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Scalable continuous synthesis of Grignard reagents from in situ-activated magnesium metal

: Menges-Flanagan, Gabriele; Deitmann, Eva; Gössl, Lars; Hofmann, Christian; Löb, Patrick


Organic process research & development 24 (2020), Nr.2, S.315-321
ISSN: 1083-6160
ISSN: 1520-586X
Fraunhofer IMM ()
continuous synthesis; grignard reagents; Grignard-Reaktion; continuous processing; magnesium; Magnesium; Flow chemistry

The continuous synthesis of Grignard reagents has been investigated under continuous processing conditions using Mg turnings at variable liquid throughputs and concentrations. A novel process window easily accessible through continuous processing was employed, namely, using a large molar access of Mg turnings within the reactor and achieving Mg activation by mechanical means. A laboratory and a 10-fold-increased pilot-scale reactor setup were built and evaluated, including integrated inline analytics via ATR-IR measurements. The main goal of this work was to explore the full potential of classic Grignard reagent formation through the use of scalable flow chemistry and to allow for fast and safe process optimization. It was found that on both the laboratory and pilot scales, full conversion of the employed halides could be achieved with a single passage through the reactor. Furthermore, Grignard reagent yields of 89–100% were reached on the laboratory scale.