Borosilicate microreactor

In another glass (borosilicate) microreactor [channel dimensions = 350 pm (wide) x 52 pm (deep) x 2.5 cm (long)], Wiles et al. (2004b) prepared a series of 1,2-azoles, illustrating the synthesis of a pharmaceutically relevant core motif. Reactions were performed using electroosmo-tic flow (EOF) as the pumping mechanism and employed separate... 

Asymmetric cyanosilylation of ketones and aldehydes is important because the cyanohydrin product can be easily converted into optically active aminoalcohols by reduction. Moberg, Haswell and coworkers reported on a microflow version of the catalytic cyanosilylation of aldehydes using Pybox [5]/lanthanoid triflates as the catalyst for chiral induction. A T-shaped borosilicate microreactor with channel dimensions of 100 pm X 50 pm was used in this study [6]. Electroosmotic flow (EOF) was employed to pump an acetonitrile solution of phenyl-Pybox, LnCl3 and benzal-dehyde (reservoir A) and an acetonitrile solution of TMSCN (reservoir B). LuC13-catalyzed microflow reactions gave similar enantioselectivity to that observed in analogous batch reactions. However, lower enantioselectivity was observed for the YbCl3-catalyzed microflow reactions than that observed for the batch reaction (Scheme 4.5). It is possible that the oxophilic Yb binds to the silicon oxide surface of the channels. 

Figure 4.20 Mukaiyama aldol reaction in a borosilicate microreactor under parallel flow (courtesy of Elsevier) [212],...

WUes and Watts [48,53] have reported the use of a rather successful heterogenic catalytic system to carry out these reactions. They have tested a borosilicate glass microreactor (dimensions 3.0 x 3.0 x 0.6 cm) consisting of two etched layers with two inlets, mixing channels, a larger etched region and the outlet. A solid-supported catalyst was dry-packed in this structure (Fig. 4). 

Apparatus and Procedure. The conventional microreactor was used to determine catalytic activities. The reactor was a 4 mm id borosilicate glass tubing, directly connected to the dual column gas chromatograph... 

Compared with the above examples, whereby an array of pharmaceutically important molecules have been synthesized under pressure-driven flow, Garcia-Egido et al. (2002) reported the synthesis of fanetizole (207), an active compound for the treatment of rheumatoid arthritis, utilizing EOF. Employing a borosilicate glass microreactor fabricated at The University of Hull, the authors demonstrated the first example of a heated EOF-controlled reaction. As Scheme 60 illustrates, using... 

One exception is the special types of photostructurable glass. For the construction of microreactors, the borosilicate types of glass as well as fused silica are the most important ingredients. 

The combination of fluoride ions and enol silyl ethers provides a useful method for the generation of enolate anions [9]. Watts, Haswell and coworkers applied a borosilicate glass microreactor, having channel dimensions of 100 pm x 50 pm and equipped with an electrosmotic flow (EOF) pumping system, to the C-acylation of enolate anions, which leads to 1,3-diketones [10,11]. A THF solution of tetrabutyl-ammonium fluoride (TBAF) was placed in reservoir A, a THF solution of benzoyl... 

A borosilicate glass microreactor (152 pm (width), 51pm (depth) and 2.3 cm (length)) that was connected to a T-shaped PEEK (poly(ether-ether-ketone)) unit (MicroTee, Upchurch Scientific) was used for the formation of sodium enolate of... 

Haswell and coworkers carried out the Wittig reaction of 2-nitrobenzyl triphenylpho-sphonium bromide with methyl 4-formylbenzoate in a microflow system [17,18]. They used a borosilicate glass microreactor with T-shaped channels (width = 200 pm and depth = 100 pm), and the reagents were added via EOF by applying a constant... 

Microreaction technology has also been applied to peptide synthesis. Haswell and coworkers demonstrated that, using a borosilicate glass microreactor, the desired... 

A conventional pulse catalytic microreactor was used with 15-65 mg of the catalyst for the cumene runs and 65 mg for the 2,3-dimethylbutane runs. The catalyst was held between 2 small plugs of borosilicate glass wool in a 5-mm ID diameter borosilicate reactor. In some experiments, the catalyst was diluted with 96% silica porous glass powder. The helium gas was purified by passage through alumina kept at liquid nitrogen temperature. The reaction temperature was measured by a thermocouple located adjacent to the reactor. The catalyst was pretreated at the desired temperature for 16 hours in a stream of helium. The products were analyzed with a dioctyl phthalate gas chromatography column at llO C. 

Watts and Has well have demonstrated dipeptide and tripeptide synthesis, as the first example of EOF-based multistep s5mthesis, in a borosilicate glass microfluidic channel, as shown in Fig. 2. A T-shaped microreactor with... 

Nitration of benzene Borosilicate glass microreactor Doku et al. [69]... 

More recently, Hooper and Watts [9] investigated the incorporation of deuterium labels into an array of small organic compounds via the base-mediated acylation of primary amines. Unlike the previous examples described here, the use of acetic-ds anhydride proved undesirable as it led to the generation of acetic-ds add as the byproduct, a problem that was circumvented through the use of acetyl-d3 chloride (Scheme 3.6). To perform a reaction, the authors employed two borosilicate glass microreactors coimected in series (reactor 1 = 201 pm wide x 75 pm deep x 2.0 cm... 

A packed-bed microreactor system built from borosilicate glass consisting of an evaporator, aheater, reactor bed and a gas collector was reported by Giorecki et al. [35]. Methanol fuel was used and reformed with a commercial Cu/ZnO catalyst provided by Siid-Chemie. 

All processes within this system s boundaries were involved in the balance. Also, the dependence of the additional expenditure of materials and energy necessary on the choice of the reactor (stainless-steel microreactor versus borosilicate glass double-walled reactor) was investigated. This aspect was analyzed with the help of different case scenarios. In order to provide a holistic view on its influence, the peripheral equipment such as the reaction vessels, control elements, thermostats and distillation equipment was also included in the balance (Figure 14.1). 

Watts and Haswell have demonstrated dipeptide and tripeptide synthesis, as the first example of EOF-based multistep synthesis, in a borosilicate glass microfluidic channel, as shown in Fig. 2. A T-shaped microreactor with 200pLmx50pLm channels was fabricated the overall reactor dimensions were 20 mm x 20 mm x 25 mm. The channels were filled with microporous silica frit to reduce hydrodynamic effects. After deprotection with one equivalent of hydrazine, tripeptide synthesis was also demonstrated. An offline high-pressure liquid chromatograph (HPLC) was used to determine the results of the synthesis. 

Stainless steel and PTFE capillary Borosilicate glass microreactor PTFE capillary PTEE capillary... 

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