Tandem hydroformylation-hydrogenation-cyclization

In almost the same manner, tandem hydroformylation/aldol condensation aldol condensation of ketoolefins, such as p,y-unsaturated ketones, gives a single cyclization product under acid catalysis. Similar to the stepwise reaction, the in situ generated aldehyde preferentially acts as the electrophilic carbonyl component, while the ketone acts as the nucleophilic enol to form the five-membered ring product. Subsequent dehydration and hydrogenation of the resulting enone readily occurs under the reductive reaction conditions used (Scheme 30) [84],... 

Tandem hydroformylation - Michael addition - hydrogenation - cyclization Scheme 22... 

Garbay reported the chemoselective reduction of a a-dehydrophenylala-nine substrate bearing a p-acrylate moiety [105]. Robinson et al. have also used a tandem, one-pot asymmetric hydrogenation-hydroformylation-cyclization approach to generate six- to eight-membered cyclic a-amino acids [136]. 

FIGURE 8 Molecular clips equipped with phosphines or phosphites used for host-guest catalysis in rhodium-catalyzed hydrogenation and hydroformylation. At the bottom are depicted the peculiar tandem cyclizations, found only for allyldihydr-oxybenzenes in the host molecule as the catalyst (37,32). (For a color version of this figure, the reader is referred to the Web version of this chapter.)... 

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