Palladium-catalyzed alkenylation and arylation

Palladium-Catalyzed Alkenylations and Arylations of Organometallic Compounds... 

The stereoselective synthesis of alkenes is basically a solved problem. Nowadays, all kinds of alkenes can be synthesized irrespective of whether their double bond is isolated or conjugated with another C=C double bond, a C=C triple bond, or an aromatic ring. This state of affairs is largely due to the discovery and the development of a number of palladium-catalyzed alkenylation and arylation reactions of organometallic compounds. 

Scheme 8.9. Palladium-Catalyzed Alkenylation of Aryl and Alkenyl Systems... 

Heck reaction, palladium-catalyzed cross-coupling reactions between organohalides or triflates with olefins (72JOC2320), can take place inter- or intra-molecularly. It is a powerful carbon-carbon bond forming reaction for the preparation of alkenyl- and aryl-substituted alkenes in which only a catalytic amount of a palladium(O) complex is required. 

Organozinc compounds are also useful in palladium-catalyzed coupling with aryl and alkenyl halides. Procedures for arylzinc,156 alkenylzinc,157 and alkylzinc158 reagents have been developed. The ferrocenyldiphosphine dppf has been found to be an especially good Pd ligand for these reactions.159... 

Scheme 8.8. Palladium-Catalyzed Vinylation of Aryl and Alkenyl Halides...

Heck in one of his first papers already demonstrated the feasibility of applying the palladium-catalyzed crosscoupling of aryl and alkenyl halides with alkenes repetitively on appropriate oligofunctional substrates. For example, twofold coupling of 1,4-diiodobenzene with styrene furnished 1,4-distyrylbenzene in 67% yield (Scheme 1). Since then, a large number of ortho-, meta-, and / r< -dihaloarenes and -heteroarenes have been subjected to twofold Heck reactions with various alkenes (Schemes 2-4). 

Tetrahydrocarbazoles and related fused systems have been accessed by a route relying on palladium-catalyzed tandem formation of alkenyl and aryl C-N bonds. For instance, the starting triflate 477 could be efficiently transformed into the target system 478 by amination with aniline (Equation 133) <2005AGE403>. Annulation of (2-triflyloxy)phenethyl carbonates with amides in the presence of a palladium catalyst has been used as a route to various N-substituted indoline derivatives <2005OL4777>. 

Huo, S., Negishi, E.-i. Palladium-catalyzed alkenyl-aryl, aryl-alkenyl, and alkenyl-alkenyl coupling reactions. Handbook of Organopalladium... 

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