Polymethylhydrosiloxane , Stille

Equation 11.29 One-pot hydrostannylation and Stille coupling (PMHS = polymethylhydrosiloxane). 

A particularly nice application of the hydrostannylation is the Stille coupling (for reviews on the Stille coupling see [119-123]) that becomes catalytic in tin, as introduced by Maleczka and coworkers [124,125]. Terminal alkynes and organobromides can be coupled in the presence of catalytic amounts of tributyltinchloride and Pd(II) and Pd(0) catalysts and stoichiometric amounts of PMHS (polymethylhydrosiloxane) to give the alkene derivatives 166-173 in good to excellent yields (Scheme 64). 

Reactions Catalytic in Tin Maleczka and Terstiege [72] have published several papers in this area. They first developed a one-pot hydrostannylation/Stille couphng protocol for reactions between 1-alkynes and bromostyrene to give 1,3-dienes. A mixture of BUjSnCl (catalytic amount), polymethylhydrosiloxane (PMHS) and aqueous sodium carbonate (to convert the chloride to bis(tri-n-butyltin)oxide that reacts with PMHS to give BUjSnH in situ) in combination with Pd2(dba)j and trifurylphosphine leads to diene formation. Use of MejSnCl instead of the tributyltin chloride [73] improves yields drastically (to up to 90%). Further improvement is obtained in the third protocol reported [74a,b], which was used to prepare... 

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