Electrochemical Synthesis of 5-Aryl-phenanthridin-6-one by Dehydrogenative N,C Bond Formation

Article abstract of DOI:10.1002/chem.201804638

Currently, the general synthesis of 5-aryl-phenanthridin-6-ones relies on the involvement of metal catalysis. Despite the urgent demand for green alternatives, avoiding synthetic routes that require transition metals for key roles is still challenging. Electrochemical efforts employing a constant potential protocol in divided cells revealed a possible alternative to the catalytic approach. A constant current protocol, undivided cells, and a remarkably low supporting electrolyte concentration enable a novel access to N-aryl-phenanthridin-6-ones by anodic N,C bond formation using directly generated amidyl radicals. Easy accessible starting materials, a broad scope of applicable functional groups, good yields, and a very simple set-up are the benefits of this sustainable method.

Full text of DOI:10.1002/chem.201804638

A Journal of
Accepted Article
Title: Electrochemical Synthesis of 5-Aryl-phenanthridin-6-one by
Dehydrogenative N,C Bond Formation
Authors: Siegfried R Waldvogel, Anton Kehl, Valentina Breising, and
Dieter Schollmeyer
This manuscript has been accepted after peer review and appears as an
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To be cited as: Chem. Eur. J. 10.1002/chem.201804638
Link to VoR: http://dx.doi.org/10.1002/chem.201804638
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Electrochemical Synthesis of 5-Aryl-phenanthridin-6-one by
Dehydrogenative N,C Bond Formation
Anton Kehl,[a] Valentina M. Breising,[a] Dieter Schollmeyer,[a] and Siegfried R. Waldvogel[a] *
Abstract: Currently, the general synthesis of 5-aryl-phenanthridin-6-
ones relies on the involvement of metal catalysis. Despite the urgent
demand for green alternatives, avoiding synthetic routes which
methodologies which are able to circumvent these drawbacks are
highly desired and a hot topic of current research.[10e,f,g] Recently,
the electroorganic chemistry witnessed a renaissance due to its
inherently safe nature and access to extraordinary reaction
pathways.[10] Electrochemistry can be seen as a green alternative
to classical organic chemistry owed to the fact that it reverts to
solely electric current as an inexpensive and sustainable oxidizing
or reducing agent, which minimizes the amount of waste
dramatically.[11] First efforts to electrochemically generate N-aryl-
phenanthridin-6-one derivatives were made in the 70’s by
establishing a constant potential setup in divided cells (scheme 1,
upper part).[12] Reductive means were used to cleave a carbon-
halogen bond in order to generate radicals for the cyclization
reaction. Unfortunately, this method is afflicted by a narrow scope,
a sophisticated setup and problematic Hg as cathode material.
attribute transition metals
a
key role, is still challenging.
Electrochemical efforts employing a constant potential protocol in
divided cells revealed a possible alternative to the catalytic approach.
A constant current protocol, undivided cells, and a remarkably low
supporting electrolyte concentration enable a novel access to N-aryl-
phenanthridin-6-ones by anodic N,C bond formation using directly
generated amidyl radicals. Easy accessible starting materials, a broad
scope of applicable functional groups, good yields, and a very simple
set-up attribute this sustainable method.
6(5H)-Phenanthridinone was first mentioned by Pictet and
Ankersmit in 1891, who employed nitrophenylbenzoic acid and
zinc dust in ammonia, although the structure could not be
sufficiently confirmed.[1] In 1893, Graebe and Wander synthesized
phenanthridinone derivatives by treating diphenamic acid with
sodium hypobromite as oxidizer. The structural assumption was
confirmed by control experiments, and reported matching
analytical data provided by Pictet and Ankersmit.[2] As far as
application of this compound class is concerned, some
derivatives were allegedly used as vat dye or dye precursors.[3]
Recently, Zeng et al. reported
a protocol to construct
phenanthredin-6-one by employing a constant current setup in
undivided cells with the aid of an anodically generated reagent
(mediator) in order to facilitate the cyclization reaction, limited only
to N-acetyl or N-pivaloyl functionalities (scheme 1, middle part).[13]
A leastwise stoichiometric amount of the mediator (NaBr),
depending on the setup, and in special cases also Na2CO3 as
additive are required. With a current efficiency of 0.4 (platinum
electrodes) this process consumes unusual large amounts of
applied charge. The authors propose, that amidyl radicals are
generated by a homolytically cleaved nitrogen-halide bond
followed by a cyclization and a final oxidation step.
Currently, phenanthridinone represents
a
structural motif
occurring in various compounds with medicinal relevance or
natural products.[4] N-Aryl-phenanthridin-6-one derivatives in
particular are applicable in electronic devices (e.g. OLED’s) or
pharmaceutically active ingredients.[5]
General synthetic approaches rely on metal assisted catalysis[6],
such as Pd,[6a-e,g,h] Ni,[6f] or Cu catalysts,[6i] organic mediators,[7]
radical initiators,[8] or photocatalysis employing Ir-complexes.[9]
These routes are accompanied by severe disadvantages such as
harsh conditions, the necessity for additives or complex ligands,
leastwise stoichiometric mediators, bases or oxidizers, leaving
groups or elaborated precursors. Furthermore, larger amounts of
reagent waste, sophisticated synthesis terms, and a necessity of
partially expensive reagents emerge as unfavorable aspects from
the aforementioned approaches. Hence, these methods exhibit a
negative footprint onto atom economy and ecology. Therefore,
[a]
A. Kehl, V. M. Breising, Dr. D. Schollmeyer, Prof. Dr. S. R.
Waldvogel Johannes Gutenberg-Universität Mainz, Institut für
Organische Chemie
Duesbergweg 10-14, 55128 Mainz (Germany)
Homepage: https://www.blogs.uni-mainz.de/fb09akwaldvogel/
E-mail: waldvogel@uni-mainz.de
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0.01 M (50% 1H NMR yield) can be decreased to 0.0025 M (51%
1H NMR yield) without affecting the yield and providing sufficient
conductivity. In most cases, the conversion of the starting material
was incomplete. This issue was addressed by changing the
cathode material in order to provide a more efficient cathodic
reaction by using electrode materials with a lower over-potential
for hydrogen evolution (table 2). Graphite and steel as cathode
materials achieved slightly lower yields than platinum or nickel,
but hold the advantage of being suitable for pharmaceutical
applications. Except for graphite, all other evaluated cathode
materials indicated full conversion of the starting material with an
applied charge amount of 2.2 F. However, nickel was chosen to
proceed with further electrolytic conversions. The optimized
parameters were tested with glassy carbon as anode once more
to check the impact onto the yield, however, no amelioration in
the yield was observed.
Scheme 1. Electrochemical approaches to phenanthridin-6-one derivatives and
our novel key step for the synthesis of N-aryl-phenanthridin-6-ones.
The application of amidyl radicals as reactive intermediates are
well-known
and
associated
with
hydroaminations,[14a]
rearrangements,[14b] and cyclization reactions.[14b,15] The
generation of amidyl radicals by oxidative cleavage of the
nitrogen-hydrogen bond is highly desirable due to the lack of pre-
functionalization. Electro-organic chemistry is able to engage this
issue by mediated[15i] or direct oxidation[15j] at the anode. Recently,
we reported a methodology to afford amidyl radicals by direct
oxidation in order to construct 5- and 6-membered heterocycles
by dehydrogenative N,N coupling reactions.[16] In order to expand
the scope of heterocycles and to demonstrate the capability of the
electrolyte system, we report a new synthetic approach for N-aryl-
phenanthredin-6-ones (scheme 1, lower part). Easily accessible
biphenyl anilides as starting material, inexpensive electrode
materials and a simple constant current protocol characterize this
synthetic route as a general applicable and straightforward
access to this particular class of compounds.
Table 1. Influence of the current density onto the yield of 2a.
Entry
Current density [mA/cm2]
Yield [%][a]
1
2
3
4
5
6
7
8
0.5
1
50
70
63
56
46
52
49
36
The synthesis of the precursors can be easily conducted in good
yields by treatment of biphenyl-2-carboxylic acid with oxalyl
chloride,[17] removing excess of oxalyl chloride and subsequent
addition of the corresponding aniline derivative.
1.5
2
The electrolytic conditions for the direct N,C coupling were
elucidated within screening studies. This optimization of
parameters was conducted in Teflon cells (volume: 5 mL), which
provide – in combination with an undivided cell setup – a time-
efficient and straightforward screening approach.[18] The
conditions for the synthesis of pyrazolidin-3,5-diones were
chosen as starting point due to their suitability to generate amidyl
radicals in the course of N,N bond formation. N-(4-Chlorophenyl)
biphenyl-2-carboxamide (2a) was chosen as test substrate, since
this particular anilide moiety had demonstrated an excellent
compatibility with the electrochemical conditions at hand.[16a,c]
Commencing with the aforementioned conditions gave a 1H NMR
yield of 50% of the desired product (table 1, entry 1). We also
tested acetonitrile and methanol as solvent. On the one hand, the
reaction in acetonitrile indicated no conversion of the starting
material, on the other hand, the electrolysis in methanol revealed
a complicated mixture containing starting material, product,
methoxylated starting material and other non-identified
compounds according to the gaschromatographic measurements.
1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) exclusively provides an
effective and selective conversion, which is based on its radical
stabilizing properties.[19] The fact that HFIP is recovered almost
2.5
3
4
5
0.2 mmol substrate, 0.01 M NBu4PF6, graphite electrodes (highly
isostatic graphite Sigrafine™ V2100), HFIP, charge 2.2 F,
undivided Teflon cell (5 mL); [a] 1H NMR yields.
Table 2. Influence of the cathode material onto the yield of 2a.
Entry
Cathode
Graphite[b]
Platinum
Nickel
Yield [%][a]
1
2
3
4
5
75
80
85
85
72
Nickel[c]
Steel[d]
entirely by distillation ensures
a
low fluorine footprint.[20]
Furthermore, boron-doped diamond (55% 1H NMR yield) and
glassy carbon (58% 1H NMR yield) were evaluated as anode
materials to give similar results regarding the conversion and yield.
Hence, we decided to stay with isostatic graphite to provide a
readily available and inexpensive anode material. A vital and
powerful parameter in electro-organic synthesis is current density.
The optimization revealed, that best results are obtained with a
current density of 1 mA/cm2 (table 1). Higher current density such
as 4 and 5 mA/cm2 result in lower yields due to degradation
reactions. In addition, the supporting electrolyte concentration of
0.2 mmol substrate, 0.0025 M NBu4PF6, anode: graphite, current
density: 1 mA/cm2, HFIP, charge 2.2 F, undivided Teflon cell
(5 mL), [a] isolated yield, [b] 3.2 F applied for full conversion, [c]
anode: glassy carbon, [d] A5-stainless-steel (VA 1.4571).
The optimized parameters were applied on a collection of
biphenyl anilide substrates and resulted in a scope of N-aryl-
phenanthridin-6-one derivatives with various functional groups
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Scheme 2. Optimized parameters for the electrochemical N,C cyclization and
scope. 5 mL Teflon cell, 0.2 mmol scale, [a] 80 mL beaker-type cell, 6.3 mmol
substrate.
and substitution patterns at the aniline moiety and the biphenyl
entity (scheme 2).
The majority of compounds were synthesized in good to excellent
yields, tolerating chloro- (2a, 2k, 2l, 2m), fluoro- (2c, 2k), bromo-
(2e), iodo- (2f), nitro- (2j), keto- (2h), ester- (2l), or nitrile (2d)
substituents, which allow subsequent reactions. The highest yield
of 85% was achieved with compound 2a, which was the
designated compound for our optimization procedures. 2a was
also employed to demonstrate the up-scaling ability of this method
by giving 78% yield (gram scale). The formation of the N,C
coupled product was confirmed via X-ray structure analysis of a
suitable single crystal of 2a (scheme 2). As anticipated, the X-ray
structure analysis revealed that the aryl moiety of the aniline is
oriented orthogonal with regards to the lactam moiety. Not much
surprisingly, derivatives with a blocked para-positon (2a, 2b, 2c,
2d, 2m) provide excellent yields. Whereas 2g exhibits a lower
yield due to possible side reactions.[15] Interestingly, derivative 2e,
2f, 2i and 2j which also exhibit a free para-position result in much
better yields compared with 2g.
Derivative 2k yields moderately even though the 4-chlorophenyl
moiety was employed. This reaction revealed an incomplete
conversion of the substrate regardless the amount of charge
applied. However, electron withdrawing (2c, 2j) as well as bulky
moieties (2b, 2m) incorporated by the aniline component work
well. In terms of the mechanism, it is likely that the cyclization is
initiated by the generation of an amidyl radical through a direct
oxidation of the substrate at the anode. The deprotonation of the
anilide could be executed by an in-situ generated HFIP anion. The
amidyl radical can be stabilized by the N-aryl system. The N,C
bond formation proceeds between the amidyl radical and the
second, in this case unsubstituted phenyl moiety of the biphenyl
scaffold resulting in a radical within the lactam system. After a
second oxidation step combined with a follow-up extrusion of a
proton, the product is accomplished.
Scheme 3. Proposed mechanism.
We established a new and sustainable access to N-aryl-
phenanthredin-6-ones by employing direct anodic oxidation. This
protocol features a high current efficiency and operates without
the necessity for a mediator. Easily accessible and inexpensive
starting materials, a simple set-up, remarkably low supporting
electrolyte concentrations, metal catalyst- and organic oxidizer-
free conditions as well as inexpensive electrode materials provide
a
straightforward and sustainable route to this class of
compounds. A variety of derivatives is possible, valuable
functionalities, which enable subsequent reactions, are tolerated.
Up-scaling of this method is easily possible.
Acknowledgements
The support by The Advanced Lab for Electrochemistry and
Electrosynthesis – ELYSION (Carl Zeiss Stiftung) and the DFG
(WA 1276/17-1) is highly appreciated.
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1278; k) T. Morofuji, A. Shimizu, J.-i. Yoshida, J. Am. Chem. Soc. 2013,
135, 5000–5003; l) R. Francke, R. D. Little, J. Am. Chem. Soc. 2014, 136,
427–435; m) A. Wiebe, D. Schollmeyer, K. M. Dyballa, R. Franke, S. R.
Waldvogel, Angew. Chem. Int. Ed. 2016, 55, 11801–11805; Angew.
Chem. 2016, 128, 11979–11983; n) S. Lips, A. Wiebe, B. Elsler, D.
Schollmeyer, K. M. Dyballa, R. Franke, S. R. Waldvogel, Angew. Chem.
Int. Ed. 2016, 55, 10872–10876; Angew. Chem. 2016, 128, 11031–
11035;
Keywords: electrochemistry • N,C coupling • heterocyclic
chemistry • green chemistry • N-aryl-phenanthrendin-6-ones
[1]
[2]
[3]
[4]
A. Pictet, H. J. Ankersmit, Liebigs Ann. Chem. 1891, 266, 138–153.
C. Graebe, A. Wander, Liebigs Ann. Chem. 1893, 276, 245–253.
Authors unknown (BASF), DE236857C, 1910.
a) D. Weltin, V. Picard, K. Aupeix, M. Varin, D. Oth, J. Marchal, P. Dufour,
P. Bischoff, Int. J. Immunopharmacol 1995, 17, 265–271; b) Z. Tu, W.
Chu, J. Zhang, C. S. Dence, M. J. Welch, R. H. Mach, Nuc. Med. Biol.
2005, 32, 437–443; c) S. D. Shnyder, P. A. Cooper, N. J. Millington, J. H.
Gill, M. C. Bibby, J. Nat. Prod. 2008, 71, 321–324; d) S. Patil, S. Kamath,
T. Sanchez, N. Neamati, R. F. Schinazi, J. K. Buolamwini, Bioorg. Med.
Chem. 2007, 15, 1212–1228; e) J. Ishida, K. Hattori, H. Yamamoto, A.
Iwashita, K. Mihara, N. Matsuoka, Bioorg. Med. Chem. Lett. 2005, 15,
4221–4225; f) T. A. Grese, M. D. Adrian, D. L. Phillips, P. K. Shetler, L.
L. Short, A. L. Glasebrook, H. U. Bryant, J. Med. Chem. 2001, 44, 2857–
2860; g) D. Bellocchi, A. Macchiarulo, G. Costantino, R. Pellicciari,
Bioorg. Med. Chem. 2005, 13, 1151–1157; h) Z. Jin, Nat. Prod. Rep.
2011, 28, 1126–1142; i) M. He, C. Qu, O. Gao, X. Hu, X. Hong, RSC Adv.
2015, 5, 16562–16574.
[11] a) H. J. Schäfer, C. R. Chim. 2011, 14, 745–765; b) B. A. Frontana-Uribe,
R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem.
2010, 12, 2099–2119.
[12] J. Grimshaw, D. Mannus, J. Chem. Soc., Perkin Trans. 1 1977, 2456.
[13] S. Zhang, L. Li, M. Xue, R. Zhang, K. Xu, C. Zeng, Org. Lett 2018, 20,
3443–3446.
[14] a) S. Z. Zard, Chem. Soc. Rev. 2008, 37, 1603–1618; b) N. Fuentes, W.
Kong, L. Fernández-Sánchez, E. Merino, C. Nevado, J. Am. Chem. Soc.
2015, 137, 964–973.
[15] a) K. C. Nicolaou, P. S. Baran, Y.-L. Zhong, S. Barluenga, K. Hunt, R.
Kranich, J. A. Vega, J. Am. Chem. Soc. 2002, 124, 2233–2244; b) Y.-F.
Wang, H. Chen, X. Zhu, S. Chiba, J. Am. Chem. Soc. 2012, 134, 11980–
11983; c) B. Janza, A. Studer, J. Org. Chem. 2005, 70, 6991–6994; d) S.
Maity, N. Zheng, Angew. Chem. Int. Ed. 2012, 51, 9562–9566; Angew.
Chem. 2012, 124, 9700–9704; e) X.-Q. Hu, J.-R. Chen, Q. Wei, F.-L. Liu,
Q.-H. Deng, A. M. Beauchemin, W.-J. Xiao, Angew. Chem. Int. Ed. 2014,
53, 12163–12167; Angew. Chem. 2014, 126, 12359–12363 f) G. J. Choi,
R. R. Knowles, J. Am. Chem. Soc. 2015, 137, 9226–9229. g) S. Z. Zard,
Chem. Soc. Rev. 2008, 37, 1603; h) C. Moutrille, S. Z. Zard, Chem.
Commun. 2004, 1848–1849; i) L. Zhu, P. Xiong, Z.-Y. Mao, Y.-H. Wang,
X. Yan, X. Lu, H.-C. Xu, Angew. Chem. Int. Ed. 2016, 55, 2226–2229;
Angew. Chem. 2016, 128, 2266–2269; j) H.-C. Xu, J. M. Campbell, K. D.
Moeller, J. Org. Chem. 2014, 79, 379–391.
[5]
[6]
a) P. Stoessel, A. H. Parham, C. Pflumm, A. Jatsch, J. Kaiser,
WO2014194971A1, 2014; b) A. Jatsch, A. Parham, R. Linge, T.
Grossmann, WO2018099846A1, 2018; c) J. T. Dalton, C. Barrett, Y. He,
S.-S. Hong, D. D. Miller, M. L. Mohler, R. Narayanan, Z. Wu,
WO2007062230A2, 2007.
a) T.-Y. Zhang, J.-B. Lin, Q.-Z. Li, J.-C. Kang, J.-L. Pan, S.-H. Hou, C.
Chen, S.-Y. Zhang, Org. Lett. 2017, 19, 1764–1767; b) Y. Yang, H.
Huang, L. Wu, Y. liang, Org. Biomol. Chem. 2014, 12, 5351–5355; c) G.-
W. Wang, T.-T. Yuan, D.-D. Li, Angew. Chem. Int. Ed. 2011, 50, 1380–
1383; d) V. H. Thorat, N. S. Upadhyay, M. Murakami, C.-H. Cheng, Adv.
Synth. Catal. 2018, 360, 284–289; e) V. Rajeshkumar, T.-H. Lee, S.-C.
Chuang, Org. Lett. 2013, 15, 1468–1471; f) X. Li, J. Pan, S. Song, N.
Jiao, Chem. Sci. 2016, 7, 5384–5389; g) J. Karthikeyan, C.-H. Cheng,
Angew. Chem. Int. Ed. 2011, 50, 9880–9883; h) T. Furuta, Y. Kitamura,
A. Hashimoto, S. Fujii, K. Tanaka, T. Kan, Org. Lett. 2007, 9, 183–186;
i) B. Banerji, S. Chatterjee, K. Chandrasekhar, C. Nayan, S. K. Killi, Eur.
J. Org. Chem. 2017, 2017, 5214–5218.
[16] a) T. Gieshoff, D. Schollmeyer, S. R. Waldvogel, Angew. Chem. Int. Ed.
2016, 55, 9437–9440; Angew. Chem. 2016, 128, 9587–9590; b) T.
Gieshoff, A. Kehl, D. Schollmeyer, K. D. Moeller, S. R. Waldvogel, J. Am.
Chem. Soc., 2017, 139, 12317–12324; c) A. Kehl, T. Gieshoff, D.
Schollmeyer, S. R. Waldvogel, Chem.-Eur. J. 2018, 24, 590–593.
[17] A. R. Blaazer, J. H. M. Lange, M. A. W. van der Neut,, A. Mulder, F. S.
den Boon, T. R. Werkman, C. G. Kruse, W. J. Wadman, Eur. J. Med.
Chem. 2011, 46, 5086–5098.
[7]
[8]
S. Wang, P. Shao, G. Du, C. Xi, J. Org. Chem. 2016, 81, 6672–6676.
M. Yuan, L. Chen, J. Wang, S. Chen, K. Wang, Y. Xue, G. Yao, Z. Luo,
Y. Zhang, Org. Lett. 2015, 17, 346–349.
[18] C. Gütz, B. Klöckner, S. R. Waldvogel, Org. Process Res. Dev. 2016, 20,
26–32.
[9]
Y. Moon, E. Jang, S. Choi, S. Hong, Org. Lett. 2018, 20, 240–243.
[19] a) A. Kirste, M. Nieger, I. M. Malkowsky, F. Stecker, A. Fischer, S. R.
Waldvogel, Chem. Eur. J. 2009, 15, 2273–2277; b) A. Kirste, G.
Schnakenburg, F. Stecker, A. Fischer, S. R. Waldvogel, Angew. Chem.
Int. Ed. 2010, 49, 971–975; Angew. Chem. 2010, 122, 983–987; c) R.
Francke, D. Cericola, R. Kötz, D. Weingarth, S. R. Waldvogel,
Electrochim. Acta 2012, 62, 372–380; d) O. Holloczki, A. Berkessel, J.
Mars, M. Mezger, A. Wiebe, S. R. Waldvogel, B. Kirchner, ACS Catal.
2017, 7, 1846–1852; e) B. Elsler, D. Schollmeyer, K. M. Dyballa, R.
Franke, S. R. Waldvogel, Angew. Chem. Int. Ed. 2014, 53, 5210–5213;
Angew. Chem. 2014, 126, 5311–5314; f) B. Elsler, A. Wiebe, D.
Schollmeyer, K. M. Dyballa, R. Franke, S. R. Waldvogel, S. R. Chem.
Eur. J. 2015, 21, 12321–12325.
[10] a) S. R. Waldvogel, S. Lips, M. Selt, B. Riehl, C. J. Kampf, Chem.
Rev., 2018, 118, 6706–6765; b) Yan, M.; Kawamata, Y.; Baran, P. S.
Chem. Rev. 2017, 117, 13230–13319; c) A. Wiebe, T. Gieshoff, S. Möhle,
E. Rodrigo, M. Zirbes, S. R. Waldvogel, Angew. Chem. Int. Ed. 2018, 57,
5594–5619; Angew. Chem. 2018, 130, 5694–5721; d) S. Möhle, M.
Zirbes, E. Rodrigo, T. Gieshoff, A. Wiebe, S. R. Waldvogel, Angew.
Chem. Int. Ed. 2018, 57, 6018–6041; Angew. Chem. 2018, 130, 6124–
6149; e) S. R. Waldvogel, B. Janza, Angew. Chem. Int. Ed. 2014, 53,
7122–7123; Angew. Chem. 2014, 126, 7248–7249; f) S. R. Waldvogel,
S. Möhle, Angew. Chem. Int. Ed. 2015, 54, 6398–6399; Angew. Chem.
2015, 127, 6496–6497; g) S. R. Waldvogel, M. Selt, Angew. Chem. Int.
Ed. 2016, 55, 12578–12580; Angew. Chem. 2016, 128, 12766–12768;
h) C. Gütz, M. Selt, M. Bänziger, C. Bucher, C. Römelt, N. Hecken, F.
Gallou, T. R. Galvão, S. R. Waldvogel, Chem. Eur. J. 2015, 21, 13878–
13882; i) J. Chen, W.-Q. Yan, C. M. Lam, C.-C. Zeng, L.-M. Hu, R. D.
Little, Org. Lett. 2015, 17, 986–989; j) S. Herold, S. Moehle, M. Zirbes, F.
Richter, H. Nefzger, S. R. Waldvogel, Eur. J. Org. Chem. 2016, 1274–
[20] I. Colomer, A. E. R. Chamberlain, M. B. Haughey, T. J. Donohoe, Nat.
Rev. Chem. 2017, 1, 88.
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Entry for the Table of Contents (Please choose one layout)
Layout 2:
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A. Kehl, V. M. Breising, D. Schollmeyer,
S. R. Waldvogel*
Page No. – Page No.
Electrochemical Synthesis of 5-Aryl-
phenanthridin-6-ones by
Dehydrogenative N,C Bond
Formation
Direct electrochemical synthesis of N-aryl-phenanthredinones by means of
anodic N,C bond formation. Easy accessible biphenyl anilides, inexpensive
electrode materials and a simple electrolysis set-up provide a straightforward
access to 6-membered ring systems in good yields.
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