Preparation of Grignard reagents from magnesium metal under continuous flow conditions and on-line monitoring by NMR spectroscopy

A convenient method for the classical preparation of Grignard reagents from aryl halides and magnesium using a fluidized bed reactor under continuous flow conditions was developed. The process was combined with quenching of the Grignard reagent by CO2 as a model reaction performed using a second flow reactor. The formation and quenching of the reagent was monitored by on-line 1H NMR spectroscopy. The combination of continuous flow operation for Grignard reagents with reaction monitoring by on-line NMR spectroscopy allows one to quickly optimize the working conditions.