Acylpalladation cascade carbopalladation

C. TANDEM, CASCADE, OR DOMINO ACYLPALLADATION AND CARBOPALLADATION PROCESSES... 

Many different combinations of carbopalladation and/or acylpalladation processes are conceivable for devising cascading di- and multicyclization processes. Those consisting only of straightforward carbopalladation processes have been systematically investigated by a number of chemists since around 1988, as detailed in Sect IV.3. Aside from these carbopalladation cascades and those allylpalladation-acylpalladation cascades discussed above, only a small number of scattered examples are known, as shown below, and this area needs to be explored further. 

C.iLa. Carbopalladation-AcylpaUadation Cascades. The reaction shown at the top of Scheme 30 is a prototypical example of the intra-intra carbopaUadation-acylpalladation cascade, while that shown at the bottom of Scheme 30 is an example of the inter-intra carbopalladation-acylpalladation cascade. 

Palladium-Catalyzed Cyclization via Carbopalladation and Acylpalladation Zipper"-mode cascade cylclization... 

In principle, carbonylative cyclization, that is, acylpalladation or Ac—Pd process, or noncarbonylative cyclization, that is, sample carbopalladation or C—Pd process, in the presence of CO and a Pd catalyst. Various possibilities with halo alkenes as representative substrates are shown in Scheme 2P Those processes that incorporate CO in the cyclization processes are discussed in Part VI including Sects. VI.4-VI.6. hi this section, those cases that do not incorporate CO during the cychzation processes but do so only after cyclization will be discussed. Such cychc carbopalladation-carbonylative termination tandem and cascade processes are represented by the Type II C—Pd process in Scheme 2, which may take place in competition with the other processes shown in Scheme 2, especially the cyclic Heck reaction (Type 1 C—Pd process) and cyclic carbopalladation involving cyclopropa-nation (Type 111 C— Pd process). 

Surprisingly, methanol was a suitable solvent for this transformation and the amount of intermolecular methoxycarbonylation products was only 2-3%. Furthermore, acylpalladation of alkenyl iodide was disfavored versus the desired intramolecular 6-exo-carbopalladation. Further examples of this type of CO-tenninaled cascade processes can be found in Sect. IV.3. 

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