Tandem carbometalation/conjugate addition

To extend the scope of the carbometallative aldol cycloreduction, the feasibility of Cu-catalyzed conjugate addition-aldol cyclization process was examined. Cu-catalyzed addition of organozinc compounds to o ,jS-unsaturated carbonyl compounds has been well established (169-171,187-189). Trapping of the Zn-enolates using aldehydes (169,188,190) and acetals/ketals (191) has been reported however, the use of ketones as electrophiles to trap Zn-enolates failed in the absence of strong Lewis acids (191). Rrische and co-workers reported the first successful example of Cu-catalyzed tandem conjugate addition-aldol cyclization with ketones, esters, and nitriles as electrophiles (Scheme 107) (192). In this cyclization process, enone-ketones 237 and 239 afforded products in good to excellent... 

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