Electroorganic Synthesis under Flow Conditions

Abstract

Despite the long history of electroorganic synthesis, it did not participate in the mainstream of chemical research for long time. This is probably due to the lack of equipment and standardized protocols. However nowadays organic electrochemistry is witnessing a renaissance and a wide range of interesting electrochemical transformations and methodologies has been developed, not only for academic purposes but also for large scale industrial production. Depending on the source of electricity, electrochemical methods can be inherently green, environmentally benign and can be easily controlled to achieve high levels of selectivity. In addition, the generation and consumption of reactive or unstable intermediates and hazardous reagents can be achieved in a safe way. Limitations of traditional batch-type electrochemical methods such as the restricted electrode surface, the necessity of supporting electrolytes and difficulties in scaling up can be alleviated using electrochemical flow cells. Microreactors offer high surface-to-volume ratios and enable precise control over temperature, residence time, flow rate and pressure. In addition, efficient mixing, enhanced mass and heat transfer and handling of small volumes leads to simpler scaling-up protocols and minimize safety concerns. Electrolysis under flow conditions reduces the possibility of overoxidation as the reaction mixture is flown continuously out of the reactor in contrast to traditional batchtype electrolysis cells. In this account, we highlight our contributions in the area of electroorganic synthesis under flow conditions over the past decade. We have designed and manufactured

Electrophotocatalytic Undirected C−H Trifluoromethylations of (Het)Arenes

“…Based on the results of the electrophotochemical C−H trifluoromethylation in batch, we became intrigued by probing the C−H trifluoromethylation in flow . To our delight, a modular electro‐flow‐cell equipped with a GF anode and a nickel cathode followed by a looped transparent tube delivered under irradiation the desired product 3 a with high efficiency, when using the PC A (Scheme ) .…”

“…Based on the results of the electrophotochemical CÀHt rifluoromethylation in batch, we becamei ntrigued by probing the CÀHtrifluoromethylation in flow. [24] To our delight, amodular electro-flow-cell equipped with aG Fa node and an ickel cathodef ollowed by al ooped transparent tube delivered under irradiation the desired product 3a with high efficiency, when using the PC A (Scheme 5). [25] Notably,t hese findings show that the electro-oxidation and the photo-catalysis steps can occur with spatiala nd temporal separation, for the organic photocatalyst.…”

Making electrochemistry easily accessible to the synthetic chemist

“…This tutorial review provides an introduction to electrochemistry and is not designed to be an extensive review of all synthetic electrochemical examples. For further information recent reviews and the references therein are recommended: certain transformations including cross coupling, [24][25][26] CH activation, [27][28][29][30][31][32][33][34][35][36] asymmetric synthesis, 14 heterocycle formation, [37][38][39] arylation, 40 fluorination, 41 organometallic catalysis, 42,43 cation pool method, 44 continuous reactor types, [45][46][47][48][49][50][51][52][53][54][55] analytical tools 56,57 and general reviews and perspectives. [1][2][3][4][5][6][7][8][9][10][11][12][13]…”

Electrosynthesis of 3,3′,5,5’-Tetramethyl-2,2′-biphenol in Flow

“…In contrast to classical chemical processes, the activation occurs reagent-less by electric current. Thus, mostly toxic, and/or expensive oxidants or reducing agents and transition metal catalysts can be avoided [45,46]. Consequently, reagent waste is circumvented.…”