G Model
CCLET 5790 No. of Pages 4
Chinese Chemical Letters
Original article
Visible-light-induced photoredox-catalyzed synthesis of benzimidazo
[2,1-a]iso-quinoline-6(5H)-ones
a
b,c,
Bin Wanga,b, Long Zoub, Lei Wanga,b,c, , Manman Sun , Pinhua Li
*
*
a
Advanced Research Institute and Department of Chemistry, Taizhou University, Taizhou, 318000, China
b
Department of Chemistry, Huaibei Normal University, Huaibei, 235000, China
c
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Shanghai, 200032, China
A R T I C L E I N F O
A B S T R A C T
Article history:
A simple and efficient visible-light-induced photoredox-catalyzed diarylation of N-methacryloyl-2-
arylbenzoimidazoles with aryl diazonium salts was developed. The reaction provides a convenient access
to a variety of benzimidazoisoquinolinones through the construction of two CÀÀC bonds in one step
under mild reaction conditions.
© 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Received 21 June 2020
Received in revised form 21 July 2020
Accepted 10 August 2020
Available online xxx
Keywords:
Benzimidazo[2,1-a]iso-quinoline-6(5H)-
ones
N-Methacryloyl-2-arylbenzoimidazoles
Aryl diazonium salts
Photoredox catalysis
Visible-light-induced organic reaction
Benzimidazo-isoquinoline fused framework is one of the most
important nitrogen-containing heterocyclic units (A, Fig. 1). As a
privileged structure, benzimidazo-isoquinoline skeleton is widely
found in biologically active natural products, pharmaceutical
compounds and material science [1–4], such as anti-diabetic
compound (B, Fig. 1) [5,6], anti-tumor agent (C, Fig. 1) [7,8], anti-
inflammatory compound (D, Fig. 1) [9–11], modulating the
potassium ion flux reagent (E, Fig. 1) [12,13], and candidate for
organic electronics (F, Fig. 1) [14]. In addition, benzimidazoiso-
quinolinone derivatives [15–17], as useful building blocks, are
important synthetic intermediates are widely applied in the
organic synthesis [18–26]. Owing to their unique properties in
biological and material science molecules and their synthetic
applications, there is a great need to develop a practical synthetic
method to prepare benzimidazoisoquinolinones.
The general procedure for the synthesis of benzimidazoisoqui-
nolinones is limited to multi-step condensation reactions, which
suffer from tedious pre-functionalization steps for starting materi-
als,harshreactionconditionsandlimitedfunctionalgrouptolerance.
Therefore, much effort has been directed towards exploring efficient
methods for their synthesis. For example, Song and co-workers
developed an elegant Cp*Rh(III)-catalyzed [4 + 2] annulative
reaction of 2-arylimidazoles and a-diazoketoesters for the prepara-
tionofbenzimidazole[2,1-a]isoquinolinesin2018(Scheme1a)[27].
Recently, Yu’s group reported a Ag-catalyzed decarboxylative
radical cascade cyclization functionalized 2-arylbenzoimidazoles
and carboxylic acids into a wide range of benzimidazo[2,1-a]
isoquinoline-6(5H)-ones and a Ag-catalyzed synthesis of phospho-
ryl-substituted benzimidazo[2,1-a]isoquinoline-6(5H)-ones from
diarylphosphine oxides and 2-arylbenzoimidazoles in one pot
(Scheme 1b) [28,29]. After then, a visible-light promoted radical
cyclization to access perfluoroalkyl-substituted benzimidazo
[2,1-a]isoquinolin-6(5H)-ones was described by same group
(Scheme 1c) [30]. Despite these achievements, these methods still
have some disadvantages, such as the need of expensive metal as
catalyst, excess oxidant or additive, and higher reaction tempera-
ture, limiting their synthetic applications. So, the development of
efficientandconvenientroutetofunctionalizedbenzimidazo[2,1-a]
isoquinolin-6(5H)-ones under mild and environmentally friendly
conditions is still desirable.
Visible light is an environmentally friendly and infinitely
available energy source that can be used to activate chemical
conversions and it induced organic reactions have become a
powerful tool in organic synthesis [31–45]. Avariety of visible-light
induced organic transformations via single electron transfer,
energy transfer, or a hydrogen atom transfer process have recently
received considerable attention [46–48]. In the presence of a
photosensitizer, a number of carbon-carbon and carbon-heteroat-
om bonds formations under visible-light irradiation were reported
* Corresponding authors at: Department of Chemistry, Huaibei Normal
University, Huaibei, 235000, China.
1001-8417/© 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: B. Wang, et al., Visible-light-induced photoredox-catalyzed synthesis of benzimidazo[2,1-a]iso-quinoline-6