Microreactor technology synthesis

Acke DRJ, Stevens CV, Roman BI (2008) Microreactor technology continuous synthesis of lH-isochromeno[3, 4-d]imidazol-5-ones. Org Process Res Dev 12(5) 921-928... 

Novel applications have been developed from the combination of microreactor technology and nonequilibrium microplasma chemistry. Here we discuss a selection from the recent literature on this topic to illustrate several main trends. We will focus on microplasmas in confined microchannels for the purpose of chemical synthesis and environmental applications. 

More recently, microreactor technology has entered the field of biocatalysis enzymes are used for synthesis rather than for diagnostics. The concept behind the use of biocatalytic microreactor systems is in fact twofold. First, a miniaturized reactor allows an efficient use of small amounts of enzyme, when enzyme kinetics determination is involved. Second, the classical advantages of microreactors in synthesis, namely, better control over heat- and mass-transfer... 

Microreactor technology offers the possibility to combine synthesis and analysis on one microfluidic chip. A combination of enantioselective biocatalysis and on-chip analysis has recently been reported by Beider et al. [424]. The combination of very fast separations (<1 s) of enantiomers using microchip electrophoresis with enantioselective catalysis allows high-throughput screening of enantioselective catalysts. Various epoxide-hydrolase mutants were screened for the hydrolysis of a specific epoxide to the diol product with direct on-chip analysis of the enantiomeric excess (Scheme 4.112). 

Hessel et al. [33] centered their book on the analysis of a series of specific examples, from gas- and liquid-phase, to gas/liquid-phase and liquid/liquid-phase reactions, where the use of a microreactor (or more generally microprocess technology) allows significantly enhance in performance. It is a very valuable source of examples taken from over 1500 publications analyzed. The recent book ofWirth [34] focuses instead on the analysis of the opportunities for organic synthesis and catalysis in the use of microreactor technology. 

Why is fast chemical synthesis needed The most appropriate answer to this question is because we can just do it with our present knowledge and technologies. Extremely fast reactions that are complete within a second used to be difficult to control on a preparative scale because we were using conventional macrobatch reactors. However, we are now able to conduct such reactions in a controlled manner with the aid of microflow systems constructed with micro-structured reactors and microreactor technology. 

Microreactor technology has also been applied in some reactions to be able to more accurately control the stereoselectivity of reactions. Skelton and coworkers have reported the application of microreactors for the Wittig reaction [14, 35], The authors used the microreactor to prepare the cis- and tr ns-nitrostilbene esters 19 and 20 using the Wittig reaction (Scheme 14.6). Several features such as stoichiometry and stereochemistry were investigated. When two equivalents of the aldehyde 22 to the phosphonium salt 21 were used in the reaction, a conversion of 70% was achieved. The microreactor demonstrated an increase in reaction efficiency of 10% over the traditional batch synthesis. The reaction stoichiometry... 

Mason B, Price K, Steinbacher J, Bogdan A, McQuade D (2007) Greener approaches to organic synthesis using microreactor technology. Chem Rev 107(6) 2300-2318... 

There is a chance that continuous flow synthesis will see a similar development in chemical synthesis as was encoimtered in analytical chemistry when HPLC was introduced into the chemist s laboratory. In this context, microreactor technology and microfluid systems will also play an important role [66,67]. 

Besides the synthesis of bulk polymers, microreactor technology is also used for more specialized polymerization applications such as the formation of polymer membranes or particles [119, 141-146] Bouqey et al. [142] synthesized monodisperse and size-controlled polymer particles from emulsions polymerization under UV irradiation in a microfluidic system. By incorporating a functional comonomer, polymer microparticles bearing reactive groups on their surface were obtained, which could be linked together to form polymer beads necklaces. The ability to confine and position the boundary between immiscible liquids inside microchannels was utilized by Beebe and coworkers [145] and Kitamori and coworkers [146] for the fabrication of semipermeable polyamide membranes in a microfluidic chip via interfacial polycondensation. 

The use of microreactor technology for polymer chemistry presents an interesting alternative to conventional processing methods, in both batch and macroscale continuous flow. Microreactors offer a better process control of many exothermic polymerization processes, leading to increased product quality such as narrower polydispersity, and they allow for the synthesis of novel polymeric materials for a range of new applications. 

Wiles, C., et al.. The apphcation of microreactor technology for the synthesis of 1,2-azoles. Organic Process Research and Development, 2004, 8 28-32. 

Ahmed-Omer B, Brandtand JC, Wirth T (2007) Advanced organic synthesis using microreactor technology. Org Biomol Chem 5 733-740... 

Continuous microreactor systems have gained a lot of interest in the field of organic synthesis as these possess enhanced mass and heat transfer properties. Microreactor technology also offers a contemporary way of conducting chemical reactions In a more sustainable fashion due to the miniaturization and increased safety, and also In a technically improved manner due to intensified process efficiency. Recent developments in this area related to the synthesis of heterocyclic compounds are recorded in this chapter. Also, telescoping, in which several subsequent reaction steps (with or without purification) can be achieved by connecting different reactors to each other, is covered. 

Since microreactor technology was first seen as an effective method for the synthesis of chemical compounds, enormous advances have been made in this area. The examples discussed in this chapter and many other illustrations in the Hterature, prove the potential of flow chemistry in chemical and phamiaceutical production and confirm the expected benefits and the intensification of chemical processes. The above-mentioned flow processes furthermore illustrate the flexibiHty of microfluidic devices, as flow chemistry allows the Hnking of individual reactions into multi-step reactions as well as preparing a series of analogues by simple modifications. A variety of technical approaches can additionally be considered for the implementation of flow processes, such as the automated and real-time in-line analysis and... 

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