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Screening in electrosynthesis
Rapid and sustainable development of tomorrow‘s innovative chemistry
Maurice Dörr1, Dirk Waldmann2, Siegfried R. Waldvogel1T

he screening system described here
accelerates and simplifies the investigation and optimization of newelectrochemical synthesis steps on a resource-efficient scale and thus contributes significantly to the establishment ofelectrosynthesis methods.
Electrosynthesis in the 21st century
Organic electrochemistry has its origins
in the 19th century [2]. However, due tothe increasing social weight of the approaching climate catastrophe and theenormous urgency to counteract it, it isexperiencing a surprisingly pronounced
renaissance and has become an important
method of the 21st century [3]. Conventional synthesis methods often require the useof heavy metals as well as other harmful
chemicals, whereas great efforts are being
made to develop metal-free and sustaina-

GIT Labor-Fachzeitschrift, Wiley-VCH GmbH, Weinheim

ble electrochemical methods [4,5,6]. Organic electrosynthesis thus provides answers
to many problems faced by chemists andrepresents a strategically important alternative to conventional methods [7]. With
careful planning, electrochemistry can produce sustainable processes in the spirit ofgreen chemistry [8]. In this context, electrons serve as a clean reagent, which canefficiently avoid reagent waste [9]. Special
attention is also paid to the use of renewable raw materials [8,10]. The rapid progressin this field is made possible by appropriately optimized workflows in the screening
phase and the use of suitable apparatus.
Small batch sizes and a high degree of parallelization enable time- and cost-efficientresearch [1].
Electrosynthesis shortens processes, saves
energy and reduces environmental impact.
The IKA Screening System is perfectly suited for constant current electrosynthesis in„multibatch” mode. The combination of both

divided and undivided batch cells enables
you to quickly carry out research on multiple electroconversions at the same time.
More information can be found on the IKA
website.

Electrosynthetic screening
An industrial process as well as any new
chemical synthesis is usually accompanied by intensive research and optimization [11]. This procedure requires a large
number of experiments to be carried outand is therefore usually time-consuming
and expensive. Accordingly, these experiments are commonly performed on asmall, resource-efficient screening scale.
In a subsequent scale-up, the results of thescreening experiments can be validated. Inorder to achieve the highest possible reproducibility of the results of electrosyntheses, it is necessary to create and adhere tohttps://analyticalscience.wiley.com

standards in the performance and description of the experiments [12]. An importantbasis for this is a uniform experimental setup that meets the special requirements ofelectrochemical screening [1].
Electrosynthetic screening has developed into a fundamental method for the
study of new reactions and is thus thebasis of many discoveries in recent electrosynthesis. For example, the study of alarge number of modern anodic homoand cross-coupling reactions was massively accelerated by this electrochemical
screening [5,6]. Within a few years, a large
number of different substrates were madeaccessible for this reaction (fig. 1). In 2006,
this conversion was first investigated using
the homocoupling of 2,4-dimethylphenol[13]. This was followed by several otherphenols [14] and in 2010 the first anodic
cross-coupling of phenols with different
arenes was found [15]. After, some phenol-phenol cross-couplings, first completely unprotected [16]- and later with theaid of protecting groups [17], as well as
the synthesis of more complex target structures under double cross-coupling [18] were followed by the exploitation of anilines [19] and various heterocyclic coupling
components [20] for this type of reaction.
After the synthesis of para-biphenols [21],the authors even succeeded in introducing
phenols with electron-withdrawing substituents into the coupling reaction [22]. Mostof the reactions listed in figure 1 (markedin green) were studied using a screening
apparatus developed at Mainz University in
the AG Waldvogel [1]. The described screening system as well as suitable accessories
are currently manufactured and commercially distributed by IKA. This opens up thegeneral entry into electrosynthesis and promotes reproducibility across laboratories.

Fig. 1: Selected anodic homo- and cross-coupling reactions. Highlighted in red: before the development of the electrochemical screening system. Labeled green: investigated with the aid of thescreening system.

The commercial screening system in detailThis screening system is available for both
divided and undivided electrolytic cells
and allows 6 or 8 electrolyses to be carried out in parallel on a single magnetic
stirring plate. The electrolysis cells can be
uniformly tempered with the aid of theheating plate and the manifold, and theelectrolysis-specific parameters of current
density and voltage can be set separately for each cell due to the multichannel
DC sources [23]. Common carbon as wellas metal-based electrode materials in therequired dimensions are also available,
opening up a wide field of potential applications. In addition to this plug and playconcept, novel electrode systems can also

Fig. 2: IKA‘s commercial screening system. Left: Setup consisting of two multi-channel DC power sources, a hot plate and the reaction block including 8 undivided cells. Top right: Reaction
block and single divided electrolytic cell plus two half cells. Bottom right: Reaction block andsingle undivided electrolytic cell.

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Fig. 3: Electrodes made of different materials for the screening system.

be easily tested here in electrosynthesis, as
the electrodes used have simple dimensions of 3 mm x 10 mm x 70 mm.
The current sources offered allow electrosynthesis up to very high current densities (>1A/cm2) and can also be usedlater on to operate larger batch-type electrolysis cells, such as those from SigmaAldrich‘s SynLectro series [24]. In addition,a gas distributor enables reactions underuniform gas flow. On the one hand, thisallows gas to be used as a reaction partner but also allows reactions to be carriedout under inert conditions, such as exclusion of oxygen. Modified Teflon cells are
now also available, which can be equippedwith gas diffusion electrodes and thus supply gaseous components to the electrosynthesis even more efficiently.

Fig. 4: Accessories for electrolysis with gaseous components. Left: Gas distributor, for dividing agas stream among the screening cells. Right: Divided screening cell for gas diffusion electrodes.

Modern screening methods
The speed of establishing electrolysis achieved by parallelization and the small screening scale enables the combination of modern exploration and optimization methods
from fields such as design of experiment ormachine learning. This linkage is emerging
as an extremely powerful tool in the exploration and optimization of new electroorganic reactions. Especially for reactions where
the effects of the reaction parameters on
the figure of merit interact with each other,
optimization sometimes proves to be very

complex [25]. Here, the combination of thescreening system with the aforementioned
advanced methods is largely responsible forthe success of the optimization process. This
technology represents the backbone of electrosynthesis research in Mainz.

Prof. Dr. Siegfried R. Waldvogel
Department ChemistryUniversity Mainz
Mainz, Germany
waldvogel@uni-mainz.de

Published at: https://analyticalscience.wiley.
com/do/10.1002/was.000600155.
11. August 2021

Dirk Waldmann
Corporate Manager R&D
IKA-Werke GmbH & Co. KG
Staufen, Germany
dirk.waldmann@ika.de

CONTACT |IKA Screening System
The IKA Screening System is perfectly suited to galvanostatic electrosynthesis in “multibatch” mode. The combination of both divided andundivided batch cells enables you to carry out research on multiple
probes at the same time. In addition, you can combine the system withother equipment in the laboratoryParallel batch electrosynthesis using parameters predefined by you:>

Up to 8 undivided or 6 divided cells simultaneously>

Synthesize sufficient quantities for GC, LC or NMR analysis processes>

Separate control for each cell>

Easy testing of identical or differing samples>

Fast identification of ideal process parameters>

Digital recording of test parameters>

Simultaneous mixing and heating>

Full temperature control (PT 1000) using heat block>

Control and automation via Labworldsoft 6.0>

Time and resources savings

Screening System Package(6 divided cells)
Ident. No. 0040003631IKA-Werke GmbH & Co. KG
Janke & Kunkel-Straße 10, 79219 Staufen, Germany
Phone: +49 7633 831-0
eMail: sales@ika.de

Screening System Package(8 undivided cells)
Ident. No. 0040003642