Heck spirocyclic oxindoles

The intramolecular Heck reaction is valuable for elaborating the spirocyclic oxindole system related to gelsemine. 

A variety of different tactics have been used to establish all-carbon spirocyclic moieties at oxindole C3. Overman and Watson have conducted an extensive investigation of intramolecular Heck reactions leading to the diastereoselective formation of spirocyclic dioxindoles, e.g., Ill and 114 (Scheme 29) [67-69]. Interestingly, while sequential Heck cyclizations of acetonide protected bis-anilide... 

These reaction conditions have been employed in two total syntheses of ( )-gelsemine 93 on similar intermediates (Scheme 15). In one synthesis the key reaction (94- 5) is heavily sterically biased due to the presence of the bulky CHjOTDS group. In spite of this obstacle, a 2 1(95/96) ratio of oxindoles favoring spirocycle 95 is produced. The reaction will also tolerate a tetrasubstituted alkene. Heck cyclization of vinylogous carbamate 97 under cationic conditions stereoselectively delivers oxindole 99 en route to... 

In 2010, Jaegli et al. reported a novel palladium-catalyzed intramolecular domino spirocyclization process for the preparation of biologically relevant spiropyrroUdine-3,3 -oxindoles 86 [32] (Scheme 6.19). Oxidative addition of the aryl halide to Pd(0) aminopalladation via the coordinated intermediate 84 leads to palladacycle 85 reductive elimination of complex 85 generates the final product. Both Heck reaction and aminopalladation processes were viable pathways from amide 83, and the route that occurs is dependent on the ligand chosen. The use of tBuMePhos as the ligand is required for the successful formation of spirooxindoles. 

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