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For some recent selected books and reviews: (a) Microreactors in
Herein, we illustrate how microreactor technology can be used as a tool for reaction screening and optimization, in addition to improving the reaction chemistry. We report the in-situ generation of azo compounds by reactive quenching of diazonium intermediates in microreactors. This involves an electrophilic aromatic substitution reaction, namely, an azo-coupling reaction performed in continuous-flow systems in the presence of a phase transfer catalyst with great emphasis on compounds that do not easily couple. Capitalizing on the benefits of a large surface area and the short molecular diffusion distances observed in microreactors, in-situ phase transfer catalyzed azo-coupling reaction of diphenylamine to p-nitroaniline was investigated. A rapid and easy optimization protocol was established which yielded a 99%, 22%, and 33% conversion of diphenylamine, carbazole, and triphenylamine, respectively, in approximately 2.4 min.
The reaction of different types of aromatic and aliphatic epoxides with sodium azide to give vicinal azido alcohols was studied in a microreactor with and without pillars in the channels. Dependent on the substrate, the regioselectivity of the ring opening is affected by the used solvent system, viz. acetonitrile–water (sometimes with 10% acetic acid to promote the reactivity of substrates) or t-butyl acetate–water containing Tween80 as a surfactant. For styrene oxide and α-methylstyrene oxide, the α/ß regioselectivity changes from 4 to 10 and 1.7 to 6.2, respectively, going from acetonitrile–water to Tween80-containing t-butyl acetate–water. The addition of a surfactant (Tween80) stabilizes the interface in the biphasic t-butyl acetate–water. Pillar-containing microreactors gave better conversions than microreactors without pillars and lab scale reactions, probably due to better mixing.
Different electrochemical microreactors for continuous flow synthesis are described in this review. Advantages of flow over batch type chemistry are highlighted as well as novel developments in construction of such devices.
be reached through additional micromixing using flow microreactor techniques. Microreaction technology is already known for causing process intensification in multiphase catalytic reactions [ 13 – 15 ]. Owing to the short diffusion paths due to
The preparation of magnetic iron oxide nanoparticles within microreactors is reported. The proportion of γ-Fe2O3 and Fe3O4 in the sample was determined, an important parameter for reproducibility in applications.