Heck-Suzuki cascade

B.ii.b. Termination by Boronates (Heck-Suzuki Cascade), Stannanes (Heck—Stille Cascade), or Cyanide Ion. The Heck reaction of aryl or alkenyl halides with norbomene can be terminated by coupling with either a boronate (Scheme 5, Eq. or an alkenylstannane (Scheme 5, Eq. 2) to stereoselectively formed vicinal biscoupling products with formation of two new C,C bonds. 

D.ii.c. Termination by Boranes (Heck-Suzuki Cascade). Similarly, boranates and boronates are suitable reagents for the transfer of aryl or alkenyl groups to rr-alkyl-, o--alkenyl-, and o--arylpalladium complexes and hence are ideal for termination of cascade reactions. Tetraphenylboranate is the reagent of choice for the phenylation of organopaUadium intermediates (Scheme 28). ... 

Scheme 3-23 An inter-intramolecular Suzuki-Heck cascade [174],...

A cascade of Suzuki-Heck reactions has been used for this purpose. Optimal yields were obtained by a... 

Grisorio, R., et al. 2005. A novel synthetic protocol for poly(fluorenylenevinylene)s A cascade Suzuki-Heck reaction. Tetr Lett 46 2555. 

Wegner, H.A., Scott, L.T. and de Meijere, A. (2003) A new Suzuki-Heck-type coupling cascade indeno[l,2,3]-annelation of polycycUc aromatic hydrocarbons. J. Org. Chem., 68, 883-7. 

Alternatively, tetrahydroanthracene 85 was also obtained directly from symmetrical ditriflate 86 by a Suzuki cross-coupling/asymmetric Mizoroki-Heck cascade reaction. In this case, reaction of ditriflate 86 with alkylborane 82, Pd(OAc)2, (S)-BINAP and K2CO3 in THF at 60 °C directly gave product 85 in high enantiopurity, albeit in 20% yield. Although the yield for this one-pot conversion was poor, this transformation represents a novel application of the asymmetric Mizoroki-Heck cyclization and remains the only reported example of cascade Suzuki cross-coupling/asymmetric Mizoroki-Heck cyclization. A series of additional synthetic transformations was required to convert 85 to pentacyclic intermediate 87, which had earlier been converted by Harada et al. [53] to halenaquinone (88) and halenaquinol (89). 

In contrast, a Heck type of reaction will take place if a, P-unsaturated ester is used as the trapping reagent for vinylpalladium intermediates. For example, Alcaide et al. discovered a Pd-catalyzed cascade regioselective spirocyclization of a-allenols cross-coupling via oxopalladation and Heck reaction. Sonogashira and Suzuki reaction can also be incorporated in the sequence instead of the Heck reaction, affording the corresponding potentially bioactive spirocyclic lactam derivatives [117] (Scheme 6.90). 

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