Hiyama transmetallation reaction

Hiyama and Mori have reported that homo-coupling reactions of vinyl-, aryl-, and alkynylsilanes are effectively promoted by an equimolar amount of CuCl and air (Scheme 10.218) [565]. The reaction mechanism probably involves formation of organocopper species by Si-Cu transmetalation and subsequent oxidative dimerization by air. The strong tendency of CuCl to activate alkynylsilanes has been used for coupling reactions with 1-chloroalkynes (Scheme 10.218) [566]. 

Transmetallation of alkenylsilanes takes place with retention of the double bond configuration, as in other cross-coupling reactions [295]. Owing to the lower transmetallation rate, competing 1,2-insertion of the alkene in the intermediate organopalladium complex (as a Heck type reaction) may take place, which affects the regioselectivity of the Hiyama reaction in some cases (Scheme 1.38) [296]. This... 

Scheme 1.38 The Hiyama reaction involving alkene insertion (as a Heck type reaction) before transmetallation.

Hiyama studied the stereoselectivity of alkyl transmetallation in the [Pd(PPh3)4]-catalyzed reaction of aryl triflates with enantiomerically enriched (S)-l-phenyl-ethyltrifluorosilane in the presence of TBAF (tetrabutylammonium fluoride) [297]. 

With the discovery of the Hiyama reaction other cross-coupling partners such as organosilicon derivatives have recently emerged as excellentreagents. 75 Various silicon substituted derivatives are suitable for transmetallation step when fluoride ions are added in the reaction medium. Organofluorosilanes bearing aryl, vinyl, or... 

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