This thematic issue demonstrates the development of flow chemistry from a prerogative of the petrochemical industry to a technology of enormous value for chemical synthesis and a key for sustainable manufacturing. Transformations viewed impracticable under batch conditions can be enabled by the precise reaction control of flow reactors: photochemical applications, handling of reactive intermediates or reactive reagents, and new heating concepts now allow for accelerated synthesis while only a small volume of the reaction mixture inside the flow reactor is exposed to extreme conditions. Technological advances, including miniaturization and automation, have rendered continuous flow processes an enabling technology for organic synthesis.
Graphical Abstract
Scheme 1: Radical chain mechanism for a photo-induced C–H chlorination reaction.
Figure 1: Components for photoflow setup: (a) MiChS LX-1 reactor and (b) MiChS LED-s (365 ± 5 nm, 60–600 W).
Scheme 2: Model reaction: photoflow C–H chlorination of ethylene carbonate (1) to chloroethylene carbonate (2...
Figure 2: Photoflow setup for the C–H chlorination of ethylene carbonate (1).
Graphical Abstract
Scheme 1: Methods for accessing 1,3,4-oxadiazoles.
Scheme 2: Synthesis of acyl hydrazones 1a–j.
Scheme 3: Iodine-mediated cyclisation of hydrazones 1a–j yielding oxadiazoles 2a–j. Reaction conditions: 1a–j...
Scheme 4: Synthesis of complex oxadiazoles.
Scheme 5: Continuous flow scale-up reaction with in-line quench and extraction.
Scheme 6: Continuous flow setup equipped with in-line extraction and purification.
Graphical Abstract
Figure 1: Reaction sequence starting from GlcNAc with ManNAc as an intermediate. Pyr is added in the second s...
Figure 2: Enzyme loading after immobilization of the epimerase and aldolase on different carriers.
Figure 3: Evaluation of immobilized epimerase on different carriers with respect to specific activity. Reacti...
Figure 4: Evaluation of immobilized aldolase on different carriers with respect to specific activity. Reactio...
Figure 5: Relative activities in repetitive batch experiments of the immobilized epimerase on polymethacrylat...
Figure 6: Relative activities in repetitive batch experiments of the immobilized aldolase on amino methacryla...
Figure 7: Recycling study of immobilized epimerase and aldolase. Assay conditions: 100 mM Tris, pH 8, 40 °C, ...
Figure 8: Measured reaction rates of the immobilized epimerase. The dashed line is the fit according to the M...
Figure 9: Measured reaction rate of the immobilized epimerase as a function of pyruvate and pressure. Dashed ...
Figure 10: Measured reaction rate (left) and the determined inhibition constant by pyruvate (right) at differe...
Figure 11: Measured kinetics of the aldolase when varying the pyruvate and ManNAc concentration (given in mM) ...
Figure 12: Circular reactor, vessel mixing was achieved with a magnetic stirrer and samples were taken directl...
Figure 13: Aldolase: Change of the equilibrium constant at different pressures. Starting concentrations were v...
Figure 14: Progress curve of the circular reactor with both reactions at varying pressures. Starting condition...
Figure 15: Residence time distributions of the stand-alone system and the reactor integrated into the system. ...
Figure 16: Reactor set-up (left to right): UHPLC pump, heated fixed-bed reactor, capillaries (ID: 25 µm or 50 ...