Linear free-energy correlation analysis of the electronic effects of the substituents in the Sonogashira coupling reaction

Relative rate constants (k_rel) for the Sonogashira coupling were determined in competitive reactions between iodobenzene and a series of para- and meta-substituted iodobenzenes and compared to the charge on iodine and the z-component of the quadrupole moment of the iodine-bearing carbon. We use an Hammett correlation analysis and the computational data to provide further evidence that the rate limiting step of the Sonogashira reaction is the initial oxidative addition of Pd to the carbon-iodine bond.