Microchip reactor

A microstructured fluidic device that is used for conducting chemical reactions is called a microreactor. A microreactor is a reactor containing microstructures for chemical reactions. The size of the microstructure inside a microreactor usually ranges from several micrometers to several hundred micrometers. Various types of microstructured fluidic devices, such as microchip reactors and microtube reactors, have been developed for chemical reactions. Micromixers often serve as microreactors because reactions take place immediately after mixing. In some cases, external energies, such as thermal, photo, and electric energies, are provided in the microspace to promote the chemical reactions. For such purposes, special microreactors have been developed. 

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Eujii, M., Rapid enzymatic transclyco-sflation and oligosaccharide synthesis in a microchip reactor. Lab. Chip 2 (2002)... 

Yields from 42 to 99% were reported. Comparative and better yields were achieved when using a microchip reactor than the conventional lab batch technology. In case of improvement, the increase in yield amounted to about 10-20% [10,12]. 

GlaxoSmithKline Pharmaceuticals in Harlow, UK, performed an enamine synthesis using a microchip reactor under electroosmotic flow conditions [13], The aim was on... 

Figure 7.2 Simple microchip reactor with a Y-shaped junction...

Microchip reactors often contain a mixing part, such as a T-shaped or Y-shaped junction. A typical example is shown in Figure 7.2. A substrate solution and a reagent solution are introduced to inlets A and B, respectively, through holes in the cover plate. The inlet tubes are connected to the holes. The two solutions are combined at a Y junction and a reaction takes place in a reactor channel etched on the reactor plate. Then, a product solution comes out from outlet C on the cover plate. 

Microchip reactors are normally used to synthesize small quantities of compounds for screening purposes (Figures 7.3 and 7.4). The flow rate is usually very low (pl/min or nl/min). Therefore, microchip reactors are... 

Figure 7.3 Glass microchip reactor (Prof. Haswell, UK)...

Figure 7.4 Microchip reactor having a metal framework for connecting tubes (Dainippon Screen Mfg. Co., Ltd)...

A catalyst can be loaded on the surface of the channel wall of a glass microchip reactor. Such a microreactor has been used for gas/liquid/solid three-phase catalytic reactions, as shown in Figure 7.27. " ... 

Figure 7.28 Microchip reactor with a catalytic membrane...

Figure 8.16 Schematic diagram of a microchip reactor for Suzuki-Miyaura coupling...

GlaxoSmithKline Pharmaceuticals in Harlow, UK, performed the Hantzsch synthesis of 2-bromo-4 -methylacetophenone and l-acetyl-2-thiourea in NMP (N-methyl-2-pyrrolidone) using a microchip reactor under EOF conditions [10] (for EOF see [11]) [10]. This is claimed to be the first example of a heated organic reaction performed on a glass chip reactor under electroosmotic flow control, whereas only room temperature reactions were made earlier. In a wider scope, the Hantzsch synthesis is a further example to evaluate the potential of microfluidic systems for high-throughput screening. 

SmithKline Beecham Pharmaceuticals in Harlow, UK, carried out Wittig reactions using a microchip reactor under electroosmotic flow conditions. 2-Nitrobenzyltri-phenylphosphonium bromide was reacted with methyl 4-formylbenzoate and four other aldehydes, 3-benzyloxybenzaldehyde, 2-naphthaldehyde, 5-nitrothiophene-2-carboxaldehyde and 3-dimethylamino-4-propoxybenzaldehyde [16, 17]. 

GlaxoSmithKline Pharmaceuticals in Harlow, UK, performed an enamine synthesis using a microchip reactor under electroosmotic flow conditions [20]. The aim was a much higher research on enamine formation in microreactors focused on eliminating the need of using Lewis acid catalysts [21]. In addition, operation under mild conditions such as room-temperature processing was favored. 

The Nervous Systems Research branch of Novartis Pharma Ltd in Basel, Switzerland, carried out the aldol reaction using a microchip reactor under electroosmotic flow conditions. Aldol reactions are well-established routes for C—C bond formation in organic chemistry. The reaction requires the formation of enolates that themselves are one of the most profound species enabling C—C bond formation [22]. Reducing processing time is a driver for microchannel processing of aldol reactions [22], which can be accomplished using reactive reactants such silyl enol ethers. For example, the reaction between 4-bromobenzaldehyde and the silyl enol ether of acetophenone was performed in a microreactor [22]. 

Kanno, K.-L, Maeda. H., Izumo, S., Ikuno, M., Takeshita, K., Tashiro, A., and Euju, M. (2002) Rapid enzymatic transglycosylation and oligosaccharide synthesis in a microchip reactor. Lab Chip, 2,15-18. 

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