920 research outputs found
Alien Registration- Feroci, Theresa M. (Portland, Cumberland County)
No full texthttps://digitalmaine.com/alien_docs/25454/thumbnail.jp
A safe and mild synthesis of organic carbonates from alkyl halides and tetrabutylammonium alkyl carbonates
No full textA safe and mild procedure for the synthesis of
mixed organic carbonates is described. Reaction of com-
mercially available tetrabutylammonium methoxide and
ethoxide with carbon dioxide yields the corresponding meth-
yl and ethyl tetrabutylammonium carbonates (TBAMC and
TBAEC). The reactions of these new compounds with several
different alkyl halides give methyl and ethyl carbonates in
high yields. The use of classic toxic and harmful chemicals
such as phosgene and carbon monoxide is avoided
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
An innovative strategy for electrochemically-promoted addition reaction
No full textA new strategy based on the catalytic release of the supporting
electrolyte agent in the electrolysis medium proved to be
effective for the direct electroactivation of suitable C–H acid-
containing compounds vs. catalytic addition processes, under
solvent-free conditions
Electrochemical carboxylation of N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one: an efficient route to unsymmetrical methylmalonic ester derivatives
No full textElectrochemical carboxylation of N-(2-bromopropionyl)-4R-phenyloxazolidin-2-one aimed at the synthesis and chiral resolution of unsymmetrical
methylmalonic ester derivatives is described. The presence of the Evans’ chiral auxiliary permits an easy resolution of the mixture of the two
diastereoisomers
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 β-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 electrochemically-based method was also exploited for the elaboration of quaternary stereogenic carbon centers. © 2002 Elsevier Science Ltd. All rights reserved
The Knoevenagel reaction in electrochemically activated solvents
No full textThe electrochemical activation of organic solvents HS (CH3CN, CH3CH,CN, DMF, DMSO) containing Et4NPF6 as supporting electrolyte (i.e. their electrolysis under galvanostatic control) allows to induce in these solutions, in the absence of any catalyst, the Knoevenagel condensation between CH-acid CH2(CN)(2) (1) and carbonylic substrates 2a-e. Reaction products 3a-e were isolated in good yields 97-48%. The progress of the Knoevenagel condensation is affected by Q (number of Faradays per mol of 1 supplied to the electrodes) and, moderately, by the nature of the solvents. The rates of the single steps were compared by elementary voltammetric analysis
Voltammetric analysis and chemical reactivity of ionic liquids (ILs) used as “green” reaction media and precursors of efficient catalysts
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