Cyclopropanation of Dimethyl Fumarate and Maleate with gem-Dihalides Catalyzed by Co(0)- or Ni(0)-Complex and Zinc

Abstract The reaction of bis(acetonitrile)bis(diethyl fumarate)cobalt(0) with dibromomethane gave diethyl trans-1,2-cyclopropanedicarboxylate in a 67% yield based on the cobalt complex. Dimethyl cis-1,2-cyclopropanedicarboxylate was obtained in a 52% yield from the reaction of dimethyl maleate with dibromomethane in the presence of acetonitrilebis(dimethyl maleate)nickel(0) accompanied by the formation of the trans-isomer in a 14% yield. The addition of zinc gave cyclopropanes in over 100% yields based on cobalt or nickel. 3-Methyl- and 3,3-dimethyl-1,2-cyclopropanedicarboxylic acid esters were produced by the reaction of dimethyl fumarate or maleate with 1,1-dibromoethane and 2,2-dibromopropane. The yield in the cobalt catalyst system decreases with an increase of substituents of gem-dibromides, while that in the nickel catalyst system does not vary appreciably. A small amount of dimethyl isopropenylsuccinate was formed as a by-product in the reaction of 2,2-dibromopropane. A mechanism is briefly discussed which involves metallacyclobutane as an intermediate.