Enones cyclic,from 1,5-dicarbonyl

The asymmetric allylic C-H activation of cyclic and acyclic silyl enol ethers furnishes 1,5-dicarbonyl compounds and represents a surrogate of the Michael reaction [136]. When sufficient size discrimination is possible the C-H insertion is highly diastereoselective, as in the case of acyclic silyl enol ether 193 (Eq. 22). Reaction of aryldia-zoacetate 192 with 193 catalyzed by Rh2(S-DOSP)4 gives the C-H insertion product 194 (>90% de) in 84% enantiomeric excess. A second example is the reaction of the silyl enol ether 195 with 192 to form 196, a product that could not be formed from the usual Michael addition because the necessary enone would be in its tautomeric naphthol form (Eq. 23). 

The asymmetric Michael addition of nonstabilised ketone enolates has proved difficult, with most success achieved using 1,3-dicarbonyls as donors. However, Shibasaki and coworkers have achieved high ees in the addition of a-hydroxyketones with both aromatic Michael acceptors such as (11.32) and also cyclic enones and alkyl vinyl ketones, using bifiinctional zinc catalysts prepared from linked BINOL (11.33). These catalysts are also effective in the asymmetric aldol reaction (see Section 7.1) and incorporate two zinc atoms, one of which activates the acceptor carbonyl group and the other forms a zinc enolate with the donor. In addition, catalysts of this type have been used to good effect in the addition of P-ketoesters to cyclic enones. 

Lee et al found that the reaction of cyclic 1,3-dicarbonyl compounds with a,P-unsaturated aldehydes did not give the Michael-type addition products observed for enones (see Section 8.4, Figure 8.26), but products from tandem Knoevenagel condensation and cyclization [210] (Figure 8.95). 

Other Metal Complexes Apart from metal complexes derived from BINOL, other metal complexes, such as the lithium-aluminum amiuo diol complex, " aluminum and nickel salen complex, ruthenium diamine complex, and ruthenium phosphinite diamine complex were also found applicable for the asymmetric Michael addition of 1,3-dicarbonyl compound to cyclic enone. All these metal complexes afforded about 90% of asymmetric induction in the Michael reaction of 2-cyclohexen-l-one and malonate. 

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