Abstract
An extension of the Michael reaction is described. CsF in the presence of Si(OR) 4 is found to be very efficient for carrying out Michael additions of monoketones and arylacetonitriles on different kinds of Michael acceptors: α, β unsaturated ketones, esters, nitriles. The reaction takes place with a stoichiometric amount of CsF and Si(OR) 4 and without solvent. Addition of different kinds of ketones can occur even with hindered Michael acceptors such as pulegone or 3-methyl 2-butene nitrile. Only the 1,4 addition product is obtained except with hindered esters such as 3,3-dimethyl ethyl acrylate; in this case, we have isolated the β diketone corresponding to the 1,2 addition product. With 2-methyl cyclohexanone, the addition takes place only on the less hindered carbon. With aldehydes, the Michael reaction is not possible because of the predominating aldolisation. With unreactive donors such as tert-butyl methyl ketone and disobutyl ketone, reactive acceptors as ethyl crotonate or cyclohexenone react only with themselves. That constitutes the limitation of the method. A mechanism at the surface of the salt is suggested; formation of enoxysilane as an intermediate is proposed.
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