solvent Free Conditions
Nahí Adriana Guerra-Navarro,Laura Nadxieli Palacios-Grijalva,Deyanira Angeles-Beltrán,Guillermo E. Negrón-Silva,Leticia Lomas-Romero,Eduardo González-Zamora,Rubén Gavi?o-Ramírez,Juan Navarrete-Bola?os
Molecules , 2011, DOI: 10.3390/molecules16086561
Abstract: A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[,6.03,10.05,9]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered.
Titanium-modified MCM-41 Prepared by Ultrasound and by Hydrothermal Treatment, Catalysts for Acetylation Reactions
Deyanira Angeles-Beltrán,Guillermo Negrón-Silva,Leticia Lomas-Romero,Martín A. Iglesias-Arteaga
Revista de la Sociedad Química de México , 2008,
Abstract: Por tratamiento hidrotérmico y por ultrasonido, se prepararon materiales tipo Ti-MCM-41 que fueron caracterizados por DRX, MEB, MET, fisisorción de nitrógeno, TDP de amoniaco y espectroscopias de IR y UV-vis. Ambos materiales mostraron ordenamiento característico de los materiales MCM-41. Se demostró que mediante la técnica de tratamiento hidrotérmico se obtuvo un material más ordenado pero, por la técnica de ultrasonido se logró mejor dispersión de titanio. Las imágenes de microscopía electrónica de barrido permitieron identificar las zonas de mejor distribución del Ti así como la cuantificación del metal en la estructura del MCM-41. La actividad catalítica de los materiales se probó en la acetilación de alcoholes aromáticos y esteroidales para obtener los ésteres correspondientes en buen rendimiento.
Titanium-modified MCM-41 Prepared by Ultrasound and by Hydrothermal Treatment, Catalysts for Acetylation Reactions
Angeles-Beltrán, Deyanira;Negrón-Silva, Guillermo;Lomas-Romero, Leticia;Iglesias-Arteaga, Martín A.;Cadete Santos-Aires, Francisco J.;
Journal of the Mexican Chemical Society , 2008,
Abstract: mesoporous materials type ti-mcm-41 prepared by hydrothermal and ultrasound-assisted techniques were characterized by xrd, sem, tem, nitrogen physisorption, ammonia tpd, uv-vis and ft-ir. both showed the mcm-41 characteristic structure. hydrothermal treatment allowed obtaining a well ordered material and ultrasound procedure gave a better titanium distribution. electronic microscopy images revealed ti dispersion zones as well as the quantity of metal in the structure. the catalytic activity of these materials were tested by acetylation of aromatic and steroidal alcohols to afford the corresponding esters in good yields.
Microwave-Enhanced Sulphated Zirconia and SZ/MCM-41 Catalyzed Regioselective Synthesis of β-Amino Alcohols Under Solvent-Free Conditions
Guillermo Negrón-Silva,C. Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora
Molecules , 2008, DOI: 10.3390/molecules13040977
Abstract: A solvent-free approach for the regioselective synthesis of β-amino alcohols inshorter reaction times and higher yields, compared to conventional heating is described. Itinvolves microwave (MW) exposure of undiluted reactants in the presence of sulphatedzirconia (SZ) or sulphated zirconia over MCM-41 (SZM) as catalyst. Both acid materialscan be easily recovered and reused.
Sulfated Zirconia-Catalyzed Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) Under Solventless Conditions: Competitive Multicomponent Biginelli vs. Hantzsch Reactions
Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Victor H. Lara-Corona,Eduardo González-Zamora,Guillermo Negrón-Silva
Molecules , 2006, DOI: 10.3390/11100731
Abstract: The catalytic ability of ZrO2/SO42- to promote solventless three-componentcondensation reactions of a diversity of aromatic aldehydes, urea or thoiurea and ethylacetoacetate was studied. Products resulting from Hantzsch and/or Biginelli multi-component reactions are obtained in the presence of solid acid catalysts using the samereactants but different temperature conditions. The sulfated zirconia catalyst can berecovered and recycled in subsequent reactions with a gradual decrease of activity.
Comparative Study of Regioselective Synthesis of β-Aminoalcohols under Solventless Conditions Catalyzed by Sulfated Zirconia and SZ/MCM-41
Guillermo Negrón-Silva,C. Xochitl Hernández-Reyes,Deyanira Angeles-Beltrán,Leticia Lomas-Romero,Eduardo González-Zamora,Juan Méndez-Vivar
Molecules , 2007, DOI: 10.3390/12112515
Abstract: Sulfated zirconia and SZ/MCM-41 were used as catalysts for the synthesis of β-aminoalcohols via epoxide aminolysis. Sulfated zirconia was prepared by sol-gel andSZ/MCM-41 was obtained by impregnation. Solid catalysts were characterized by XRD,SEM-EDS, UV-Vis, FT-IR pyridine desorption and Nitrogen physisorption. Both acidmaterials were useful as catalysts, even when they were recycled several times. The β-aminoalcohols were characterized by FT-IR, 1H- and 13C-NMR and GC-MS.
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