The selective reaction of 1,2-diols with electrophiles mediated by dialkyltin oxides has proven value both within and beyond carbohydrate chemistry.  In general, a 1,2-diol like 1 is reacted first with an equivalent amount of dibutyltin oxide 2a (R = Bu) under dehydrating conditions to provide an intermediate stannoxane 3a (Eq 1). This is then reacted in a separate step with an electrophile to provide a mono-functionalized product 4, often with high regioselectivity. Tosylation is shown in Eq1, but acylation and a number of other transformations can be accomplished by this procedure.Recently, Martinelli and coworkers described an important advance in selective sulfonylation byintroducing a one-step procedure that requires only 2% of the tin oxide along with triethylamine (Eq1). This procedure is attractive because only a small amount of tin must be removed from the final product; however, chromatography is still required and the tin is not recovered for reuse. Even when catalytic amounts of tin are used, environmental concerns dictate that it be recovered rather than dis-carded whenever possible.

Fluorous chemistry has recently become and important tool for synthetic organic chemists.  Compounds containing perfluoroalkyl tags can be easily separated from a reaction mixture into the fluorous phase by either liquid-liquid extraction with a fluorous solvent or solid-liquid extraction with fluorous silica gel.  If suitable carbon spacers are used the fluorous compound mimics the behavior of its alkyl equivalent.  We therefore applied our fluorous techniques the development of a new fluorous tin oxide 2b for use in Martinelli’s catalytic tosylation of 1,2 diols.  The proposed separation scheme for this fluorous tin oxide is shown in Figure 1. 

            The fluorous tin oxide can be used both stiochoimetrically and catalytically to effect the selective monotosylation of several 1,2 diols and can be readily recovered by liquid-liquid extraction with FC-72 (a fluorinated solvent) or solid-liquid extraction with fluorous silica gel.  After isolation, the fluorous tin oxide was reused with similar results.  This work has been accepted for publication in Tetrahedron Letters, and is funded by the National Institute of Health.