An insight into the C–S coupling mechanism of aryl Grignard reagents with aryl arenesulfonates

Abstract

The reaction rate and thermodynamic parameters in the reaction of phenylmagnesium bromide with phenyl tosylate in THF:toluene binary solvents and also in toluene were analyzed. The relative changes in the rate constants are strictly bound to changes in the equilibrium constant of complex formation between the sulfonate and the Grignard reagent by replacement of a donor THF molecule as well as the transfer rate of the carbanion to the sulfonate in the complex. These results provide another support for asynchronous S N a mechanism comprising a four-center transition state mechanism.