Versatile Synthesis of Cyclopropanecarboxylic Acid Derivatives by the Ni(CO)<sub>4</sub>-Induced Reductive Carbonylation Reaction of<i>gem</i>-Dibromocyclopropanes
Reductive carbonylation of gem-dibromocyclopropanes was achieved by treatment with tetracarbonylnickel in the presence of alcohols, amines, thiols, or imidazole in DMF leading to the corresponding cyclopropanecarboxylic acid derivatives, respectively. Use of disulfides as an initial nucleophile resulted in carbonylation with sulfenylation at the geminal position. This method was applied to the intramolecular