3-exo-tet Cyclization of 2,2-disubstituted 1,3-dihalopropanes with indium in aqueous and ionic liquid solvent system

The 3-exo-tet cyclization of 2,2-disubstituted 1,3-dihalopropanes with In powder in THF solution of 20% H2O, dioxane solution of 20% H2O, and ionic liquids, such as [bmim]Br, [bmim]Cl, and [bmin]BF4, respectively, was efficiently carried out to form the corresponding 1,1-disubstituted cyclopropanes in good yields. The cyclopropanation of 2,2-disubstituted 1,3-dihalopropanes with In powder in ionic liquids, such as [bmim]Br, [bmim]Cl, and [bmin]BF4, was markedly accelerated compared with that in a THF solution of 20% H2O and a dioxane solution of 20% H2O. The mechanism was proposed to involve the radical 3-exo-tet cyclization of the formed 3-halopropyl radical.

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