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Strategic Application of Residence-Time Control in Continuous-Flow Reactors.

Mándity IM, Ötvös SB, Fülöp F - ChemistryOpen (2015)

Bottom Line: As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals.Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity.Such a fine reaction control cannot be performed in conventional batch reaction set-ups.

View Article: PubMed Central - PubMed

Affiliation: Institute of Pharmaceutical Chemistry, University of Szeged Eötvös u. 6, H-6720, Szeged, Hungary.

ABSTRACT
As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals. Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity. This review furnishes a brief insight into flow reactions in which high chemo- and/or stereoselectivity can be attained by strategic residence-time control and illustrates the importance of the residence time as a crucial parameter in sustainable method development. Such a fine reaction control cannot be performed in conventional batch reaction set-ups.

No MeSH data available.


Related in: MedlinePlus

CF set-up for the selective DIBALH reduction of ethyl hydrocinnamate (M=mixing unit, R=tubular reactor).24
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fig11: CF set-up for the selective DIBALH reduction of ethyl hydrocinnamate (M=mixing unit, R=tubular reactor).24

Mentions: The partial reduction of esters with diisobutylaluminium hydride (DIBALH) is not a popular route for aldehyde synthesis, as overreduction to the corresponding alcohol is a significant problem even at low temperatures. Jamison and co-workers exploited the benefits of CF processing together with careful residence-time control and revitalized the DIBALH reduction of esters to yield various aldehydes selectively.24 The residence-time dependence was investigated as a function of the reactor volume at constant flow rate and also as a function of the flow rate at constant reactor volume. The reduction of ethyl hydrocinnamate was initially studied at −78 °C; methanol was introduced separately as a quenching agent to avoid overreduction (Figure 11). Interestingly, the conversion improved when the residence time was shortened at constant reactor volume by increasing the flow rate, and it was observed that at very high flow rates the outcome of the reaction was independent of the residence time (Table 3). These results indicate that the examined reaction proceeds very rapidly, and higher flow rates tend to improve mixing. At such elevated flow rates, the reaction outcome is influenced by the rapid mixing in the reactor channels. It is noteworthy that full conversion and complete selectivity were observed even at very short residence times. The methodology was extended to the selective reduction of a series of further esters.


Strategic Application of Residence-Time Control in Continuous-Flow Reactors.

Mándity IM, Ötvös SB, Fülöp F - ChemistryOpen (2015)

CF set-up for the selective DIBALH reduction of ethyl hydrocinnamate (M=mixing unit, R=tubular reactor).24
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522171&req=5

fig11: CF set-up for the selective DIBALH reduction of ethyl hydrocinnamate (M=mixing unit, R=tubular reactor).24
Mentions: The partial reduction of esters with diisobutylaluminium hydride (DIBALH) is not a popular route for aldehyde synthesis, as overreduction to the corresponding alcohol is a significant problem even at low temperatures. Jamison and co-workers exploited the benefits of CF processing together with careful residence-time control and revitalized the DIBALH reduction of esters to yield various aldehydes selectively.24 The residence-time dependence was investigated as a function of the reactor volume at constant flow rate and also as a function of the flow rate at constant reactor volume. The reduction of ethyl hydrocinnamate was initially studied at −78 °C; methanol was introduced separately as a quenching agent to avoid overreduction (Figure 11). Interestingly, the conversion improved when the residence time was shortened at constant reactor volume by increasing the flow rate, and it was observed that at very high flow rates the outcome of the reaction was independent of the residence time (Table 3). These results indicate that the examined reaction proceeds very rapidly, and higher flow rates tend to improve mixing. At such elevated flow rates, the reaction outcome is influenced by the rapid mixing in the reactor channels. It is noteworthy that full conversion and complete selectivity were observed even at very short residence times. The methodology was extended to the selective reduction of a series of further esters.

Bottom Line: As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals.Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity.Such a fine reaction control cannot be performed in conventional batch reaction set-ups.

View Article: PubMed Central - PubMed

Affiliation: Institute of Pharmaceutical Chemistry, University of Szeged Eötvös u. 6, H-6720, Szeged, Hungary.

ABSTRACT
As a sustainable alternative for conventional batch-based synthetic techniques, the concept of continuous-flow processing has emerged in the synthesis of fine chemicals. Systematic tuning of the residence time, a key parameter of continuous-reaction technology, can govern the outcome of a chemical reaction by determining the reaction rate and the conversion and by influencing the product selectivity. This review furnishes a brief insight into flow reactions in which high chemo- and/or stereoselectivity can be attained by strategic residence-time control and illustrates the importance of the residence time as a crucial parameter in sustainable method development. Such a fine reaction control cannot be performed in conventional batch reaction set-ups.

No MeSH data available.


Related in: MedlinePlus