Heck-Suzuki reaction sequence

The 2-indolinone system has been found in a large number of pharmaceutically active compounds. This framework could be constructed by a tandem Heck-Suzuki reaction sequence [137]. Intramolecular Heck reaction of 390 afforded a cyclized intermediate that, in situ, reacted with boronic acid 187 to produce 391 in a single pot sequence. The reaction made use of copper thiophene-2-carboxylic acid (CuTC) to generate base-free conditions for the Suzuki reaction. 

Stille coupling was also developed in tlie early 1980s and is similar to Suzuki coupling in its sequence. It is used to couple aryl or vinyl halides or triflates with organotin compounds via oxidative addition, transmetallation, and reductive elimination. The oxidative addition reaction has tlie same requirements and preferences as discussed earlier for tlie Heck and Suzuki reactions. The reductive elimination results in formation of tlie new carbon-carbon bond. The main difference is that tlie transmetallation reaction uses an organotin compound and occurs readily without the need for an oxygen base. Aryl, alkenyl, and alkyl stannanes are readily available. Usually only one of tlie groups on tin enters into... 

The domino Suzuki coupling-Heck reaction sequence involving dihydroaromatic alkenyl-substituted boronic esters (186) with diiodobenzene, bromoiodobenzene, or iodoaniline derivatives yields substituted phenanthrene (187) and phenanthridene derivatives regiospecifically (Scheme 52).218... 

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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