37 documents found, page 1 of 4
Catalytic cyclization of propargyl bromoethers via electrogenerated nickel(I) t...
Mendes, Jorge António Silva; Duñach, E.; Esperanca, J. M. S. S.; Medeiros, Maria José; Ribeiro, J. F.; Silva, Maria Manuela; Olivero, S.Cyclic voltammetry and controlled-potential electrolysis have been employed to investigate the reductive intramolecular cyclization of propargyl bromoethers derivatives, catalyzed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane) nickel(I), [Ni(tmc)](+), as the catalyst, in N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl) imide, [N-1 1 1 2(OH)][NTf2] and 1-eth...
Student skill development with the real world: Analyzing tert-Butyl alcohol con...
Gonçalves, Bruna Fernandes; Botelho, Gabriela; Medeiros, Maria José; Smith, Michael JohnIn the activity described in this communication, the authors present a simple experiment that can be implemented with moderate operational costs and that allows students to acquire the manipulative skills necessary for chromatographic analysis of a familiar fuel that still plays a fundamental role in providing energy for transport of passengers and goods. The use of gasoline formulations in a laboratory activit...
Electrochemical cyclizations of organic halides catalyzed by electrogenerated n...
Duñach, E.; Medeiros, Maria José; Olivero, S.This review concentrates on the intramolecular cyclizations of organic halides catalyzed by nickel complexes using an electrochemical methodology, as an alternative to the classical radical or transitionmetal catalyzed or mediated processes.
Structural, morphological, ionic conductivity, and thermal properties of pectin...
Mendes, J. P.; Esperança, J. M. S. S.; Medeiros, Maria José; Pawlicka, A.; Silva, Maria ManuelaNew polymer electrolytes (PEs), potentially interesting for solid-state electrochemical devices applications, were synthesized by a solvent casting method using pectin and ionic liquid (IL) N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N1 1 1 2(OH)][NTf2]. The resulting electrolytes besides being moderately homogenous and thermally stable below 155 ºC, they also exhibited good m...
Ionic liquids for the electroreductive radical cyclization of unsaturated bromo...
Neto, M. J.; Duñach, E.; Esperança, J. M. S. S.; Esteves, Ana Paula; Medeiros, Maria José; Silva, Maria ManuelaRoom temperature ionic liquids, such as N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium ethylsulfate, [C2mim][C2SO4], have been used for the electroreductive intramolecular cyclization of unsaturated bromo derivatives 1 in Ni(II)-catalyzed reactions. Controlled-potential electrolyses led to five-membered-ring compounds in moderate ...
Electrosynthesis of heterocyclic compounds by radical cyclization in environmen...
Mendes, J. P.; Esperança, J. M. S. S.; Esteves, A. P.; Silva, Maria Manuela; Medeiros, Maria JoséWe investigated the reductive intramolecular cyclization of bromopropargyl ethers derivatives, catalyzed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane)nickel(I), [Ni(tmc)]+ as the catalysts in N,N,N-trimethyl-N-(2- hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide,[N1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C2mim][NTf2] by cyclic ...
Gellan gum-Ionic liquid membranes for electrochromic device application
Neto, M. J.; Sentanin, F.; Esperança, J. M. S. S.; Medeiros, Maria José; Pawlicka, A.; Bermudez, V. D. Z.; Silva, Maria ManuelaBiopolymer-based materials have been of particular interest and they are alternatives to synthetic polymers based on the decreasing oil resources. The polymer electrolytes were doped with choline-based IL N,N,Ntrimethyl- N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N1 1 1 2(OH)][NTf2]), or Er (CF3SO3)3 or both. The polymer electrolytes were employed in the production of glass/ITO/WO3/electroly...
Synthesis of five-membered heterocycles by indirect electrochemical approach in...
Duraes, C.; Lombard, J.; Pereira, S.; Esteves, Ana Paula; Medeiros, Maria JoséRadical cyclization continues to be a central methodology for the preparation of natural products containing heterocyclic rings. Hence, some electrochemical results obtained by cyclic voltammetry and controlled-potential electrolysis in the study of electroreductive intramolecular cyclization of ethyl (2S, 3R)-2-bromo-3-propargyloxy-3-(2’,3’,4’,6’-tetra-O-acetyl-beta-D-glucopyranosyloxy) propanoate (1a), 2-brom...
The study of indirect electroreductive cyclization of propargyl derivatives usi...
Neto, M. J.; Esperança, J. M. S. S.; Esteves, Ana Paula; Medeiros, Maria José; Silva, Maria ManuelaRadical cyclization continues to be a central methodology for the preparation of natural products containing heterocyclic rings. The use of electrogenerated nickel(I) complexes as mediators for cathodic intramolecular cyclizations proved to be successful in the formation of carbocyclic products. In this work, the indirect electroreductive intramolecular cyclization of bromoalkoxylated derivatives 1 catalyzed by...
Indirect electrochemical cyclisation of bromoalkoxylated derivatives using envi...
Duñach, E.; Medeiros, Maria José; Olivero, S.The electrochemical intramolecular cyclization of bromoalkoxylated derivatives 1 using Ni(II) complex as mediator of electron transfer was carried out in ethanol by constant-current electrolysis in one-compartment cell in the absence of sacrificial anodes as an environmentally friendly systems. It is demonstrated that the electroreduction reaction of bromoalkoxylated derivatives was catalyzed by the electrogene...