Carbanion-induced decompositions of beta,gamma-unsaturated peroxides containing electron-deficient double bonds.
The treatment of a beta,gamma-unsaturated peroxide, containing an electron-deficient double bond, by a carbanion Z(-) led to the transformation of the compound by a process involving the addition of the carbanion to the double bond, followed by an S(N)i reaction on the peroxidic bond, with the liberation of an alkoxylate anion. When the carbanion was regenerated by proton abstraction from a ZH substrate by this oxyanion, the anionically induced decomposition occurred using catalytic amounts of sodium ethoxylate to initiate it. When this abstraction was not efficient, stoichiometric amounts of carbanion were necessary to decompose the unsaturated peroxide. These induced decompositions are a good source of epoxides, which were the end reaction products. However, in some cases, this heterocycle could give secondary reactions as a result of the attack of the liberated 1,1-dimethylethoxylate on it. The importance of these reactions depended upon the nature of the precursor of carbanion ZH.
Cramail
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Laboratoire de Chimie Organique et Organométallique, associé au CNRS UMR 5802, Université Bordeaux 1, F-33405 Talence-Cedex, France.
Degueil-Castaing
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Maillard
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B