Best, Michael

The best Michael reactions are those that take place when a particularly stable enolate ion such as that derived from a /i-keto ester or other 1,3-dicarbonyl compound adds to an unhindered a,/3-unsaturated ketone. Tor example, ethyl acetoacetate reacts with 3-buten-2-one in the presence of sodium ethoxide to yield the conjugate addition product. 

The conjugate addition of a carbon nucleophile to an a./3-unsiituratcd acceptor is known as the Michael reaction. The best Michael reactions take place between unusually acidic donors (/3-keto esters or /3-diketones) and unhindered n,/3-unsaturated acceptors. Knamines, prepared by reaction of a ketone with a disu Instituted amine, are also good Michael donors. 

The simplest and best Michael acceptors are those a, 3-unsaturated carbonyl compounds with exposed unsaturated (3 carbon atoms, such as exo-methylene ketones and lactones and vinyl ketones, and we shall see in the next section that these need to have their high reactivity modera ted in most applications. 

However, most a,[3-unsaturated ketones can be made to do conjugate addition by suitable choice of enol(ate) equivalent and conditions. Now we need to look at the best Michael acceptors, their reactions, and how to make them. 

Acrylonitrile CH2=CHCN is one of the best Michael acceptors for enol(ate)s. The reaction is known as cyanoethylation as it adds a -CH2CH2CN group to the enol(ate). 

In the hrst group, we are extremely grateful to J. Gilbert Ashbum, Edward Bernasek, Fred W. Best, Michael F. Borgerding, N.M. Chopra, Christopher R.E. Coggins, William... 

With base, methyl benzyl ketone forms its more stable enolate, which undergoes smooth and rapid conjugate addition to acrylonitrile. Acrylonitrile is one of the best Michael acceptors for enolates. 

The best Michael reactions are those that take place when a particularly stable enolate ion such as that derived from a /3-keto ester or other 1,3-dicarbonyl... 

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See also in sourсe #XX -- [ ]

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