Cross-coupling reactions vinyl electrophiles

Palladium(0)-catalyzed cross-coupling reactions between organic electrophiles (usually vinyl or aryl halides or triflates) and a variety of organometallic reagents and boronic acids have become a popular... 

Unlike other cross-coupling reactions, for which the scope has rapidly expanded in recent years, the range of electrophilic substrates that can be used successfully in the Sonogashira protocol is still rather limited. Vinylic substrates (iodides, bromides, chlorides, triflates, and more recently tosylates) typically yield the best results. For aromatic substrates, iodides and triflates are preferred over bromides, which in turn give far better yields than aryl chlorides. This latter aspect of the reaction is particularly frustrating when one considers the recent advances in the activation of aryl chloride substrates for reactivity in other cross-coupling protocols. ... 

TRIORGANOINDIUM COMPOUNDS AS EFFICIENT REAGENTS FOR PALLADIUM-CATALYSED CROSS-COUPLING REACTIONS WITH ARYL AND VINYL ELECTROPHILES... 

Table 7.2 Cross-coupling reactions between triorganoindium compounds and aryl and vinyl electrophiles.

The most important palladium-catalyzed processes include Heck vinylation of halides and sulfonates and various cross-coupling reactions in which a nucleophilic intermediate (stannane, organo-zinc halide or boronic acid) is coupled with an electrophile (halide or sulfonate). These coupling reactions are usually restricted to arylation and vinylation because of the tendency of alkylpalladium species to undergo elimination. The pyrrole and indole rings can participate in cross-coupling as either the nucleophilic or electrophilic component. 

The Pd-catalyzed cross-coupling reactions of metal nucleophiles with carbon electrophiles are of considerable value for the regio- and stereocontrolled synthesis of functionalized organometalhc compounds, in particular, silanes, stannanes, and boranes, which are important reagents for Pd-catalyzed carbon-carbon cross-coupling as shown in Sects. in.2.2-in.2.4. Symmetrical bimetallic compounds such as disilanes, distannanes, and diborons are usually used as metal nucleophiles. The present metallation is applicable to aryl, benzyl, vinyl, acyl, and aUyl (Sect. V.2.3.3) electrophiles. 

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