One- and two-electron reactions from the rearrangement of α-ketocyclopropanes by O-stannyl ketyls

This work summarizes an investigation of the bifunctional reactions of tin(IV) enolates and radicals derived from the cleavage rearrangement of ketocyclopropanes with tributyltin hydride. The intermediates provide an unparalleled dual reactivity in synthesis, allowing for independent transformations with both electrophiles and radicophiles. Reactions of the enolate with aldehydes led to aldol products in diastereoselectivities up to 20:1 favoring the erythro product. Reactions with alkyl halides were also successful, constructing new carbon-carbon bonds by a nucleophilic displacement reaction. These reactions provide a neutral, mild, and novel alternative to the classical methods of ketone enolate alkylation performed with hindered bases. Finally, the radical portion of the cleaved intermediates, separated from the enolate by a methylene unit, was reacted with allylstannanes to prepare new gamma-carbon bonds to an allyl unit. Overall, these new trialkyltin-associated radical anion intermediates allow entry into the rapidly developing manifold of one- and two-electron reactions.