Recyclable Hypervalent-Iodine-Mediated Dehydrogenative Cyclopropanation under Metal-Free Conditions.

A method is developed for the synthesis of cyclopropanes from the C(sp)-C(sp) single bonds of β-keto esters with activated methylene compounds under metal-free conditions in the presence of 5-trimethylammonio-1,3-dioxo-1,3-dihydro-1λ-benzo[d][1,2]iodoxol-1-ol anion (AIBX), a recyclable water-soluble hypervalent iodine(V) reagent developed by our group. This mild, efficient method has a wide substrate scope and good functional group tolerance and is complementary to existing cyclopropanation strategies. The method can be used to construct polysubstituted ring-fused cyclopropanes and is amenable to further synthetic transformations for construction of complex biologically active molecules as well as asymmetric cyclopropanes (90% de) when a chiral ester auxiliary is used.