Cascade carbopalladation nucleophilic terminations

Brase S, de Meijere A (2002) Palladium-Catalyzed Cascade Carbopalladation Termination by Nucleophilic Reagents. In Negishi E, de Meijere A (eds) Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley, New York, p 1405... 

IV.3.2 Palladium-Catalyzed Cascade Carbopalladation Termination by Nucleophilic Reagents... 

A cascade Heck reaction with termination by nucleophiles is considered to start with an oxidative addition of a heteroatom-carbon bond (starter) onto a palladium(O) species (startup reaction), followed by carbopalladation of a nonaromatic carbon-carbon double or triple bond without subsequent dehydropalladation (relay), a second and possibly further carbopalladation of a carbon-carbon double or triple bond (second etc. relay). The terminating step is a displacement of the palladium residue by an appropriate nucleophile. It is crucial for a successful cascade carbopalladation that no premature dehydropalladation takes place, and that can be prevented by using alkynes and 1,1-disubstituted alkenes (or certain cycloalkenes) as relay stations since they give kinetically stable alkenyl- or neopentylpalladium intermediates, respectively. In addition, reaction of haloalkenes with alkenes in certain cases may form rr-allyl complexes, which are then trapped by various nucleophiles. 

IV.3.2 CASCADE CARBOPALLADATION TERMINATED BY NUCLEOPHILES 1407 B.ii. Termination by Carbon Nucleophiles... 

There are hardly any examples for the use of sulfur nucleophiles in terminating cascade carbopalladation sequences, in contrast to oxygen and especially nitrogen nucleophiles. One reason for this might be found in the problems associated with the high degree of coordination of the palladium with the less oxidized sulfur nucleophiles such as thiols. However, arylsulfinates are excellent nucleophiles for cascade termination reactions, as has been shown by Grigg et al. (Scheme 34). ... 

F.i.a. Soft Nucleophiles. As mentioned before, dialkyl malonate enolates are useful terminators for cascade carbopalladations, leading eventually to rr-allylpalladium intermediates. This has been demonstrated by Ma and Negishi in their studies regarding allenes as relays for medium- to large-ring synthesis (Scheme... 

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