Enolate anions, addition reactions nucleophilic displacements with

When the enones 1 were treated with the ai-haloalkanols 2 and base, the deformylated cfv-prod-ucts rac-3 were obtained exclusively13. Clearly this reaction is initiated by conjugate addition of the O-nucleophile. The diastereoselective step, however, is the subsequent intramolecular displacement of halide by the intermediate enolate anion. 

Cyclopropanes have also been obtained by reaction of enamines with a-chloro electrophilic alkenes. After Michael addition the chlorine undergoes nucleophilic displacement by the regenerated enamine or enolate anion - (Scheme 112). Bicy-clo[1.1.0]butanes may be obtained by cycloaddition of trimethyl ethylenetricarboxylate followed by a base catalysed displacement of the amine moiety (Scheme 113). 

The enolates (48) and (49) of the transition metals tungsten, rhenium and molybdenum can be successfully prepared by the nucleophilic displacement of a-chloro ketones and a-chloro esters with the appropriate transition metal anion (Scheme 6). They are isolated as C-bound enolate derivatives and, except for the rhenium enolate (49), do not undergo thermal aldol additions to benzaldehyde. However, Bergman and Heathcock et al. have found that an aldol reaction of complex (48) with benzaldehyde can occur on irradiation via the rearranged q -oxaallyl derivative (50), where the metal aldolate (51) can then be... 

There are two major reactions of enolates (1) displacement reactions with alkyl halides or other suitable electrophiles and (2) nucleophilic addition to carbonyl compounds. Reaction of 58 with butanal to give 59 and reaction of 61 with bromopentane to give 62 are simple examples of each process. Enolate anions function as carbon nucleophiles and their reactions are fundamentally the same as those discussed in Section 8.3.C for acetylides. Although there are interesting differences, treating an enolate anion as a carbon nucleophile is very reasonable. 

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