Organic synthesis by Twin Screw Extrusion (TSE): continuous, scalable and solvent-free

D. E. Crawford, C. K. G. Miskimmin, Ahmad B. Albadarin, Gavin Walker, S. L. James

Research output: Contribution to journalArticlepeer-review

71 Citations (Scopus)
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Abstract

Mechanochemistry provides a method to reduce or eliminate the use of solvents by carrying out reactions through the grinding of neat reagents. Until recently a significant drawback of this form of synthesis has been the limited ability to scale up. However, it has been shown that twin screw extrusion (TSE) may overcome this problem as demonstrated in the continuous synthesis of co-crystals, Metal Organic Frameworks (MOFs) and Deep Eutectic Solvents (DES), in multi kg h−1 quantities. TSE has provided a means to carry out mechanochemical synthesis in a continuous, large scale and efficient fashion, which is adaptable to a manufacturing process. Herein, we highlight the potential of this technique for organic synthesis by reporting four condensation reactions, the Knoevenagel condensation, imine formation, aldol reaction and the Michael addition, to produce analytically pure products, most of which did not require any post synthetic purification or isolation. Each reaction was carried out in the absence of solvents and the water byproduct was conveniently removed as water vapour during the extrusion process due to the elevated temperatures used. Furthermore, the Knoevenagel condensation has been studied in detail to gain insight into the mechanism by which these mechanochemical reactions proceed. The results point to effective wetting of one reactant by another as being critical for these reactions to occur under these reaction conditions.
Original languageEnglish
Pages (from-to)1507-1518
Number of pages12
JournalGreen Chemistry
Issue number6
Early online date17 Jan 2017
DOIs
Publication statusEarly online date - 17 Jan 2017

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