Claisen condensation tandem reaction

A similar method has been described by Badia and co-workers who used chiral amides derived from pseudoephe-drine.139 Moreover, a zirconium-mediated Claisen-aldol tandem reaction of an a,cr-dialkylated ester with several aldehydes has been reported (Scheme 39).140 After the initial Claisen condensation, zirconium enolate intermediate 92 reacts with various types of aldehydes through aldol-type reaction and subsequent lactonization, providing the corresponding pyran-2,4-diones. 

Claisen condensation equivalent, 10, 174 Claisen rearrangement equivalent, 10, 176 enolate alkylation equivalent, 10, 171 Mannich reaction equivalent, 10, 174 as strategic reaction, 10, 171 intermolecular carbene insertion, C-H activation-Cope rearrangement characteristics, 10, 177 as strategic reaction, 10, 178 tandem aldol reaction-siloxy-Cope rearrangement equivalent, 10, 181... 

The Dieckmann condensation in tandem with the Claisen condensation or Michael reaction can be used to assemble highly functionalized carbocycles, including the 1,2-, 1,3", and 1,4-dione species depicted belowd ... 

A C-C=0 bond in 1,3-dicarbonyl compounds is known to be cleaved by a simple alkoxide base via retro-Claisen condensation (Eq. (6.9)) [20]. A number of reactions have been reported in which catalytic transformation and base-promoted retro-Claisen condensation occur in tandem [21]. In addition to such examples, several other metal-catalyzed transformations of C-C=0 bonds in 1,3-dicarbonyls have been developed in recent years. 

A related amination/rearrangement/cyclization tandem sequence had been introduced by Cossy [49]. Starting from cyclic epoxyketones 224 the reaction with propargylamines 225 caused an oxirane-opening condensation process to generate the enaminoketones 226. Upon heating in toluene to reflux, aza-Claisen rearrangement delivered the intermediate allenyl imines 227, which... 

---