Fluorous Tin Hydrides:  A New Family of Reagents for Use and Reuse in Radical Reactions

Eight members of a new family of highly fluorinated (fluorous) tin hydrides have been synthesized and studied as reagents for radical reactions. Tin hydrides of the general formulas [Rf(CH₂)_n]₃SnH and [Rf(CH₂)_n]Me₂SnH have been prepared where Rf is C₄F₉, C₆F₁₃, C₈F₁₇, or C₁₀F₂₁ and n is 2 or 3. These reagents are highly soluble in fluorinated solvents, and partition coefficients between perfluorohexanes and several organic solvents have been measured. The reagents are generally useful for reductive radical reactions and hydrostannation reactions that would typically be conducted with tributyltin hydride. Stoichiometric and catalytic procedures have been developed, and both feature very easy separation of the tin products from the organic products by convenient liquid−liquid or solid−liquid extractions. The tin reagents are recovered from reactions in high yields and are routinely reused. Rate constant measurements suggest that the fluorous tin hydrides are about as reactive as (or in some cases, slightly more reactive than) tributyltin hydride. The reagents show excellent potential for large-scale application in “green” (environmentally friendly) processes. In addition, they are useful for combinatorial and parallel synthesis applications both as reagents and as scavengers in phase-switching procedures.