We investigate the mechanisms that govern plugging in microreactors during Pd-catalyzed amination reactions. Both bridging and constriction were shown to be important mechanisms that lead to clogging in our system and greatly limited the utility of microsystems for this class of reactions. On the basis of these observations, several approaches were engineered to overcome the challenge of plugging and to enable the continuous-flow synthesis of a biarylamine. Bridging could be eliminated with acoustic irradiation while constriction was managed via fluid velocity and the prediction of growth rates.

A continuous-flow palladium-catalyzed amination reaction was made possible through efficient handling of solids via acoustic irradiation. Various diarylamines were obtained with reaction times ranging from 20 s to 10 min.

With the development of new photocatalytic methods over recent decades,t he translation of these chemical reactions to industrial-production scales using continuous-flow reactors has become at opic of increasing interest. In this context, we describe our studies towarde lucidating an empirically derived parameter for scaling photocatalytic reactions in flow. By evaluating the performance of ap hotocatalytic CÀNc ross-coupling reaction across multiple reactor sizes and geometries,i tw as demonstrated that expressing product yield as afunction of the absorbed photon equivalents provides apredictive,empirical scaling parameter.Through the use of this scaling factor and characterization of the photonic flux within each reactor,t he cross-coupling was scaled successfully from the milligram scale in batch to am ultikilogram reaction in flow.

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A simple and inexpensive photoreactor with a throughput of kilograms of material per day has been developed. This achievement was enabled by using high-power Light Emitting Diodes (LEDs) to provide high light density, leading to minimization of the footprint of the reactor. A study of the impact of tube diameter enabled maximization of the photon absorbance without increasing photocatalyst loading. Further optimization of reaction conditions using a design of experiments (DoE) elucidated reaction sensitivities that allowed the reaction rate, yield, and productivity to be maximized upon scale-up. The reactor has been operated continuously for 6 h leading to reaction performance that provided 12 kg of material per day at 90% conversion.