Conjugate enolates definition

Reactions of this type are referred to in a variety of terms, many of which are rather confusing and nondescriptive. They sometimes are classified as 1,4-additions, implying that addition occurs across the terminal positions of the conjugated system. A synonymous term is conjugate addition. When the nucleophile is a carbanion, the reaction is called a Michael addition. Thus, by this definition, Equation 17-7 represents a Michael addition. Another, perhaps more typical, example is the addition of an enolate to a conjugated ketone ... 

Proton transfer can occur in any medium, depending on the charge type. A solution that contains equal concentrations of a base and its conjugate acid has a pH that is equal to the pAabH (Section 3.2.1). The pH of the medium will be close to the p abH of the anion needed for reaction, because the anion must have a high enough concentration to react at a reasonable rate. As an illustration, if a ketone enolate, pATabH = 19.2, is needed for reaction, the medium will definitely be very basic. 

Smith et al reported that the hydrogenation of 2-methylcinnamic acid and 2-methylpent-2-enoic acid on 1 % Pd-sihca catalysts modified with l-(iS)-e c/o-bomyloxytrimethylsilane in MeOH at 25°C results in chiral products with ee s of 22.5% and 11.6%. These results noted that modified Pt and Pd catalysts can hydrogenate enantioselectively systems with 1,3-conjugated bonds, but the transfer of these aspects for hydrogenation of 1,4-double bonds as in methyl acetoacetate (MAA) has definite difficulties because it needs to assume the enol form (En) to react (Scheme 5.32.). 

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