The internal redox esterification of α,β-unsaturated aldehydes and alcohols was carried out using different ionic liquids (ILs) as catalysts and reaction solvents. The basic ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim]OAc), exhibited the best activity for this reaction. The influences of the amount of ionic liquid catalyst and reaction time on yield of saturated ester have been investigated. The results showed that ionic liquid anions have a crucial effect on the redox esterification of α,β- unsaturated aldehydes and alcohols. The nucleophilic carbenes generated in situ from the ionic liquid cation were believed to be actual active species for this reactions.
OXIDATION OF ALCOHOLS BY TRANSITION METAL COMPLEXES-IV THE RHODIUM CATALYSED SYNTHESIS OF ESTERS FROM ALDEHYDES AND ALCOHOLS
Both RhH(CO)PPh3)3 and a catalyst made in situ from RhCl3.3H2O, PPh3 and Na2CO3 catalyse the reaction of a range of aldehydes with simple primary alcohols to give esters together with alcohols formed by reduction of the aldehydes.The proportion of ester can be increased by adding an efficient hydrogen acceptor.The reaction can also be used to produce 5- and 7-membered lactones from aromatic dialdehydes.Propan-2-ol and the in situ catalyst reduce some aromatic aldehydes to the corresponding alcohols without concomitant ester formation.
Grigg, Ronald,Mitchell, Thomas R. B.,Sutthivaiyakit, Somyote
p. 4313 - 4319
(2007/10/02)
Photoreactions of α-sulfonyloxyketones
Earlier work on the photochemistry of α-sulfonyloxyketones uncovered their propensity to form the corresponding α-ketocarbonium ions on photolysis.Typical reactions such as intramolecular cyclizations, carbonium ion rearrangements, and solvent trapping were found.This paper describes an attempt to extend this reaction to a general synthetic technique for polyene cyclizations.During the course of this work two other major reaction pathways were found.The first is an α-keto carbonium ion to acylium ion rearrangement and the second is a photoreduction-elimination process that leads to an α-keto radical rather than the corresponding cation.
Charlton, James Leslie.,Lai, Hoi Kiong.,Lypka, Gerald Nicholas
p. 458 - 462
(2007/10/02)
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