Application of Fluoride-Catalyzed Silane Reductions of Tin Halides to the in Situ Preparation of Vinylstannanes

We have found that either Bu 3 SnCl/PMHS/KF (aq) or the combination of tributyltin fluoride, PMHS, and catalytic quantities of tetrabutylammonium fluoride can serve as in situ sources of tributyltin hydride for both free radical and palladium-catalyzed hydrostannylation reactions. These methods are tolerant of a variety of functional groups, including silyl ethers. Furthermore, Me 3 SnCl is also reduced under these conditions, providing a relatively convenient and safe manner by which Me 3 SnH can be formed and reacted. We have also observed that the Bu 3 SnCl/siloxane/fluoride combination offers improvements over the existing protocols for transforming 1-bromoalkynes into trans -1-(tributylstannyl)-1-alkenes. Specifically, the KF/PMHS methodology allows the 1-bromoalkyne to be formed and reacted in a single pot and with substoichiometric amounts of tin. Finally, alternative reductants such as Red-Sil are also amenable to the method.