B conjugate addition

Figure 11 Three possible mechanisms for the dehalogenation of frans-3-chloroacrylate. (a) Addition of water to the double bond, followed by enzyme-catalyzed or chemical decomposition of a short-lived halohydrin intermediate to afford malonate semialdehyde, (b) Conjugate addition reaction where the chlorine atom is displaced by a water-derived hydroxyl group, followed by tautomerization of the enol intermediate, (c) Conjugate addition reaction where the chlorine atom is displaced by an active site carboxylate group, followed by hydrolysis of the covalent ester intermediate, and tautomerization of the enol intermediate.

Alternative preparations of 2-allyl-3-methylcyclohexanone include a) lithium-ammonia reduction of 2-allyl-3 methylcyclohex-2-enone (see Note 13), which can be prepared by alkylation of 3-methjdcyclohex-2-enone or by alkjdation of 4-carboethoxy-3-methylcyclohex-2-enone [Hagemann s ester 2-Cyclohexene-l-carboxylic acid, 2-inethyl-4-oxo-, ethyl ester], followed bj hydrolysis and decarboxylation and b) conjugate addition of lithium dimethylcupratc [Cuprate (1-), dimethyl-, lithium] to 2-cyolohexen-l-one followed by trapping of the enolate with allyl iodide or allyl bromidein an appropriate solvent. 

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