Radical 3-exo-tet cyclization of 1,3-dihalopropanes with SmI2 to form cyclopropanes

The preparation of 1,1-disubstituted and monosubstituted cyclopropanes from corresponding 2,2-disubstituted and 2-monosubstituted 1,3-dihalopropanes, respectively, with SmI2 in THF was efficiently carried out. The reaction mechanism was proposed to proceed in a radical 3-exo-tet manner based on Baldwin's rule.