Alkynes carbopalladations

Currently, there seems to be a widespread tendency to call many reactions proceeding via carbopalladation the Heck reaction. However, this practice is clearly incorrect, since the scope of carbopalladation is significantly wider than that of the Heck reaction. The alkyne carbopalladation reaction shown in Scheme 4, which is not accompanied by /J-dchydropalladation may not be viewed as an example of the Heck reaction. In fact, this chapter focuses its attention on various carbopalladation reactions that may not be considered as examples of the Heck reaction. Although some of such processes are combined with the Heck reaction in many cases. 

The Pd(II)-catalysed 5-exo-dig carbocyclization of the alkynyl ketone (49) to produce (50) has been rationalized by DFT calculations, which suggest that the reaction proceeds via enolization assisted by (AcO)2Pd, followed by intramolecular alkyne carbopalladation, Z E isomerization, and protiodepalladation. ... 

Very recently, Suarez and Greaney explored a novel sequence of Pd-catalyzed indole C—H activation/alkyne carbopalladation/arylation of alkynyl indoles with dia-ryliodonium salts, furnishing functionalized indole alkenes in good to excellent yield, with the reaction being selective for the Z-alkene [74] (Scheme 6.51). 

Palladium-catalysed arylative cyclization of the alkyne-tethered enals or enones (493), initiated by alkyne carbopalladation (494), has been developed. In the presence of (5)-SEGPHOS (496), the products (495) were obtained in <97% ee ... 

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