Cp2ZrCl2-Mediated Three-Component Coupling Reactions of CO2, Ethylene (or Alkynes), and Electrophiles Leading to Carboxylic Acid Derivatives

Zirconacycles 1 and 2 can be simply generated from Cp2ZrCl2, EtMgBr, and an atmospheric pressure of CO2. The treatment of Cp2ZrCl2 with EtMgBr followed by exposure to CO2 generates zirconacycle 1, which can react with various electrophiles to give a variety of carboxylic acid derivatives. Unsaturated zirconacycles 2 can also generated from Cp2ZrCl2, EtMgBr, alkynes, and CO2. Complexes 2 react with electrophiles to give (alpha),(beta)unsaturated acids stereoselectively.