Organic synthesis using ketyl radicals mediated by $SmI_2$

Abstract

$SmI_2$ is widely utilized in reduction of various functional groups and reductive coupling and cyclization reaction based on its strong oxophilicity. In a reductive coupling of propargyl ester as a ketyl radical acceptor and ketones or α-keto amides using $SmI_2$, α,β-unsaturated γ-hydroxy alcohols were obtained in good yields. It has been found that coupling of α-keto amide and propargyl esters gave the coupled products in relatively low yields. α-Iodomethyl cyclic β-keto esters were treated with $SmI_2$ to give one-carbon expanded products in good yields. Catalytic $NiI_2$ as well as HMPA greatly enhances the efficiency of this reaction. It is noteworthy that α-bromomethyl cyclic β-keto ester also gave the ring-expanded products in excellent yields