1,721,480 research outputs found
Electrochemically induced hydrogenolysis of 1,1-dibromoalkenes to vinyl bromides
No full textVinyl bromides 2a-f, useful intermediates in organic synthesis, have been obtained under mild conditions and in good yields via electrochemical reduction of 1,1-dibromoalkenes 1a-f (readily available substrates). The reduction has been carried out in MeCN-tetraethylammonium perchlorate (TEAP) solutions, in the presence of a proton donor, at a Au, Hg, C or Ag cathode. The use of specific reducing agents, catalysts and bases, employed in the classical procedures, has been avoided. The isomeric E/Z ratio in vinyl bromides 2a-f is affected by the cathode materia
Electrochemically-initiated Michael addition of chiral acetoacetic derivatives to methyl vinyl ketone: stereocontrolled construction of quaternary carbon centers
No full textStereoselective conjugate addition of chiral -dicarbonyl derivatives to methyl vinyl ketone was promoted by electrolysis, using a catalytic amount of electricity. With respect to the metal-catalyzed methods, the electrochemical, metal-free conditions resulted in enhanced reactivity of the electrogenerated enolates, so that the Michael addition was found to occur under mild conditions and short reaction times, affording products with significant diastereoisomeric excesses. When Oppolzer’s sultam was used as the chiral inductor and prolonged reaction times were employed, a reversal in the stereoselectivity was observed, evidencing kinetic control in the electrochemically-induced addition and subsequent thermodynamic equilibration. The electro- chemically-based method was also exploited for the elaboration of quaternary stereogenic carbon centers
Erratum: Internal redox amidation of α,β-unsaturated aldehydes in ionic liquids. the electrochemical route (Electrochimica Acta (2013) 89:(692-699))
No full textAn Efficient Combined Electrochemical and Ultrasound Assisted Synthesis of Imidazole-2-Thiones
No full textThe electrochemical reduction of 1,3-dialkylimidazolium ionic liquids gave the corresponding N-heterocyclic carbenes that, after reaction with elemental sulfur and ultrasound irradiation, yielded 1,3-dialkylimidazole-2-thiones in very high yields. The reaction is very clean, produces no side-products and avoids the use of any other added reagent
A simple and convenient method for preparation of sulfides
No full textTetraethylammonium hydrogen carbonate (TEAHC) and tetraethylammonium carbonate (TEAC) obtained respectively by chemical and electrochemical way, react with thiols in acetonitrile affording, after addition of a suitable alkylating reagent, the corresponding sulfides in high to excellent yields
The reaction of amines with an electrogenerated base. Improved synthesis of arylcarbamic esters
No full textThe electrogenerated base of 2-pyrrolidone reacts with amines and anilines yielding the corresponding alkyl and aryl carbamates, after addition of carbon dioxide and ethyl iodide. Arylcarbamic esters are obtained in very good yields under mild reaction conditions with respect to the methods so far reported. (C) 2000 Elsevier Science Ltd. All rights reserved
Reaction of the Electrogenerated Cyanomethyl Anion with Carbonyl Compounds: A Clean and Safe Synthesis of beta-Hydroxynitriles
No full textThe electrogenerated cyanomethyl anion reacts with carbonyl compounds to yield the corresponding beta-hydroxynitriles in moderate to high yields. The reported methodology is very clean and safe, avoiding the use of any classical base or catalyst. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009
Electrogenerated cyanomethyl anion in organic synthesis
No full textSuitable electrochemical methodologies for the generation of cyanomethyl anion and some electrochemically induced cyanomethylation reactions of electrophilic substrates are described and discussed. In addition, the electrochemical syntheses of carbamates and chiral oxazolidin-2-ones (under mild conditions and avoiding the use of hazardous chemicals), via a new carboxylating reagent (CH2CN-/CO2), are reported in this article
Room Temperature Ionic Liquids (RTILs) Versus Volatile Organic Compounds (VOCs) in Organic Electrosynthesis: The Requirement of a Careful Comparison
No full textAn atlas of X- and gamma-ray pulse profiles of the Crab pulsar (PSR 0531+21): An analysis of energy and time variations
No full textWe present an atlas of X and gamma-ray pulse profiles of PSR 0531+21 (Crab pulsar) measured since 1967. This atlas, containing 250 profiles, is useful to study in detail the behaviour with time and energy of this important source and to test models of the emission geometrical pattern. The atlas database is also accessible from Mosaic. An analysis of the energy dependence and time changes of the Crab pulsar light curve (and in particular of the P2/P1 ratio), based on the atlas database, is presented
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