Tributyltin Hydride (Bu₃SnH)

Introduction

The realization of compatibility of radical methods with a range of functional groups without further protection has led to an increased interest in the use of radicals in organic synthesis. Bu₃SnH is a well-known radical reagent because of its relatively weak and nonionic bond interaction between tin and hydrogen that can be cleaved homolytically. [1] Thus it has been explored extensively in reductive cleavage, [2a] radical dehalogenation, deoxygenation [2b] and intramolecular radical cyclization [2c] as well as in the synthesis of various heterocyclic compounds, natural products and many pharmaceutically important drugs. [2d-j]

Bu₃SnH is commercially available as a colourless liquid and can be stored under refrigeration. It can be prepared via reduction of tributyltin oxide with hydrosiloxane. [3a] It can also be generated easily in situ by the action of NaBH₄ or Et₃SiH on Bu₃SnCl. [1] [3b]

The problems associated with this reagent are that it is highly toxic and removal of tin impurities from the product is often very difficult. This has been overcome recently by using a mixture of KF and silica gel as the stationary phase in column chromatography to reduce the level of tin impurities in the product to 30 ppm. [3c]

References

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