Chem. Commun.: Black Tech! Solvent free, multi-step, continuous production synthesis process

Mechanochemistry can be used to carry out chemical reactions, and reduce or eliminate the use of solvents, so that the risk of chemical synthesis is less, the production efficiency is improved, the cost is reduced, and the overall economy is more Recently, this kind of synthesis process has been improved from batch milling experiment to continuous extrusion process Extrusion is a general term used to describe a series of technologies involving the transportation of materials to a limited space In the process of processing, shear force and extrusion pressure will be applied to the material at the same time Through the external force, chemical reaction can be initiated and the desired product can be obtained when leaving the extruder Previously, it has been reported that the use of hot melt extrusion (HME) to produce CO ‐ crystals The basic structure of twin-screw extruder (source: chem Commin.) fine chemicals such as drugs, food additives and spices are usually manufactured by complex processes, with many complex reaction steps These steps can be time-consuming and expensive, and often require environmentally harmful solvents These solvents not only need for reaction, but also include organic solvents or aqueous solvents used in post-treatment These solvents become the largest waste in industrial production, which are troublesome, expensive and difficult to recycle Therefore, solvent-free reaction is an important direction of green chemistry, which is of great significance for large-scale production and environmental protection Standard screw configuration (source: chem Commun.) Deborah Crawford and her team at Queen's University Belfast, UK, have shown that the use of mechanochemical technology called twin screw extrusion can synthesize fine chemicals in a single continuous process without any dissolving or purification steps Twin screw extrusion is mainly used in the field of food to produce grains and chips, and in polymer processing to mix and react polymers It uses two screws that rotate side by side, rotating in parallel After feeding solid or semi-solid reactants, the engaged screws grind tightly and mix the materials together to force them through the confined space The rotating screw provides shear and limited space provides compression These forces lead to reactions Knoevenagel condensation reaction and Michael addition reaction synthesis 2 (source: chem Commun.) Deborah Crawford reported in this paper the use of twin screw extrusion (TSE) to manufacture metal organic frameworks (MOFs) and deep eutectic solutions (DES) Due to the advantages of using TSE to synthesize high quality materials, post-treatment and purification are not needed in most cases They successfully used this technology to complete four kinds of organic condensation reactions (Knoevenagel condensation, imine formation reaction, Michael addition reaction and aldol reaction) Among them, Michael addition reaction was found to be chemically selective Crawford's team lined up the screws like an extendable telescope Arranging the screws and feeding different reactants at different locations means that the team can combine multiple steps and three or more raw materials can react in one continuous process This will greatly improve production efficiency MCR reaction application (source: chem Commin.) Crawford explained that raw materials are added along the extruder barrel, and the second, third and fourth transformations are carried out on the starting substrate, and there is no need to add extra process between each step They first integrated Knoevenagel condensation with Michael addition, and then applied it to more complex petasis reactions (used to make amines and amino acids), which had never been realized before Crawford added that we have demonstrated the ability to produce kilogram grade products per hour using this process in conventional laboratories In industrial production, the use of larger extruders can achieve tons per hour of production capacity This process has great potential for large-scale production If multiple extruders are operated in parallel, a large number of compounds can be easily produced, and it has many advantages such as controllable, safe, continuous, efficient and low pollution Paper link: http://pubs.rsc.org/en/content/articlelanding/2017/cc/c7cc06010fා! Divabstract correspondence Author: https://