Addition to a,3-Unsaturated Aldehydes and Ketones

P carbon atom of an a 3 unsatu rated carbonyl compound is elec trophilic nucleophiles especially weakly basic ones yield the prod ucts of conjugate addition to a 3 unsaturated aldehydes and ketones... 

Conjugate Nucleophilic Addition to a, /3-Unsaturated Aldehydes and Ketones 727... 

The preparation and some synthetic applications of lithium dialkylcuprates were described earlier (Section 14.11). The most prominent feature of these reagents is then-capacity to undergo conjugate addition to a, 3-unsaturated aldehydes and ketones. 

Most reactions of tertiary enamines have been performed with (5)-prdine derivatives. The first examples of 1,4-additions to a, 3-unsaturated aldehydes and ketones exhibited mediocre selectivities (ee < 60%) [173]. However, the reactions of two enamines of cyclohexanone, 7.109 and 7.110, with methylacrylate lead to the expected adducts with a high enantiomeric excess but a poor chemical yield [173] (Figure 7.72). The addition of an (.S)-prolinol-derived enamine to an a-tri-methylsilyl-a,P-unsaturated ketone also gives useful selectivity [162]. Seebach and coworkers reacted enamine 7.110 (R = Me) with a,P-unsaturated gem-diesters or 2-aryl-l-nitroethylenes and obtained the expected 1,4-adducts with a high selectivity [162] (Figure 7.72). Martens and Lubben [294] proposed the use of enamine 7.111 for similar purposes, but the selectivity was not as high as with 7.110 (R = Me) (Figure 7.72). 

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