Reaction of gem-Dibromocyclopropanes or Iodobenzofuran with Trialkylmanganate

Treatment of gem-dibromocyclopropanes with trialkylmanganate, derived from manganese(II) chloride and three equivalents of Grignard reagent or alkyllithium, followed by an addition of electrophiles provided dialkylated cyclopropanes in good yields. It was found that the reaction of gem-dibromocyclopropanes with alkylmagnesium halide proceeded in the presence of a catalytic amount of manganese(II) chloride. The use of iodobenzofuran in place of gem-dibromocyclopropane gave a ring opening product, 2-alkenylphenol.