Natural product synthesis cascade carbopalladation

D.i.b. Insertion of Another Alkenyl Unit In certain cases, however, the 3-exo-trig process may be retarded and an additional alkene moiety participates in the cascade carbopalladation. A pioneering example of this kind has been demonstrated by Overman and co-workers in their total synthesis of scopadulcic acid A, starting from an iodoaUcenyl-substituted methylenecycloheptene derivative (Scheme 24). The first intramolecular carbopalladation occurs across the disubstituted double bond of the exomethylene group, and the trisubstituted endocyclic double bond acts as the terminator to give a tricyclic system, which was further elaborated to the natural product (Scheme 24). It is remarkable that all three quaternary carbon centers can be created by intramolecular Heck reactions. 

Some representative examples of the application of the halopalladation-cyclic carbopalladation cascade to the synthesis of natural products are shown in Table 3. 

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