Alkenyltins Stille coupling

In organic synthetic procedures, alkenyltin compounds are often prepared with a view to subsequent transmetalla-tion with lithium, or to the Stille coupling reaction with a palladium catalyst (Equations (70) and (71)). 

The a-substituted alkenylmetals used in Pd-catalyzed cross-coupling have been mainly those containing Mg, Zn, B, and Sn, as shown in Table 12 as well as Schemes 54-57. Of these, a-substituted alkenylmetals containing Mg and Zn can readily be prepared by direct oxidative metaUation of 2-halo-l-alkenes that are easily accessible by Markovnikov addition of HX to 1-alkynes (Scheme 54). a-Substituted alkenyltin compounds have been prepared and used in the construction of bicyclic diene systems via intramolecular Stille coupling, as shown in Scheme 55. ... 

Some trans-a,, along with cw-a,/3-substituted alkenyltin compounds have been prepared and used in intramolecular coupling reactions to synthesize cyclic compounds,as shown in Scheme 69. The reaction could be mediated by stoichiometric CuCl instead of catalytic Pd complexes,while the use of Cu(I) as a cocatalyst in Stille coupling has been demonstrated. 

In the Stille coupling, Pd catalyzes the direct linkage between alkenyl halides and alkenyltin compounds ... 

Deshpande [74], has carried out carbon-carbon bond formation on a solid support using a polymer-supported aryl iodide and vinyl (or aryl) tins. In the area of natural-product synthesis. Overman and co-workers have carried out total syntheses of (—) and (+)-strychnine which include an aryltin/CO/alkenyltin coupling step [75] (a technique introduced earlier by Stille [1]). Very recently, Heathcock and co-workers have reported total syntheses of (—)-papuamine and (—)-haliclonadiamine which include a key step in which a 1,3-diene unit is constructed by coupling two alkenyltin moieties thus reaction (Scheme 4-27) only proceeds in the presence of copper (I) iodide [76]. 

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