Microwave Reactions Under Continuous Flow Conditions

Abstract

Microwave chemistry has already impacted significantly on the everyday synthesis of organic molecules. The adoption and integration of this liberating technology has permitted a resurrection of many synthetic transformations that were previously considered too extreme in their conditions (temperatures, pressures, reaction times) to be synthetically useful. Furthermore, whole arrays of additional chemical transformations have been devised under microwave heating that allow access to more diverse chemical architectures via more expedient routes. Continuous flow processing of chemical intermediates taking advantage of the unique heating mechanism and characteristics of microwave irradiation will certainly be the next evolutionary step forward in this area. The synergistic combination afforded by the simultaneous application of these two core processing tools will enhance still further the synthetic capabilities of tomorrow's chemists. This short review aims to highlight the current developments and future potential offered by continuous flow microwave mediated synthesis.

Intensification of organic reactions with hybrid flow reactors

“…Avoiding stirring or shaking greatly reduces the mechanical degradation of the catalyst so that it retains its activity for a longer time. As shown by Ley and coworkers [12], the ability to couple the rapid and controlled heating profiles provided by MW irradiation with the fast optimisation and processing capacities of flow chemistry can noticeably favour process intensification in organic synthesis [13].…”

Efficient and General Continuous‐Flow Hydroarylation and Hydroalkylation of Styrenes

“…The hydroarylation of halo-substituted styrenes with anisole was achieved under CF-MW conditions and the diarylethane products were obtained in good yields (71-88%; Table 3, entries [2][3][4][5]. Similarly, the reaction of 4-methyl-substituted styrene with anisole 2c also proceeded well providing the product in 89% yield (Table 3, entry 8).…”

“…[2] Moreover, microwave technology has been incorporated into flow processes providing faster, cleaner and more selective reactions with higher yields as compared to traditional batch methods. [3][4][5] Thus, chemists in industry and in academia have begun to focus on reactor design and the development of new flow processes. [6] Hydroarylation and hydroalkylation reactions are important synthetic methods for the synthesis of di-A C H T U N G T R E N N U N G arylmethanes.…”

The Spread of the Application of the Microwave Technique in Organic Synthesis

“…Several MW-assisted continuous flow accomplishments on g or kg scale have been reported in the literature [19,[41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Their capacity may reach 500 kg product per day [55].…”