Stannanes palladium-catalyzed coupling with halides

The same methodology has also been applied to the synthesis of stannylated furans. Heating bis(tributylstannyl)acetylene and 55 in a sealed mbe at 185°C for 10 days provided 3,4-bis(tributylstannyl)furan 139 and 3-(tributylstannyl)furan 140 in 22 and 10% isolated yield, respectively (Fig. 3.41). These stannanes underwent palladium-catalyzed couplings with aryl, vinyl, and benzylic halides as well as acid chlorides. 

Scheme 8.12. Palladium-Catalyzed Coupling of Stannanes with Halides and Sulfonates... 

The added advantage of the C (1 )-stannylated glycals is their abUity to participate in palladium-catalyzed coupling reactions with organic halides, a process independently reported by Beau [75] and Friesen [81]. Vinyl stannane 237 can be benzylated, allylated or acylated provided that appropriate catalysts are used [75,77] and representative examples are given in Scheme 59. The C-arylation of... 

Pyrrolyl- and indolyl-stannanes and -boronic acids, which can be prepared from the corresponding organolithium derivatives, have received increasing use in palladium-catalyzed coupling reactions with aryl halides (Scheme 82) (91S613,92JOC1653). 

Palladium-catalyzed coupling of stannanes with halides and sulfonates... 

In 2001, Nolan described the palladium/imidazoilium salt-catalyzed coupling of aryl halides with hypervalent organostannanes.The imidazolium salt 36 in combination with Pd(OAc)2 and TBAF was found to be most effective for the cross-coupling of aryl bromides and electron-deficient aryl chlorides with aryl and vinyl stannanes. 

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. 

Mann et al. showed that various acetophenones can be synthesized by carbonylative coupling of aryl triflates with SnMe4 [65]. Under mild conditions using the catalyst system Pd(OAc)2/dppp, good yields (70-94 %) were obtained (Scheme 4.32). In 2002 Mido and colleagues reported the palladium-catalyzed carbonylative coupling of tributyl(l-fluorovinyl)stannane with aryl halides and aryl triflates [66]. In the presence of a catalytic amount of palladium catalyst and CsF in DMF, aryl 1-fluorovinyl ketones were formed in good yields. 

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