Impact of residence time distributions in reacting magnesium packed beds on Grignard reagent formation – selectivity of Grignard reagent formation (part 2)

Abstract

Grignard reagents are used as intermediates in the production of complex molecules, since they can be used to form new carbon–carbon bonds, e.g. in the formation of active pharmaceutical ingredients. Side product formation like Wurtz coupling diminishes the selectivity in Grignard reagent formation and therefore side product formation needs to be reduced. It was found that the different pumping behaviours of a syringe pump, a valveless rotary piston pump and a micro annular gear pump and the obtained residence time distributions have an impact on the selectivity of the Grignard reagent formation. Selectivity can also be enhanced by the available magnesium surface and by choosing a tubular flow reactor instead of a batch reactor, showing the importance of choosing the right equipment and parameters for the specific reaction system.